Influence of Type of Dietary Fat (Olive and Sunflower Oil) upon Gastric Acid Secretion and Release of Gastrin, Somatostatin, and Peptide YY in Man

The effects of adaptation to two diets differingin the type of dietary fat on the gastric acid secretoryresponse to food and on the circulating levels ofgastrin, somatostatin and peptide YY (PYY) were examined in humans. The study involved 18cholecystectomized subjects previously submitted to a30-day adaptation period to diets containing olive(group O) or sunflower oil (group S) as the fat source. During the experiments, physiologicalstimulation was achieved by ingestion of 200 ml of oleicacid- (group O) or linoleic acid-enriched (group S)liquid mixed meals. These resulted in an immediate rise in gastric pH. In group S, the return to thepremeal value was completed within 60 min, and a furtherdecline to values significantly lower than the basalones was observed at the end of the study period. In contrast, ingestion of the meal containingolive oil attenuated and prolonged the pH decrease afterthe meal, this being associated with the suppression ofpostprandial gastrin response. Food ingestion induced no significant changes in plasmasomatostatin concentration in either group, and nosignificant differences were revealed between themduring the basal or postprandial situations. Plasma PYYlevels were consistently higher in group O throughoutthe entire study period, although significance wasreached only at resting. In conclusion, our results showthat a 30-day adaptation period to diets containing olive oil as the main source of dietary fatresults, compared with those containing sunflower oil,in an attenuated gastric secretory function in responseto a liquid meal in humans. The effects of olive oil were associated with a suppression of serumgastrin and higher levels of PYY.