The increasing frequency with which GMOs are found in the food system has led many activists to campaign against these genetically modified organisms, or at the very least, to ask the government to require the labeling of all GMO products.

But are GMOs really dangerous? Like any other controversial topic, the answer to this question isn’t clear-cut, and it’s particularly difficult for people who aren’t scientists to delve into. Even when research appears to indicate problems with GMOs, other scientists have stepped forward to criticize the way the studies were conducted, as in the case of research by Dr. Gilles-Eric Seralini from the University of Caen in France. Although that doctor’s study was retracted from one journal, it was eventually reviewed and published in a different journal, leaving readers to wonder who is accurate, the Genetic Literacy Project reported.

In September 2014, Forbes magazine published a story about GMO research that said, “The debate over the risks associated with GMO food is effectively over.” The magazine reported on research that found GMOs to be safe, pointing to more than 2,000 studies showing that result, as well as a massive study that looked at “29 years of livestock productivity and health data from both before and after the introduction of genetically engineered animal feed.”

Special: GMO Foods: Are We Unknowingly Poisoning Our Families?

Not all agree. “The contention that GMOs pose no risks to human health can’t be supported by studies that have measured a time frame that is too short to determine the effects of exposure over a lifetime,” Robert Gould, M.D., president of the board of Physicians for Social Responsibility, told Consumer Reports.

One thing to note is that many criticisms of GMO food products found on the web focus on the possible health issues associated with the use of Roundup, the Monsanto herbicide. Quite a few genetic crop modifications are done to make seeds resistant to Roundup so farmers can spray crops with Roundup to get rid of weeds without harming the crops. The concern with those studies is that farmers are increasing their use of the insecticide because they have Roundup resistant crops – not that the GMOs themselves are actually causing health problems.

Many consumers continue to be concerned about the dangers of GMOs and point to other studies that indicate problems. Here are four of those studies:

1. Seralini’s study, which was published first in the “Food and Chemical Toxicology” journal, then retracted and finally republished in another journal, “Environmental Sciences Europe,” found tumor growth and significant disease in rats that ate genetically modified corn, Project Literacy said.

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2. A study published in 2013 and done by Thailand’s Environmental Toxicology Program is widely quoted in anti-GMO literature. This study found that glyphosate, an ingredient of Roundup, may cause breast cancer to proliferate, according to information published by the National Institutes of Health. Many breast cancers see increased growth from estrogen, and it appears glyphosate could function like estrogen.

“These results indicated that low and environmentally relevant concentrations of glyphosate possessed estrogenic activity,” the study abstract said. “Glyphosate-based herbicides are widely used for soybean cultivation, and our results also found that there was an additive estrogenic effect between glyphosate and genistein, a phytoestrogen in soybeans. However, these additive effects of glyphosate contamination in soybeans need further animal study.”

3. A study by the British Medical Association, quoted by the Center for Food Safety, found that: “There should be a ban on the use of antibiotic resistance marker genes in GM food, as the risk to human health from antibiotic resistance developing in microorganisms is one of the major public health threats that will be faced in the 21st century.” The study examined the risk of using antibiotic resistance marker genes and whether doing so might increase antibiotic resistance in people.

4. The Center for Food Safety addressed concerns from several studies that indicated potential cancer issues with GMOs. “Along with its approval of GE foods, the FDA in 1993 also approved the use of genetically engineered recombinant Bovine Growth Hormone (rBGH), used to induce dairy cows to produce more milk.

At the time the FDA assured consumers that the milk was safe. Since then, however, regulatory bodies in both Canada and Europe have rejected the drug, citing numerous animal and human health concerns,” the site said. “Perhaps of most immediate concern for consumers is that research shows that the levels of a hormone called insulin-like growth factor-1 (IGF-1) are increased in dairy products produced from cows treated with rBGH.

The Canadians and Europeans further found that the FDA had completely failed to consider a study which showed that the increased IGF-1 in rBGH milk could survive digestion and make its way into the intestines and blood streams of consumers. These findings are significant because numerous studies now demonstrate that IGF-1 is an important factor in the growth of breast cancer, prostate cancer, and colon cancer.”

Special: GMO Foods: Are We Unknowingly Poisoning Our Families?


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