We are often told that there is a scientific consensus that GM (Genetically Modified) foods are safe to eat. A closer look at the evidence, however, shows that this claim is false. There is no such consensus – and a significant body of evidence shows that GM foods can be toxic or allergenic.
Some of this evidence is collected in the book I wrote with two genetic engineers, GMO Myths and Truths. Peer-reviewed, animal feeding studies show that a GMO (Genetically Modified Organism) diet can cause health effects such as immune responses, liver and kidney toxicity, and abnormalities in the gut, pancreas, and blood. No study finding a problem with a GM food or crop has ever been replicated. The standard response has been to sweep the findings under the carpet. In several cases, the researchers who carried out the experiments have been attacked in seemingly orchestrated smear campaigns. Some have paid with their careers and funding.
A smorgasbord of unethical practices
GMO industry does its own safety testing: GM foods are tested for safety before commercialisation by the same companies that stand to profit from their sale – a recipe for bias. Typically, such studies are conducted on rats for a maximum of 90 days, a small fraction of the rat’s natural lifespan of three years. This is too short a period to detect long-term health effects.
Even with these limitations, some industry studies have revealed problems in GM-fed animals. Monsanto’s tests with GM Bt maize were re-analysed by scientists, who reported toxicity in the liver and kidneys of the GM-fed animals. In trials commissioned by Mahyco, Monsanto’s Indian partner, rats fed GM Bt insecticidal brinjals suffered organ damage, according to epidemiologist Dr. Lou Gallagher, who analysed the studies. Gallagher commented, “Release of Bt brinjal for human consumption cannot be recommended given the current evidence of toxicity to rats in just 90 days and the studies’ serious departure from normal scientific standards.”
Nonetheless, similar Bt brinjals have been released in Bangladesh and sold unlabelled in markets. Now the Indian government is considering releasing a GM mustard, for which no thorough toxicity testing appears to have been done.
Few long-term studies: Adverse effects seen in short animal feeding studies with GMOs are often dismissed as unimportant, without scientific justification. The only way to know whether the effects matter is to extend the study length and see if initial changes develop into serious disease. This is hardly ever done. Many scientists have criticised the lack of long-term feeding studies on GM foods. One review stated that “serious debates” about effects found in long-term and multigenerational feeding studies remain. Another noted, “As these foods are new inventions, not much is known about their long term effects on human beings”.
GMO proponents claim that long-term feeding studies on GM crops abound. They cite an article that reviews supposedly long-term animal feeding studies on GM foods and concludes that they are safe. But many of the studies are not long-term, in that they only lasted for a small fraction of the animals’ natural lifespan. Some of the studies found problems in the GM-fed animals, which were dismissed by the review authors. And the authors used unscientific double standards to dismiss findings of toxicity from GM foods as unreliable, while findings of safety are accepted at face value!
The “trillion meal study”: Another scientific article was touted by one GMO proponent was the “trillion meal study” that proved GMOs are safe to eat. The article, co-authored by a former Monsanto employee, analysed 28 years’ worth of field data on 100 billion farm animals from before and after the introduction of GM feed in the USA. The authors concluded that there were no adverse effects from GM feed. Yet, the data was completely uncontrolled. There is no way of knowing how many animals ate GMOs, for how long, and in what proportion of their diet. Over 90% of the data were on 49-day-old chickens. These data tell us nothing about long-term health risks to humans or other mammals.
French agency confirms lack of long-term studies: The scarcity of long-term studies with GM foods has been confirmed by the French food safety agency ANSES in a review of the scientific literature for long-term studies on herbicide-tolerant GM crops, which make up over 80% of all GM crops. The agency found only two studies. One reported health problems in mice fed GM soybeans. Another found no problems in rats fed GM glyphosate-tolerant soybeans. However, the soybeans do not appear to have been sprayed with the herbicide in line with usual farming practice, as glyphosate was only found at the limit of detection. This is not normal, as GM glyphosate-tolerant soybeans have been found to contain high residues of glyphosate, a chemical that has been declared a “probable human carcinogen” by the World Health Organization’s cancer agency IARC (International Agency for Research on Cancer).
Herbicide cocktails: The issue of herbicide residues in GM crops will become increasingly problematic. Widespread spraying of GM crops with glyphosate herbicides has led to the spread of glyphosate-resistant superweeds. Industry’s answer has been to engineer GM crops to tolerate other potentially even more toxic herbicides, such as 2,4-D, an ingredient of Agent Orange. No proper toxicity testing has been carried out on these chemical cocktails.
Appeal to authority: GMO proponents often appeal to authority by stating that eminent scientific organisations agree that GM foods are safe. But this claim is fraudulent and misleading. Many of these bodies issued nuanced statements that do not suggest all GMOs are either safe or dangerous.
A statement (issued by the American Association for the Advancement of Science (AAAS), then headed by GMO promoter Nina Fedoroff, did claim that GMOs are safe and opposed mandatory labelling in the USA. But it was condemned by 21 scientists, including members of the AAAS, as “an Orwellian argument that violates the right of consumers to make informed decisions”. The scientists warned that the herbicides with which GMOs are grown “may induce detrimental health effects even at low exposure levels”.
Over 120 health-related organisations do not agree that GM foods are safe and/or support mandatory labelling. They include the American Public Health Association (APHA), the British Medical Association, and the Public Health Association of Australia. In any case, ‘expert’ opinion is only as reliable as the data on which it is based, and the data is inadequate.
What eminent scientists said
In 2015, over 300 scientists signed a statement titled, “No scientific consensus on GMO safety”, which was published in a peer-reviewed journal. The statement concludes, “The scarcity and contradictory nature of the scientific evidence published to date prevents conclusive claims of safety, or of lack of safety, of GMOs. Claims of consensus on the safety of GMOs are not supported by an objective analysis of the refereed literature.”
Attempts to marginalise these scientists by likening them to deniers of man-made climate change, are dishonest. The main connection between climate change and GMO safety is that corporate interests and their scientific allies have misled the public on both. And several prominent GMO lobbyists are also climate science deniers.
Americans as guinea pigs
It is often claimed that Americans have been eating GM foods for years with no ill effects. But this statement is scientifically nonsensical, as no epidemiological studies have been carried out on humans eating GM foods. What is known is that Americans have got markedly more sick since GM foods were introduced in the mid-1990s. Is there a link to GM foods? There is no way of knowing. GM foods are not labelled in the US, so any increase in disease cannot be traced back to them.
To paraphrase Jose L. Domingo of the Faculty of Medicine and Health Sciences at the Rovira i Virgili University in Spain, when it comes to health risks of GM foods, there are “many opinions, but few reliable data.”