Modified genes in our food supply may be modifying us, says Jeffrey M. Smith.

More than half the people in the U.S. say they don't want to eat genetically modified (GM) food, but many of them probably aren't sure why, or how to avoid it, Jeffrey M. Smith, author of Seeds of Deception and Genetic Roulette, explained Saturday to an audience of food retailers and manufacturers at Natural Products Expo West in Anaheim, CA.

The Details: There's a push in the U.S. to get genetically modified organisms (GMOs) out of our food supply. Other countries have already done this, and Smith, executive director of the Institute for Responsible Technology, hopes U.S. consumers will start paying closer attention to the issue. He estimates that if just 5 percent or so start rejecting GM food, it'll force a big change.

How do foods become genetically modified? In the traditional cross-breeding process, two varieties of, say, tomatoes might be crossed for a more robust fruit. But today's technology inserts out-of-species genes, often from bacteria and viruses, into the DNA of plants like corn, soybean, cotton, and canola, introducing genetic matter into our food that's never been there before. The process allows conventional growers to douse even larger amounts of poisonous herbicides onto the modified plants without killing the crop. That introduces more chemicals into the groundwater and waterways near the farm, but it also increases the amount of chemical residue on the foods. Some crops have even been modified so the plant produces its own pesticide.

Smith reports that GM foods are being blamed for allergies, new toxins, and immune problems. For instance, Smith says soy allergies rose by 50 percent in the United Kingdom after GM soy was introduced. In animal studies, feeding mice GM foods has caused digestion problems, smaller livers, reproductive problems, and infant mortality. Livestock that have grazed on GM cotton fields have died abruptly, too. And Smith points out that if pesticide genes transfer into the bacteria in our gut - as the only human study on the subject suggests they can - we're in for some serious changes in our bellies. "They might turn our intestinal bacteria into living pesticide factories," he says.

What it means: Since the U.S. Food and Drug Administration doesn't require safety testing of these foods (the FDA takes the word of the biotech companies on that), you'll have to do a little detective work if you want to lower your exposure to GMOs. Fortunately, there are alternatives.

Here's how to clear your cart of GM foods:
  • Know the big 4. Food makers are not required to indicate GMO content on their labels. Corn, soy, canola, and cotton are the most prominent GM crops; that doesn't mean all these crops are genetically altered, but many are. If you favor cane sugar over other types, you'll avoid GM sugar beets, Smith says. In much smaller numbers, zucchini, yellow crookneck squash, and sweet corn could be GM; about half of Hawaiian papayas are GM.
  • Look at the label. Some food companies are taking the voluntary step of labeling products that are GMO-free. And if you buy organic versions of any food, you'll avoid GMOs, since they aren't allowed in certified organic products.
  • Go for grass-fed. Look for meat and dairy producers that feed their animals grass, not GM grain. The GMO process might cause grain to produce toxins that are taken up by the cattle and passed on in milk and meat, Smith warns.
  • Sidestep processed foods. When you buy processed foods, there are ingredients from all over added to the mix. And it won't say on the label if that includes any GMOs. Ingredients that could be genetically modified include aspartame, corn gluten, corn oil, corn syrup, cornmeal, cornstarch, high-fructose corn syrup, fructose, glucose, soy flour, soy lecithin, soy protein, tofu, xanthan gum, monosodium glutamate (MSG), caramel color. (You can find more in The Non-GMO Shopping Guide, listed below.)
  • Get the guide. The Non-GMO Shopping Guide is as essential as a shopping list for anyone who wants to avoid GMO food. It lists brands that refuse to use GM ingredients, and also lists companies that may be using them. For instance, Nature's Path, Amy's Kitchen, and Eden products don't include GM ingredients, but Aunt Jemima, Betty Crocker, Morning Star, Boca, Kellogg, General Mills, Post, and Quaker products could, among many others.
  • Host a GMO-free potluck. This is a good way to get your family members and neighbors educated and engaged about the safety of our food supply. Direct them to the shopping guide and they'll find out it's not so hard to go GMO-free - you just have to know what to look for. Your dinner could inspire some to try the 30-day challenge at Campaign for Healthier Eating in America.