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vitamin A |
Also found in: Dictionary/thesaurus, Medical, Wikipedia, Hutchinson | 0.01 sec. |
vitamin Aalso called retinolFat-soluble alcohol, most abundant in fatty fish and especially in fish-liver oils. It is not found in plants, but many vegetables and fruits contain beta-carotene (see carotene), which is readily converted in the body to vitamin A. It functions directly in vision, especially night vision. A derivative, retinaldehyde, is a component of the visual pigments, including rhodopsin, in the retina. Humans require vitamin A in very small amounts. Unlike carotenes, it is toxic in large amounts and is readily destroyed by exposure to heat, light, or air. |
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| Dietary studies have suggested that people who consume large amounts of vitamin A in foods, multivitamins, or both are more likely to suffer hip fractures than are people who ingest modest amounts. For example, recent studies suggest that high doses of vitamin A may raise the risk of hip fracture and that the latest recommended levels of vitamin K may be too low to protect your bones. Their report concluded that fruits and vegetables provide the body with half as much vitamin A as previously thought. |
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vitamin A
