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Weanling male rats were fed for 6 weeks vitamin D-deficient rations which contained 2 levels of protein with varying levels of supplemental calciferol. Vitamin D decreased the concentration of free lysine but had no apparent effect on free methionine or valine in plasma. Increasing the level of the vitamin significantly increased the concentration of cholesterol and total lipids in liver of rats fed 9% of casein but had no significant effect on that of animals fed 18% of casein. Increasing the protein intake decreased the level of lipids in liver of animals fed no vitamin D supplement or either level of the supplementary vitamin. The results suggested that amino acid-calciferol ratio may be important in lipid metabolism.

Plasma amino acids and liver xanthine oxidase activity were determined in rats fed a control diet with and without calciferol or fed diets providing 9% casein with and without added zinc and calciferol. Reduction of dietary protein resulted in a significant decrease in xanthine oxidase activity, concentrations of plasma threonine, methionine, isoleucine, leucine and phenylalanine, and in elevated histidine levels. Addition of calciferol to diets containing added zinc decreased the levels of plasma isoleucine, leucine, threonine and lysine. Lysine in plasma was also decreased by calciferol supplementation of the low protein diet and by the addition of zinc to this diet. Xanthine oxidase activity was lowest in animals fed the low protein diet without calciferol and zinc. The apparent interaction between zinc and vitamin D closely approached significance at the 5% level. The results indicated that xanthine oxidase activity in animals fed low protein decreased with increased plasma lysine, which was observed in animals maintained without dietary sources of zinc and calciferol.

The effect of dietary arginine, methionine and vitamin E on selected free amino acids in plasma and on lipids in liver was investigated. Weanling male rats were fed a vitamin E-deficient ration supplemented with methionine, arginine or methionine plus arginine with and without vitamin E. Supplementary feeding of arginine, methionine or a combination of these amino acids increased in plasma the concentration of the supplementary amino acid. The effect of vitamin E deficiency on growth had become apparent only in animals fed added arginine or methionine. Vitamin E had no effect on the concentration of arginine, methionine or tyrosine in plasma. Feeding of supplementary methionine or tocopherol decreased the concentration of cholesterol in liver. Vitamin E decreased the amount of total lipids in liver of all animals. The data suggest that a marked change in the proportion of arginine and methionine in plasma may accelerate the development of vitamin E deficiency in the rat.

The effect of riboflavin and methionine supplementation of a riboflavin-deficient ration which contained 18% of casein, on the concentration of amino acids in plasma and riboflavin-containing coenzymes, cholesterol and total lipids in liver of rats was studied. The addition of 0.2% of l-methionine to a riboflavin-deficient basal ration which contained 18% of casein decreased the concentration of plasma valine in young rats fed 10 µg of riboflavin. A marked increase in plasma methionine was observed in animals fed 2.0% of methionine. A comparison of data for animals fed 2.0% of methionine and the basal ration showed an increase in plasma lysine for animals fed 10 µg of riboflavin.

The x-ray density coefficients of the left os calcis and of the second phalanx of the left fifth finger of 524 men and women from forty-nine to more than eighty years of age, and of thirty-eight men and women twenty-five to forty-nine years of age, were determined by a standardized technic. The subjects resided in California, Colorado and Utah; the study was part of a regional cooperative study of nutritional status. The density of the soft tissue covering the centers and ends of the finger bone was calculated as was the total density of os calcis and covering soft tissue.

To study the effect of vitamins A and E on lipids in selected rat tissues, groups of rats were fed weekly 70, 400 or 1200 IU of vitamin A with or without 10 mg of α-tocopherol. After 12 weeks, analyses were made for liver and plasma cholesterol and liver total lipids and vitamin A. Statistical analysis of group means showed that plasma cholesterol of vitamin E-deficient animals fed 1200 IU of vitamin A was significantly higher than that of corresponding animals fed tocopherol. Feeding tocopherol significantly decreased liver cholesterol in animals fed 400 or 1200 IU of vitamin A. Liver cholesterol of animals fed 400 or 1200 IU of vitamin A with tocopherol was significantly less than that of similar animals fed 70 IU of vitamin A. Total lipids in liver, which were not significantly affected by vitamin A, decreased in animals fed vitamin E with 400 or 1200 IU of vitamin A. The storage of vitamin A was significantly increased by increased intake of dietary vitamin A and by feeding vitamin E.