Determination of Vitamin B 1 Requirement of Infants by Means of Urinary Excretion of Thiamin

Abstract

In order to determine the level of vitamin B₁ intake which will give optimum conditions for development for the young infant, a series of 5-day balance studies have been conducted on each of 12 healthy male infants during the first 6 months of their lives. Thus far a total of 98 metabolism periods have been completed. The vitamin B₁ intake of the infants has been controlled either through the amount and type of milk fed each day, or by the additions of pure thiamin to the formulas. The range of total intake has been from 21 to 313 units of thiamin per day. Periodically for each infant, quantitative collections of urine and feces have been made for 5 consecutive days. These materials, as well as the various milks, have been assayed biologicallv for their thiamin content.

It was apparent early in the study that infants had absorbed thiamin from milk formulas very completely since only small quantities of the vitamin were excreted in the stools and in general the amounts of thiamin excreted in the urine increased with increases in intake. In the accompanying chart the amounts of urinary thiamin have been plotted in relation to the intake. A study of these plotted results reveals 2 shifts in the pattern of urinary excretion which seem significant. Below 80 units of intake per day a constantly low quantity of thiamin was excreted in the urine. At 140 units or more of intake, the thiamin appeared to be excreted in much larger amounts as higher levels of the vitamin were fed. The average urinary thiamin for successive increments of 20 units of intake were as follows: 6, 6, 4—19, 22, 34—47, 104, 77, 76, 34, 118, 83, 90, 96. The 2 bars are placed in the sequence at 80 and 140 units of intake per day. These data seem to indicate that 80 units may be the minimum requirement, and 140 units the maximum amount needed for this age infant. Perhaps the range from 100 to 150 units of thiamin may be considered the optimum intake for a young healthy infant, and that above this level of ingestion excess vitamin is excreted rapidly in the urine. The optimum for the baby, however, cannot be determined by economy of vitamin alone, and infants may require a considerable continuous wastage.