The Minimum Daily Requirement of Thiamine of Man

Abstract

Determination of excretion of thiamine after administration of a test dose of 1.0 mg. of thiamine hydrochloride subcutaneously appears to be a valid test for assessment of the condition of tissue stores of thiamine and, respectively, of cocarboxylase. Determination of pyruvic acid in the blood after administration of dextrose intravenously or orally appears to be a valid test for detection of a biochemical defect of thiamine deficiency, provided that other causes of abnormal elevation can be excluded. Abnormal elevation of values for pyruvic acid in the blood after administration of dextrose was observed under various abnormal conditions. No rise was observed in cases of severe diabetes mellitus when insulin was not given. However, a rise was noted when insulin was provided just before or at the time of the administration of the dextrose. Also, in states of mild diabetes, in hypoglycemia induced by administration of insulin and in hypermetabolism, abnormally high values for pyruvic acid in the blood after administration of dextrose have been encountered. Restriction of the thiamine intake of two subjects to from 0.1 to 0.175 mg. per 1000 calories was associated with rapid depletion of the tissue stores of thiamine and early development of a biochemical defect. Restriction of the thiamine intake of four subjects to 0.22 mg. per 1000 calories was associated with a slow depletion of the tissue stores of thiamine and slow development of the biochemical defect. An intake of 0.45 mg. per 1000 calories was associated in three of five subjects with a slight degree of depletion of tissue stores of cocarboxylase, and in four of the five with slow development of a mild degree of biochemical defect. Although the disturbance of metabolism at this level of intake of thiamine was slight, such an intake (0.45 mg. of thiamine per 1000 calories) cannot be regarded as representing more than the minimum daily requirement of thiamine for these five subjects who subsisted on a diet to which carbohydrate, protein and fat contributed in proportions conventional for the majority of American and European diets. In the light of these findings, and to provide some safeguard against higher proportions of nonfat calories in some diets, individual variability and other causes of increased minimum requirement, the daily allowance of 0.6 mg. of thiamine per 1000 calories, recommended by the Food and Nutrition Board of the National Research Council, is certainly none too high.