Thiamin deficiency could result either from inadequate intake of thiamin or consumption of food containing antithiamin factors. Dietary surveys conducted in northeastern Thailand indicated that both thiamin and caloric intake of subjects under studies were sufficient. In Thailand, correlation exists between the consumption of food containing antithiamin factors and the prevalence of thiamin deficiency. Betel nuts and raw fermented fish possess antithiamin activity. Abstention from both betel nut chewing and raw fermented fish consumption resulted in a significant reduction of thiamin pyrophosphate effect. The thiamin pyrophosphate effect again increased significantly when the subjects resume their chewing habits. Cooking of fermented fish destroyed thiaminase, resulted in a significant decrease of thiamin pyrophosphate effect of the subjects. Thiamin supplementation (10 mg/day) could further reduce their thiamin pyrophosphate effect. This amount of thiamin could counteract the effect of raw fermented fish consumption but was not sufficient to neutralize the effect of betel nut chewing.
Consumption of food high in tannins can cause thiamin deficiency. The interactions between tannic acid and thiamin were studied by allowing them to react at pH 7.5, 60 C, and determining free remaining thiamin by the thiochrome method and by recording changes in ultraviolet absorption profiles at intervals. The reaction was biphasic, having a rapid initial phase which was oxygen-independent, followed by a slower phase which was oxygen concentration-dependent. Ascorbic acid completely inhibited the reaction if present at the beginning of the reaction and could partially reverse the reaction if added during the first 30 min.
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