Lectins, the carbohydrate binding proteins present in most plants, could be the cause of many chronic diseases, according to British allergist David Freed.

Lectins are known to be toxic and inflammatory and aren't readily destroyed by enzymes or cooking. But from his research, Freed has concluded that these proteins are able to get past the gut wall and deposit themselves in distant organs.

According to Freed, recognition of the role which lectins play in ill health could drastically alter the way we approach healthcare. For instance, the lectins present in tomatoes, peanuts, wheat and potatoes have been implicated in autoimmune dysfunction. Specifically, those in wheat and soya are potential causes of insulin-dependent diabetes.

Another suspect in lectin disease is rheumatoid arthritis (RA). In diet responsive RA, one of the commonest triggers is wheat. The wheat lectin binds to the necessary sugar N-acetylglucosamine and makes it unavailable to RA sufferers. This may be one reason why some sufferers have found glucosamine helpful as an anti arthritic.

Lectins can also strip away the mucous coating of the small intestine, leaving it open to bacterial and protozoal infection. They can also stimulate stomach acid secretion. Not surprisingly, they have also been linked in research to peptic ulcer.

The final and most worrying problem is that lectins can be powerful allergens (BMJ, 1999; 318: 1023-4).