**11. Lectins in edible plants**

Many lectin-containing plants are common constituents of the diet of humans and farm animals. Since lectins are known to act on cells in a variety of ways, such as agglutination, mitogenic stimulation and killing, and they are often resistant to heat and proteolytic enzymes, including those of intestinal bacteria, the effects of consumption of these proteins deserve special consideration. For many years it has been known that they occur in legumes such as soybeans, kidney beans, lima beans, mung beans, lentils, garden peas and peanuts that are a major food source for humans and animals in one part of the world. Although lectin containing foods are frequently consumed in cooked or otherwise processed form, such treatments may not always be adequate to completely inactivate the lectins present. Thus, lectins have been detected in roasted peanuts (Wang et al., 1999). Slow cooking of beans, without boiling, does not always eliminate lectin activity as observed with kidney beans cooked for 11 hr at 82 oC or for 5 hr at 91 oC. The stability of plant lectins in the stomach is evidenced, for example, by the finding that when Concanavalin A, PHA or WGA were intragastrically administered into rats between 50 and 90% of the lectin was recovered after 1 hr from the stomach by homogenizing the tissue in phosphate-buffered saline containing the appropriate specific sugar. Moreover, in the few experiments with humans that ate lectin-containing foods, namely tomatoes (Kilpatrick et al., 1985), red kidney beans (Pusztai et al., 1989) or peanuts, either raw or roasted (Wang et al., 1999) the lectins have not only withstood the acidity and the proteolytic enzymes of the intestinal tract, but a significant proportion of the amount ingested has reached the circulatory system with unimpaired hemagglutinating and immunological activities. In rodents, a diet containing lectins provoked intestinal and systemic immune responses to these proteins (Gomez et al., 1995). Furthermore, human serum was found to contain antibodies to the lectins of peanut, soybean and wheat germ (Tchernychev and Wilchek 1996).
