Consumer's Guide To Natural Toxicants In Foods Consumer's Guide To Natural Toxicants In Foods

By R.F. Matthews and L.M. Ravelo

Now more than ever consumers are concerned with the safety of their food supply. In the past few years, there has been an increasing perception that chemicals in foods, especially pesticides, may affect consumers' health.

Naturally Occuring Chemical Components

Chemicals in our food supply can occur naturally or can be introduced by man. Naturally occurring chemical components of fruits and vegetables may be toxic. They serve as defense mechanisms against herbivorous animals, insects, bacteria and fungi. Natural chemicals can also occur as contaminants of foods, such as the toxins of microorganisms (i.e. aflatoxins). Man-made chemicals can become part of our food supply from a number of sources: pesticides and fertilizers, chemicals that are produced during processing and/or added (i.e. additives) and chemicals that leach from food-packaging materials. The man made chemicals become part of foods as a result of our efforts to provide consumers with a year-round supply of quality foods.

Of all the chemicals in our food supply, natural chemicals are considered to be a much greater risk than all the other chemicals combined. This is because we are ingesting at least 10,000 times more natural chemicals than man-made chemicals (by weight).

All these naturally occurring chemicals have been found to induce a specific toxicological risk when evaluated by the methods used to evaluate the effects of man-made chemicals. Some of the chemicals present in this menu are capable of producing cancer. The carcinogens of this group are hydrazines, nitrate (when converted to nitrosamines), carbamate, methyglyoxal, tannins, benzo(a)pyrene, safrole, and eugenol. Others such as quercetin, furan derivates, malonaldehyde, heterocyclic amines, and psoralens are mutagens. They are capable of inducing mutations (alteration in genetic structure which is passed from one generation to the next). Hydrogen peroxide and the psoralens are both carcinogens and mutagens. Alcohol is a teratogen: capable of inducing birth defects. Other toxic chemicals such as carotatoxin and tomatine affect the nervous system. Di and tri sulfides produce antithyroid activity in animals. Tyramine causes blood pressure elevation. Myristin is a human hallucinogen. Isoflavones have estrogenic effect (mimic female sex hormone activity) in animals. The glucosinolates interfere with the use of iodine.

Are Chemicals in Our Food Always Hazardous?

The "Holiday Dinner Menu" (below) is not an attempt to incite fear but to emphasize that the body is capable of consuming with relative safety potentially toxic substances that occur naturally. Man-made chemicals are metabolized in much the same manner as chemicals of natural origin. The body is equipped with an efficient, specialized system for elimination of toxicants: the liver. This organ maintains a balance of nutrients, minerals and other substances necessary to life and is capable of eliminating from the body small quantities of many chemicals.

Some chemical nutrients required for normal growth and development are toxic when consumed at levels only 10 times greater than required levels. For example, vitamin A may be toxic at only 15 times the recommended dietary allowance. Vitamin D may be toxic at only 9 times the recommended dietary allowance.

Current evidence has shown the presence of some possible "anticarcinogens" in vegetables and fruits. Vitamin C, vitamin A and its precursors, vitamin E, selenium, fiber, purines, and glutathione have been found to counteract the effect of some carcinogens. For a safe diet it is recommended to eat a wide variety of foods in moderate amounts.

Benefits of Eating Fruits and Vegetables Far Outweigh the Concern for Pesticide Residues

No human diet is entirely free of mutagens and carcinogens. Having a "zero risk" or "absolutely safe" food supply is almost impossible. Still we have the safest food supply in the world. Benefits of eating fruits and vegetables far outweigh the concern for pesticide residues. The American Cancer Society recommends daily consumption of fresh fruits and vegetables to reduce the risk of cancer. Life expectancy in the United States has continued to increase with our current ood supply.


Table 1.

Table 1. Holiday Dinner Menu.
What's on the Plate
What's in it
Cream of Mushroom Soup
Fresh Vegetable Tray
Carrots,Radishes,Cherry Tomatoes,Celery
carotatoxin, myristicin,isoflavones, nitrateglucosinolates, nitratehydrogen peroxide, nitratequercetin glycoside, tomatinenitrate, psoralens
Roast TurkeyBread Stuffing(with onions, celery,black pepper and mushrooms)Cranberry Sauce
heterocyclic amines,malonaldehydebenzo(a)pyrene, di- andtri-sulfides, ethyl carbamate,furan derivatives, dihydrazines,psoralens, safroleeugenol, furan derivatives
Red Wine, Water
tannins, alcohol, carbamate,methylglyoxal, tyraminenitrate
Adapted from: American Council on Science and Health.

Courtesy of the University of Florida, Institute of Food and Agricultural Sciences (UF/IFAS)

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