Available data do not support the hypothesis that consumption of genetically-engineered (GE) foods has caused higher rates of obesity, raised the risk of type II diabetes, led to greater prevalence of chronic kidney diseases, or increased the incidence of cancer, a committee of the National Academy of Sciences, Engineering and Medicine (NAS) has concluded.
The Academy has published the report on ‘Genetically-Engineered Crops: Experience and Prospects,’ after reviewing existing studies, talking to 80 diverse speakers and considering 700 comments received from members of the public.
NAS is a private, non-governmental institution set up in 1863 by a law signed by President Abraham to advise the United States on issues related to science and technology.
The committee said the design and analysis of many animal feeding studies were not optimal but there was sufficient evidence in the literature that animals were not harmed by eating GE-derived foods. It is difficult to assess health effects of any food, whether produced through conventional breeding or in conjunction with GE, the committee said. Analysis of long-term data on the health and feed-conversion efficiency of livestock spanning time before and after the introduction of GE foods found no adverse effects.
Biologists have used genetic engineering of crop plants to express novel traits since the 1980s. But only two traits – insect resistance (IR) and herbicide tolerance (HT) – were in widespread use in 2015, the committee said.
Most GE traits and crop varieties that have been developed are not in commercial production. Those with insect resistance and herbicide tolerance were available in fewer than 10 crops in 2015 and covered 12 percent of the world’s planted cropland. The most commonly grown GE crops with one or both traits mentioned above were soybean (83 percent of soybean hectares), cotton (75 percent), maize (29 percent) and canola (24 percent).
GE crops were planted globally on 180 million hectares in 2015; over 70 million ha in the US, over 90 million ha in Brazil, Argentina, India and Canada, and the rest across 23 countries.
Maize, soybean, cotton, canola, sugar beet, alfalfa, papaya, squash, poplar, brinjal, potato and apple are the currently grown GE crops.
The committee concludes that GE soybean, cotton and maize have generally had favourable economic outcomes for producers. But these differ depending on pest abundance, farming practices and agricultural infrastructure. Crops with insect-resistant traits derived from the soil bacterium Bt generally decreased yield losses and the use of insecticides.
In some cases, widespread planting of these crops decreased the abundance of specific pests in the landscape and contributed to reduced damage even to crops that did not have the Bt trait. Planting Bt crops tended to result in higher insect biodiversity on farms than planting similar varieties without the Bt trait that were treated with synthetic insecticides.
However, in locations were resistance management strategies were not followed, as in India, damaging levels of resistance evolved in some target insects (namely, pink bollworm).
Herbicide-tolerant crops sprayed with the weed killer glyphosate often had small increases in yield compared with those without the trait. In farm-level surveys, the committee did not find lower plant diversity in fields with HT-crops. In areas where planting of HT crops led to heavy reliance on glyphosate, some weeds evolved resistance and present a major agronomic challenge, the committee said. Sustainable cultivation of Bt and HT crops will require use of integrated pest and weed management practices, it added.
The committee has commented on the alleged carginogenicity of glyphosate as well. In 2015, the International Agency for Research on Cancer (IARC) of the World Health Organization had changed its classification of glyphosate from possibly carcinogenic to humans to probably carcinogenic to humans. But, the committee says, the European Food Safety Authority concluded after the report was released that glyphosate was unlikely to pose a cancer risk to humans. Canada’s health agency found that current food and dermal exposure to glyphosate, even in those who worked directly with it, was not a health concern as long as it was used as directed in product labels . The US Environmental Protection Agency found that glyphosate did not interact with estrogen, androgen, or thyroid systems. Thus there was disagreement among expert committees on the potential health harm that could be caused by the use of glyphosate on GE crops and in other applications.
Overall, the committee found no conclusive evidence of cause-and-effect relationships between GE crops and environmental problems. But assessing long-term environmental change was complex and difficult for definitive conclusions to be reached. The decline in overwintering monarch butterfly populations was a case in point. Studies and analysis of monarch dynamics reported as of March 2016 did not show that suppression of milkweed by glyphosate was the cause of monarch declines, it said. But there was as yet no consensus among researchers that increased glyphosate use was not at all associated with decreased monarch populations. Overwintering monarch populations had increased moderately in the last two years. Continued monitoring will be useful, the committee said
The committee found no evidence of differences between the data from the United Kingdom and Western Europe, where diets contain much lower amounts of foods derived from GE crops, and the data from the United States and Canada in the long-term pattern of increase or decrease in specific health problems after the introduction of GE foods in the 1990s.
The committee found no evidence of Bt transgenes or proteins in the milk of ruminants. Consuming dairy products should not lead to exposure to Bt transgenes or proteins, it declared.
The data did not indicate that genetic diversity among major crop varieties had declined since 1996 after the widespread adoption of GE crops in some countries, the committee said.
GE crops have benefited many farmers on all scales, but genetic engineering alone cannot address the wide variety of complex challenges that farmers, especially smallholders, face, it said.
The committee said national regulatory processes for GE crops vary greatly and mirror social, political, legal and cultural differences among countries. These, in its view, were likely to continue and pose trade problems. Emerging genetic technologies have blurred the distinction between genetic engineering and conventional plant breeding to the point where process-based regulatory systems are hard to defend, it added. The committee has recommended that new varieties ─ whether GE or conventionally bred ─ be subjected to safety testing if they have novel intended or unintended characteristics with potential hazards. GE crop governance should be transparent and participatory.
(Top photo: Genetically-engineered corn in the Philippines. Courtesy:ABLE-AG)