Effects of soy proteins containing trypsin inhibitors in long term feeding studies in rats.

Pancreatic hypertrophy that occurs in rats fed raw soy flour containing about 1200 mg tripsin inhibitor (Tn/lOO g diet was reversed by switciti.ng the rats to control diets or to diets containing 30% toasted defatted soy l1our. No panCTeatic hypertrophy occurs in rats fed commercial, edible gr:!de soy 11 ours, concentrate or isolate from time of weaning to adulthood (ca. 300 days). Tl content of the soy diets r:lnged from 1i 8-4 20 mg/I 00 g. Except for pancreas enlargement in rats fed raw soy !lour. gross and microscopic examination of panC7eata revealed no abnormalities. The gross appearance of heart, )(jdney, spleen, and liver was nonna!. Soy flour, protein ;;oncentrate. and protein isolate in a formulated corn-soy diet provided optimum growth and maintai::led body weight only ii supplemented with vitamin B·I:! in long tenn feeding studies with rats. in the absence of sue-I). supplementation. rats fed soy diets initially gr:w at a rate equal to or ~ater than t..'1ose fed a com. parable corn--casein control diet; bur, with ;;ontinued feeding for ca. 300 days, body: weight oi rats fed the casein control was significantly greater than that of the soy flour-fed r:lts. Those fed soy isolare ceased to grow; and rats fed soy concentr:lte iost weigllt. '"'0 significant differences were found in organ weig.I).ts between groups fed soy products anu casein, except for increased kidney, liver, and testes weights relative to body weight with the group fed soy concentrate. Supplementation of the soy diets with vitamin B1 2 stimulated growth to the greatest extent, calcium ;lantothenate or riboflavin had an intermediate effect. other vitamins had little or no effect: whereas a complete miner:Ll mix was detrimental. Supplement;;· tion of the soy diets with vitamin B12 stimulated growth to the greatest extent. calc:um pantot.'lenate or roboiiavin had an intermediate efiect. oti-.er vitamins had little or no effect: whereOlS a complete mineral mix. was detrimental. Supplementation of the conrrol diet was with.out effect. Tne dietary protein level in these diets was 20%, with casein or soy protein representing 75% of total protein. When fed continuously to rats from weaning to adulthood, properly proceS3ed soy protein products. when balanced I ' , 0_ J. AM. OIL. CH::MISTS' ;:;OC.. ~ arch IQ79 (VOL. 56)