Effects of Added Casein on Goitrogenic Action of Different Dietary Levels of Soybeans.

Abstract

The goitrogenic effect of raw soybeans was confirmed by feeding diets containing 35% or 60% raw commercial beans to male albino rats for 7 weeks starting when weaned. The effect was apparent by comparison with animals fed a diet like the 60% soybean diet, but with the goitrogenic effect of the beans destroyed by heating. All diets provided less than 2% of the rat''s iodine requirement. A 60% raw soybean diet produced significant increases in wet and dry weights of the thyroid gland. A 35% raw soybean diet produced a significant increase only in dry weight of the gland. A 35% raw soybean diet containing 17% purified casein, and a 60% raw soybean diet containing 15% casein, were also fed. The casein did not alter the I contents of the diets, but did obliterate the effects of the soybean diets on wet and dry weights of the thyroids. Since the growth retarding effects of the well-known soybean trypsin inhibitor, and the goitrogenic effect of raw soybeans, are both now recognized to be reversible by either heating the beans or by adding casein to raw soybean diets, a question is raised as to whether these two effects might have a related, or identical, basis.