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Food, Nutrition and Health
FNH 200
Nooshin Alizadeh- Pasdar

MODULE 12: Toxicants in Food and Foodbourne Disease What are Toxicants? - toxicant = a poison or a poisonous agent - poison = chemicals that in very small quantities cause illness or death; chemical that has a lethal dose of 50mg or less of chemical/kg body weight - when refer to toxicant in foods, general reference to substances responsible for whole spectrum of results: relatively minor discomfort to sickness to poisoning to death - toxicity = inherent capacity of a substance to damage a biological system when tested by itself; substances vary in toxicity - hazard = thing or action that can cause adverse health effects in animals, plants, humans; the capacity to produce injury under the circumstance of exposure  More complex than toxicity because includes consideration of use; 2 components involved in assessing hazard: a) inherent capacity to cause harm (toxicity) b) ease or probability of contact between substance and target object - risk = likelihood of occurrence and magnitude of the consequences of an adverse event Dose Response and Risk Analysis - “all substances are poisonous; there is none which is not a poison. The right dose differentiates a poison and a remedy” (Swiss physician Paracelsus) - every toxicant has some set of exposure conditions in which it is toxic and non-toxic, described by dose-curve response  Threshold = dose at which a substance begins to have undesirable effect; upper limit of no effect zone; value unique for each substance  Slope = steep: little flexibility in trying to avoid harmful exposure; unique for each substance - both toxicity and hazard important in evaluating risks of toxicants - proper toxicological evaluation should account for all differences between human and animal, among different humans; consider species differences, age, gender, environment of animals used Types of Toxicants Naturally occurring toxicants: Naturally occurring toxicants: ENVIRONMENTAL TOXICANTS CONSTITUENTS CONTAMINANTS Cholinesterase inhibitors Mycotoxins Food Packaging residues  Solanine in potatoes  Aflatoxin  Monomers of plastic  Patulin resins  Ochratoxin A Cyanogenic glycosides  Vomitoxin Pesticide residues  Amygdalin in apple  Zearalenone seeds Ex) aflatoxin in mouldy  Herbicides peanuts, vomitoxin in wheat  Insecticides  Fungicides Glucosinates Ex) malathion residues on  Sinigrin in cabbage Bacterial toxins fruit  botulinum toxin  Staphylococcal toxin Protease inhibitors Heavy metals  Protease inhibitors in  Lead soy beans Seafood toxins  Mercury  Histamine  Cadmium  Saxitoxin Ex) lead in veggies; mercury in Nitrites  Domoic acid large ocean fish  Green leafy plants  Tetrodotoxin (eg. Swordfish) Allergens Animal drugs  Beta-lactoglobulin in milk, peanut proteins, soy proteins  Antibiotics  Hormones Ex) penicillin in milk Radioisotopes  From soil or  radioactive fallout - constituents = chemical entities part of normal composition of foods - contaminants = result of external organism or activity; due to presence of moulds, bacteria or because plant/animal grown in environment which permitted toxicant to become part of food - environmental toxicants = not naturally occurring in natural environment; introduced into environment by humans and not intended to become part of food (ex. Pesticides) - relative hazard ranking: regulatory concern (minimal to greatest concern)  food additives, agricultural chemicals, natural toxicants, environmental contaminants, nutritional properties, microbiological contaminants Examples of Natural Consituents as Toxicants 1) Cholinesterase inhibitors - variety of chemicals that inhibit the activity of cholinesterase (enzyme found in nerve tissues; involved in transmission of nerve impulses)  Solanine - found in potatoes, primarily in skin - normally at levels of 2-13mg/100g fresh weight (most 3-6 mg/100g) - insoluble in water; not lost or destroyed when potatoes are cooked - clinical symptoms: gastrointestinal disturbances, neurological disorders, solanine poisoning => death - not readily absorbed; excreted by feces and urine - injected dose 100mg => drowsiness, increase sensory sensitivity, breathing difficulty; higher dose => vomiting, diarrhea - solanine itself quite a potent toxicant; however, hazard of solanine poisoning by consumption of potatoes quite low - green potatoes from improper storage => high risk of solanine poisoning 2) Cyanide glycosides - produce hydrogen cyanide (HCN) when treated with acid or hydrolytic enzymes - in higher plants, ferns, moths, insects - rapidly absorbed from gastrointestinal tract => fatal and nonfatal symptoms - humans’ lethal dose between 0.5-3.5 mg/kg body weight  amygdalin - bitter almonds, fruit pits, apple seeds -hydrolyzed to form HCN, glucose, benzaldehyde - beta-glycosides – enzymes responsible for hydrolysis of cyanogenic glycosides - hydrolysis of cyanogenic glycosides occur during cutting, crushing, bruising, maceration of tissue prior to consumption - preparations to hydrolyze glycosides and destroy beta-glucosidase can minimized hazard but cannot completely eliminate cyanogenic glycosides - hazardous if eaten in large quantities (an apple seed by accident is fine) 3) protease inhibitors - legume species - interfere with proteolytic enzymes; inactivate enzymes that break down proteins in their constituent amino acids => body cannot fully hydrolyze proteins causing amino acid deficiencies 4) nitrates => nitrites - nitrates in plants, especially green leafy plants - nitrates not toxic but bacteria reduce to nitrite = toxic - nitrites react chemically with hemoglobin, interfere with oxygen transfer in blood; also precursor for nitrosamines = potent carcinogens 5) allergens - induce allergic reactions (peanuts, seafood, milk, eggs, etc) - consideration of individual differences in assessing risk and hazards Examples of Natural Contaminants as Toxicants 1) mycotoxins - produced by moulds - direct (mould growth on food) or indirect contamination (using contaminated food ingredient) - highly toxic – cancer, mutations, deformities in embryo (teratogenic) - invisible to eye and unchanged by heat - can spread through food - things to consider when encounter mouldy food:  was food refrigerated?  Amount of mould  Type of mould  Prevent mold be minizing contact of food with air as well as package and refrigerate properly  Aflatoxins - potent liver toxins in all animals, carcinogens in some species - peanut butter considered contaminated and unfit for sale if contained aflatoxins in excess of 15ppb 2) Bacterial toxins - Clostridium botulinum - Staphylococcus aureus - can cause food poisoning due to food intoxications because chemical toxin produced by bacteria that produces toxin, not bacteria themselves 3) Seafood toxins - animal tissues less frequently contaminated with natural toxicants because their genetic makeup similar to humans - mostly marine algae or through action of microorganisms  Histamine - scombroid fishes (tuna, bonito, mackerel) - scombroid poisoning = allergic-type reaction to high levels of histamine - histadine = naturally occurring amino acid high in scombroid fish, converted o histamine by bacteria on dead fish - high quantities can cause high blood pressure and cause fish to smell bad  Saxitoxin - paralytic shellfish poisoning (PSP) - symptoms: tingling in mouth, lips, fingertips, incoherent speech - red tide = plentiful microscopic plankton which are toxic dinoflagellates =>
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