Vitamin A is fat-soluble, stored in body fat; you don't need to eat it every day in order to get enough. But it is vital for many body systems. It helps form a substance known as rhodopsin, necessary for good vision-particularly night vision-and plays a key role in the visual process of the retina. The vitamin helps keep the inner linings of your body, your mucous membranes, your skin, and your eyes in good health and resistant to infection. There is good evidence that it may energize the cells of your immune system.
Vitamin A helps fight cancer and the degenerative diseases of aging by soaking up what are called "free radicals" destructive molecules that interfere with normal cell activities, disrupt essential enzymes and damage the membranes of your cells, and lead to mutations and cell damage. It also aids the development of bones, glands, hair, nails, and teeth. Both Vitamin A and beta-carotene are essential for healthy development of the cells lining your digestive tract. Vitamin A occurs in foods in two forms: Retinol, or preformed vitamin A, is found only in foods that come from animals; retinoids, like beta-carotene, occur in both animal and plant foods. Beta-carotene is called a "precursor" to vitamin A-that is, the body converts it into usable vitamin A. They both play a role in nerve chemistry, and neurotransmitters.
Vitamin A by itself can have significant toxicity if you overdose, but beta-carotene is not toxic even in large doses-because your body converts only what it needs, you can't easily overdose. For that reason, most nutritionists recommend that instead of straight vitamin A, you take the safer, effective beta-carotene.
Good for These Symptoms:
Signs of Deficiency:
RDA: 1,000 I.U. vitamin A for men 800 I.U. for women
Optimal Level: 17,500 I.U. beta-carotene
Maximum: 25,000 I.U. vitamin A; Unknown for beta-carotene
Signs of Toxicity: