Are genetically modified foods safe?

Q: I hear a lot about genetically modified foods. But what does GM actually mean?

A: In the old days, farmers used simple breeding techniques to develop new strains of plants or animals. They selected the traits they desired in each succeeding generation. Today, food scientists have a whole new toolbox. Using viruses to smuggle genes inside cells or physically inserting genes into nuclei, the scientists alter DNA—the fundamental blueprints that make organisms what they are. Why do it? Scientists are looking for traits that Mother Nature never thought of—or perhaps thought better of. In 1994, Calgene (later a subsidiary of Monsanto) introduced the Flavr Savr tomato, designed to ripen without becoming overly soft, giving it a longer shelf life. According to a study published in 2006, University of Missouri researchers developed pigs with a roundworm gene that converts other fats into omega-3s. Genetic modification has become routine with feed crops for animals. By creating corn and soybeans that resist herbicides, farmers can kill weeds without killing their crops. And by engineering insect-resistant corn, producers aim to increase yields and reduce pesticide use. Some have suggested that this kind of genetic engineering is the only way to feed an expanding human population.

Q: How can I tell if I’ve got GM foods in my shopping cart?

A: In the U.S. and Canada, manufacturers are not required to label genetically modified foods. Even so, there are a few ways to tell: Most of the acreage of corn, soybeans, cotton, Hawaiian papaya, and canola in the United States is GM. But if you are picking up an apple, orange, banana, broccoli, or most any other fruit or vegetable, it is likely not GM. On fresh produce, check the little sticker with the four-digit price look-up (PLU) code (the one that tells cashiers how to ring up fruits and vegetables). If the code is preceded by an 8, it is genetically modified. Food products labeled organic are not GM. A package of tofu labeled organic is GM-free, while one without this label may well have come from genetically modified soybeans. Organic produce is indicated by a 9 prefix on the PLU sticker.

Q: Are GM foods dangerous?

A: Who knows? A 2004 National Academy of Sciences report noted that testing methods must be improved before firm conclusions can be drawn. Could genes from food insinuate their way into your own DNA? Could they enter the bacteria that normally inhabit your digestive tract, giving them traits we don’t want? For example, if plants that are genetically engineered to produce their own pesticides were to transfer this ability to your gut bacteria, the result could be unintended toxicity. Some argue that GM foods are safe, having shown no adverse effects on humans. However, a report published in 2009 in the journal Nutrition Reviews suggests that the effects of eating GM foods may be subtle, affecting cellular functions without any grossly obvious abnormalities. New foods can spell new allergies. When soybeans were engineered to contain a transferred Brazil nut gene, people who were allergic to Brazil nuts were also allergic to the modified soybeans. Environmentalists worry that implanted genes can easily spread as far and wide as the wind can carry them, modifying the biology of plants or animals along the way.

Q: Should I avoid eating GM foods?

A: In my view, yes. They provide no health benefits, and no one is sure about the risks. Health concerns aside, a major reason to avoid GM foods relates to the welfare of animals. When animals are made to mature faster, grow larger, or produce more milk, they are likely to suffer in the process, as seen with the obese chickens and turkeys and overproducing dairy cows on “conventional” farms. Genetic engineering may further push the limits of what animals can be forced to do. Animal experiments are, of course, integral to producing genetically modified animals. And producers of genetically modified plants typically subject the new foods to animal tests to prove their safety. Meanwhile, GM opponents conduct animal tests of their own to prove its dangers. I would suggest that the foods best supporting human health are those to which we have adapted over the millennia. When confronted by challenges in feeding an expanding human population, we may do better to promote plant-based diets, which feed people more efficiently than feeding grains to animals, and to consider how to contain population growth, rather than look to biotechnology to try to keep pace with human fecundity.