Genetically Modified Organisms (GMOs) are complicated and controversial, and for the average person, separating good science from industry promotion in a meaningful way is nearly impossible. It’s also incredibly important.

So we poured through the research and talked to scientists to find to out what you need to know about the controversial crops and how they may affect your health.

Here’s what we learned.

What are GMOs? 

GMOs are created by inserting a piece of DNA from the cells of one plant or animal into the cells of another. This reprograms the cells’ genetic blueprint, giving it new properties. Most commercial GMOs are created to withstand herbicides or produce insecticides. For example, one of the most common, Roundup Ready Soybeans, was engineered so that farmers can spray their crops with the herbicide Roundup to kill weeds without also killing the soybean plants.

What are GMOs in?

In the United States, GMOs are estimated to be present in about 80 percent of processed foods. Ninety-five percent of soy and close to 90 percent of corn crops contain GMOs, and they are barely tested or regulated and not required to be labeled.

How GMOs affect your body and health

“There’s a growing body of scientific literature around the health risks of GMOs, and the papers that are showing the risks are deep and systematic science,” says Dr. John Fagan, a genetic engineer and expert who founded Earth Open Source and is an anti-GMO advocate. Because the genetic interference disrupts the plant’s functioning, it may also, in turn, disrupt your body’s, he explains.

Some of the health risks that have been suggested in numerous animal studies include kidney and liver problems, reproductive issues, and increased risk of cancer. Studies have also shown that GMOs may be allergenic, and may reduce the nutritional value of foods. For example, one study showed that genetically-modified soy had less healthy isoflavones.

The biggest long-term study to date, published last fall in the journal Food and Toxicology, showed a marked increase in tumors and premature death among rats fed genetically-modified corn. But while the study made waves, it was also met with intense criticism from many scientists, who cited major flaws in its design. And some studies have shown little to no health risks, including this literature review of recent research published in the same journal last year.

Side effect: More exposure to chemicals

Another concern, aside from the effects of the GMOs themselves, is that as foods are engineered to withstand herbicides, more of the toxic substances are sprayed on the plants, increasing herbicide residues found in foods. (Since farmers don’t have to worry about killing the plants, they end up spraying the herbicide much more liberally.)

“When Roundup Ready Soy was first approved for use in Europe, the government increased the threshold of Roundup that could be found in the soy,” Dr. Fagan notes. So your tofu may come with an extra serving of Roundup, which has been linked to cancer, birth defects, neurological disorders, and other health issues.

The controversy

Conflicting research is tricky enough to sort out, but it’s even worse when larger forces are at play. Much of the research that’s cited as proving GMOs are safe (but not all) is done by the companies that create them (yes, seriously). Also alarming: these studies tend to be done over 90 days or less, so as not to expose possible long-term health risks.

And anti-GMO advocates say that companies such as Monsanto (manufacturers of RoundUp Ready soy, corn, herbicides, and more) engage in campaigns to control the research that’s being done and discredit studies that show risks.

“Much of what they’re doing is attacking the scientists. They’re not bringing up counter-science, they’re just throwing the kitchen sink at these guys,” says Dr. Fagan. “In addition to that, they have done everything they can do to control whether research can be published.”

In the end, it seems like the debate over the safety of GMOs in our food supply is only just beginning, and hopefully, skilled, independent scientists will put even more muscle into providing us with concrete answers. —Lisa Elaine Held