The resounding claim of GMO proponents is that GMOs have been proven safe. Some scientists are quite emphatic about this, such as Dr. Pamela Ronald from UC Davis, who says:
"Genetically engineered crops currently on the market are as safe to eat and safe for the environment as organic or conventional foods."
Dr. Roger Clemens, from the USC Department of Pharmacology, also weighs in, saying:
"They're tested and evaluated in voluminous documentation that would fill this backyard. We don't know of any health risk at this particular time."
Dr. Clemens also defends food additives, sugar, and processed foods, but I digress...
The problem with concluding that GMOs are safe is that the argument for their safety rests solely on animal studies. These studies are offered as evidence that the debate over GMOs is over. Nothing could be farther from the truth.
Animal studies have value in that if something demonstrates harm in animals, it will also likely cause harm in humans. Although some animal studies have found harm from a GMO diet, these hotly debated studies are not the point of this article. The point is, if an animal study does not find harm with a particular substance, it could still cause harm in humans.
A good example of this is what's happened with artificial sweeteners. The U.S. Food and Drug Administration (FDA) approved artificial sweeteners for use using animal toxicology studies. Once these sweeteners were added to the food supply -- and labeled as such -- scientists were able to do epidemiological studies (also called observational studies) in humans. Several of these studies found that artificial sweeteners are linked with negative health effects.
The Framingham Observational Study found that both diet and regular sodas are associated with metabolic syndrome (a constellation of symptoms such as abdominal obesity, high blood sugar, elevated triglycerides, and high blood pressure that are linked to an increased risk of heart disease). Yet another study revealed that diet sodas may increase the risk of diabetes. The Nurses' Health Study found that two or more diet sodas a day were associated with a 30 percent decrease in kidney function over time. Yet none of these results were found in animal studies. Clearly, there are still many unknowns about the impact of artificial sweeteners on human health.
Dr. Walter Willet, from the Harvard School of Public Health, sums things up nicely by saying:
It's difficult to make blanket statements about the safety or risks of low-calorie sweeteners because all are very different in their structure and how they work in the body. The reality is, some studies have been done in animals, but we really don't have good long-term data on humans with any of these.
And the same is true for GMOs.
Considering that biology, gene regulation and expression, and the impact of a substance on a particular gene can vary so much, it makes perfect sense that animal research is not the best model to determine the long-term health effects of GMOs in humans.
In fact, Dr. Ralph Heywood, past scientific director of the Huntington Research Centre (U.K.), found that the agreement between animal and human toxicology tests is below 25 percent. He has determined that there is no way of knowing what kind of toxic effect will show up in animals versus humans.
Instead of animal studies, epidemiological studies have been identified as the best way to verify the effects of a substance and its risk to humans.
Ultimately, we need GMO labeling so we can do the epidemiological studies that are essential to determine their risk. Without long-term data -- in humans -- no one can make the claim that GMOs are proven safe.