Evidence of the specific harm genetically modified (GM) foods can cause is finally beginning to surface.

In a recent study of rats fed on GM potatoes, damage to the small intestine was detected. Researchers in Aberdeen found that potatoes modified to express the Galanthus nivalis lectin, or GNA, caused an increase in mucosal thickness of the stomach, when compared with those fed on potatoes which had not been genetically modified.

The GM-exposed rats also had a more pronounced immune response to the diet and an alteration in the intestine. The authors suggest that any plant containing lectins, such as the GM soya bean, may have the potential to produce these same symptoms.

Although these results are preliminary and concern animal studies, which may not apply to humans, they open the door for more comprehensive research into the adverse effects of GM foods. Lectins are increasingly being considered for incorporation into GM foods to protect them from attack by insects.

Previous research has shown that other types of lectins, such as those found in peanuts, can damage the gut. Another paper in the same journal analysed the effect of GNA on human cells and suggested that the results found in rats may also be relevant to humans (Lancet, 1999; 354:1354-5).