Utilization of wheat by adult man: excretion of vitamins and minerals

SUMMARY Urinary excretions of niacin, N 1 -methylnicotinamide, pantothenic acid, riboflavin, thiamin, vitamin B 6 , and vitamin B 12 , and urinary and fecal excretions of calcium, phosphorus, magnesium, and sulfur were measured in 12 adult men between the ages of 23 and 30 during a 74-day period when they were fed a wheat diet supplying 46 g protein/day or this diet in which 20% of the nitrogen supplied by wheat was equinitrogenously replaced by pinto beans, rice, or peanut butter. The data indicate that the thiamin in wheat is well utilized by adult man. The rather constant excretion of vitamins would suggest that substitution of pinto beans, rice, or peanut butter for a portion of the wheat under these conditions did not substantially affect the utilization of these vitamins in the wheat diet. Low fecal excretions of calcium, magnesium, phosphorus, and sulfur resulted in positive balances for these minerals. Differences between mean excretions of subjects receiving the wheat diets were not significant. Calcium balances were more positive when subjects received the pinto bean diet, which also supplied more lysine and calcium than the other diets. Lower calcium balances of men receiving the peanut butter diet were due to higher fecal excretions of calcium. It is suggested that one aspect of the mechanism of metabolic adjustment to low protein intake involves greater retention of dietary sulfur, greater conservation of absorbed sulfur, and a reduction in the catabolism of sulfur-containing amino acids.