Physiological Availability of the Vitamins

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Abstract
Certain substances, capable of adsorbing the B vitamins, are taken regularly and in appreciable quantities over long periods of time for the treatment of various clinical disorders. Human availability studies have been conducted to determine the influence of the concomitant ingestion of two such adsorbents, fuller's earth and kaolin, on the availability of thiamine. These materials were shown to adsorb the vitamin very readily from aqueous solution. Whereas the availability of thiamine was markedly reduced by the fuller's earth, no interference occurred when kaolin was taken along with thiamine. Indeed, the latter adsorbent appeared to protect the vitamin during its passage through the gastrointestinal tract so that a greater-than-theoretical value for available thiamine was obtained. In vitro tests have not proved satisfactory for predicting the influence of an adsorbent on vitamin availability. The present experiments cast doubt upon the wisdom of taking continuous large doses of adsorbing agents, unless precautions are taken to insure sufficient vitamin intake.