462 IX. CAROTENOIDS AND VITAMINS A 



tration. Following massive doses in oil (600 mg.), a hypercarotenemia ob- 

 tained for seventy-two hours before the peak value was reached. ^°^ 



According to Szymanski and Longwell,^"- it is possible to predict the 

 blood carotene levels in man from the quantities present in the diet. The 

 formula for expected plasma carotene in ug. % (Xo) is as follows: 



Xo = 0.46 /fi + 0.06 h + 86 



/o is the average daily intake of \dtamin A (carotene) from plant sources in 

 I.U. per kilogram body weight over the preceding three months, while h 

 is the same value during the period three to six months before the date of 

 the prediction. 



In the case of cattle, Davis and Madsen^"' obtained the following aver- 

 ages for plasma carotene (,ug./100 ml.) when the carotene intake was ex- 

 pressed in Aig./kg. of body weight: Low intake, 14 /zg./lOO ml. ; 30 Mg-, 46; 

 45 ug., 41; 60 fig., 81; 130 ug., 103; /iifir/i (pasture), 813. 



When massive doses of carotene are ingested over a prolonged period, 

 especially by individuals who have hepatic disease, diabetes mellitus, or 

 myxedema (which conditions tend to prevent a normal utilization of caro- 

 tene), and also by entirely normal individuals, excessively high blood caro- 

 tene values result, with the concomitant deposition of the pigment in the 

 subcutaneous tissue. This produces a condition known as "carotenemia," 

 or "carotinosis," which outwardly simulates jaundice. Normal children 

 may develop carotenemia after an excessive intake of carrots, ^o** Hubbard 

 squash (Cumirbita maxima), ^'^^^'mikan,'' or Japanese orange {Citrus nobilis) , 

 Lour., var. microcarpa) ,^°^ as w^ell as after other foods rich in carotene.^"® 

 Carotenemia is an apparently harmless metabolic condition which does 

 not have the unfavorable prognosis of hypervitaminosis A. The caroten- 

 emia and skin coloration rapidly disappear when the carotene intake is re- 

 duced. Although plasma vitamin A is usually normal in cases of caroten- 

 emia, indicating that the accumulation of the provitamin is not the result 

 of its failure to be converted to vitamin A, there is one report^"^ of this type 

 of condition in which carotene passed into the blood in such quantities that 

 the normal carotene : xanthophyll ratio was reversed. 



When massive doses of vdtamin A are administered to cows, a marked 

 depression in the carotene levels of blood obtains, even though the carotene 



302 B. B. Szymanski and B. B. Longwell, /. Nutrition, 45, 431-442 (1951). 



303 R. E. Davis and L. A. Madsen, /. Nutrition, 21, 135-146 (1941). 



304 A. F. Hess and V. C. Myers, /. Am. Med. Assoc, 73, 1753-1745 (1919). 



305 H. Hashimoto, J. Am. Med. Assoc, 78, 1111-1112 (1922). 



306 H. Koch, Biochem. J., 37, 430-433 (1943). 



307 H. Cohen, Quart. J. Med., 18, 397-398 (1949). 



