Human exposure to genetically modified microorganisms through drugs, food additives and new GMOs poses serious risks to public health. A scientific review (Lerner et al., 2024) published in Microorganisms provides a stimulus for the reform of food and drug safety regulations. (1)
1) Gut microbiota under threat
Gut dysbiosis – that is, an imbalance in the composition and function of the microbiome (the community of beneficial microorganisms also known as ‘bacterial flora’) – is associated with the Western lifestyle (ultra-processed foods, primarily) as well as with several inflammatory, neurodegenerative, neurodevelopmental, infectious, metabolic, tumoral and autoimmune (AD) diseases.
A possible cause of microbiome imbalance is indicated by researchers in the introduction of genetically modified microorganisms into the human intestine. The advancement of harmful genes is made possible by horizontal gene transfer, which is the main mechanism of bacterial evolution. Researchers point to some examples.
2) Antibiotic and drug resistance
The mechanism of horizontal gene transfer allows the entry of microorganisms resistant to antibiotics, antimicrobials, phages (viruses that parasitize bacteria) and cancer drugs.
Multidrug resistance genes are also conveyed through contaminated and industrially transformed nutrients. The vectors are different. The authors of the study recall evidence on Lactobacillus reuteri, antibiotics and antibiotic residues in foods of animal origin.
‘The emergence of the resistome represents a global health threat driven by the increasing unnecessary use of antibiotics and anti-cancer therapies’, say the researchers, who wonder whether genetically modified microorganisms are screened for genes resistant to antibiotics and other drugs.
3) Genetically modified microorganisms in foods and probiotics
Genetically modified microorganisms are widely used, without consumers knowing.
The food industry uses them to produce vitamins, flavorings, enzymes and preservatives. The authors of the study dedicate an in-depth study to microbial transglutaminase, a problematic enzyme present in many industrial foods, but not declared on the label because it is classified as a processing aid.
3.1) Microbial transglutaminase
Microbial transglutaminase is a genetically modified enzyme with potential proinflammatory, immunogenic, allergenic, pathogenic and potentially toxic effects. It has recently been indicated as a potential inducer of celiac disease. (2) It is used as a glue to assemble surimi, sausages, yogurt, tofu and in gluten-free baked products.
3.2) Probiotics and antibiotic resistance
Probiotics, generally considered useful and safe, pose risks of significant side effects, such as antibiotic resistance.
In the engineered version, i.e. genetically modified, they show clinical benefits for intestinal inflammatory, infectious, tumoral and metabolic diseases. (3) However, the authors of the study point out, they could influence the composition of the intestinal microbiota, which is known to be crucial for human health.
3.3) Genetically modified plants
Genetically modified plants are proposed as a solution to increase agricultural production thanks to resistance to drought, parasites and crop diseases, and high doses of pesticides (glyphosate, first and foremost). However, there are risks for humans, animals and the environment, warn the researchers, according to whom genetically modified plants ‘can invade the microbiome or the human genome’.
3.4) Drug treatments
Insulin, growth hormones and vaccines are also produced (more cheaply) with genetically modified microorganisms.
In medicine, moreover, ‘recently developed techniques of bacterial-mediated drug delivery using genetically modified microbes are spreading with the aim of locally delivering recombinant therapeutic proteins to the human gut. They are often called live biotherapeutics, but they deliberately carry potential risks’, according to the researchers.
4) Imbalanced homeostasis and diseases
Genetically modified microorganisms are potentially involved in chronic human diseases characterized by deranged intestinal homeostasis. Namely:
– autoimmune diseases, such as type 1 diabetes, multiple sclerosis, celiac disease and psoriasis,
– neurodegenerative conditions. It is assumed that genetically modified microorganisms can potentially promote neuroinflammatory/degenerative diseases, related to dysbiosis, as we have seen, (4)
– metabolic diseases. All components of metabolic syndrome are related to a perturbed intestinal microbiome,
– allergies. Food allergy is highly related to intestinal dysbiosis,
– cancer induction. Horizontal gene transfer ‘occurs between prokaryotes and eukaryotes and microbes, viruses or fungi are related to human cancer induction. A recent example is the involvement of engineered E. coli Nissle 1917 in colorectal cancer. In contrast, prokaryotes are increasingly being reported as key players in cancer immunotherapy, applying engineered biotechnologies to combat the spread of metastases.
Since prevention is the most cost-effective way to fight cancer or other human chronic diseases, strictly regulating and controlling GEMs (genetically modified microorganisms, ed.) and avoiding the entry of MGEs (mobile genetic elements, ed.) into the human microbiome or genome are the most rewarding means to protect people from such morbid and deadly conditions.’
– neurodevelopment and behavior. Gut microbiota is a potential biomarker of the risk of mental and behavioral morbidities. Basically, gut eubiotic diversity and synergistic composition influence brain function, thus playing a vital role in emotional processing.
Several neuropsychiatric conditions are dysbiotic-dependent:
- Alzheimer’s disease,
- attention deficit hyperactivity disorder,
- amyotrophic lateral sclerosis,
- anorexia nervosa,
- bipolar disorder,
- generalized anxiety disorder,
- major depressive disorder,
- multiple sclerosis and schizophrenia,
- female and male infertility. Gut microbes also have potential causal effects on female and male fertility.
5) Primum non nocere
The authors of the study encourage regulators worldwide to adopt a more holistic and aligned approach to risk assessment and regulatory oversight of food ingredients, immune factors, enzymes and any category of food substances produced with GEM (genetically engineered microorganisms) that can enable safe and sustainable food choices and consumption by consumers. ‘It is important to remember that prevention is the most cost-effective strategy and that primum non nocere should be the focus’.
Marta Strinati
Footnotes
(1) Lerner A, Benzvi C, Vojdani A. The Potential Harmful Effects of Genetically Engineered Microorganisms (GEMs) on the Intestinal Microbiome and Public Health. Microorganisms. 2024; 12(2):238. https://doi.org/10.3390/microorganisms12020238
(2) Lerner, A.; Matthias, T. Microbial transglutaminase should be considered as an environmental inducer of celiac disease. World J. Clin. Cases 2019, 7, 3912–3914 DOI: 10.12998/wjcc.v7.i22.3912
3) Ma, J., Lyu, Y., Liu, X. et al. Engineered Probiotics. Microb Cell Fact 21 , 72 (2022). https://doi.org/10.1186/s12934-022-01799-0
(4) Marta Strinati, Dario Dongo. Direct Causal Relationship Between Gut Microbiota and Alzheimer’s, the Study. FT (Food Times). 4.1.24.
Professional journalist since January 1995, he has worked for newspapers (Il Messaggero, Paese Sera, La Stampa) and periodicals (NumeroUno, Il Salvagente). She is the author of journalistic surveys on food, she has published the book "Reading labels to know what we eat".
