DECREASED PLASMA-LEVELS OF CHOLECYSTOKININ IN HEALTHY-MALES AFTER CHRONIC INGESTION OF A HEAT-TREATED SOYA PRODUCT

Administration of raw soya containing a trypsin inhibitor stimulated e xcessive release of cholecystokinin (CCK) which led to pancreatic hype rtrophy, hyperplasia and cancer in the rats (Booth et al. (1964) Proc. Sec. Exp. Biol. Med., 116, 1067). More postprandial CCK release in he althy humans was observed after ingestion of a single dose of raw soya than heat-treated soya (Calam et al. (1989) Br. J. Nutr., 58, 175). T he effect of chronic ingestion of a heat-treated soya product on postp randial CCK release was investigated in six healthy adult males after ingestion of a 36-oz. portion of soymilk daily for 1 month and at 2-3 months after termination of soymilk ingestion. Subjects fasted for 15 h, ingested Lipomul(1.5 g/kg) and provided blood at timed intervals fo r CCK analysis. The results show that I-month ingestion of soymilk dec reased the magnitude of Lipomul-induced postprandial CCK release in pl asma of all six subjects by 5-60% (P < 0.05) compared to those obtaine d at 2-3 months after the withdrawal from soymilk ingestion. Plasma pa ncreatic polypeptide (PP) levels were similarly decreased in five of t he six subjects by 19-67% (P = 0.03) in line with the regulation of PP by CCK. Thus, prolonged exposure of humans to a heat-treated soya inh ibited slightly meal-induced CCK release in contrast to that found in rats after raw soya diets.