21.7: Widening the Perspective in Food Safety

In this chapter and the last, a few categories of non-nutritive food substances have been discussed in relation to food safety. It should be clear by now that the categories aren’t always clearly defined, and the hazard represented by any one substance can’t be assessed in isolation.

The overlap of pesticides, food additives, and natural food substances has been emphasized, as has the importance of dosage. There are many more interactions to consider.

Nutritional status can make a difference in the effects of a toxicant—lead is more readily absorbed by (and thus more toxic for) those who are iron deficient. Also, using several methods of preservation allows the use of smaller amounts of preservatives—routine refrigeration of processed meats means less nitrite is needed.

As another example, increasing a plant’s drought resistance can help reduce hazards for other foods. The damage to our corn crops wrought by the 1988 drought exposed the corn to greater infection by the molds which make aflatoxin, a potent carcinogen. The toxin appeared in milk when cows ate aflatoxin-contaminated corn, and dairies in many states had to dump milk. (Michigan, in 1989 had to dump about 400,000 pounds of milk due to high levels of aflatoxin.)

We apply rigid controls to food additives, sometimes forgetting that the chemical composition of food changes constantly. How else does cheese and fruit ripen and rot? Or beef age? Or cake ingredients combine to make a cake—that later turns stale? How else do we increase the iron content of spaghetti sauce by simmering it in an iron pot? Or form carcinogens by grilling meat? Or release, by cooking, poisonous hydrogen cyanide gas from lima beans? From the moment of food’s first creation in plants from carbon dioxide and water to the moment our metabolism returns it to carbon dioxide and water, food’s chemical composition is in constant flux.

Our food is rife with natural toxins. Yet these substances are considered safe when consumed in a normal varied diet by healthy people. One reason is that the toxicity of one substance can be offset by another substance in the food. For example, adequate dietary iodine can help prevent the goiter caused by the toxic effect of goitrogens.

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Goitrogens, which in large amounts can cause goiter, are a natural component of such foods as cabbage and cassava.

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A particularly important factor is that the toxicities of various food toxicants aren’t additive. Eating small amounts of different toxicants together in the diet is much safer than eating one of them in a larger amount.6 So the wider the variety of foods in our diet, the less the chance that any one chemical will be present at a hazardous level.

Today’s varied diet also includes food grown in a variety of geographical locations, as noted at the start of this chapter. It wasn’t that long ago that the distribution of goiter reflected the distribution of iodine in the soil, goiter being most common in areas of the U.S. where iodine was lacking. Advances in food processing and preservation removed goiter from our roster of common diseases—by the addition of iodine to salt during processing, and by the preservation that widened the distribution of produce and improved the odds of at least some food rich in iodine arriving at any given kitchen table.

Knowing that there are a lot of natural toxins in food doesn’t mean that we should be unconcerned about what’s added to food, either intentionally or unintentionally. Rather, we should widen our concern to include the natural toxicants in food and the contributions of the disease-producing microbes that get into our food. (Furthermore, we might weigh food hazards against other health hazards.)

In this way only, can we make reasonable assessments of benefits versus risks, and take best advantage of what advances food science has to offer. If a natural carcinogen is found in high concentration in a plant, we might want to genetically modify the plant’s ability to make it—or alternatively, decide against eating the plant altogether. As another example, irradiating produce to kill microbes can lessen the need for post-harvest pesticides. We should balance one “worry” against another.

Worrying about food additives, pesticide residues, and such—whether or not a given worry is justified—is a measure of how fortunate we are in this country. For much of the world’s people, the focus is on simply getting enough food to prevent starvation and malnutrition. If all that’s available is aflatoxin-contaminated grain, eat it they must.