Public Health Lecture 7, Fall 2024

Summary

This document is a lecture on public health, specifically focusing on components like nutrition, proteins, and carbohydrates. It covers topics such as the health of people, different types of nutrients, and deficiency manifestations.

Full Transcript

PM906: Public Health Fall 2024 Lecture 7 Flashback Course outline Can be summarized in two terms: Health of People Nutrition Good nutrition is a basic component of health and malnutrition is widely...

PM906: Public Health Fall 2024 Lecture 7 Flashback Course outline Can be summarized in two terms: Health of People Nutrition Good nutrition is a basic component of health and malnutrition is widely prevalent in many parts of the world. Such problem can be solved by controlling the increase in population or through increasing the food supply through the application of genetic engineering in agriculture. Approximately 50 nutrients are required by the human body. A deficiency in essential nutrients that cannot be synthesized by the body causes recognizable disorders that disappear when the deficient food element is corrected. Human body requires energy that is supplied by food intake. The supplied energy is required to support normal functions, physical activity, growth, repair of damaged tissues and maintaining body temperature at 37°C. Energy is provided by oxidation of dietary CHO, fats and proteins. Required nutrients include: The essential amino acids, the essential fatty acids, water-soluble and fat soluble vitamins, minerals, adequate energy substrate (CHO or fats), indigestible fibers and additional water. Excessive amounts of consumed nutrients are harmful to body; therefore the intake level must be adjusted according to the requirements. Nutritional requirements vary not only from one individual to another but from one day to the next for a given subject. Undernutrition: A quantitative error of the diet (mixture of different foods) leading to deficiency in calories or energy. The Six Classes of Nutrients Macronutrients 1.Carbohydrates 2.Lipids 3.Proteins 4.Water Micronutrients 1.Vitamins 2.Minerals Food Guide Pyramid Proteins A protein is a complex organic nitrogenous compound composed of amino acids chain. It is present in different sources as : animal protein (high biological value proteins, HBV) plant proteins (low biological value, LBV). Sources: I- Animal food proteins: Such as meat (20 %): white meat mainly fish and poultry & red meat (muscles of farm animals), eggs (containing 12 % proteins); milk (3.5 %) and milk products such as cheeses. All animal proteins of HBV are biologically complete except gelatin. HBV protein contains all the nine essential amino acids, which are essential for growing children and animals & cannot be synthesized by man. They should be supplied by diet and include: leucine, isoleucine, methionine, threonine, valine, phenyl-alanine, tryptophan, lysine and histidine. * Egg protein: Considered as reference protein because of best amino acid rearrangement regarding HBV, easy digestibility & suitability for human metabolism. II- Plant food proteins: Such as pulses, grains, cereals and nuts. All plant proteins are of LBV proteins i.e. biologically incomplete except soyabeans. LBV protein is lacking one or more of essential amino acids. e.g. * Wheat protein is deficient in lysine. * Maize protein is deficient in lysine & tryptophan. * Rice protein is deficient in lysine and threonine. Therefore, mixing of plant proteins together in the same meal is beneficial for compensation of deficient amino acids such as addition of wheat flour to maize flour to compensate the deficiency of tryptophan in maize flour. Biological value of proteins 1- Body building and repair of injured cells. 2- Synthesis of plasma proteins, gamma globulins, enzymes, hormones and Hbs. 3- Necessary for movement of body fluids due to osmotic pressure obtained by albumin. 4- Buffering action and maintenance of normal tissue reaction. 5- Supplying 10% of calories daily. Deficiency manifestations A- Adults: Hypoproteinemia may lead to loss of weight; high incidence of communicable diseases (due to lowered immunity, and lowered gamma globulins), nutritional edema, weakness and easy forgeability (Marasmus). Marasmus is due to poor food intake or starvation characterized by wasting. B- Infants and preschool children: Protein Energy Malnutrition or Kwashiorkor (PEM). Kwashiorkor is a protein deficiency in infants & young children getting diet rich in CHO and deficient in proteins. Usually results in oedema (moon face and anemia). Carbohydrates (CHO) Composed of carbon, hydrogen and oxygen. Sources A- Animal sources: Lactose (milk sugar) and glycogen (animal starch). B- Plant sources: Simple sugars e.g. glucose & fructose (monosaccharides), sucrose, maltose & galactose (disaccharides). Complex CHO e.g. starch (polysaccharides) present in cereals (grains), roots (sweet potato), tubercles (potato) and fruits (bananas). Cellulose (dietary fibers) is a non digestible and non absorbed carbohydrate thus passing unchanged in stool forming large bulk while they are of low caloric value. Biological role of CHO 1- Simple and cheapest source for energy, constituting more than 60% of balanced diet. 2- Essential against oxidation of fats otherwise ketosis (formation of ketone bodies) may result due to impaired fat combustion. 3- Excess CHO may lead to obesity, CHD, hyperlipidemia and hypertriglyceridemia. 4- Dietary fibers: Has a filling effect in stomach thus may reduce body weight. They may be very helpful to obese persons and prevent constipation, cancer colon, haemorrhoids and anal fissures. Fats or Lipids These are sources of energy and they are essential sources for absorption of fat-soluble vitamins. Vegetable fats and oils are good sources of essential fatty acids. Sources 1- Animal fat: obtained from animal food: such as milk products (full– cream milk, butter, cream, cooking fat, cheese and yoghurt), egg yolk and fatty meat of cattle, poultry and fish. 2- Vegetable oils: Obtained from * Plant foods: Sesame, olives, peanuts, soybeans, nuts * Prepared oils: These are extracted form some plant seeds such as cotton seeds, olives, corn, palm oil and sunflower seed. Margarine: Manufactured by hydrogenation process of vegetable oils that become saturated. Biological Value 1- Combustion for energy production (9 k cal/ gm of fat). 2- Provide fat soluble vitamins and their absorption; A, D, E & K. 3- Provide essential fatty acids that are needed for maintenance of skin structure in young children. 4- Form the normal subcutaneous fat depot, for insulation. 5- Give fat support to viscera and some organs (kidney). Dietary fat-associated disorders 1- Excess consumption of fat causes a- Obesity b- Hazards of high cholesterol diet as cholesterol is found in animal foods, specially egg yolk, meat and milk products that contributes to CHD. c- Digestive disturbance. 2- Metabolic disorders of dietary fat: Saturated fatty acids of animal fats and margarine are associated with fat disorders that are related to serum lipids, especially LDL and VLDL and low level of HDL which are responsible for: a- Arteriosclerosis. b- Cardiovascular diseases (CHD & hypertension). Vitamins Vitamins are essential organic compounds required in small quantities for the normal metabolism of the major nutrients and the normal physiologic functions of the body. With few exceptions, the body cannot synthesize vitamins which should thus be supplied as such in diet. Most members of vitamin B group and vitamin K can be synthesized by the intestinal flora. Carotene is converted in the body into vitamin A. Vitamin D is formed in subcutaneous tissues when exposed to the sun. Vitamins should thus be obtained from a variety of food substances as no single food contains all the vitamins and in adequate amounts. b- Pernicious anemia (Vit. B12 deficiency): Vegetarians, pregnant and some stomach cases are susceptible. For vegetarians, Vit. B12 is supplied by animal foods and no intestinal biosynthesis. For pregnant women Vit. B12 requirement is increased. In case of stomach disease; atrophy of mucosa, total gastrectomy there is no secretion of the intrinsic factor which is necessary for Vit. B12 absorption in the small intestine. c- Vitamin C deficiency: Camps may be exposed as they depend on canned food only, and no fresh vegetables and fruits. Unless supplemented with Vit. C they are affected by scurvy. Minerals Human body may contain over about 30 minerals (inorganic elements), which are present in macro or micro quantities and are essential for the normal vital processes of the body e.g. formation of teeth & bones, maintenance of body osmotic pressure & specific functions (blood formation & enzyme activity). The important elements which are liable to a deficient supply are calcium, iron and iodine. Vulnerable groups (neonate, children, pregnant & lactating mothers and elderly persons) are susceptible to iron deficiency anemia due to the following causes: 1- Preterm baby has no sufficient iron store in liver, since body stores are acquired in the last intra-uterine weeks. 2- Infants and young children where no adequate body stores (for around 6 months), milk is poor in iron and faulty weaning. 3- Adolescent girls due to blood loss in menstrual cycle. 4- Pregnant and lactating mothers because of nutrition ignorance, extra-needs not satisfied for calcium (osteomalacia). N.B. a- Mountains, deserts and oasis are goitrous areas which are confined areas, away from the sea, where the soil is poor in iodine, and thus grown vegetables and fruits (the main source of dietary iodine) are poor in iodine (goiter). b-Prevalence of dental caries is high in infancy period, and prevention is still a problem due to: 1.Fluorine deficiency (low content in potable water supply) which is responsible for teeth fragility. 2.Inadequate calcium, phosphorous and Vit. D supply especially during period of teeth formation and pregnancy. 3.Negligence of oral hygiene as regular maintenance of oral hygiene all time is difficult. Food Microbiology: Microbes and food Microbes need food. Food “needs” microbes. While microbes consume food, they make it better. OR spoil it. OR cause disease (poisoning). Some diseases are foodborne (fecal-oral route; see past lectures) 10 Food Microbiology: 1. Microbes and food spoilage Changes can be: Microbial synthesis of substances (e.g. pigments, slime) Microbial degradation ⚬ Fermentation: ‫ تعفن‬،‫تخمر‬ Carbohydrate food ---- saccharolytic microorganism ------> acids + alcohols + gases ⚬ Putrefaction: ‫ نتانة‬،‫تحلل‬ Protein food ---- proteolytic microorganism ----------------> amino acids + amines+ ammonia + hydrogen sulfide ⚬ Rancidity: ‫تزنخ‬ Fatty foods --- lipolytic microorganism -----------------> fatty acids + glycerol Food Microbiology: 2. Food poisoning It occurs when people consume food contaminated with a toxigenic microorganism or a toxin made by a microorganism. ⚬ The most common is staphylococcal food poisoning ⚬ The most deadly is botulism It could be: a.Non-microbial: ■ E.g., insecticides, lead, arsenic, mercury ■ Food itself is toxic (e.g., some types of mushrooms) b.Microbial Food Microbiology: 2.B. Microbial food poisoning Toxin type (faster) Infective type Staphylococcus enterotoxins Salmonellosis ⚬ Typically in starchy meals & E. coli milk products (cream, cheese) Botulism (canned food) Bacillus cereus Fungal aflatoxins: ⚬ Aspergillus flavus liver cancer Milk Microbiology: Milk-borne diseases a.Of animal origin (zoonotic): Bovine T.B., Brucellosis, Salmonellosis, Q fever, Anthrax. a.Of human origin: Diphtheria, T.B., Typhoid, Dysentery, Cholera, Polio virus, Streptococcus pyogenes, Hepatitis A. Milk Treatment: 1.Boiling 2.Pasteurization (Rapid heat then cool) 3.Sterilization (Heat + pressure) ■ (in regions with hot climate) Milk Microbiology: Pasteurization Heating a liquid food to a specific temperature for a definite length of time, and then cooling it immediately: ⚬ HTST (high temp., short time) ⚬ UHT (ultra high temp.) It aims to reduce the number of viable pathogens so they are unlikely to cause disease. It slows microbial growth in food, and kills bacteria, viruses, cysts, and worms. Milk Microbiology: Examination of milk 1.Methylene blue reduction test: ⚬ Indicator of the number of viable bacteria in milk ⚬ The greater the number of bacteria in milk, the quicker will the oxygen be consumed, and the sooner MB is reduced to become colorless. 2.Phosphatase test: ⚬ Phosphatase is an enzyme naturally present in raw milk. It is inactivated by heat that is more than needed to destroy TB. (pasteurization). ■ Thus a phosphatase-negative milk denotes adequate heat treatment (and no TB risk). (T/F, Give Reasons) ■ A phosphatase-positive pasteurized milk is an evidence of defective pasteurization. (T/F, Give Reasons) Milk Microbiology: Examination of milk 3.Turbidity test: ⚬ It is used to: ■ distinguish between sterilized (no ppt) and pasteurized milk (ppt). ■ determine if sterilized milk products have been sufficiently sterilized. ⚬ Sterilization of milk causes denaturation of all heat-coagulable proteins; otherwise, these proteins will become precipitated by ammonium sulfate (NH₄)₂SO₄. ⚬ Any signs of turbidity after ammonium sulfate treatment indicate that the milk has not been effectively heated to sterilization temperatures. 4.Examination of specific pathogens: ⚬ E.g., T.B. and Brucella

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