Absorption of carotene in man.

Abstract

1. For determining vitamin A in feces, non-carotene yellow pigment giving positive Carr-Price reaction is removed by using weakly activated almina and developing with 1.25per cent acetone-petroleum benzine as a solvent system and the vitamin A fraction thus separated is analyzed for vitamin A.2. For determining carotene in feces, α- and β-carotene fractions are separated by calcium hydroxide chromatography using petroleum ether as a developing solvent and the fraction thus obtained is analyzed for β-carotene photometrically.3. An appropriate assay method for determining percentage absorption of carotene contained in foodstuffs in human experiment was described.4. The percentage absorption of the β-carotene contained in several main carotene-rich foodstuffs and that in oil as well as that of vitamin A in oil were determined in several Japanese and the results were given.5. The increase in carotene and vitamin A levels in serum was successively determined at timed intervals after ingesting varying amounts of vitamin A or carotene in man. It was found that the carotene and vitamin A levels became maximum 5 and 3 hours respectively after ingesting carotene, whereas vitamin A level in serum reached a maximum value 3-4 hours after ingesting vitamin A. After ingesting carotene, the vitamin A level in serum reached a maximum value earlier than the carotene level and the value of the former was higher than the latter. It is therefore presumed that a considerable part of the carotene is converted in the intestine in man, though some of the carotene appear in blood without change.6. If the increased maximum values of serum vitamin A levels were plotted against the amounts of vitamin A ingested, the increased vitamin levels were roughly proportioned to the amounts of the vitamin ingested up to 130mg. On the contrary, if the varying amounts of β-carotene were ingested, the increased maximum serum carotene levels did not rise appreciably after ingesting more than 32mg of carotene, indicating the poor absorption of β-carotene when ingested in larger amounts. The rise in vitamin A levels in serum was also insignificant. In short, carotene is absorbed in man far less than vitamin A, when given in larger doses.7. If the vitamin A in organs is determined 24 hours after administering carotene or vitamin A to rats, the majority of the vitamin was stored in liver, whereas the vitamin increased insignificantly in other organs.8. If the vitamin A in liver is determined successively after administering vitamin A or β-carptene, the vitamin levels were highest about 12-15 hours after intake.9. If the vitamin A levels in liver 15 hours after administering varying amounts of carotene or vitamin A of the same I.U. were determined, those after carotene intake was about 40per cent of those after receiving vitamin A of the same I.U.10. The vitamin A levels in liver were compared 24 hours after administering carotene or vitamin A with or without varying amounts of α-tocopherol. Those after giving tocopherol were somewhat (4-16%) higher than those without supplementation, but the effect was not marked. Taking a gain in body weight of rats into consideration, a remarkable effect of tocopherol has been reported in the literature, but the rise in vitamin A levels in liver was not siginificantly effected in this experiment by giving varying amount of tocopherol.