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The Availability of Vitamins from Yeasts

V. Differences in the Influence of Live Yeast on the Absorption of Pure Thiamine Hydrochloride, Pure Riboflavin and Nitrogen by Human Subjects, and the Effect of Distribution of the Vitamin Doses¹

Department of Home Economics, University of Wisconsin, Madison

A higher percentage of a dose of thiamine hydrochloride was returned in the urine of human subjects when the supplement was ingested with meals rather than between meals. The urinary return of riboflavin was not similarly influenced.

Pure thiamine hydrochloride ingested with fresh bakers' yeast failed to be returned in the urine, presumably through almost complete. failure of absorption by the digestive tract. This was the same effect as that observed previously in respect to food thiamine ingested with live yeast. Hence, the "interference" by fresh yeast is not attributable per se to the effect of an anti-enzyme in the digestive tract.

In the same experiment live yeast interfered less with riboflavin than with thiamine in that only the riboflavin of the live yeast cell, not that in the food or in pure form, appeared to be withheld from absorption; nitrogen was least affected, inasmuch as an average of 80% of the nitrogen of the yeast cell itself was returned in the urine. That these differences in excretion were actually due to differences in absorption tended to be borne out by fecal assays.

These observations make necessary some further elaboration of the hypothesis that food thiamine is interfered with by live yeast because of competition between the absorbing membranes of the live yeast cell and of the digestive tract, with a resulting retention of the absorbed thiamine within the yeast cell.

This work was supported in part by the Research Committee of the Graduate School from funds supplied by the Wisconsin Alumni Research Foundation, and in part by a commercial grant from the Jos. Schlitz Brewing Company of Milwaukee.

² Present address: Nutrition Division, Department of Health, New York, N. Y.

³ Present address: American Meat Institute Foundation, Chicago, Illinois.

Manuscript received 18 February 1949.