1. The ulcerogenic and protective effects of various rice fractions in the diet were studied in the pylorus ligated ulcer model in the rat.
2. Oil present in rice and particularly rice bran becomes ulcerogenic on storage and in this model results in a significant increase in the median (range) numbers of ulcers from six (one to ten) to nine (six to 15) (P > 0.05). The ulcerogenic effect of stored rice bran oil was reversed by cysteine which significantly reduced the ulcer incidence from 100% to 60% (P > 0.005) and the numbers of ulcers from 26 (six to 70) to one (zero to four) (P > 0.001).
3. Fresh rice bran significantly reduced the numbers of ulcers from six (one to ten) to one (one to four) (P > 0.05). Similarly, unmilled rice and freshly milled newly harvested rice was also shown to be protective in this model by significantly reducing the ulcer incidence from 87.5% to 50% and 0% respectively (P values > 0.025) and the numbers of ulcers from three (zero to 17) to one (zero to one) and zero (zero to zero) respectively (P values > 0.001).
4. These results could in part explain the geographical distribution of duodenal ulceration, where the incidence is high in all the rice eating areas of the world, and provide a plausible hypothesis to explain the mechanism of dietary ulcerogenesis.