Many of the objections to genetically engineered (GE) or genetically modified (GM) foods focus on the safety of the foods, and the suggestion that these foods do not receive adequate testing.

This issue received special attention in September 2000, when traces of StarLink corn, a variety of Bt corn not approved for human consumption, was detected in processed food products (taco shells). StarLink corn plants contain a gene from the bacterium Bacillus thuringiensis that encodes an insecticidal protein, called Bt toxin. During pre-market safety tests, it was determined that this variant of Bt toxin was more stable than the other types of Bt used by other companies, and that it therefore might not break down as easily during digestion. The concern was not that the protein would have toxic activity in humans (since it requires conditions found only in insects to work), but that the undigested protein might be recognized by the immune system, causing an allergic reaction.

The Food and Drug Administration therefore placed restrictions on how Aventis (the maker of StarLink) could market the corn. StarLink corn was approved for use only as animal feed, not for the production of foods intended for human consumption (corn flakes, tortillas, etc.).

It has not yet been determined how corn containing the StarLink Bt gene ended up in the taco shells. In other cases where GM crop genes have been found among non-GM foods, the source was identified as storage facilities that were not completely emptied of the GM foods. It is also possible, however, that a grain broker misrepresented what he or she was selling, or that pollen from a StarLink field made its way to regular fields.

GM foods, then, do undergo extensive safety tests before being sold, in much the same way that the safety of pharmaceuticals are evaluated (both types of products are reviewed by the FDA). Companies must demonstrate that the GE foods are nutritionally equivalent to their non-GM counterparts and that they present no significantly health risks (such as allergies) to those who consume them. They examine the product of the new gene (e.g., Bt) as well as the effects of the foods in laboratory animals.

The composition of GM foods does differ from non-GM foods; for example, Bt corn contains the insecticidal protein from Bacillus thuringiensis, whereas regular corn does not. In most cases (except, for example, StarLink), the new protein is broken down into amino acids during digestion so that the digested form of the GM food is indistinguishable from the digested form of the non-GM food (which also break down into amino acids). In other words, nutritionally speaking, the foods are essentially equivalent.

During the BIO 2001 convention in San Diego, there was a radio program in which a caller asked whether the chemical composition of GM foods differs from non-GM foods. The guest who opposed GM foods told him, "Yes, there are tests to detect the new gene, the new nucleic acid, which is of course a chemical, so yes, they are chemically different." But detecting the additional DNA just tells you that the gene is there; it's just more DNA, not a different kind of molecule. What the caller was really asking is whether there are different chemicals found in GM foods relative to non-GM foods. And the answer, in general, is no, there are no differences.

There may be cases, however, where one does find chemical differences. For example, companies have been working on seed crops that contain oils that are less likely to cause heart disease, or crops such as Golden Rice, which provide vitamins not available in the non-GM crop. These are compounds that you may not normally find in the non-GM plants.

Safety testing of new crops is a very reasonable precaution, and in fact should be required not only of GM crops, but also for crops generated by conventional means. In one well known case, for example, traditional breeding of insect-resistant celery resulted in a variety that caused severe rashes and lesions on the skin of those who handled it in the fields and in grocery stores. New foods from different areas of the world are also beginning to appear in our stores, and they may also present significant allergy risks and should be evaluated.

One of the more important (and also one of the more difficult to understand) concepts related to food safety is that scientists don't believe that anything can be proved to be 100% safe. While it is possible to demonstrate the absence of harm, to scientists that doesn't mean it will never cause harm because you can never predict the future with 100% accuracy. My (science-based) view of the world says that I could wake up tomorrow and they could tell me that Asians (like me) could die if they eat quinoa; all of the evidence I've seen and all of the experience I've had says that that won't happen, but science says I have to leave that open as a possible outcome. And so sometimes people ask scientists if they can prove that GM foods are "safe", and they are disappointed when the answer is "no". But the longer answer that people don't always hear is, "No, we cannot prove that GM foods are safe any more than we can traditional foods."

GM foods offer many possible benefits, from improved nutrition to a decrease in the use of chemical inputs used to grow them. But because they are foods, and because so many people come into contact with the end products, consumer safety is of utmost importance. The current approval process involves extensive nutritional studies and other safety-oriented evaluations. I believe that they provide an adequate means of determining which products are suitable for human consumption and which are not. The current methods for handling and sorting the products (e.g., StarLink corn), however, may not be adequate and should be reexamined.

(September 2003)

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