INHIBITION OF STARCH DIGESTION BY ALPHA-AMYLASE INHIBITOR REDUCES THEEFFICIENCY OF UTILIZATION OF DIETARY PROTEINS AND LIPIDS AND RETARDS THE GROWTH OF RATS

Digestion/absorption and nutritional utilization of starch, protein an d lipids were studied in rats fed diets containing purified kidney bea n alpha-amylase inhibitor at levels of 0, 1.6, 3.3 and 6.6 g/kg diet. At the two higher levels, the growth rate of rats and the apparent dig estibilities and utilization of dietary starch and protein were signif icantly less than in control rats, and losses of nitrogen, lipids and carbohydrate resulted in a significant reduction in dry body weight. S ome organs of the body were also affected: the relative dry weights of the intestines and the pancreas were higher, whereas liver and thymus weights were lower than in control rats. As starch digestion in the s mall intestine was negligible at higher inhibitor concentrations, the cecum was practically blocked by solidified digesta. This effect and t he ensuing bacterial fermentation stimulated the growth of this tissue by hyperplasia and hypertrophy. However, as the distension was not al ways sufficient, the organ was occasionally ruptured and the rats had to be killed. Inhibitor doses in this work were comparable to those in clinical studies, implying that the use of the inhibitor is not witho ut health risks. Moreover, diets rich in alpha-amylase inhibitor such as those containing transgenic plants with high levels of inhibitor ge ne expression cannot be recommended in intensive animal production.