2009
Rabia Hamid and Akbar Masood
Abstract
Lectins are carbohydrate binding proteins present in most plants, especially seeds and tubers like cereals, potatoes and beans. It is now well established that many lectins are toxic, inflammatory, resistant to cooking and digestive enzymes and present in much of our food and sometimes cause "food poisoning."
The global pattern of varying prevalence of diseases such as coeliac disease, autoimmune diseases, rheumatoid arthritis, obesity, cardiovascular disease and insulin dependant diabetes mellitus, suggests that some dietary factor specific to plant foods could initiate these diseases.
Of the food lectins, grain/cereal lectins, dairy lectins and legume lectins are the most common ones associated with aggravation of inflammatory and digestive diseases in the body and improvement of these diseases and/or symptoms when avoided.
Recent research has suggested that these lectins may effectively serve as a vehicle allowing foreign proteins to invade our natural gut defenses and cause damage well beyond the gut, commonly in joints, brain, skin and various body glands. With continued exposure of the gut by these toxic food lectins a persistent stimulation of the body’s defense mechanism in a dysfunctional manner occurs, which manifests as an autoimmune disease.
If the lectins in diet are causative in initiating all these diseases, it should be possible to identify the responsible constituents and modify or remove them so as to make the diet healthier. Here we present a brief account of lectin toxicity research and show how these proteins have become the focus of intense interest for biologists.
Conclusion
The subject of lectins is very broad and deserves more discussion. There are even some lectins that are beneficial to the body, such as those found in some species of edible snails, which may be capable of preventing the metastasis of cancer cells (Schumacher et al., 1994). The involvement of lectins in our health and their relationship to degenerative disease is still an emerging science. Studies performed on animals will continue to be the model in the future for the study of lectins.
The glycosylation of the human gut is basically similar to that of higher animals and it may be confidently predicted that the effects of dietary lectins will have similarities in both humans and animals. In short, dietary lectins, by their chemical reactivity with cell surface receptors on the intestinal epithelium, are metabolic signals for the gut and are capable of modulating immune and hormone functions (Pusztai, 1993).
Studies in laboratory animals have shown that ingested lectins have a wide range of effects that might be relevant to human diseases. These include changes in the differentiation (Jordinson et al., 1996) as well as the proliferation of intestinal and colonic cells (Ryder et al., 1994a, b).
Dietary lectins may also affect the intestinal flora (Pusztai et al., 1993) and bacterial lectins in turn can activate intestinal cells (Grant et al., 1995) which might be an important contributory factor in the prevalence of many diet associated diseases.
