Issues of “Safety” in the Food Supply
An essay on food safety that is still appropriate appeared originally in "Food Technology", March 1975.
"There is a current popular tendency to assume that the words "natural" and "safe" are synonymous, and that "synthetic" ("processed") means "harmful". Adding to this misconception are repeated charges that most food additives are harmful to health, and almost anything that wasn't put there by Mother Nature must be harmful. At the same time increasing government requirements concerning food labeling mean that ingredient lists on the labels of food products get longer and contain more chemical terms. The list of unfamiliar terms, even when they simply designate familiar food products under their scientific rather than popular names, have led many consumers to assume that our food supply has become increasingly artificial and that this is a dangerous state. This assumption overlooks two basic facts: Many "natural" foods contain a variety of substances which are potentially harmful if consumed in large quantities. The same physiological mechanisms which allow the body to consume these to "natural" foods safely, also apply to foods to which additives have been incorporated for wide variety of functional and nutritive benefits. The purpose of this article is to point out that many potentially harmful substances are present in the diet without presenting a significant hazard to the eater, this applies equally to "natural" foods and to processed foods. This is possible because a substance may be Toxic - i.e., inherently capable of producing injury when tested by itself without being Hazard, - i.e., likely to produce injury under the circumstances of exposure, as in the diet. Our concern therefore, should not be directed with the intrinsic toxicity of a particular chemical component of food, whether natural or added, but rather with the potential hazards of those materials when we eat the foods in which they are present.”
The problem of distinguishing between toxicity, safety and hazard may be illustrated by considering some well-known poisons and some common safe foods.
Curare is a chemical is used by South American Indians in the Amazon and Orinoco valleys for making the tips of darts and arrowheads poisonous. When hit, the prey is instantly paralyzed. The same chemical is also used in human and veterinary medicine as a skeletal muscle relaxant.
Strychnine is a common poison in used killing animals, such as coyotes. However has been used as a stimulant for the central nervous system in cases were the central nervous system has been affected by" poisons" - it is acting as an antidote to poisons! It can also act is stimulant in weak or debilitated animals.
Digitalis and derivatives are deadly poisons extracted from the foxglove plant. They have been used as poisons in fictional murder mysteries and in a real-life murder mystery that took place in a hospital in central Canada. The fact that the compound are available in hospitals is, in itself, indicative of their use in medicine. The deaths were considered to be due to overdose is of digitoxin, a useful drug for the regulation of Heart rate and blood pressure.
Potatoes are one of the staple carbohydrate foods of the world. However, if their discoverer, Sir Walter Raleigh, were to introduce them today as a new food crop it is certain that they would not be approved for human consumption. The reason for this is that they contain highly toxic glycoalkaloids, alpha-solanine and alpha-chaconine. Studies have shown in even one single high dose of these compounds given to pregnant animals leads to high fetal mortality and reabsorption. Although the level of these compounds is very low in normal tubers, they can reach dangerous levels in green potatoes and sprouting potatoes. Over 30 deaths and 2000 case of poisoning have been associated with consumption of potatoes. Note: toxic dose is considered to be 3-6 mg/kg body weight, compared with 5 mg/kg for strychnine.
Almonds, lima beans, peach pits, apple seeds and cassava, all contain toxic cyanogenic glycosides which release hydrogen cyanide in the stomach and intestinal tract. Linamarin is one found in lima beans and cassava, and amygdalin is one found in almonds, peach pits, and apple seeds.
Cabbage, cauliflower, and most members of the Brassica family contain a group of chemicals known as goitrigens, that interfere with the activity the thyroid gland.
Nutmeg, the delightful spice associate with eggnog, pumpkin pies and custards, contains a highly potent hallucinogenic compound called myristicin.
Soybeans, the crop has been heralded as the panacea for the world shortage of protein contains, in the natural unprocessed state: anti-digestive factors, goitrigenic factors, anti-vitamin factors, anti-mineral factors, allergenic factors, and anti-redblood cell factors
The list of both "poisons" and "safe foods" could go on and on. Rhubarb, shrimp, carrots, raw eggs, parsnips (The most potent mutagenic agent in early trials of the Ames test was parsnip juice.). Clearly, "safe" and "toxic" are not absolute terms. Common sense and experience tells us potatoes are not normally hazardous although they may contain traces of toxic chemicals. Therefore is paramount when considering the safety the foods we eat to determine whether they present a hazard, and to recognize that the presence of toxic material may not present hazard. It is also necessary to distinguish between acute toxicity (effects of high-level exposure for short-time) and chronic toxicity (low-level exposure for longtime).
Internet References to ‘Naturally’ occurring substances that can cause illness
Safrole - http://homearts.com/cl/garden/57pharb2.htm
Solanine - http://www1.ivillage.com/food/experts/nutrition/articles/0,5370,5518,00.html
Avidin - http://www.calzyme.com/catalog/avidin.html
Thiaminase - http://www-biol.paisley.ac.uk/Courses/Enzymes/glossary/Nutrient.htm http://agri.gov.ns.ca/pt/lives/furfacts/feedherr.htm
Saponins - http://helios.bto.ed.ac.uk/bto/microbes/saponins.htm
oxalic acid - http://www6.phys.com/b_nutrition/03encyclopedia/02terms/o/oxali_aci.html
comfrey teas - http://gardening.wsu.edu/library/vege011/vege011.htm
senna - http://www.mindspring.com/~millersrexall/herbs/153.html
Relevant Textbooks: 参考図書
Nutrition: Concepts and Controversies (8th Edition) 1999
Sizer and Whitney. Page 518.
Prespectives in Nutrition (4th Edition) 1999
Wardlaw. Page 685.
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