Vitamin A, B, C, D Deficiencies

Vitamin A Deficiency

In men maintained for six months on less than 100 international units of vitamin A daily after a preliminary massive dose period of thirty days there was no change in plasma vitamin A levels, visual thresholds or scores in moderate and exhausting work tests. The fact that vitamin A did not disappear from the plasma in these subjects indicates that their reserves were not exhausted. The depletion of vitamin A stores in the body lakes a very long time so that there is a substantial margin of safety in most cases.

Performance may be restricted by lack of vitamin A because of the effects on vision. People subsisting for long periods on diets very low in vitamin A develop night blindness. Vitamin A intake may affect color vision. The daily administration of carotene to factory workers was followed by a 75 per cent reduction in the number of rejections for off-color parts of stoves assembled by them. Among normal persons subsisting on diets not markedly deficient in vitamin A there is little relation between vitamin A intake, blood vitamin A concerttration and dark adaptation.

Vitamin B Deficiency

Diets containing about one-third of the recommended optimum intake of vitamin B complex do not lead to deterioration in physical capacity within two weeks if the physical and environmental stresses are not great. Subjects put on a vitamin deficient diet containing 0.16 mg. thiamine, 0.15 mg. riboflavin and 1.8 mg. niacin per 1,000 Calories displayed no change in work capacity, psychomotor test scores or clinical condition during the two weeks' deficiency period. 22 A similar lack of effect was observed when riboflavin only was limited to 0.31 mg. per 1,000 Calories.

Thiamine is concerned in carbohydrate metabolism. When thiamine is deficient, lactic and pyruvic acids accumulate in abnormal amounts and muscular activity is depressed. Ten healthy men placed on a more severe thiamine restriction, doing harder physical labor and in a colder environmental temperature, showed a clear diminution in physical test scores in one week. A trained subject who was fed a diet deficient in thiamine and riboflavin during a hot summer showed a significant decrease in performance on a bicycle ergometer.

Vitamin B deficiency over a long period produces a deterioration in fitness for exercise even in the absence of hard physical labor or environmental stress. Subjects on a reduced thiamine, riboflavin and ascorbic acid intake during a twelve-week period experienced a reduction in work performance.

The requirements for thiamine, riboflavin and niacin are probably proportional to the intensity of the metabolism. It is justifiable to advise an increased intake of B vitamins when work is increased and when the stress of the environment is great. With a reasonably good diet this is guaranteed by simply increasing the total food intake.

Vitamin C Deficiency

Low levels of vitamin C intake do not measurably reduce work performance. Men receiving only 40 mg. of ascorbic acid daily did not differ significantly in fitness for exercise, nor in susceptibility to heat exhaustion, from men receiving 540 mg. daily.

Vitamin E Deficiency

Rats on diets deficient in vitamin E show degenerative changes in muscles, and diminished capacity for treadmill running. Whether man shows similar responses to vitamin E deficiency has not yet been determined.