Here in the United States, upwards of 70 percent of corn and 90 percent of soy are genetically modified. Given that corn and soy end up in just about everything -- livestock rations (and thus meat, milk, and eggs), nearly all processed foods, and even our gas tanks, avoiding genetically modified organisms (GMOs) is tricky.

One way is to shun all processed food and animal products, and simply eat fruit, non-soy veggies, and non-corn grains. (I assume U.S. fruits and veggies aren't GM, despite a recent, and likely erroneous, report to the contrary.)

A less strenuous way, theoretically, would be to buy only certified-organic foods, since USDA code restricts GMOs from organic food. But that strategy is iffy, because GMOs are capable of "contaminating" non-modified seed strains. Corn, particularly, is a "promiscuous pollinator" -- pollen from GM fields can blow onto organic fields, introducing their "traits" into crops.

Reuters reports that organic farmers, processors, and retailers are organizing to fight GMO contamination. They want the USDA to set up a system to test and certify organic foods as GMO-free.

Evidently, the problem isn't abstract. Albert Straus, who runs the highly regarded Strauss Organic Family Creamery in northern California, supplements his pasture-based feed system with organic corn for lactating cows.

He started testing the organic corn he buys a year ago, and found that fully one-third of it had been contaminated by GMOs.