Food Toxins Lecture Notes PDF

Lecture 8 Food toxins Objectives. To know: 1) What are the natural food toxins? 2) The natural plant toxins. 3) What are the marine food toxins? 4) What are the fungal toxins? 5) What are the types of pollutants? 6) Heavy metals toxicity. 7) The pathogenic agents tha...

Lecture 8 Food toxins Objectives. To know: 1) What are the natural food toxins? 2) The natural plant toxins. 3) What are the marine food toxins? 4) What are the fungal toxins? 5) What are the types of pollutants? 6) Heavy metals toxicity. 7) The pathogenic agents that are very common cause of food poisoning. 8) What are the differences between bacterial food infection and bacterial food poisoning? 9) What is the Seafood poisoning? 10) Government Food Safety Control Agencies in the United States 2011/2012  Natural food toxins Many natural substances are harmful to health when consumed in foods at a high dose. For example, fat-soluble vitamins cause toxic effects when excessive amounts are consumed and these can be fatal at a high level of intake. However, toxins are substances that cause harmful effects when foods are consumed at levels comparable to those which may be eaten by consumers. These may be natural components that accumulate in food during processing or storage or they may be introduced into plants or animals that are consumed as foods.  Natural food toxins Some toxins, e.g. polychlorinated biphenyl are accumulative but other toxins, e.g. glycolalkaloids, are completely harmless when consumed repeatedly at sub-toxic doses. Food components may cause toxic effects within hours, days or weeks after eating of the food or they may have mutagenic or carcinogenic effects in which a change in the genetic information of a cell may lead to cancer or other disease states over a period of years.  Some Types of food toxins 1. Natural plant toxins. 2. Marine toxins 3. Fungal toxins 4. Pollutants 5. Pathogenic agents  Natural plant toxins Toxic components Harmful effects Symptoms Gycoalkaloids: Commonly found Levels of over 200mg/kg Gastric pain followed by at low level in potatoes, but high fresh weight inhibit the nausea, vomiting and level may be found in green enzyme cholinesterase respiration difficulties, potatoes. that is essential for the which may cause death. transmission of nerve impulse. Cause Neuro-larthyrism, Damage the central β -N-oxalyl-L-ά,β-di-amin-opropio- which affects humans, nervous system, which nitrile especially young men, causes paralysis of the Present in peas, chick-peas following long term legs with general consumption of the peas. weakness. β-L-glut-amyl-amino-propio-nitrile Cause Osteo-larthyrism, Skeletal deformities and Present in peas, chick-peas which affecting the weakness in aorta and structure of the connective tissue. connective tissue and bone.  Marine food toxins Toxic components Harmful effects Symptoms Terodo-toxin found in liver, Fatal above a dose of 1-5- Total paralysis and ovaries, skin and intestine of 4mg respiratory failure type of fish, common in Japan. It blocks movement of causing death within Great skills are required by chef sodium ions across the 6-24 hours. There is no to separate the muscles, which membranes of nerve fibers, known antidote to the are free of toxin. inhibiting the transmission poison. of nerve impulses. Saxi-toxin, found in the flesh of Fatal dose 4mg; 1mg cause Numbness of lips, shellfish, e.g. mussel that have mild intoxication hands and feet that fed on certain types of algae develop into vomiting produce toxin that accumulates coma and death in the flesh of shellfish. Most shellfish breakdown the toxin within 3 weeks after ingestion, but some species may retain the toxin for several months. Present in Europe, North America, South Africa, Japan  Fungal toxins (myco-toxins) ▪ Many species of fungi produce metabolites that are toxic to humans (myco-toxins). ▪ Mycotoxins remain in the food even after the mold has been removed or has died. ▪ The mycotoxins produced by the fungus Aspergillus flavus are known as aflatoxins. ▪ Toxin-producing fungi usually produce only two or three aflatoxins under a given set of conditions. ▪ Aflatoxins are carcinogenic at very low level of intake, usually occur in moldy grains, Soya beans and nuts. ▪ Aflatoxins may also be transmitted to human via animals in meat or eggs. ▪ Aflatoxin B1 is one of the most known chemical carcinogens. A high risk of liver cancer is induced in rats by feeding diet containing 15μg/kg aflatoxin B1. ▪ Aflatoxins and many other mycotoxins are quite stable during normal food processing methods. ▪ Some mushrooms are toxic but sometimes they can rendered edible by cooking, and only a few species are lethal if consumed.  What are the Types of pollutants? Pesticides e.g. Chlorinated hydrocarbons, organophosphates, carbamates, and pyrethroids. Herbicides e.g. Triazine, phenoxy, ammonium, and benzoic acids. Heavy metals e.g. Mercury, cadmium and lead.  Pesticides and herbicides ❑Several chemical classes are used in agriculture to control weeds (herbicides) or insects (pesticides). ❑Pesticides may be present in milk or meat of animals that have drunk water contaminated by pesticide remainders. ❑ Maximum remainders levels of many pesticides in fruits, vegetables and other plant and animal products are specified in legal regulations.  Heavy metals toxicity Heavy metals is the term used for a group of elements that are on the "heavier" end of the periodic table. Some heavy metals - such as Cobalt, Copper, Iron, Manganese, and Zinc - are essential to health in trace amounts. Others are non-essential and toxic to the human body. These include Mercury, Cadmium, Lead, Antimony, Chromium, and Arsenic.  1-Mercury toxicity ❑Mercury toxicity came to public attention after a mass poisoning in Japan in 1965. ❑It occurs in several toxic forms, Methyl-mercury is the most absorbed and toxic form. ❑Clinical signs of poisoning appear when methyl mercury was consumed at 4μg /kg body weight, and a safe level of methyl mercury ingestion is less than 200μg /week. How can Mercury enter food chain? 1- Mercury released into the environment from mining and coal-burning power plants. 2- It accumulates in waterways, then is converted by bacteria into organic methylmercury. 3-Methylmercury enters the food chain and reaches high levels in the long- lived, large fish such as shark, swordfish, tuna, and king mackeral.  What are the dietary sources of mercury poisoning? 1) The consumption of fish is the most significant source of ingestion- related mercury exposure in humans. 2) Eating foods containing mercury residues from processing, such as can occur with high-fructose corn syrup. 3) Consumption of flour made from seed grain tainted with methyl mercury (which affected at least 6,500 people in Iraq) and meat from animals raised on mercury-tainted grain (in New Mexico, USA).  Dangerous Health Effects of Mercury 1) Poor memory and Alzheimer’s disease. 2) Chronic fatigue, and depression. 3) Loss of sight, hearing, and an inability to coordinate movement. 4) Increased salivation. 5) Severe kidney damage 6) Disorders in insulin function and imbalanced blood sugar levels, this case can cause the development of type-2 diabetes. 7) Skin discoloration, swelling, and shedding of skin. 8) Affected children may show red cheeks, nose and lips, loss of hair, teeth, and nails, and increased sensitivity to light. 9) Activates the immune system and causes the development of auto- antibodies (cause auto-immune diseases)  Health concerns mercury for pregnant and nursing women Exposure of pregnant and nursing women to mercury poisoning can harm a developing child. HOW? Methyl-mercury is 5 to 10 times more toxic to developing embryos than it is to adults; fetuses and infants of women who consume large amounts of fish and seafood are at highest risk of mercury serious neuropsychological defects. These defects include deficiencies in: 1. Language 2. Attention 3. Memory 4. Motor function 5. Visual- function How can pregnant and nursing mothers reduce health risk of mercury to their infants? Women of child-bearing age, nursing mothers, and young children should: 1) Completely avoid shark, swordfish, king mackerel, or tilefish because they contain high levels of mercury. 2) Limit consumption of albacore ("white") tuna to no more than 6 oz (170 g) per week, and of all other fish and shellfish that are lower in mercury to no more than 12 oz (340 g) per week.  Minamata disease ANd9GcRUHAL7Q7X4-KqyyQ2Gf1PJyvEIDbYUmwvh1is-QxsNEi_xFsbV4Om2rg Minamata disease was first discovered in 1965 at Minamata city in Japan; it was caused by severe mercury poisoning. What are the symptoms of Minamata disease ? 1) Ataxia (lack of coordination of muscle File:Tomokos hand.gif movements). 2) Numbness in the hands and feet. 3) Damage to vision, hearing and speech. 4) In severe cases paralysis, coma and death follow within weeks of the onset of symptoms.  2. Cadmium toxicity ❑ Cadmium is readily absorbed when eaten. ❑ Most foods contain less than 50μg cadmium/kg, and ingestion of cadmium should be kept below 400-500μg per week. ❑ Long-term exposure to cadmium causes damage to renal tubules, anemia, and liver dysfunction.. ❑ Cadmium is highly toxic even in low concentrations, and can accumulated in organisms. ❑ A maximum acceptable concentration of cadmium in drinking water is 0.005 mg/L (5 µg/L). ❑ A tolerable weekly intake of cadmium for an adult is 0.4 to 0.5 mg. How can cadmium be taken up by food? 1) Cadmium is present in some fertilizers which add to the soil. It is taken up by crops such as leafy vegetables, root crops, rice and other cereals much more than other toxic metals. 2) Cadmium can also contaminate shellfish and meat.  How can we exposed to cadmium through foods? BY: 1) Eating food with cadmium in it: a- The lowest levels of cadmium in food of plant source are in fruits and the highest levels are in leafy vegetables and potatoes. b- The highest levels of cadmium in food of animal source are in shellfish, liver and kidney meats of adult animals. 2) Drinking canned evaporated milk and soft drinks. 3) Drinking water that has been in contact with cadmium.  Dangerous Health Effects of Cadmium Most of the cadmium that enter the body is stored in kidney and liver, and can stay there for many years, and cause dangerous health effects as follows: 1) Renal damage, resulted in kidney failure. 2) Reduce bone mineral density. 3) Increasing loss of visual function. 4) Damage to peripheral nerves with symptoms of numbness, muscle weakness etc. 5) Thyroid hormone deficiency. 6) Cadmium and cadmium compounds may be carcinogens.  Itai-itai disease Itai-itai disease is named for the severe pains (Japanese: itai) caused in the joints and spine It was first recognized in cadmium accumulated in the people eating contaminated rice. What are the symptoms of Itai-itai disease? 1) It starts by spinal and leg bone pain. 2) The symptoms can persist and progress for several years, until the patient: a- Is unable to walk, becomes bedridden b- Suffer from skeletal deformities and anemia c- Suffer from severe kidney problems, leading to death.  3-Lead toxicity Lead exposure both acute (a few days) and chronic (5 to 30 yr) affects numerous body systems and the severity of symptoms increases with the concentration of lead in the blood. What are the dangerous health effects of Lead? 1-Lead cause disorders of the functions of heart, bones, intestines, kidneys, and reproductive systems. 2-It also affects the development of the nervous system and is toxic to children, causing permanent learning and behavior disorders. 3-At very high levels, lead poisoning can be fatal.  Symptoms of Lead toxicity? Symptoms are different in adults and children, and appear in children at lower blood lead levels than in adults. A. The main symptoms in adults are headache, abdominal pain, memory loss, kidney failure, weakness, pain in the extremities. B.The symptoms in children are loss of appetite, abdominal pain, vomiting, weight loss, constipation, anemia, kidney failure, learning disabilities, hearing loss, loss of speech skills. How can lead get into food and drinking water? 1) Food can contain lead if lead-containing dust gets onto crops while they are growing or during food processing. 2) Lead can also get into food through food containers such as glazed pottery dishes. 3) Acid foods and drinks will leach lead out of dishes much faster than non-acid foods. 4) The major sources of lead in drinking water are lead plumbing.  What are the precautions that can be taken to reduce your exposure to lead in food? 1) Avoid the use of glazed pottery dishes to serve or store food, avoiding the storage of beverages in leaded glass decanters. 2) Eat a variety of foods, and eating foods rich in calcium, iron and Vitamin C so your body will absorb less lead from specific food sources that have been exposed to lead.  Treatment of heavy metals poisoning 1)The first step in treating any heavy metal toxicity is to identify the toxic elements and begin the removal process. 2)The easiest screening process for toxic metals is a hair analysis. 3)Additional testing by the use of chelating drugs along with a 24-hour urine collection to determine levels of heavy metals. 4) Treatment usually involves the use of metal chelating drugs or intravenous chelating agent (a substance that binds toxic metals and carries them out of the body). 5) For many patients, intravenous Vitamin C and replacement mineral are also recommended to support the body through the metal removal process. 6) Symptoms will often begin to improve within weeks or even days of treatment. Therapy may last from 6 months to 2 years.  Pathogenic agents Pathogenic agents are very common cause of food poisoning. They are classified into two groups: 1- First group includes organisms associated with endogenous animal infections and transmit to human by consuming meat or fish infected with different species of bacteria, fungi, viruses, and protozoa. This group will be studied in detail in the courses of food microbiology and parasitology. 2-Second group includes bacterial species that associated with exogenous contaminations of foods, which may cause food poisoning in human. Species of Staphylococcus and Campylobacter are the most commonly responsible for bacterial food poisonings.  Staphylococcus o The source of contamination with Staphylococcus is usually the infection of the hands of the workers preparing the foods. o Its toxins make no changes in the normal odor, taste or appearance of the food, so the person eating it is not warned.  Campylobacter o This organism multiplies in cooked meat and meat dishes and develops its toxins in foods held for extended periods at warming or room temperature. Thus many outbreaks occur from food eaten in school cafeterias, college, dining room and restaurants.  Differentiate between bacterial food infection and bacterial food poisoning. Bacterial food infection Bacterial food poisoning Resulted from eating food Caused by the ingestion of contaminated by large colonies of bacterial toxins that have been certain species of Escherichia, produced in foods by the growth of Shigella and Listera specific kinds of bacteria e.g. that cause specific diseases. Staphylococcus and Campylobacter before food is eaten. Symptoms begins after 3-21 days Symptoms toxins are ingested of infection. directly, so symptoms develop rapidly, usually within1-6 hr after the food is eaten. The most common bacterial food poisoning Causative Food sources Symptoms organisms Staphylococcus Custards, ▪ Sever abdominal aureus processed meat, pain, cramps, cheese, ice cream, vomiting, diarrhea, potato salad, headache, sauces. perspiration. ▪ Appear suddenly 1- 6 hr after eating. ▪ Subside generally within 24 hr Cont., Causative organisms Food sources Symptoms Clostridium perfringens Cooked meat, ▪ Mild diarrhea, and meat dishes vomiting. held at warm or ▪ Appear 8-24 hr after room eating. temperature. ▪ Lasts ≤ 24 hr Clostridium botulinum Improperly ▪ Range from mild home-canned discomfort to death foods, smoked within 24 hr. and salted ▪ Initial nausea, fishes, sausage. vomiting, weakness, sometimes lead to fatal breathing paralysis.  Seafood poisoning ▪ Bacterial decomposition of fish that is stored at unacceptably high temperatures or for long time is the main cause of seafood poisoning. ▪ Seafood poisoning has been attributed to the formation of histamine by bacterial decomposition of the amino acid histidine in fish. ▪ However pure histamine has low oral toxicity, another components in fish such as cadaverine and putrescine are important factors for the appearance of histamine toxicity. ▪ Seafood poisoning is often called scombroid poisoning because fish of the scombroidea species including mackerel and tuna are widely consumed. ▪ Other fish species e.g. sardines may also cause outbreaks. ▪ Symptoms appear within 2 hours of fish being eaten. They include pain, vomiting and diarrhea.  Government Food Safety Control Agencies in the United States System shared in the regulation of Food Safety Control in includes the: 1) USDA - United States Department of Agriculture 2)FDA - Food And Drug Administration 3)HACCP - Hazard Analysis Critical Control Points 4)FFDCA - Federal Food, Drug and Cosmetic Act 5)DSHEA - Dietary Supplements Health and Education Act