Allergy tests on GM corn and soy (1/9/2005)

Portuguese researchers gave skin prick allergy tests to at a group of allergy-prone adults and children to see whether they reacted differently to GM corn and soy than to conventional varieties. They found no differences in their reactions (item 2).

GM Watch editor, Claire Robinson, comments on the findings.


I have several points to make on this study.

1. Skin prick allergy testing is not generally considered to be a reliable way to detect food allergies; it is more commonly used to detect respiratory allergies to airborne substances. (For confirmation of this from a highly orthodox source, see the National Institutes of Health website: )

It is common that a person shows no reaction to a skin prick test of a substance and yet when exposed in 'real life', reacts to that substance. And conversely, it is common that a person has a strong skin reaction to a substance and has no apparent reaction when exposed in 'real life'. I am a case in point - I have no reaction to milk from skin prick testing but cannot tolerate it in real life; and I have a strong skin prick response to tomatoes but can eat them with impunity!

2. For the above reasons, allergists recommend elimination diets as the best way to detect food allergies. The food is eliminated for the diet for several weeks and then introduced; the patient's responses are monitored.

3. Commonly, all a skin prick test will show by way of positive response is a localized inflammatory reaction on one organ, the skin. In rare cases, after a skin prick test, a systemic reaction will take place, with other bodily organs/systems becoming involved, and the patient gets asthma or stomach pains depending on their individual susceptibility.

But this is the exception. In most cases of skin prick testing, a positive response will be confined to the skin. However, in real life exposure to the same allergen, a positive response will involve many bodily organs and systems. So a substance that during skin testing only produces an inflammatory response on the skin, could in real life produce an inflammatory response in other organs too. It is this response in other organs that we need to worry about. After all, no one died of a weal on their skin, but people do die of anaphylactic shock when the respiratory organs are affected.

4. Given the above, the positive skin prick response found in allergic people to both GM foods and their non-GM counterparts is only the very beginning of the investigation. It shows only that there is an inflammatory response on the skin with the GM and non-GM food. This may mean very little, as with me and tomatoes, or it may mean much. The next step would be to test each of the foods in elimination / re-introduction diets and see if the GM foods (compared with the non-GM foods) affect the other, more important, bodily organs as well as the skin. Such testing would, I suspect, involve at least two stages: the patient-reported and physician-observed changes after the food is re-introduced after a period of abstinence; and then detailed examination of tissues. I do not know if the tissue examination is possible in live humans! - it's usually only done in animals, but perhaps some form of blood test, biopsy or colonoscopy examination is possible (unfortunately the last two are invasive and carry risks). I have been told that animals do not respond to allergens as humans do, so animal testing may not be the way forward for allergy testing. BUT animal testing does show up tissue damage, as was seen in Dr Arpad Pusztai's experiments. So perhaps a combination of patient-reported and physician-observed changes for the allergies, and then animal testing for toxicology/anti-nutrient effects, would serve to test for safety of GM products.

5. Given all the above, it's obvious that the allergy tests as described below show virtually nothing.

2.No allergy problems for GM soy and corn

NEW YORK - Despite concerns from some critics of genetically modified crops that the foods may raise consumers' risk of allergic reactions, a new study finds no evidence that this is the case.

The study, by researchers in Portugal, adds to evidence that several widely used strains of GM corn and soybeans do not promote food allergies.

All of the products - three corn strains engineered to resist certain crop-ravaging insects and a soybean variety that tolerates a common weed killer - have been on the market since the 1990s.

The new study looked at a group of allergy-prone adults and children who had consumed products containing the biotech foods at some point since their approval in Europe.

The researchers, led by Rita Batista of Portugal's National Health Institute in Lisbon, gave 77 study participants allergy tests to see whether they reacted differently to the GM corn and soy than they did to conventional varieties.

None of them did, according to findings published in the Journal of Allergy & Clinical Immunology.

Much of the corn and soybeans grown in the US is transgenic, meaning a gene or genes has been inserted into the genome of the plants to give them a desired trait.

European countries have been much slower to embrace the technology, as consumers there are far more wary of what some call "Frankenfoods." One of the concerns some critics have raised is the potential for allergic reactions to the foreign proteins in GM foods; if a gene were transferred from an allergenic source, that could make the resulting GM food more likely to trigger allergies.

The products tested in the current study included two manufactured by US biotech giant Monsanto, a corn variety known as MON 810 that is engineered to resist certain insects, and Roundup Ready soybeans, which are designed to tolerate the company's Roundup weed-killer.

The researchers also tested two pest-resistant corn varieties made by the Swiss firm Syngenta and one herbicide-tolerant strain manufactured by Germany's Bayer Crop Sciences. None of these products, the study authors note, contain genes derived from sources known to trigger allergies.

Batista and her colleagues used skin prick tests to place protein extracts from the corn and soy strains under participants' skin. They found that though adults and children with a history of sensitivity to corn and soy had skin reactions to the extracts, their reactions were the same to GM and non-GM varieties.

"The transgenic products under testing seem to be safe in terms of allergenic potential," the researchers write. They do, however, call for routine postmarket testing to monitor the possibility of allergic reactions to GM foods.



Back to the Archive