Vlll. VITAMIN' A DHFICIENCY IN HUMAN BEINGS 163 



oxt'opt for the human volunteer studied by StolTcns el al. and the patients 

 studied by ^'oumans and Corlette; in these subjects imi)ainneiit oi' dark 

 adaptation was absent or (luestionable, but there was efTective response of 

 the lesions to highly potent eoneeutrates of vitamin A. One report by 

 Uadhakrishna llao^' is notable in that it describes cases of advanced kerato- 

 malacia with skin changes comparahle to those observed by Pillat^^ and 

 presents for the first time the histopathologic changes involved. 



Although the Sheffield human experiment' was unfortunately inconclu- 

 sive concerning the specificity of skin lesions of vitamin A deficiency, it 

 indicates that 2 years or more are recjuired to seriously deplete the vitamin 

 A stores of healthy young adults. During the second year of deficiency, 

 plasma levels of vitamin A were reduced to a critical point (less than 40 

 1. 1", per 100 ml.) in only 4 subjects; only 3 of these had evidence of night 

 l)lindness, and only 1 showed cutaneous changes which suggested inade- 

 ciuate vitamin A. These improved slowly over a period of G months of ther- 

 apy (1300 I.U. daily — as compared to 80,000 I.U. daily, used in the studies 

 of Steffens et al.*-). Had it been possible to extend these depletion periods 

 into the third 3'ear, it seems likely that more convincing cutaneous mani- 

 festations would ha\'e appeared. 



The results of another human experiment, the "Minnesota experiment"*^ 

 on the effects of prolonged partial starvation, suggest that general un- 

 dernutrition may play some part in the genesis of cutaneous lesions at- 

 tributed to avitaminosis A. In 24 of 31 subjects maintained for 23 w^eeks 

 on a partial starvation diet (a low-fat diet providing 1810 I.U. of vitamin 

 A daily, chiefly as carotene; this represents a submarginal daily intake of 

 vitamin A), there was noted a mild to moderate papular eruption which 

 bore certain resemblances, grossly and histologically, to the follicular hy- 

 perkeratosis of vitamin A deficiency. Plasma levels of vitamin A were as 

 high at the end of the experimental period as at the beginning. A dry scaly 

 skin and dry lusterless hair were also noted in more than half the subjects. 

 This report also cites numerous references to descriptions of similar altera- 

 tions of the skin during famines, wars, and sieges. On the other hand, those 

 who studied the nutritional status of civilian population, internees, and 

 refugees in Europe immediately after World War II found surprisingly 

 little evidence of skin lesions or other clinical evidence of avitaminosis A. 

 They attributed this to the fact that when the normal food supply is re- 

 stricted the consumption of greens, vegetables, and cereal grains increases 

 markedly and provides a reasonably abundant, and sometimes an excess, 

 supply of carotene. 



*^ A. Keys, J. Brozek, A. Henschel, O. Mickelsen, and H. L. Taylor, The Biology of 

 Human Starvation, Vols. 1 and 2. University of Minnesota Press, Minneapolis, 

 1950. 



