Those who claim that GM foods are unsafe are being selective with the data, since many other studies show safety
Studies that claim safety for GM crops are more likely to be industry-linked and therefore biased
“In a study involving 94 articles selected through objective criteria, it was found that the existence of either financial or professional conflict of interest was associated [with] study outcomes that cast genetically modified products in a favourable light.”
– Diels J, et al. Association of financial or professional conflict of interest to research outcomes on health risks or nutritional assessment studies of genetically modified products. Food Policy. 2011; 36: 197–203
When it comes to hazardous products, the bias of industry-sponsored or industry-linked studies is well documented. Every time industry-linked studies are compared with studies on the same product from the independent (non-industry-linked) scientific literature, the same verdict is reached: industry studies are biased towards conclusions of safety for the product.
The best known example is tobacco industry studies, which successfully delayed regulation for decades by manufacturing doubt and controversy about the negative health effects of smoking and passive smoking.53 More recently, studies sponsored by the pharmaceutical and mobile phone industry have been shown to be more likely to portray their products in a favourable light than non-industry-funded studies.54,55,56
The case of GM crops is no different. Reviews of the scientific literature on the health risks of GM foods demonstrate that the studies that show safety are more likely to be industry-linked and are therefore inherently biased:
- A review of 94 published studies on health risks and nutritional value of GM crops found that they were much more likely to reach favourable conclusions when the authors were affiliated with the GM industry than when the authors had no industry affiliation. In the studies where there was such a conflict of interest, 100% (41 out of 41) reached a favourable conclusion on GMO safety.57
- A literature review of GM food safety studies found that most studies concluding that GM foods are as nutritious and safe as non-GM counterparts were performed by the developer companies or associates.58
In spite of the fact that industry-linked studies have been shown to be biased, approvals for GM crops are based solely on such industry studies.
Another tactic used by GM proponents is to point to lists of studies which they say show that GM foods are safe, but which actually show nothing of the sort. An example is on the GMO Pundit blog site, which claims that the over 400 cited studies “document the general safety and nutritional wholesomeness of GM foods and feeds.”59
But closer examination reveals:
- Most of the studies cited are not safety studies on GM foods. In other words, they are not animal feeding studies that look for health effects in animals fed GM foods. Some are compositional studies that compare the levels of certain major nutrients, such as fat or protein, in a GM crop with levels in a non-GM crop. Others are feed conversion studies that measure how efficiently a livestock animal converts GM feed into a food product, such as meat or milk.
- Many of the studies, on examination of the actual data, show problems with GM foods. These include unintended differences in a GM food compared with the non-GM counterpart and harmful effects in animal feeding trials. In fact, some of these studies are cited in this report as evidence that GM foods are not safe. Readers are encouraged to examine the original studies, where available, and form their own conclusions.
In contrast with these lists on GM proponents’ websites, the two peer-reviewed literature reviews cited above identified and evaluated the studies that specifically examine the food safety and nutritional value of GM foods. Their conclusions were clear: industry-linked studies are more likely to conclude safety, whereas independent studies are more likely to find problems.57,58