CWROTENOIDS 



eventually to perforation of the bone, (i-carotene examined in a 

 similar wav was without effect. 



ABSORPTION OF CAROTENOIDS 



In general, carotenoids are very badly absorbed by mammals and 

 a considerable proportion of any ingested carotenoids is excreted in 

 the faeces. This is not the case with vitamin A which is readily 

 absorbed, i s, 2 5 2. 2 5 3 



{a) Humatis 



In humans the experience of a group of workers in England con- 

 firmed Clausen's original statement-^* that human faeces contain 

 carotenoid in more or less the same ratio as that of the ingested food, 

 but Wald, Carroll and Sciarra ^ ^ ^ found that only 8 per cent, of ingested 

 xanthophylls but 65 per cent, of ingested carotenes was excreted. 



Absorption from vegetable foodstuffs is generally poor but is even 

 worse if the foodstuffs are uncooked or not finely divided. 1 s, 2 5 2- 2 7 9 

 Although reported figures are somewhat variable it is well proved 

 that absorption is facilitated by the presence of lipids^^'^^s, 257, 259, 

 2 6 7, 2 7 5 especially lecithin, ^ s gyen when there are adequate 

 amounts of tocopherols in the diet. 2 s 1, 2 s 2 There are also indications 

 that the efficiency of absorption depends on the type of fat in the 

 diet, 2 5 9, 2 6 3 although Virtanen ^ ' * thinks that this is not so. Very 

 recently, however, Aldersberg and his colleagues ^ ^ -^ have shown 

 conclusively that butter is a better vehicle than cotton-seed oil and 

 Deuel and his group that carotene has a greater biological activity when 

 fed incorporated into margarine than into limpid cotton-seed oil. ^ ^ * 



It is claimed that carotene adsorbed on to a protein coagulate, obtained 

 by heating leaf juice, is 50 per cent, better absorbed than is carotene in 

 carrots ; ^ ** ^ it should be noted, however, that a water-soluble carotene 

 protein complex is present in carrots (see p. 54). Absorption is 

 reduced in fevers, ^ ^ jaundice, ^ ^ and coeliac disease. ^ ° It is probably 

 poor absorption in the last-named condition which accounts for the 

 subnormal plasma levels observed {see Table 42) for their increase 

 following treatment parallels the improved clinical condition. 



From a clinical point of view it is important to note that adminis- 

 tration of mineral oils reduces the absorption of carotenoids, 286-290 

 the pigments being easily soluble in the oils which are not absorbed. 

 Mahle and Patton, ^ » 2 however, have recently made the important 

 observation that hydrophilic mucilloids, which can replace mineral 



250 



