Unit 3: Health and Disease in the Caribbean PDF

Unit 3 Health and Disease in the Caribbean INTRODUCTION Good health is central to a good quality of life for all of us. It is also essential for the economic and social stability of a country or nation as ill health on a l...

Unit 3 Health and Disease in the Caribbean INTRODUCTION Good health is central to a good quality of life for all of us. It is also essential for the economic and social stability of a country or nation as ill health on a large scale reduces productivity and increases the cost of health care. According to certain statistics, health in the Caribbean has improved in recent decades. Life expectancy has increased. More people are living longer, shifting the balance in the distribution of age groups in the population. The proportion of the population over 60 years is increasing while the proportion under 15 years is declining as the birth rate decreases (CAREC, 2001). This sounds good but it raises a serious issue; in years to come there will be fewer people of working age to support increasing numbers of elderly citizens. Many debili- tating diseases in the elderly result from years of poor eating habits and lifestyle choices. The importance of maintaining a healthy life style while we are young cannot be over emphasized. Another improvement is the reduced incidence of many communi- cable diseases, but the increasingly rapid rate of the spread of HIV/AIDS infection is of grave concern. Added to this is the fact that chronic nutrition-related diseases are increasing as our life styles change. Diseases like heart disease, diabetes, and hypertension FD12A 159  are now the leading causes of death in the region. We hope that after completing this Unit you will have a better understanding of these health issues and a new awareness of what is required of us to improve and maintain the health of the region. Good health concerns us all. OVERVIEW There are three sessions in this Unit. After introducing the concepts of health and disease we begin with a brief review of some of the common diseases of the region. These include non-communicable disorders associated with poor nutrition and/or life styles and communicable diseases, the ones we “catch”. Particular attention is paid to AIDS because of its increasing incidence in the region. This session also includes a short discussion on substance abuse, because of its association with sexually transmitted infections and other causes of ill health. In the second we consider the changing patterns of nutrition in the Caribbean and some of the attendant problems, including obesity. The final session of the unit begins with a brief review of the genetic basis of inheritance then describes three inherited disorders. Biotechnology and gene therapy are mentioned only briefly as they are covered in more detail in Unit 4. LEARNING OBJECTIVES After completing this unit, you should be able to: 1. Identify the main diseases prevalent in the Caribbean 2. Explain the importance and difficulties of controlling HIV/AIDS in the Caribbean 3. Outline nutrition trends in the Caribbean and discuss their implications 4. Analyse the links between diet, lifestyle, and the pattern of chronic diseases prevalent in the region 160 FD12A  5. Comment on substance abuse and its implications for regional health and productivity 6. Describe the causes of some genetic diseases 7. Discuss the possible implications of disease for regional health and productivity 8. Discuss the importance of understanding the causes of disease as exemplified by the diseases included in this Unit 9. Discuss the importance of reasoned behavioural lifestyle choices, which will promote good health FOR THE STUDENT You should focus on the ways in which knowledge of a disease affects the ability to prevent or treat the disease rather than details of the disease itself. Consult the learning objectives for guidance as you go through the Unit. READINGS Bajaj, Jasbir S. Emerging epidemic of diabetes mellitus. West Indian Medical Journal, 50 (Suppl. 1): 15–16, 2001. Caribbean Epidemiology Centre (CAREC). Overview of health in the region. 2001. http://www.carec.org/overview_health.htm. Douglas, Ken-Garfield. Drugs among our children. The Gleaner, p. B6, September 19, 2001. Figueroa, J. Peter. World Aids Day Press Conference. The Gleaner, p. A1, November 25, 2000. HIV/AIDS in Africa. UNAIDS Fact Sheet. December 2000. Introduction and General Considerations. Recommended dietary allowances for the Caribbean. Kingston, Jamaica: Caribbean Food and Nutrition Institute Mona, 1994. Mackoon, Lindsay. 360,000 living with AIDS in the Caribbean. The Gleaner, p. A1, November 1, 2001. Novel Gene Therapy Approach for Cystic Fibrosis in First FD12A 161  Human Trials. ScienceDaily Magazine. Source: University Hospitals of Cleveland, 2002. Roberts, Michael, Michael Reiss, and Grace Monger. Cancers in Biology. Thomas Nelson and Sons Ltd., pp 564–566. Terms of reference of expert group on Caribbean food and nutrition surveillance system. Recommended dietary allowances for the Caribbean. Kingston, Jamaica: Caribbean Food and Nutrition Institute Mona, 1994. The editorial. Cajanus, 33(1): 1–3, 2000. 162 FD12A  Session 3.1 Some Diseases Common in the Region Introduction How do we know when we are sick or well? The concepts of health and disease are not as easy to define as they appear to be. According to the World Health Organisation (WHO) health is “a state of complete physical, mental and social well-being not merely the absence of disease or infirmity”. To be healthy a person must feel well in body and mind and all our organs and systems must be func- tioning efficiently. Given this definition, are you sure you are healthy? Disease is even more difficult to define as there are a number of serious conditions that cannot really be called “diseases”, for example, broken bones. However, a good working description might be “any disorder of any bodily or mental function”. Disease can be broadly categorised into two groups. Communicable diseases include all diseases caused by other living organisms. These organisms may be transmitted from one person to another either directly or indirectly, causing them to spread. In our first session we will look briefly at a few examples of communicable diseases, including AIDS, in some detail. This will be followed by a discussion of some non-communicable diseases. Non-communicable diseases cannot be “caught” from the external environment. They have their origins within us. We cover diabetes, hypertension, heart disease, and cancer, at present the four most important “killers” in the Caribbean. They are of interest not only because of their heavy social cost but because they are largely preventable or controllable. Substance abuse is also included here because of its connection to AIDS, other STDs and other conditions of ill health. FD12A 163  Communicable diseases A brief look at incidence in the region The incidence of many communicable diseases in the region has been reduced. With few exceptions, those that have the potential to be fatal are on the wane. This can be credited to the health services of the region and a reasonable basic standard of living compared to many other developing countries. A few countries are free of malaria. Nevertheless, we remain vigilant as travel to sources of infection can cause its return. Cholera, yellow fever, and typhoid are mostly confined to specific areas. Successful vaccination campaigns have eliminated many vaccine- preventable diseases. Smallpox and poliomyelitis have been eradi- cated, and we are the first region in the world to have got rid of indigenous measles (CAREC, 2001). High rates of childhood vaccina- tion, higher than in the United States, have been responsible for this. Vaccinations against diptheria, whooping cough, tetanus and polio are required for acceptance into public schools in some territo- ries. Dengue fever remains a problem. Outbreaks of this mosquito borne viral disease have increased in frequency and intensity over the past ten years. The mosquito that spreads the disease, the Aedes aegypti, is present throughout the region. In 1998, there was an outbreak in Jamaica, and in the following year, Trinidad and Tobago had its first major outbreak of dengue haemorrhagic fever which is potentially fatal. Tuberculosis is also of concern. After years of decline, the incidence level began to increase in the early 1990s. Figures of 37.5, 25.4, and 22.7 per 100,000 in the population are estimated for Guyana, Bahamas, and Trinidad and Tobago, respectively. In Haiti and the Dominican Republic, the figures are much higher. Some of this increase is no doubt associated with the increasing incidence of HIV/AIDS. But in addition to this is a weakening of the infrastruc- ture to deal with the disease. There has been a reduction of funding and trained staff because it was felt that tuberculosis was no longer a cause for concern in the English speaking region. 164 FD12A  ACTIVITY How would you describe the health status of the Caribbean with respect to communicable diseases, excepting STDs? (Hint: Comment on the overall picture for the region. Mention exceptions by disease and country and in concluding briefly touch on prospects for the future.) Sexually transmitted diseases (STDs) Many of the traditional sexually transmitted diseases (STDs) have declined in recent years. These include the bacterial diseases syphilis and gonorrhoea and the viral disease Herpes genitalis (Herpes simplex virus 2 or HSV2) which causes genital sores. However, about 10 to 15% of sexually active women have been shown to have the bacter- ial infection Chlamydia (CAREC, 2001). The rate of infection with these diseases is important, since their presence in individuals may make infection with the AIDS virus easier. Acquired Immune Deficiency Syndrome (AIDS) AIDS is caused by infection with the human immunodeficiency virus, HIV-1. The time between infection and the appearance of symptoms varies, and may sometimes be years. Incidence in the Caribbean In terms of the percentage of Table 3.1 the population infected with % Population with HIV HIV-1, the Caribbean now ranks second only to sub-Saharan Africa. The following table Haiti 5.17 Guyana 2.13 shows the percentages of the Cuba 0.02 population in the 15–49 years Barbados 2.89 old age group infected with Dominican Republic 1.89 HIV-1 in the Caribbean, as of Belize 1.89 December 1997. Jamaica 0.99 Bahamas 3.77 Trinidad & Tobago 0.94 On the surface these figures may not seem alarming (UNAIDS Report 1998, cited in World compared to the figures for Bank Study 2001) FD12A 165  some of the African countries which run as high as 35.8% in Botswana and 20% in South Africa. The important point is that they are increasing, not decreasing, as they should. More AIDS cases were reported in the Caribbean in the three years between 1995 and 1998, than in the 15 years since the beginning of the epidemic in the 1980s. A 1999 estimate put the number of people living with HIV or AIDS in the region at 360,000. Some 85% of these cases are in Haiti and the Dominican Republic. Cuba has relatively few cases. The infection is now moving into the younger age groups. The majority of diagnosed cases are between the ages of 25 and 34. This means that the infection probably occurred between the ages 15 and 24, if time is allowed for the infection with the virus to develop into AIDS (the incubation period). The increase in this particular age group is a major concern as they represent our future labour force and their health will impact significantly on our social and economic well being in years to come. HIV transmission in the Caribbean The predominant mode of transmission in the region is by hetero- sexual intercourse (60%). As a result of this, the number of women with the disease is rising and with that the possibility for infection of children before or at birth, or through breast-feeding. Infection through blood products is less than 3%, but this is not good enough. We must improve the safety of our supplies still further throughout the region. Sharing needles by substance abusers is not a common source of infection but high crack-cocaine use seems to be associated with high risk of HIV, as shown in the Bahamas, Trinidad and Tobago and Jamaica (CAREC, 1999). This association may result from impaired decision making, as in the case of alcohol and mari- juana users. For example, it is highly likely that persons under the influence of a drug will have unprotected or indiscriminate sex, sometimes to support their habit. Populations at high risk provide a pool of infection for further trans- mission of the virus. In addition to substance abusers, other high- risk groups include: young people (they may be unprotected by condom use, especially as sexual activity tends to begin early) 166 FD12A  male homosexuals newborns of HIV-positive mothers pregnant women (Cuba has no sign in this group) commercial sex workers persons with a history of STDs. (As at 2000, some 39% of AIDS cases in Jamaica had a history of other STDs (Figueroa, 2001).) Treating AIDS In the English-speaking Caribbean, AIDS is the largest cause of death in the 15–44 year group (63% in 1996). The high rate is due to many factors, including lack of access to drugs to treat HIV, and to medicines to deal with the secondary infections, like tuberculosis. The absence of strategies to prevent mother to child transmission (vertical transmission) is another factor. Both of these are linked with the inability of governments and/or people to afford the required drugs. n Anti-HIV drugs are A programme to help prevent vertical transmission is now in place especially expensive. Zidovudine (AZT) in Jamaica where one in 100 pregnant women are HIV infected, and costs US$3,000 per one child so infected is born every week. There is free voluntary year per case. Newer treatments are even testing of pregnant women. Women found positive are given two more expensive at tablets of Nevirapine at the onset of labour, and the child a single US$1,000 per month per patient. dose of the drug within the first 72 hours of its life. Breast-feeding is Nevirapine discouraged in these mothers, since the virus may be passed on in (Viramune) may be as good as AZT in this way, and mothers are provided with a substitute formula. The reducing vertical programme started in four parishes and is being extended to cover transmission, and is fortunately cheaper the entire island. Vertical transmission has been reduced consider- at about US$4.00 per ably in the industrialized countries by providing drug assistance for child. the mothers. We can do the same. The social cost One enormous challenge associated with the AIDS epidemic is the plight of children of parents with the disease, whether or not the parents are alive or the children are left as orphans. A second is our economic inability to treat and care for patients properly. A third is the adverse effect the epidemic is having on our economy from three angles: FD12A 167  The enforced reduction of our labour force leading to decreased productivity. The burden it creates on our health systems: UWI/CAREC estimates are that some 3.5% of our gross national product could be spent on AIDS over the next 20 years, and we still shall not have spent enough. The effect it will have on our tourism and foreign investment: We are perhaps the most tourist-dependent region in the world, and tourism is very sensitive to disease. Preventing AIDS – what needs to be done The emphasis has to be on preventing the disease. Public understand- ing of the disease and how it is spread is not good enough at pres- ent. As with the nutrition-related diseases, the situation calls for aggressive educational programmes. These need to be geared to reach all ages and levels, but especially the young. In the Caribbean, sexual activity sometimes starts at the ages of 10 and 11 so school populations below and above these ages need to be targeted. School dropouts and street children must also be reached. Further research is also needed, but this is not likely to be very successful if cases are not reported. HIV/AIDS, by law, is a notifi- able disease only in Jamaica, St Lucia, and Belize. Perhaps this should be standard throughout the region. Should there be manda- tory testing of rapists as happens in the Bahamas and Bermuda? These are issues that must be addressed at the level of the policy- makers. The presence of a CARICOM-led task force on HIV/AIDS which has developed a Caribbean Regional Strategic Plan of Action for HIV/AIDS, 1999–2004 is evidence of some recognition at the policy level of the seriousness of the situation. As the director of the Medical Research Foundation in Trinidad is reported to have pointed out very recently, the HIV virus is the cause of AIDS, but is not the cause of the pandemic. It has spread rapidly because of certain contributing factors (Mackoon, 2001). We need to publicise and eliminate these factors if we are to succeed in stemming the spread of the disease. 168 FD12A  ACTIVITY Self-check: Answer the following questions to find out how much you remember. Find the answers for those you have forgotten in the passage you have just read. 1. What causes AIDS? 2. What are the main ways in which it is transmitted? 3. Which country in the Caribbean has the lowest incidence of AIDS? 4. Which countries have the highest incidence in the English- speaking Caribbean? 5. Which age group is now at greatest risk of becoming infected and why is this cause for concern? 6. What is vertical transmission and how can it be reduced? 7. What is the most important reason for our inability to treat and care for those with AIDS? 8. What measures should form part of an HIV/AIDS preven- tion plan? CRITICAL THINKING ACTIVITY The incidence of many communicable diseases, including other STDs, has been reduced. Why do you think HIV/AIDS has remained a serious problem for such a long time? Non-communicable diseases Non-communicable diseases include a wide range of disorders. They include the so called “human-induced” or self-inflicted diseases such as lung cancer and alcoholism, inherited diseases, mental illness, nutritional disorders, and metabolic disorders, some of which are also linked to nutrition. There are no rigid boundaries between the different groups. Non-communicable, nutrition-related diseases such as diabetes, heart disease, and hypertension along with cancer, now rank as the leading cause of death in the region. Between 1984 and FD12A 169  1989, 24–57% of all deaths in the region were due to these diseases. Malnutrition and infectious diseases accounted for only 2% to 7% of deaths over the same period. Some of these nutrition-related diseases are influenced by hereditary factors. They seem to “run in families” (see Session 3.2, The Basis of Inheritance), although the disease itself is not inherited. The precise genetic linkages are not known but such families seem to be pre- disposed to developing the disease. Diabetes, hypertension, and heart disease all fall into this group. What they also share in common is that they can be prevented, delayed or controlled by changes in lifestyle such as diet, exercise, and stress relief and abstention from smoking and excessive use of alcohol. It is important to note that changing lifestyle after being diagnosed with any of these diseases is not nearly as effective as taking preventive measures. (As they say in one of our islands, “You better take in front before in front take you”!) Diabetes mellitus In diabetes mellitus, blood levels of glucose (the simple sugar that our bodies use as a source of energy) are higher than normal, because the body either does not produce, or does not use insulin efficiently. Insulin is a hormone (secretion of a gland that goes directly into the blood stream) produced by special cells in the pancreas. Insulin promotes the uptake of glucose from the blood into cells for use or storage, thereby lowering blood sugar. Blood sugar levels between 70 and 110 milligrams per decilitre are considered normal. In most persons the level rises after a meal, but goes back to normal after about two hours. This does not happen naturally in diabetics. Excess stays in the blood, unavailable to the cells that need it, and is excreted in the urine. In persons with Type I (insulin dependent diabetes mellitus (IDDM)) the insulin-producing cells in the pancreas have been destroyed. These diabetics develop the disease at an early age, usually before 30. To survive, they must take insulin injections. Not many people have this type of diabetes. Most diabetics have Type II (non-insulin dependent diabetes mellitus (NIDDM)). In these diabetics, normal levels of insulin may be 170 FD12A  secreted but the cells that should, do not respond to it. Some young people have this type of diabetes but it tends to develop in older age groups. Type II diabetes may be controlled by a diet and exercise regimen, or by using oral drugs along with this. In some cases, it may become necessary to use insulin. Diabetes may cause several long-term complications. Heart attacks and strokes are more common. Damage to the blood vessels of the eye can cause poor vision. Poor blood supply to, and damage to the nerves of the skin reduce sensitivity, making injuries more likely, and wounds heal slowly. More women than men have diabetes. This may be linked with the fact that more women than men are obese, obesity being an important risk factor. The high rates of diabetes and its complications exert a heavy toll on hospital services in the Caribbean. The estimated cost of medica- tion, treatment in hospital for amputations of infected limbs, eye disease, and other related services for diabetics is in excess of US$30 million annually. A study recently co-ordinated by the Commonwealth Caribbean Medical Research Council (CCMRC) showed that in Trinidad’s Port-of-Spain General Hospital, diabetic patients occupied approximately 26,659 bed days per year. This cost the hospital over US$1.8 million. n Think about it: In how many different In Trinidad and Tobago, the average cost of one diabetic admission ways might having a family member with was calculated as approximately US$516. This sum would cover the severe diabetes cost of treating up to nine diabetics in a government primary care affect other family setting for one year. We can only imagine what it will cost 10 years members? Given the cost to the from now if preventive action is not taken seriously. Many of these society, should admissions would be avoided with better preventive management in testing and attendance at these primary health care settings (cited in Henry et al., 1997, from primary care clinics Gulliford et al., 1995). be made mandatory? Hypertension n MmHg, a unit of Hypertension (high blood pressure) is a condition in which the pres- pressure equal to that exerted by a sure of the blood in the arteries is persistently abnormally high. column of mercury 1 Mostly, the cause is not known, but excess fat in the diet, long-term millimetre high under standard gravity. smoking, excessive alcohol intake, and obesity seem to be among the Normal atmospheric contributory factors. pressure is 760mmHg. FD12A 171  When we check our blood pressure, we measure the pressure of the blood against the walls of a large artery. Two figures are recorded. The higher is taken when the heart contracts (systole) and the other when it relaxes between beats (diastole). For example, a reading of 120/80 (mmHg) means that the systolic pressure is 120, and the diastolic 80 mmHg. Blood pressure differs with age, activity and time of day. Normal figures for an adult range between about 120/80 mmHg and 130/85 mmHg, but the characteristic is very individual. Persistently higher readings may suggest to the doctor a need for monitoring, depending on the individual and other factors. A diet with severely reduced salt intake is believed to improve the condition, as does exercise and measures to relieve stress. A low-fat diet is often recommended as well. Various kinds of drugs are used to control blood pressure; some are expensive and others have unpleasant side effects in some people. Studies on Caribbean populations show that on average, 30% of adults have hypertension, compared to 12–15% of adults over 35 years, who have diabetes mellitus. In the Bahamas the prevalence of hypertension in males increased from 8.6% in the 20–40 year old group, to 23.1% in the 40–60 age group, and 32.7% in the 60+ age group. The trend in females was similar. So the disease, whilst most common in the elderly, is not limited to this group. Heart disease Hypertension and heart disease are on the increase in the Caribbean. This increase parallels, as it does in other parts of the world, an increase in the quantity of fast foods, junk foods and other lifestyle changes regarded as modern. The glamorous but stressful lifestyle of the busy executive who attends numerous cocktail parties and does not get enough sleep or exercise is a recipe for developing hyperten- sion and heart disease. At equal risk is the underpaid night watch- man who eats starchy foods with lots of greasy gravies or the stressed out, overworked, overweight housewife who snacks all day. A recent report (CAREC, 2001) puts heart disease first in a list of leading causes of death in the region (strokes, diabetes, cancer and injuries are the others in that list). High levels of fat in the diet are known to contribute to heart 172 FD12A  disease. Fatty deposits in the coronary artery which supplies the heart muscle with oxygen and food, can obstruct the flow of blood to the muscle. With exertion, or when the artery becomes completely blocked, the blood supply may become insufficient, caus- ing weakening or death of the heart muscle from lack of oxygen. This is accompanied by intense pain and the weakened heart muscle may fail to pump adequate amounts of blood either to itself or to the brain and other tissues. It may then cease to function altogether. This is what has happened when someone is said to have had a massive heart attack. When small branches of the coronary artery are blocked only a part of the heart muscle is affected and a person may experience pain for a short time and have a mild heart attack. This warning is sometimes ignored. There is little data on blood cholesterol levels in the Caribbean population. In order to prevent these nutrition-related chronic diseases, healthy lifestyles should be acquired early in life. As a region, this depends on education campaigns based on the most recent scientific evidence. The success of these educational efforts will depend on the entire population, that is, on each one of us. CRITICAL THINKING ACTIVITY 1. Think carefully. How much of the foregoing information have you heard before? List what you knew. 2. Have you ever given serious consideration to changing any aspects of your lifestyle as a consequence of what you knew before? Would you consider it now? 3. Do you think that governments should have a specific policy in place to help prevent these diseases or should it be left to personal choice? 4. What other methods, besides education, might be effective? Cancer There are probably few people in the Caribbean who have not lost a relative or friend to cancer. Although much more is known about the disease than was known 20 years ago it is still in many ways a FD12A 173  mystery. There are many different kinds of cancer. What they have in common is that they are all uncontrolled growths that if left untreated invade normal tissues to their detriment. The relationship between nutrition and cancer is a complex one. The most obvious link is perhaps the occurrence of carcinogens (cancer-promoting agents) in some foods. However, these various carcinogens may only form a small part of the link between diet and cancer. Besides, not all persons exposed to them develop cancers. Research in this area is continuing but it seems likely that dietary components such as fibre, fresh fruits and vegetables, and foods such as garlic and onions, may play a protective role against the development of some cancers. Other dietary factors seem to have a negative impact. These include high intake of fat (especially satu- rated fat) and cured or smoked foods such as ham, bacon, pig tails, smoked herring and so on. A comparison of the mortality rates for malignant neoplasm in the Caribbean with the rates in Canada and the USA shows that the rates in some of the countries of the sub-region are almost as high as the rates for North America (World Health Organization, 2000) (see Figure 3.1). Figure 3.1 All cancer mortality by country – 2000 140 120 100 80 Deaths / 100,000 60 40 20 0 ca s lize ad e ados Jamai ahama Be Trinid urinam Guyan a n USA anada rb bbea C Ba B S Cari 174 FD12A  The problem has increased over the years. Between the 1960s and 1990s the increase in mortality from nutrition-related cancer among the countries of the region ranged from a low of 1.3% in Belize to 12.9% in St Vincent, with the figure in Jamaica showing an increase of 5.7%. Cancer was the third leading cause of death in Jamaica (82.2/100,000 population in 1990). The increase coincides with the change in dietary patterns over the same period. CRITICAL THINKING ACTIVITY Chronic nutrition-related diseases are more prevalent in the elderly. With increasing life expectancy, the proportion of this group in the population is growing. 1. What are the implications of these facts for family life and the health services in your territory? 2. Can our resources stretch to adequately provide treatment, prevention, and care, for all age groups? 3. Should preference be given to any particular age group if there is not enough to go around? Substance abuse Substance abuse and its related health problems fall into the cate- gory of self-inflicted diseases. Despite this, they include effects that are caused by changes in the functioning of the nervous system making them very difficult for the affected individual to control. The social and economic effects of substance abuse go far beyond those of most other diseases, for example, an increase in crime. One of their many health-related effects is their association with the spread of HIV/AIDS and other STDs. Many of those admitted to our psychiatric institutions are substance abusers. In addition risk-taking behaviours, motor vehicle accidents, homicides and suicides are linked to substance abuse. The most frequently abused substances in the region, in descending order of frequency are alcohol, tobacco, marijuana, cocaine, and some psychotropic drugs. The habits begin young – at school. FD12A 175  Alcohol and tobacco are socially acceptable, and this makes the temptation to use them much harder to resist. Alcohol abuse has been associated with road fatalities, violence, family disputes, sexual abuse, and poor job performance. Long term use causes liver damage that may be eventually fatal. Smoking tobacco is associated with lung cancer, heart disease, bronchitis, and emphysema. Emphysema is caused by the gradual breakdown of the thin walls of the tiny air sacs in the lungs. Eventually this results in decreased surface for gaseous exchange. People affected with emphysema show severe breathlessness and in later stages have an uncontrollable racking cough. It has also been shown that children living in homes where parents smoke have a higher incidence of diseases such as sinusitis, tonsillitis, and other bronchial diseases. Marijuana (ganja, “herb”) is used in most Caribbean countries and has been for a long time. Its use has been associated with deteriora- tion in mental function and with behavioural disorders (Mahy and Barnett, 1997). Smoking ganja also affects the lungs just as smoking tobacco does. However, marijuana has been shown to be of thera- peutic use in some areas. One use that is well recognized is the reduction of the pressure within the eye. The extract Canasol, devel- oped by Caribbean researchers, Manley West and Albert Lockhart, is registered and used in the treatment of glaucoma (National Commission on Ganja, Jamaica 2001). Many of our young people experiment with alcohol, tobacco, and marijuana, according to surveys done among them in Jamaica, Trinidad, and Belize. According to Garfield Douglas (2001) very few people begin to use alcohol and tobacco as adults – first use has occurred usually by the end of high school. He also suggests, that cigarettes, alcohol, and marijuana are likely to act as “gateways” to using other drugs like cocaine. Clearly, prevention of the larger use of drugs should focus on the young, to delay the onset of tobacco and alcohol use. 176 FD12A  CRITICAL THINKING ACTIVITY 1. What do you think should be done about decriminalizing marijuana? 2. Does the scientific evidence help you to make up your mind? 3. What are the arguments for and against such a step in the Caribbean? The debate on whether the use of ganja should be decriminalized continues. Sympathisers point to the easing of restrictions in several European countries. Others feel it is no more dangerous than alcohol. Some fear the repercussions on trade with the United States, which is openly against the idea. The use of cocaine and crack-cocaine is also growing among adoles- cents (Mahy et al., 1997). Unfortunately, Caribbean countries are increasingly being used as transshipment points for drugs, increasing the likelihood of greater substance abuse in the region. QUICK REVIEW Some important points to remember l Non-communicable disease – breakdown in the functioning of the body, cannot be transmitted from person to person. l Types of non-communicable diseases – human induced, mental, metabolic, nutritional, and genetic disorders. l Leading causes of disease related deaths in the region – hypertension, heart disease, diabetes, and cancer. l Incidence of hypertension and heart disease reduced by a low fat diet, increased exercise, limiting alcohol intake and smoking, and reducing stress. l Cost of treating results of hypertension, heart disease, and diabetes is very high. Primary preventive care costs compara- tively little. l A key factor in preventive management of nutrition-related disease is education. FD12A 177  l Causes of cancer still not well understood. High intake of saturated fats and cured/smoked foods suspected. Some foods may contain carcinogens, others appear to be protective. l Throughout the region (and worldwide) increased incidence of these diseases coincides with changes in eating habits away from the traditional diets. l Substance abuse associated with increases in HIV/AIDS and other diseases. l Substance abuse has many social effects, including destruc- tion of family life, crime, abuse, and poor job performance. l In all cases prevention is cheaper and more effective than attempts at cures and treating the effects. CRITICAL THINKING ACTIVITY 1. Substance abuse is associated with unemployment, loss of productivity, upsetting family life and other personal rela- tionships, and with the spread of HIV/AIDS. (a) What measures do you think would most effectively help to curb it, especially in our young people? (b) Can science and medicine help? How? 2. We are the most tourist-dependent region in the world (CAREC, 2001). (a) What effects do you think (a) the communicable diseases and (b) substance abuse in the region are having on our tourism industry? (b) To what extent might these conditions be the result of our extensive tourist industry? (c) What suggestions do you have for dealing with any adverse effects you see? 178 FD12A  Session 3.2 Nutrition and Associated Problems Introduction Over the past four decades or so, nutrition in the Caribbean region has undergone a major transformation. Traditional diets tended to be low in animal protein, high in complex carbohydrates (e.g. yam and sweet potato) and fibre, with “reasonable” amounts of fat. The more modern diet that has come with urbanization and so-called development is high in animal protein and fat, processed refined carbohydrates, and little fibre. The fast food culture has not helped. Salt preserved foods, such as salted codfish, have always formed part of the Caribbean diet. These are still commonly used in addition to the new sources of salt: fast and junk foods. This transformation in our diet has lessened some old problems but brought new ones which are proving more difficult to deal with. What we eat is our choice. However that choice can be skilfully manipulated by marketing specialists. Glossy photographs of chicken and chips look much more inviting than a dead fish in a glass case which you will have to go home and prepare yourself. Similarly, canned foods are advertised as “full of goodness” that cannot be compared to the vitamins and minerals available in fresh fruits and vegetables. In this section, we shall look briefly at the nutritional status of the region, considering food consumption trends, and food availability and accessibility. After this session we hope you will make better decisions about what to eat and be able to contribute to the debate on policies that encourage importation and consumption of large quantities of foreign foods to the detriment of local agriculture and our health. FD12A 179  Food consumption trends For many years, the most important nutritional concern for the region was energy-protein malnutrition. Many children were getting neither the total calories, nor the protein supply they needed to develop properly, both before and after birth. So we focused our efforts on increasing the overall calorie and protein supply available to our country’s populations. Recent reports on food availability in the region suggest that we now have a sufficiency, or over-supply, of energy and nutrients to meet the nutritional needs of the population. On average, all coun- tries in the region have available more than the 2,250 calories and 43 g protein requirement per person suggested by the Caribbean Food and Nutrition Institute (CFNI) (Figure 3.2.a). We achieved this increased supply largely through enhancing the availability of foods from animals, fats and oils and refined sugar. Over the past 40 years, for example, average fat availability in the region has moved from 50 g to 80 g per person per day. Caribbean populations consume far more fat than recommended by CFNI (Figure 3.2.b). Figure 3.2 (a) Energy availability in the Caribbean: (b) Fat availability in the Caribbean: Calories/person/day 1961–1994 Grams/person/day 1961–1994 (Heavy horizontal lines indicate recommended daily allowance, RDA, levels. Courtesy of Dr. Fitzroy Reid, Caribbean Food & Nutrition Institute, CFNI) But while we met calorie and protein needs, we ate fewer cereals, fruits, vegetables, legumes, roots, and tubers. As a result, what we now have is a very significant decline in under-nutrition rates, but 180 FD12A  an enormous increase in the incidence of chronic diseases that might more properly be thought of as related to a kind of “over-nutrition”. These diseases include diabetes, hypertension and heart disease, and some nutrition-related cancers. At the same time, iron deficiency anaemia remains a problem, especially in pregnant women and pre- school children (Cajanus, 2000). We now face a very complex challenge. We must maintain the over- all gains in nutrition levels, but make our populations more aware of how to select their diets in order to avoid or delay the chronic diseases mentioned above. To meet this challenge, we need to collect information in each territory on the factors that determine what people choose to eat. This includes availability of foods from each food group, access, patterns of consumption in different communi- ties, and existing beliefs about food. With these findings in hand we would be able to make informed decisions and develop appropriate policies and plans to improve our nutrition status. Based on a diet supplying 2,250 calories per person per day, CFNI has recommended that staples (cereals, roots, and tubers) should supply 45% of that energy; legumes, nuts, fruits, and vegetables 25%; food from animals 15%; fats and oils 10%, and refined sugar only 5%. In order to stay healthy we should: aim to meet those nutrient goals decrease our dependency on imported foods discourage the growing popularity of those fast foods that are high in fat, animal protein, and refined carbohydrates This requires early and continuing education of a quality that can successfully counteract the effects of the marketing techniques that target our populations. Collaboration at the regional level is essen- tial, since Caribbean countries are similar in many ways. But our ethnic and economic differences demand that each country must work out its own specific solutions. FD12A 181  ACTIVITY 1. Summarise the main trends in nutrition in the Caribbean at present under the following heads: overall calorie and protein availability, types of foods consumed, and specific problems. (You may check the upcoming section titled “Nutrition problems” for additional information.) 2. Outline the activities required to improve the eating patterns of our citizens. Food supply We need to ensure that food is not only available to all the people all the time, but that such food provides the nutrients needed for people’s full development, both physical and intellectual. Further, we should be able to do this on an on-going basis. What we do now should not put in jeopardy the natural resources needed to ensure future generations the same advantage. In other words, the food supply must be sustainable (available over time). The two most important factors that determine whether or not people do get the food they need are availability and accessibility. We noted earlier in the section that adequate calories and protein are available in the region. Whether adequate supplies of the right foods are accessible to all is another matter. The fact that some under- nutrition exists side by side with obesity in the region suggests that the distribution of available food supplies needs to be examined. 182 FD12A  Although living conditions have improved greatly in most Caribbean countries, poverty still persists throughout the region. Food may be available but not affordable for those people living below the poverty line. In 1995 it was estimated that 38% of the total population was living in poverty. Levels varied throughout the region – ranging from 65% in Haiti to 5% in the Bahamas. The following data show differences in access to food for those who earn the least in our society. Minimum wage earners in Barbados, Belize, Montserrat, and St Kitts and Nevis in 1993–1994 needed to use between 15% and 28% of their earnings to have a well-balanced 2400 kilocalorie per day diet. In Grenada, this figure was between 43% and 34%, while in Guyana costs went from 80% in 1993 to 63% in 1994. Figures varied widely in Jamaica for the period. In December 2000 the cost of feeding a family of five adequately for one week was estimated at J$1,828 (US$40). The present minimum wage in Jamaica is only J$1800 per week. We also need to consider a third factor with regard to food supply. Even if food is available and accessible, is it being assimilated so that the body can use it effectively? Infestation by worms may prevent absorption or badly prepared food may inhibit the absorption of certain nutrients. If minerals that are needed in very small quanti- ties are not being assimilated for any reason, deficiencies will continue even though enough food is being eaten. ACTIVITY 1. Distinguish between the terms “available” and “accessible” as applied to food supply. 2. What other factor determines whether citizens receive an adequate supply of food? FD12A 183  Nutrition problems Deficiency problems Problems with deficiency diseases seem, for the most part, to be localized. In Jamaica, for example, high prevalence of marginal vita- min A deficiency, wasting, and anaemia varied in different regions (CFNI, 1998). Data from nutrition risk mapping, also in Jamaica, suggest that rapid urbanization and the consequent stress on infra- structure, together with poverty, are associated with the presence of some pockets of persistent malnutrition. In countries with indige- nous populations, there is some evidence of greater prevalence of nutrition deficiency among those groups. Energy-protein malnutrition (EPM) The term energy-protein malnutrition means just what it says – a deficiency in the diet of the calories and protein needed for good health. Children are particularly prone to this type of malnutrition, as Dr. Cicely Williams of Westmoreland, Jamaica, discovered. Dr. Williams, who qualified in 1923 with the first group of women admitted to Oxford University Medical School, found in her work in Ghana (then the Gold Coast), West Africa, that many children had symptoms she had noticed in Jamaican children while she was growing up. They had swollen bellies, diarrhoea, fever, and were very weak and listless. She discovered that giving children a diet rich in protein and calories could reverse the condition. Figure 3.3 (left) Child suffering from kwashiorkor. The child’s legs show oedema (accumulation of fluid), healing of infected lesions, and “crazy pigment skin” characteristic of zinc deficiency. The child is apathetic when undisturbed and irritable when touched. Figure 3.4 (right) Child suffering from marasmus, characterised by no oedema, severely reduced muscle mass and marked irritibality. The child is receiving an intravenous drip for severe dehydration and has a nasogastric tube inserted. Hands are taped to prevent removal of the tubes. (Both photographs courtesy of Professor Terrence Forrester, Tropical Metabolism Research Institute, UWI.) 184 FD12A  She therefore called the condition protein-energy malnutrition (PEM), and the disease it produced kwashiorkor, the term used in West Africa (meaning the disease the old baby gets when the new one comes – in other words when the baby is weaned). In the Caribbean, we also see “mirasmi” babies – babies with marasmus, which is another way in which this type of malnutrition shows itself. Much research into this type of malnutrition has taken place since Dr. Williams’ original discovery. Whereas the original emphasis in treatment was on the protein in the diet, more emphasis is now being placed on the energy aspect. So the term now used is energy- protein malnutrition (EPM). Throughout the region, the incidence of EPM has declined signifi- cantly over the past 25 years. Since the late 1980s and early 1990s, levels of undernutrition in pre-school children have declined to less than 5% in nine countries. Rates between 5 and 10% have been reported in six others, and only one country had a level higher than 10% (cited in Henry et al., 1997, p.192: original source Sinha D. 1995). Severe forms of EPM like kwashiorkor and marasmus are no longer a problem, but chronic low level EPM remains. It shows up as stunting, the child’s height being below the average for healthy children of the same age. Food and nutrition surveys show this decline in EPM. In Grenada, surveys conducted by the Food and Nutrition Council showed a decline in undernutrition in children 3–5 years old, from 39.6% in 1985 to 8% in 1990. Hospital data from Jamaica, 1994, showed that 2.3 % of the 0-59 month old admissions were diagnosed with EPM, as compared to 5% in 1993. (National Survey by the Planning Institute of Jamaica). The survey also showed that the 0–5 months and 6–11 months age groups had the largest proportion of admissions for malnutrition – 38.8% and 50.8% respectively. This is surprising since EPM levels tend to increase with age between ages 0 to 5 years. The feeling is that, as the Ghanians observed, this is associated with poor weaning practices. The figures suggest a need to re-emphasise the importance of breastfeeding. FD12A 185  Iron deficiency Iron deficiency anaemia affects between 6 and 65 % of pregnant women throughout the countries. The Turks and Caicos Islands (65%), Guyana and Belize (52%) and Jamaica (51%) register the highest proportions of pregnant women so affected. National surveys carried out in five countries by CFNI, indicate that among children under 5 years old, between 34 and 57 of every hundred have this type of anaemia. Among adults (15–60 years) in Guyana, 42% were anaemic. Among this group, females were more than twice as likely to be affected as males. These deficiency levels are believed to result from insufficient iron in the diet and inability to use what is taken in. To reduce these deficiencies four strategies have been adopted: iron supplementa- tion, dietary modification, iron fortification, and the control of intestinal parasites. In Jamaica, for example, since 1984 flour forti- fied with iron has been available. Barbados, Belize, Grenada, Guyana, and St Vincent and the Grenadines also currently have iron fortification programmes. All English-speaking Caribbean countries have in place iron supple- mentation programmes aimed primarily at pregnant women and infants. Their impact is not yet clear. Infrequent and delayed (late in pregnancy) attendance at clinics and unwillingness to follow the programme have been problematic. Vitamin A deficiency CFNI surveys over the period 1996–1998 have identified vitamin A deficiency in small sections of the population in Antigua, Dominica, Guyana, Jamaica, and St Vincent. Severe deficiency was identified in less than 1.3% of the population. Marginal deficiency was, however, identified in 1.1% – 10.6% of preschoolers, school children, and preg- nant women. The picture in Jamaica was noticeably different, with 58.1% of children 1–4 years old, 18.8% of school children, and 33.6% of pregnant women recorded as marginally deficient in this vitamin (CFNI, 1997a, b; 1998). Iodine deficiency Iodine deficiency is not generally regarded as a problem in the Caribbean. However a study done in Guyana identified levels of 186 FD12A  42.8% in pregnant women and 27.6% of female children, and 26.1% of male children 5–14 years old. In 3.9% of the female and 2.5 % of male children, the deficiency was regarded as severe (CFNI, 1997b). Iodine can be supplied as iodized salt. The latter is available in most countries. CRITICAL THINKING ACTIVITY 1. The data on deficiency diseases presented in this section makes comparisons difficult. Why is this so? 2. Select any one country mentioned above and write a short paragraph on some aspects of the deficiency problems of that country. 3. What aspect of malnutrition do you think requires the most urgent attention in the region? Explain why you hold this opinion. Problems of nutrient over-intake and choice Obesity We have already noted that there is more than enough food calories available in the region to satisfy our nutritional needs. We now need to be concerned, not by undernutrition but overnutrition. The real cause for concern is no longer how much we eat but what we eat, that is, the type of nutrients consumed. The trend towards more animal, fatty, and refined foods, including sugar-based types, is not good. In addition, as the region “develops”, we have adopted a more sedentary lifestyle. These are important contributors to obesity. Even casual observation suggests that much obesity is present in the n Body mass index is calculated as Caribbean. Recent studies of obesity among adults of 20+ years weight in kilograms suggest that some 30–32% are overweight, and 19–21% are obese divided by height squared, in metres (CFNI unpublished data). When does overweight become obesity? (kg/m2). Early World Health Organization (WHO) standards categorize persons studies used different with Body Mass Indices (BMI) of 25 and over as overweight. Among measures e.g. weight for height charts, these, persons with a BMI 25 to 29 are regarded as pre-obese and making comparison persons with BMI 30 and over are regarded as obese. Within coun- difficult. WHO recommends the use tries, geography, level of education, and gender seem to be associated of BMI. with differences in obesity. Females consistently show higher FD12A 187  proportions of obesity than males as shown by studies done in Dominica, Guyana, Trinidad, and Jamaica. Among Jamaicans, over- weight is more frequently associated with lower education levels. More rural residents than urban are pre-obese but there seem to be no urban/rural differences at higher levels of BMI. In Trinidad, however, more rural residents are obese, compared with residents in the city or towns. Several studies worldwide have suggested that obesity is the major link to the development of nutrition-related chronic diseases which now rank as the leading cause of death in the region. Refer to Session 1 of this Unit where the link between nutrition and these diseases was discussed in more detail. Dealing with the problem Any effective strategy for dealing with the nutrition problems of the Caribbean must take into account l the need for an effective public health campaign, l training health professionals to use a more client-oriented approach to the care and education of their clients, and l enlightened regional and national health care policies based on up-to-date research Public education The following comment was made about Jamaica, but it could well be said of the whole Caribbean region: Many of the risk factors affecting the health of Jamaicans are either not perceived by the population as such or they are only superficially understood. These include obesity/overweight, cigarette and/or marijuana smoking, heavy alcohol intake, a fatty, high salt diet with lots of refined sugars, sedentary lifestyle, failure to adequately treat hypertension and diabetes, multiple sex partners and poor health-seeking behaviour. (Figueroa 2001) Only education can improve this superficial understanding. People must be taught how lifestyle factors affect health, and what steps should be taken to preserve health and well-being. Early in life, we 188 FD12A  should encourage careful attention to diet and involvement in regu- lar physical activity. We should try to ensure that citizens with family histories of nutrition-related diseases have regular medical checks, hopefully delaying or avoiding altogether the onset of these diseases. Smoking and substance abuse should be discouraged. To be effective, however, the educational process must be interactive and participatory. As Garcia (1999) points out in addressing the problem of diabetes education in Cuba, conventional health care and education focuses on the illness rather than the individual. “It is assumed that doctors and nurses know everything while people with diabetes know nothing.” Patients are mere objects when this is the approach. Education has to move away from just giving information to providing positive support, based on patients’ own life experiences. ACTIVITY 1. Do you agree with the statements above about the way many health care professionals view their patients? (Consider experiences that you have had with health care professionals that made you feel ignorant and undereducated in health matters or guilty). 2. Write out a short “conversation” between a public health nurse and a group of patients to show what you consider to be a more productive approach to dealing with people. (Select as your topic information from one of the diseases covered in this session.) You might like to consider including the following: l A suitable greeting l A period for allowing patients to get to know each other or talk about themselves l Allowing patients to share experiences with each other and ask questions as you talk Health-care policies Some important gains have been made with respect to health-care policies. Regional governments and policymakers are conscious of the role of food and nutrition in the achievement and maintenance FD12A 189  of good health. This issue was a key component of the Caribbean Co-operation in Health (CCH) initiative, launched by the CARI- COM Ministers Responsible for Health as far back as 1986. The overall goal was to “prevent malnutrition in all its forms and prevent and control those diseases conditioned by nutrition practice and behaviour”. CARICOM Ministers at a 1991 meeting, approved the goals and targets of the CCH. Targets set for CARICOM coun- tries to develop were: 1. National food and nutrition policies 2. Food and nutrition strategies 3. Nutritional surveillance systems 4. Programmes and activities for preventing the most prevalent nutritional disorders 5. Nutrition component to health education programmes 6. Regional policy for training in nutrition 7. Reduced health risks from food contamination A report to the 1992 meeting of the CARICOM Ministers Responsible for Health, indicated that all countries had by then developed some form of nutritional surveillance system. Satisfactory progress was also being made in several countries in developing national food and nutrition policies, strategies, and preventive activ- ities in relation to anaemia, EPM and obesity, as well as in the devel- opment of educational materials for use by teachers (Henry et al., 1997). Later reports out of PAHO/WHO show that this trend has continued (PAHO/WHO, 1998). CRITICAL THINKING ACTIVITY 1. How can we improve our food production and distribution systems to ensure that the poorest among us can obtain the needed nutrients, without either encouraging a culture of “hand-outs” or suppressing human dignity? 2. Can genetically manipulated (GM) foods help? (See Unit 4.) 190 FD12A  But national plans for health care are enormously affected by economic constraints. Treatment and care costs are high, and for each individual who has a chronic disease (diabetes, hypertension or heart disease), a lifetime of such costs is often involved. Therefore, the best approach is an integrated one that emphasizes preventive and health promotion measures, while supporting treatment and care. All programmes and plans should reflect these two considera- tions. The aim is to cover all stages of life – pregnancy, early infancy, childhood, adolescence, and adulthood. For example, care and nutrition in pregnancy need special attention. These are crucial stages of growth and development. Research has shown that nutrient deficiencies during pregnancy affect the foetus and may have detrimental effects that last a lifetime. Breastfeeding needs to be actively encouraged and child growth monitored contin- uously even in countries where malnutrition is reduced. This will lead to early identification of those with deficiencies and those most likely to develop nutrition-related diseases (high risk). These individ- uals can then be targeted for treatment when it will be most effec- tive. The preventive and monitoring activities suggested above should be given priority in health-care budgets. Together they cost much less per person than treating those who are already ill. We need to support policies that advocate these measures so that we can reduce expenditure on expensive equipment that can care for only a few persons at a time, after they have fallen into crisis. This brief treatment of the status of nutrition in the Caribbean and its associated problems raises a number of questions. Some of these are suggested below. You may think of others. They need to be considered carefully if we are to reach our goal of adequate nutrients for all and a healthy society. In this context, it is important to note the enormous contributions of the Caribbean Food and Nutrition Institute and the Tropical Metabolism Research Unit of the UWI to research and understand- ing of nutrition and its problems, and to public education in the region. FD12A 191  ? ? CRITICAL THINKING 1. Fast foods are popular because they are convenient and satisfying. (a) Are they better or worse than our traditional foods? (b) Suggest how we might change the character of the present fast food offerings to make them more nutritious but still tasty? 2. To move from our present focus on treatment of disease, we need to actively promote health. Should governments assist this effort by placing some restrictions on the types of foods sold in certain places e.g. schools, government canteens etc.? (a) Would you consider this encroaching on your individual freedom? (b) What other measures can we use to effectively educate the most needy sections of our populations? 3. As we seek to satisfy our own food needs, what steps should we take to conserve the natural resources that future genera- tions will need to help feed themselves? Will GM foods provide a solution or hinder this cause? (See Unit 4 for more on GM foods.) 192 FD12A  Session 3.3 Genetic Diseases Introduction Sometimes persons are born with an illness or a disability and there is nothing we can do about it. In some cases, it is in their genes. In the same way that they inherit a dimple from a father, an unusual hairline from a mother, hair texture from both of them and a crooked first finger from a grandfather, they have inherited the disorder from one parent or both or perhaps a grandmother. Other nutrition-related or lifestyle disorders seem to depend on genetic factors to a certain extent. There is little we can do about genetic diseases at present but genetic engineering offers some hope for the future and in some cases the symptoms and signs can be treated successfully. Despite our inability to cure genetic diseases, understanding how they are inherited is important. People can make informed choices if they can find out whether or not they carry the genes for certain diseases and what the chances are of passing them on to their chil- dren. Couples may opt not to have children, but if they do choose to have children, they will be better prepared to deal with any disabilities caused by a genetic disease. A number of ethical issues surround inheritance and the more we know the better we will be able to contribute meaningfully to debate on these issues. As a society, we should support parents in their efforts to obtain improved benefits and facilities for the treat- ment or training of affected children so that as adults they are less dependent on the state. A better understanding of these disorders should also reduce the prevailing prejudice and fear of accepting persons with genetic disabilities as legitimate members of our society. FD12A 193  OVERVIEW Before we consider genetic disorders or diseases, we need to under- stand how we inherit our characteristics from our parents. Understanding this is also important for dealing with some aspects of the unit on biotechnology that follows this one. In the first section of this session we shall deal with the basis of inheritance. The way genes store information and control the functioning of our cells and our bodies and how they pass on that information is dealt with in some detail. We then look at two examples of inherited disorders that are common in the region; sickle cell anaemia and Down’s syndrome. Two other inherited disorders are treated briefly before the final section on biotechnology and genetic diseases. FOR THE STUDENT It is not intended that you learn to describe the detailed structure of DNA but you do need to take some time to understand it so that the rest of the section makes sense. Similarly, understanding of how different diseases are inherited is important but you need not learn how to replicate the genetic diagrams included. 194 FD12A  The basis of inheritance Each cell of an organism carries within it a full set of the genetic instructions that define its characteristics. These instructions (or as they are commonly called, genes) are carried on structures called chromosomes within the nucleus of each of the estimated 50 tril- lion cells in your body. A chromosome is a long, spiral strand of a material called deoxyribose nucleic acid (DNA). We will deal with this in an upcomig section of this session. This intricately and precisely folded molecule, carries on it all the information required to make your body and control its every function. Chromosomes also have segments that regulate the activities of the chromosomes themselves. Figure 3.5 Chromosomes from a human male cell stained to show certain characteristics more clearly. Source: W. Ganong, 1997. Review of Medical Physiology, Appleton & Lange, Connecticut, USA. For each kind of organism, there is a specific number of chromo- somes. In humans this number is 46, made up of 23 pairs (see Figure 3.5). Human chromosome pairs are numbered 1 to 23 accord- ing to their length, shape and banding pattern as revealed by specific stains. The 23rd pair (XY) determines the sex of the individ- ual. Note that this “pair” does not really match. Can you see the difference? The dark bands are characteristic segments of the DNA, not genes. Chromosomes pass on instructions for development, growth, and general functioning, from generation to generation by means of FD12A 195  special reproductive cells called gametes, for example, sperms and eggs. Most organisms have male and female gametes. How are the instructions passed on? This is done in two ways. The astonishing thing is that the basic mechanism is the same in all organisms. Cell division for growth (mitosis) For growth to take place, one cell divides into two, two into four, and so on. The new cells increase to the size of the one from which they came, before they themselves split into two again. Each new cell has the same number of chromosomes and the exact number of genes in the same order on the chromosomes as the cell from which it came (the parent cell). This number is the number for the species. This is the way cell division takes place in almost every part of your body (with one exception). It is termed mitosis (Figure 3.6). Figure 3.6 Mitosis – cell division for growth Parent cell – 4 chromosomes present in pairs (in this case, F M M F 2 pairs): one of each pair from father (F); one from mother (M) Each chromosome replicates to FM form two identical strands of M F DNA (chromatids) in prepar- ation for division. Cell divides into two: one strand from each chromosome goes to each daughter cell The cells grow, but the DNA strand in each chromosome will not replicate into two strands unless the cell is going to divide If the cell is dividing over and over how does the number of chromo- somes remain exactly the same? Before mitosis each chromosome makes an exact copy of itself to form a chromosome with two strands held together at a single point. Each strand in the double- stranded chromosome is called a chromatid. 196 FD12A  Cell division for gamete formation (meiosis) In mitosis you get back exactly what you start with! A cell divides to form two exact copies of itself. Cell division for gamete forma- tion is somewhat different, (the exception mentioned above). Gametes are reproductive structures, in our case, the male sperms and the female eggs. Remember that our body cells have 46 chromo- somes. Sperms and eggs have only 23 chromosomes i.e. half the number found in body cells. There is a very practical reason for that which should be fairly obvious if you think about it. Cells with the capacity to produce gametes divide in a two-step process. Figure 3.8 Meiosis – reduction division Step 1: One cell becomes two, but each daughter cell gets one of each chromosome pair, and so has 23 unpaired chromosomes. Note that one will get the X and the other the Y chromosome (see above). This step is called a reduction division because of the halv- ing of the chromosome number. Step 2: These two cells divide to become four, each with 23 chromo- somes. In a male, these four cells become the gametes (sperms), half FD12A 197  having X chromosomes and half Y. The process is called meiosis (see Figure 3.7). By convention, we represent this half or haploid number as n, and the full diploid number in the body cells as 2n. The haploid number of humans is 23 and the diploid number is 46, thus we have n chromosomes in our gametes and 2n in all our other body cells. Interestingly, in females Step 1 in meiosis starts in the ovaries of the foetus i.e. before birth, then stops. About 1 million of these “pre- eggs” survive until after birth, remaining dormant until puberty when the process restarts. Then one is selected for release at ovula- tion each month. In her lifetime a woman will release only some 400–500 eggs. The rest degenerate. Passing on the instructions to the next generation What happens to the chromosomes after fertilization? When a new individual is formed, there is fusion of the male and female gametes. We say that the sperm fertilizes the egg. At fertil- ization both gametes join together to form a zygote with 46 chro- mosomes. Of this number, 23 are paternal chromosomes from the sperm and 23 are maternal chromosomes from the egg. The process of meiosis ensures that the diploid number of chromosomes (2n) remains constant from one generation to the next. Also important is the fact that sperms may have either an X or a Y chromosome. All eggs have X chromosomes. After fertilization, if the sperm had an X the child would be female. If it had a Y chromo- some the child would be male. Can you complete the diagram in Figure 3.8 to show how sex is inherited? The zygote divides repeatedly by mitosis to become multicellular. We refer to it as an embryo, and later, once recognizable organs begin to form, as a foetus. 198 FD12A  Figure 3.8 The inheritance of sex Male Cell Female C ell XY XX MEIOSIS X GAMETES X FERTILIZATION XY How do chromosomes carry instructions? Chromosomes contain DNA (deoxyribose nucleic acid). DNA carries the instructions for proteins to be made by the cell (cells are mostly protein). In 1952, Cambridge University scientists James Watson and Francis Crick, proposed that the DNA molecule is shaped like a double helix. The molecule is double stranded, and the two strands are twisted on each other into a spiral or helix (see Figure 3.9a, next page). Each strand is made up of alternating phosphate and sugar (deoxyribose) units. The two strands are linked together by pairs of bases, adenine (A), thymine (T), cytosine (C), and guanine (G). There are differences in the size and shape of the bases, such that adenine is always linked to thymine, and cytosine to guanine (Figure 3.9b). FD12A 199  Figure 3.9 (a) The DNA double helix with two “backbones” of sugar-phosphate linkages – see (b). Each sugar has an organic “base” attached (A, T, G or C). (b) The two “backbones” are held together loosely by linkages between complementary bases, so that two identical replicas of the original (old) molecule are produced, with a matching sequence of base pairs. This sequence determines the sequence of amino acids in the proteins coded for by the particular DNA sequence – successive triplets of base-pairs code for particular amino acids. Source: (a) from: J.D. Watson, 1968, The Double Helix. The New American Library, Inc., USA.) Here is the key to the mystery of how these chemicals are able to carry so much information. The sequence of the bases on each DNA strand forms a code that directs the production of specific proteins. Each DNA strand is therefore a list of different instructions for making different proteins that the cell needs to carry out its specific functions. To understand this fully, we must first describe the struc- ture of proteins. Proteins make up most of the cell structures, and enzymes that control what each cell does are also made of protein. Each protein is made of hundreds or thousands of smaller molecules called amino acids, arranged in a particular way. A succession of three bases on the DNA strand codes for one amino acid. The sequence of these triplets, as they are called, gives the sequence for linking specific amino acids together to make a particular protein. Proteins are not made inside the cell nucleus but outside in the cyto- plasm. DNA does not leave the nucleus so a messenger molecule, mRNA, copies the code from the DNA and takes it from the nucleus into the cytoplasm. Structures in the cytoplasm called ribosomes 200 FD12A  then follow the instructions and assemble the protein. A length of DNA that codes for one protein is called a gene. Genes give us our characteristics. How we inherit our characteristics Genes are carried from parent to offspring in the gametes. So each of our body cells has two genes for each character – one gene coming from the male parent, and the other from the female parent. We can look at the inheritance of sickle cell anaemia to see how the process works. Haemoglobin is a complex protein molecule found in red blood cells. It gives the blood its red colour but more impor- tantly, it carries oxygen around the body so cells can use glucose for energy. A segment of the DNA at a particular point along chromosome No. 11 of both parents codes for (determines the sequence of amino acids in) one chain of the haemoglobin molecule (it has four) (see Figure 3.10). This is the gene for the haemoglobin A protein chain (HbA). Figure 3.10 Simple diagram of the structure of haemoglobin In most people both of the genes for HbA in the maternal and paternal chromosome 11 will be identical. In the Caribbean and else- where, some people have a different haemoglobin. A single base pair in the entire sequence coding for HbA is different. Thus, a different amino acid is substituted into the haemoglobin chain. This slightly different haemoglobin is termed haemoglobin S (HbS), and behaves differently from normal HbA, causing sickle cell anaemia. We will explain this further in a later section of this session. FD12A 201  Each variant of a gene is called an allele; HbA and HbS are alleles of the Hb gene. Let us take this single characteristic – the haemoglobin molecule, and work out the possibilities for the offspring from parents with different alleles for this gene. To do this, we need to understand the terms dominant and recessive as they apply to alleles. Sometimes one allele of a gene compensates for and masks the effects of the other allele when they are present together. In this case the allele A (coding for HbA), will mask the effect of the allele S (coding for HbS), preventing its effects from showing up in a person. When this is so, we say the allele A is the dominant allele, and S the recessive allele. We call the alleles (variants of genes) in the cells, the genotype for the characteristic. In this case the possible combinations of genotypes for haemoglobin are AA, AS and SS. What shows up on the outside, that is, whether the person has the symptoms of sickle cell anaemia or not, is termed the phenotype. Figures 3.11 and 3.12 show how you can work out the probable phenotypes for children born to parents with certain genotypes. Figure 3.11 n Can you explain why all the children of this couple are normal although there are two different genotypes shown? Probable phenotypes of children of a father with sickle cell “trait” (see the section on biotechnology and genetic diseases) and a mother with normal genotype. Note that the diagram also shows that fertilization takes place randomly; any sperm has an equal chance of fusing with any egg. So we look at both possibilities. 202 FD12A  Figure 3.12 Probable phenotypes of children of a father and mother, both with sickle cell “trait” (AS genotype). n How many ways are there to get children carrying the alleles for sickle cell anaemia? If you were counselling these parents, what would you tell them about their chances of having a normal child? The inheritance of sickle cell anaemia represents the simplest situa- tion. Sometimes more than two alleles (variants) for one characteris- tic may exist in a population. Each gamete will still have only one allele and each body cell two. For example, there are three alleles for human blood groups, A, B and O, but A and B are both dominant to O, so there are four possible blood groups (phenotypes); Group A, Group B, Group O and Group AB. How many different genotypes are possible? Some characteristics are determined by the interaction of several genes as with skin colour or height, but that is a very complex matter. Some genetic “accidents” and the conditions they cause Genetic “accidents” are mutations Normally in nature, the DNA instructions are passed on accurately. Sometimes, however, there is an accident or mutation. For example, in meiosis the separation of the paired chromosomes may not be perfect. If for example, one pair does not separate, some of the resulting gametes will have 24 chromosomes instead of 23 and others only 22. At other times, the number of chromosomes may be right, but the molecule of DNA itself is affected. Bases may be left out, or the sequence may be changed, so that proteins with altered characteristics are formed, as in the case of HbS above. Any gene can undergo a mutation, and there are about 30,000 genes in humans. So, theoretically, thousands of genetic diseases are possi- ble. But many embryos formed from gametes with genetic defects FD12A 203  die, either before birth (in a miscarriage) or shortly after. Others live with the conditions or diseases caused by the mistakes. These condi- tions may show varying degrees of severity. We look briefly at four of these conditions. One of these, Down’s syndrome, involves a whole chromosome. The other three involve single genes. Down’s syndrome The condition is named after the English physician who first described it just over 130 years ago. The cause, however, was not known until the microscope and staining technology became avail- able. In 1959, a French physician Lejeune, showed that individuals with Down’s syndrome had three copies of chromosome 21, not two as is normal. In Down’s syndrome, one gamete, usually the egg, has 24 chromo- somes, because during meiosis, instead of separating into different daughter cells, both maternal and paternal copies of chromosome 21 go into one daughter cell. The matching cell with 22 chromosomes has no copy. When a sperm with 23 chromosomes fertilizes the egg, the child formed has 47 chromosomes instead of 46, three copies of chromosome 21 instead of two. Embryos formed with fewer chro- mosomes than normal usually die. Individuals with Down’s syndrome show abnormalities of the face, eyelids, hands, and other body parts. Typically they are short, with relatively small skulls, and a flat, rounded face. They are mentally retarded, sometimes severely. They also tend to be susceptible to infections, especially of the respir