If you think it’s difficult to find credible information on COVID-19, try searching for science-based information on genetic modified organisms (GMOs.) I recently received an email pitch for a protein supplement, and it made a very specific statement about GMOs that I was not familiar with:
The statement that GMOs can cause bowel hypersensitivity and inflammation seems testable, so I asked the manufacturer for evidence. The customer service representative that replied suggested that I do a Google search for “GMOs can create bowel hypersensitivity” to find out more. (Yes, that was their actual response). That choice of keywords gave disappointing results, so I undertook my own search to try to answer that question. It took me long enough that I felt it was worth documenting.
Attitudes about genetic engineering
GMOs have been a recurring topic at this blog since its inception, given the anti-science arguments that underpin much of the anti-GMO movement. Over the past year, however, most of the discussion on genetic engineering at this blog has been in studying their application in the development of COVID-19 vaccines and refuting some of the concerns about this technology. It has been fascinating to see the evolving public dialogue on the genetically engineered COVID-19 vaccines (Moderna and Pfizer) move from initial apprehension into being (at least where there is a choice) the most sought-after vaccines. Given the efficacy and safety profile of these vaccines, their use in hundreds of millions of people, and their role in ending the COVID-19 pandemic, it will be interesting to see what this does to general attitudes about genetic engineering and especially the anti-GMO movement, where there has been a persistent gap between public perceptions and the actual evidence.
What foods are GMO?
Protein supplements are among the most popular dietary supplements, taken by athletes and non-athletes alike. By far the most popular source of protein in these products is whey protein, which is a by-product of cheese manufacturing. Whey is cheap and most people can tolerate it well. Some people prefer non-whey-sources, and there are several other vegetable-based protein products that are used in supplements.
Not many individual foods are GMOs, but GMOs do end up in a lot of commercially-prepared food. The FDA has a helpful page that on GMO crops that notes that GMOs may be ingredients in many of the foods we eat, such as corn starch, corn syrup, canola oil, granulated sugar, and soybean oil. There are a small number of fruits and vegetables that can be purchased that are GMO, such as potatoes, summer squash, apples and papayas. Despite the relatively small number of GMO foods, many products are labelled “non-GMO”, even when there has never been a GMO version available (e.g., rolled oats).
So let’s take a look at the supplement above to first see if GMOs are even relevant, considering the ingredients:
- Soy protein isolate – most soy grown is GMO
- Pea protein concentrate – there are no GMO peas
- Cricket powder – crickets are not genetically modified
- Cocoa powder – there is no GMO cocoa
- Natural flavours – a vaguely-worded statement; presumably non-GMO
- Stevia – non-GMO
- Sea salt – there is no G to M in salt.
Given the ingredients, we can now look for evidence that GMOs, particularly soy, causes gastrointestinal hypersensitivity and inflammation.
GMOs and allergies
The original advertisement claims that GMOs can create bowel hypersensitivity and intestinal inflammation. This would be presumably be caused by some sort of immune response to a GMO protein (food allergens are usually proteins) that doesn’t occur with its non-GMO counterpart. These concerns go back over two decades, to research that found that a Brazil nut protein that was transferred into soybeans by genetic engineering caused skin test reactions to those with Brazil nut allergies. The product was never commercialized. Evaluating GMO products for allergic potential is a requirement for new GMO crops: The European Food Safety Authority has 2017 document titled “Guidance on allergenicity assessment of genetically modified plants” that provides a detailed explanation on how allergenicity is to be assessed.
I started my search by reviewing clinical practice guidelines and other references on the impact of diet on inflammatory bowel disease. I looked for guidance from major gastroenterology associations (USA, Canada, UK, Australia) and could find no reference at all to GMOs. Up-to-Date, a commonly used medical reference, doesn’t make any recommendation against GMO foods in the management of inflammatory bowel disease. Given there was no advice against GMOs, I was not optimistic that there was much to substantiate these claims.
My next step was to turn to the primary literature, where I searched pubmed.gov: first for papers on diet and inflammatory bowel disease, and then on GMOs and gastrointestinal effects. I looked for both systematic reviews, review articles, and clinical trials. A few papers stood out:
A 2008 paper from Nature Biotechnology, titled “Allergenicity assessment of genetically modified crops – what makes sense?” makes the following statement:
Furthermore, to date there is no documented proof that any approved, commercially grown GM crop has caused allergic reactions owing to a transgenically introduced allergenic protein, or that generation of a GM crop has caused a biologically significant increase in endogenous allergenicity of a crop.
This seemed like a pretty definitive statement, albeit from a review paper. A 2017 systematic review published in the Annals of Allergy, Asthma, & Immunology was the most comprehensive summary of the evidence. It concluded (bolding is mine):
Based on the data to date identified in this systematic review, we conclude that, in reference to the first query, GM products do not appear more allergenic than their conventional counterparts as determined by IgE binding studies in well-characterized sera from humans with allergy and animal models, case series of direct provocation and ingestion, and simulated digestion studies. These are methods approved by the World Health Organization for determining allergenicity of GM products. We did identify limited evidence that genetic modification, in some instances, resulted in the product having decreased IgE binding capacity in subjects with allergy compared with its conventional counterpart, which could indicate hypo-allergenicity, although this concept requires more robust study. It is important to emphasize that known allergens to an individual, be it in a GM form or conventional form, will still be allergenic in that individual and it should be avoided. This review also highlights that there is no evidence that eating GM products in individuals who are not allergic to conventional forms of those items would result in allergy or increase the risk of developing an allergy to that item.
For the second query, there were no animal or human studies identified that evaluated the effect of the consumption of GM products and the overall risk of developing a food allergy or other allergic disease. Thus, given no controlled studies and no proven medical evidence to support or refute an association between use of GM products and the development or risk of developing food allergies, no data outside the NAS report conclusion are available to evaluate this hypothesis. This would represent a knowledge gap where future study could be highly informative. In conclusion, although individuals with allergy should avoid conventional and GM forms of that particular food, GM foods do not appear to be more allergenic than their conventional counterparts, and no data exist that consumption of GM proteins causes allergy to develop to that particular food in individuals who are not allergic at baseline.
No evidence to suggest GMOs are more allergenic
Despite statements made by manufacturers of GMO-free products, there is no credible evidence to substantiate claims that GMO foods increase the risk of bowel hypersensitivity and inflammation of the intestines. Over 1,300 regulatory assessments of GMO crops from around the world have concluded that GMO crops are as safe as their conventional counterparts. Consumers may have different reasons for not wanting to purchase GMO-free foods, but fears about the potential for negative effects of GMOs on the gastrointestinal tract are unfounded.