CONTROL procedures for vitamin-containing pharmaceutical products are based on conformance of analytical values with the labeled statement. The physician and nutritionist are interested in the physiological availability in addition to labeled contents. In recent years, the importance of physiological availability, rather than analytical content, has been repeatedly emphasized.1 Oser and associates2 have indicated that "the nature of precautions taken to insure stability of vitamins in pharmaceutical capsules or tablets which are usually swallowed whole raises the question of physiological availability of the vitamins." They have shown that a given amount of thiamine in one capsule is four times as available in another capsule. Some pharmaceutical preparations contained riboflavin rendered so insoluble as to be physiologically unavailable.3 Thiamine was found to be relatively unavailable from live yeast.4
The availability of the fat-soluble vitamins, particularly vitamin A, in liquid media has been the subject of intensive study since it was shown that acute deficiency
SOBEL AE, ROSENBERG AA. PHYSIOLOGICAL AVAILABILITY OF VITAMIN A FROM CAPSULES. AMA Am J Dis Child. 1952;84(5):609–615. doi:10.1001/archpedi.1952.02050050083005
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