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A new study came out last month out of France. In it, researchers found that rats on diets consisting of 11%, 22%, and 33% Roundup-resistant genetically modified corn developed far more mammary tumors than control rats on non-GMO corn diets. GMO diet rats died earlier and in greater numbers. Why is this study notable amidst all the other studies that seem to show the safety of GMOs? Well, it’s one of the few long term GMO feeding studies, lasting a full two years, which, to a rat, is the equivalent of 60 of our human years. The other safety studies which found no evidence of toxicity in GM foods tend to last just 90 days, or 15 rat years. In other words, the French study studied rats over the course of an entire lifespan, whereas other studies have looked at rats for a relatively brief snippet of their lives. Cancer generally develops over a lifetime, as you probably know, so this would appear to be more relevant to human health than the shorter trials.
Of course, there has been a huge outcry against the study and its author. Critics have said the sample sizes (ten rats per group of each sex) were too small, but judging from the official guidelines of the Organization for Economic Co-Operation and Development (OECD), which states that oral toxicity experiments using rats must use at least 20 animals per group (10 males and 10 females), the French study was just doing what other GMO studies have done. Even if the sample sizes are inadequate, couldn’t that be rectified by running a longer, larger, later study to attempt to replicate its findings?
Obviously, genetically modified organisms (GMOs) are a testy subject, and people from both sides of the argument make articulate, seemingly logical points about why the other side is completely and utterly wrong. I don’t claim to have the answer either way, but hopefully this post will help you make a decision that works for you.
To date, it’s true that there exists no conclusive hard evidence that GM foods are dangerous to people. There are no human feeding trials, and, because GM foods aren’t labeled (at least in the United States) and people don’t know what they’re eating enough to give an accurate account of their food intake, epidemiological studies on the effects are impossible to conduct. You can’t ask people how often they’ve eaten GM foods over the past ten years if the average person doesn’t even know what GMOs are. There are some animal studies, like the one mentioned above, but there have been mixed results, with some independent studies showing potentially problematic differences in health outcomes between GMOs and non-GMOs, and industry studies showing no significant differences.
Personally, I’m not so worried about a fish gene being put into a tomato, or insect genes in strawberries on their own merits. I’m worried about whether that particular gene codes for the production of a lectin that might harm the person that eats the crop. I’m worried about the amount of Roundup that farmers will therefore spray on the crops, having been given carte blanche to use gallons of the stuff. I’m worried about the Roundup-resistant weeds and Bt-resistant bugs that are popping up in response to all the Roundup being applied and Bt-crops being used. I’m worried about the more toxic herbicides and pesticides being used to take care of these new superweeds and superbugs. Didn’t a wise man once say that “Life finds a way“? Though he was a fictional character talking about the unintended consequences of using frog DNA to “plug” the holes in dinosaur DNA, I think he was right.
A lot of people are worried about the potential of unintended effects to arise. I think John Hagelin said it well in his statement to the EPA:
Numerous eminent molecular biologists recognize that DNA is a complex nonlinear system and that splicing foreign genes into the DNA of a food-yielding organism can cause unpredictable side effects that could harm the health of the human consumer. Yet, the genetic engineering of our food — and the widespread presence of genetically altered foods in American supermarkets — is based on the premise that the effects of gene-splicing are so predictable that all bioengineered foods can be presumed safe unless proven otherwise.
Take a recent example of transgenic modification applied to cassava, a staple starchy tuber for millions (if not billions) of people across the globe. This is the stuff that’s high in cyanide, requires extensive processing to remove said cyanide, and has an extremely paltry protein content (the lowest of all staples foods, in fact). Transgenic insertion of a gene into the plant increased the protein content four-fold and reduced the cyanide content by up to 55%, turning a decent staple into a fantastic, protein-rich one — at least on paper. The increased protein came from a novel chimeric storage protein called zeolin, which was cobbled together using zein (from corn) and phaseolin (from beans, used in “carb blocker” products). For someone who relies on cassava for, well, everything, the increased protein is welcome and perhaps even necessary. But zein (also known as corn gluten) is a prolamine, a type of plant protein that many people have trouble digesting, as well as an herbicide in its own right (PDF). Wheat gluten is another (in)famous prolamine. Phaseolin is a “carb blocker”; it literally reduces your absorption and digestion of glucose. The zeolin may not have the same properties as zein or phaseolin, and even if it did, those properties may be worth it if it’s the best source of protein in the area, but I think this example shows that genetic engineering has the potential to have unintended effects.