Impact of Genetically Modified Organisms (GMOs) on Health

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The GMOs are not, by definition, not natural and could then have potential impacts on our health. In 2002,  Robert Naquet (CNRS, chairman of the Ethics Committee in Life Sciences) reviewed  the potential risks for the consumer and the means used to evaluate them, principles that are still relevant today. 

The first stated issue of GMO research is both health and nutrition. The theme of this discussion focuses on “GMOs” as they are perceived in the general public, their safety or their dangers for the consumer that we are. The doctor I am, can not ignore their immediate or potential utility in other areas of health. I will be brief but can not help but briefly mention some examples showing their interest in the diagnosis , treatment and creation of vaccine products.

GMOs and progress of medical research

A French world first in gene therapy was conducted in April 2000. Children with severe immune deficiency were able to get out of the protective bubble in which they lived, thanks to gene therapy. One year after the introduction of a drug gene into the cells of their bone marrow , these children found a completely normal and functional immune system . Unfortunately, since the intervention, four of them have developed leukemia that has proven fatal for a child. The others are healed and live a normal life.

Drugs are already produced and marketed by genetically modified bacteria . Growth hormone(previously extracted from pituitaries taken from cadavers, with the risk that one of them is known to carry Creutzfeld – Jacob disease), and insulin may be mentioned. the importance of which is well known in the treatment of diabetes .

Complex work is being done to synthesize drugs by successive introductions of foreign genes into organisms, such as yeast . Changes genetic certain mammals used to obtain molecules with therapeutic interest, for example, through milk. Other plants, such as transgenic tobacco , produce human hemoglobin . 

Research is underway for the expression of vaccines in fruits .

GMOs and consumer health

The ingestion of GMO may have health benefits, such as golden rice. There is in the rice, located in the shell of the seed, a provitamin A necessary for the vision. Some populations (several million), especially in Asia, ingest, as single food, pruned rice (without the hull) resulting in vitamin A deficiency responsible for several thousand individuals, significant and irreversible visual disturbances. The addition, by transgenesis , of provitamin A in rice albumen justifies the current efforts in this area.

However, the ingestion of products containing GMOs or GMOs has created and still creates uncertainty about the presence of an undesirable substance that could be dangerous for itself or for the animal. This questioning is normal because research on this type of GMO is intended to give plants resistance to pathogens and tolerance to specific herbicides . What will produce on our body the ingestion of such products?

The projects focus on improving the quality of plants in agronomic and nutritional terms. Nutrients are missing from some plants that are the basis of food for some populations. The ultimate goal is to improve the nutritional quality of these plants, which would act on human health (as seen for golden rice). Is it in each case a reality or a fiction maintained by multinationals?

Questions that are not always possible today to answer in a precise way, but to which the researchers work by attacking the problems from various angles:

  • the assessment of the possible effects of genetically modified foods on human nutrition;
  • the degradation of GMOs during digestion ;
  • what are the potential dangers? ;
  • the risks of allergy ;
  • potential effects of using plant viral DNA on human health;
  • food safety assessment of genetically modified (GM) products.

Evaluation of the possible effects of genetically modified foods (GM) on human nutrition

Research is underway for the optimal assessment of the effects that such food types may have.

This research should take into account:

  • the effects of small changes that would be due to the consumption of GM foods, in a balanced diet;
  • potential health effects of subgroups of the population, such as the subgroup that would have a particularly high consumption of this type of food;
  • the composition of this new type of food, its preparation and its expected role in the diet. The new GM food is thus compared to the traditional food, and any difference between the two is evaluated;
  • nutritional implications that are assessed at normal and maximum consumption levels;
  • effects of storage, processing, cooking on the nutrient composition of these GM products;
  • physiological and morphological characteristics of infants, children, the elderly, pregnant or breastfeeding women , and people with chronic diseases.

Research should be done first on animals (observation of changes in the liver , kidneys , lungs , brain and cardiovascular organs), before studying their effects in humans (measurements of the general health, development and well-being of people). Regulations on the labeling of these GM foods for nutritional improvement are being negotiated.

The degradation of GMOs during digestion

In food , GMOs come in two main forms:

  • Fresh products (fruits and vegetables): modified genes are directly subjected to digestive enzymes ;
  • Processed or derived products ( tomato concentrate , flour, sugar …): the manufacturing process can denature the molecules (transgenic or not).

The degradation of GMOs as of all foods, is done in two ways in the digestive tract :

  • mechanically by chewing, stirring in the stomach ;
  • chemically under the effect of digestive enzymes that degrade foods and transform them into simple compounds ( amino acids , nucleic acids , sugars …).

After these chemical and mechanical treatments, it is very unlikely that a molecule will remain functional in the body after digestion. To find out if all these degradations are sufficient to destroy a transgenic molecule, gastric and intestinal survival tests have been proposed. These pose major practical problems:

  • you need a lot of molecules to do these tests. But it is difficult to extract enough from the plant;
  • moreover, the modifications of the proteins , which one could observe, depend on the host , which can modify their toxicity ;
  • Finally, in performing these tests, we do not always take into account people with reduced digestive capacity (elderly people, children) who are more sensitive to poisoning.

What are the potential dangers?

Many insect resistance genes work by disrupting the digestive functions of the parasite . Some of them, such as enzymatic inhibitors , are resistant to hydrolysis in the digestive tract of the insect. One can imagine that by the same mechanism they could induce similar effects in Mammals:

  • a disturbance of the digestive system;
  • a modification of the toxicity of the plant. It is possible that the introduced gene does not produce a toxic substance, but that it disturbs the functioning of the plant, which could lead to the production of a new toxic substance or the increase in the production of certain toxic proteins. already existing (tomato tomato, potato solanine );
  • an increase in the resistance of microorganisms to antibiotics would be another potential hazard for humans.

The risks of allergy

Currently, 1 to 2% of adults and 6 to 8% of children are considered to be allergic to one of eight allergenic food groups ( crustaceans , nuts, eggs, fish , milk, peanuts, soy , wheat ). Can GMOs increase these numbers?

We can not predict how many individuals will be allergic to new molecules.

However, we can take some precautions:

  • compare the new molecules with already known allergens;
  • do not use plants known to be allergens as a source of new genes;
  • ensure rigorous standards, while recognizing that zero risk does not exist;
  • do allergy tests on animals.

Potential effects of using plant viral DNA on human health

There are two types of plant viral DNA sequences commonly used for the construction of genes to be inserted into GM plants:

  • the promoter, which is necessary to prime the expression of the inserted gene and which is usually the derived promoter of cauliflower mosaic virus ;
  • the sequence including the genes that code for the creation of the outer protein envelope of viruses, and that once expressed in the host plant, will give proteins that will interfere with other viruses infecting the plant.

This thus confers resistance to the host plant. This introduction of viral DNA into a plant was not done without questioning: it has been suggested that the introduction of viral DNA sequences into GM plants could produce new viruses by recombination , or “genetic exchange”, with:

  • either residues of viral DNA sequences that are present in the genomes of all species ;
  • either natural animal or plant viruses that are infectious.

There are, however, natural barriers to recombination and especially genetic barriers between the plant and animal worlds. It is virtually impossible for a plant virus to infect an animal and therefore humans. It is said that genetic modification could activate transposable elements that are already present in the human genome.

The transposable elements being mobile, they are able to insert into the host genes and thus to damage them, which could induce pathological effects such as tumors. There is evidence that these transposable elements (which account for up to 40% of the total DNA of animals and higher plants) have been repeatedly transferred between different species during evolution. Thus, it seems unlikely that the accidental mobilization of transposable elements during the construction and use of GM plants can have a significant impact on human, animal or plant biology, when compared with what normally happens in natural conditions. The conclusion of this study is that the risks of GM plants to human health are negligible.

Food Security Assessment of Genetically Modified (GM) Products

In 1993, the  Organization for Economic Co-operation and Development (OECD) published the findings of a research group that introduced the notion of equivalence in substance in order to develop ways of assessing food safety. GM. This notion says that GM foods can be proven equivalent to natural foods. GM plants could thus be evaluated as “healthy” for human health by comparing them with their conventional analogue. The natural plant is thus considered as the control. The FAO / WHO identifies three results of such a comparison between GM food and traditional food, which are thus used for the health evaluation of a GM product:

  • GM food can be considered toxicologically and nutritionally equivalent in substance to conventional food. For example, the oil from a GM plant is essentially equivalent to the oil of the same natural plant, because in the oil there is no trace of DNA or detectable proteins. If such equivalence can be shown for GM foods, no further health assessment is needed;
  • it is possible that there is equivalence in substance apart for some differences. Sometimes GM foods include compounds deliberately introduced by genetic modification. In this case, the health assessment is limited to examining the possible effects of these differences on plants or humans;
  • the GM product can be considered as not substantially equivalent. This GM product should be subject to a precise health assessment. For the moment, the health assessments of GM products take into account the genetic modification procedure (DNA sequence and integration site in the host plant), the nutritional parameters (phenotypic information and chemical composition), the risks of allergy. and toxicological evaluations.

Dr. Kimberly Seltzer

Postdoctoral Scholar, UC Berkeley Research Assistant, MIT

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