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Facts About Vitamin A and Carotenoids |
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Part 1: What is vitamin A?
Vitamin A: What is it?
Vitamin A is a family of fat-soluble
vitamins. Retinol is one of the most active, or usable, forms of vitamin A,
and is found in animal foods such as liver and eggs. It can be converted to
retinal and retinoic acid, other active forms of the vitamin A family. Some
plant foods contain orange pigments called provitamin A carotenoids that the
liver can convert to retinol. Beta-carotene is a provitamin A carotenoid found
in many foods(1-3). Lycopene, lutein, and zeaxanthin are also carotenoids commonly
found in food, but your body cannot convert them to vitamin A.
Vitamin A plays an important role in vision, bone growth,
reproduction, cell division and cell differentiation, which is the process by
which a cell decides what it is going to become (1, 4-7). It also maintains
the surface linings of your eye and your respiratory, urinary, and intestinal
tracts (8). When those linings break down, bacteria can enter your body and
cause infection (8). Vitamin A also helps your body regulate its immune system
(1, 4, 9). The immune system helps prevent or fight off infections by making
white blood cells that destroy harmful bacteria and viruses. Vitamin A may help
lymphocytes, a type of white blood cell that fights infections, function more
effectively. Vitamin A also may help prevent bacteria and viruses from entering
your body by maintaining the integrity of skin and mucous membranes (10, 11,12).
Some carotenoids, in addition to serving as a source
of vitamin A, have been shown to function as antioxidants in laboratory tests.
However, this role has not been consistently demonstrated in humans (13). Antioxidants
protect cells from free radicals, which are potentially damaging by-products
of the body's metabolism that may contribute to the development of some chronic
diseases (2, 14-16).
Next page > How much vitamin A do you need? > Page 1, 2, 3, 4, 5, 6
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