The FDA has not required that GMOs be tested for adverse health effects, but there are individuals and laboratories that have proceeded with testing anyway. Plentiful results can be found on the Institute for Responsible Technology website. http://www.responsibletechnology.org/gmo-dangers/65-health-risks/1notes

Adverse health effects associated with GMOs include allergies, infertility, liver damage, abnormal development of organs, immune cell disturbances, immune problems, accelerated aging, faulty insulin regulation, and on and on.

But the FDA has never required testing on humans, so there is a dearth of long-term human studies.

“The only human feeding study ever published showed that genes can transfer from genetically modified crops into the gut bacteria and continue to function,” says Jeffrey Smith, GMO expert, activist and author of Seeds of Deception: Exposing Industry and Government Lies about the Safety of the Genetically Engineered Foods You’re Eating. “This means that long after we’ve stopped eating GMOs, we may still have genetically modified proteins produced continually inside us. This was done using soybeans that were Roundup Ready [made resistant to Monsanto Roundup pesticides]; the folks in the study had Roundup Ready gut bacteria.

“Elsewhere, thousands of farm workers in India are getting allergic and flu-like symptoms from just touching cotton that has had Bt [a naturally occurring soil bacteria that’s been genetically introduced into several crops] modified into it. When they allow animals to graze on the cotton plants after harvest, thousands die. And unfortunately the corn that we eat is genetically engineered to produce this same toxin,” says Smith.

The dangers for children, however, are the most worrisome. “Children are most at risk for the potential dangers,” Smith points out. “A young and fast-growing body will treat the food differently than an adult body; it’ll incorporate the food into the organs and into the body, as opposed to just using food for fuel.”