EXPERIMENTAL HUMAN VITAMIN A DEFICIENCY AND THE ABILITY TO PERFORM MUSCULAR EXERCISE

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Abstract
Following 30 days of high vit. A nutrition, 5 young men were maintained on a diet very low in vit. A for about 6 mos. The diet was supplemented with brewer''s yeast, ascorbic acid, vit. D, Ca phosphate, Fe and Cu. At regular intervals the cone and rod dark adaptation, plasma vit. A and total carotenoids, and feces carotene and xanthophyll were measured. Within 1 wk. on the A-deficient diet the feces carotenoids had fallen to about 1% of previous values. Plasma carotenoids also quickly fell to very low levels. Plasma vit. A however maintained its initial maximal values in all subjects, throughout the deficiency period. The visual thresholds of 3 subjects also remained constant and minimal; in 2 subjects they rose slowly to levels 0.7-1.1 log unit above normal. After 3-4^ mos. on the deficient diet, and again about 6 wks. after return to a normal A-supplemented diet, the physical fitness of the subjects for moderate and exhausting exercise was detd. No significant differences in performance were found. It is concluded that relatively sedentary subjects originally well supplied with vit. A may undergo as much as 6 mos. of vit. A deprivation without developing objective evidences of deficiency.