Determination of a Curve of Response to Synthetic Crystalline Thiamin, for Use in the Vitamin B1 Assay of Foods by the Rat-Growth Method

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Abstract
To determine the growth response of rats to graded doses of thiamin, 192 rats were given a thiamin-free diet at 21 days of age; at depletion of thiamin stores after about 20 days, twenty-five rats were used as controls, and 167 rats were fed daily doses of synthetic crystalline thiamin at six levels (1, 2, 3, 4, 8 and 16 μg.) for a period of 5 weeks. The results show a definite curvilinear relationship between the mean gains in weight after 3 weeks and after 5 weeks and the quantity of thiamin administered; y = 3.0 + 62.3 log X for 3 weeks, and y = 9.2 + 84.9 log X for 5 weeks. A statistical analysis of the results of a 5-week feeding period and those of a 3-week feeding period shows that the shorter period gives as significant results as the longer period. The number of rats necessary for a significant biological assay of foods for their thiamin content for a particular colony has been determined to be twelve. When supplements providing quantities of thiamin between 1 and 4 μg. are fed to groups of twelve rats six times a week, the responses should be sufficiently accurate to distinguish differences of 1 μg. Curves of response relating the doses of thiamin to gains in weight are given for the 3-week and the 5-week feeding periods.