Vitamin A is a group of compounds that play an important role in vision, bone growth, reproduction, cell division, and cell differentiation (in which a cell becomes part of the brain, muscle, lungs, blood, or other specialized tissue.

			Vitamin A helps regulate the immune system, which helps prevent or fight off infections by making white blood cells that destroy harmful bacteria and viruses. Vitamin A also may help lymphocytes (a type of white blood cell) fight infections more effectively.

			Vitamin A promotes healthy surface linings of the eyes and the respiratory, urinary, and intestinal tracts. When those linings break down, it becomes easier for bacteria to enter the body and cause infection. Vitamin A also helps the skin and mucous membranes function as a barrier to bacteria and viruses.

			In general, there are two categories of vitamin A, depending on whether the food source is an animal or a plant. Vitamin A found in foods that come from animals is called preformed vitamin A. It is absorbed in the form of retinol, one of the most usable (active) forms of vitamin A. Sources include liver, whole milk, and some fortified food products. Retinol can be made into retinal and retinoic acid (other active forms of vitamin A) in the body.

			Vitamin A compounds that are found in colorful fruits and vegetables are called provitamin A carotenoids. They can be made into retinol in the body. In the United States, approximately 26% of vitamin A consumed by men and 34% of vitamin A consumed by women is in the form of provitamin A carotenoids. Common provitamin A carotenoids found in foods that come from plants are beta-carotene, alpha-carotene, and beta-cryptoxanthin. Among these, beta-carotene is most efficiently made into retinol. Alpha-carotene and beta-cryptoxanthin are also converted to vitamin A, but only half as efficiently as beta-carotene.

			Vitamin A in foods that come from animals is well absorbed and used efficiently by the body. Vitamin A in foods that come from plants is not as well absorbed as animal sources of vitamin A.

			Some provitamin A carotenoids have been shown to function as antioxidants in laboratory studies; however, this role has not been consistently demonstrated in humans. Antioxidants protect cells from free radicals, which are potentially damaging by-products of oxygen metabolism that may contribute to the development of some chronic diseases.

			Retinol is found in foods that come from animals such as whole eggs, milk, and liver. Most fat-free milk and dried nonfat milk solids sold in the United States are fortified with vitamin A to replace the amount lost when the fat is removed. Fortified foods such as fortified breakfast cereals also provide vitamin A. Provitamin A carotenoids are abundant in darkly colored fruits and vegetables. The 2000 National Health and Nutrition Examination Survey (NHANES) indicated that major dietary contributors of retinol are milk, eggs, beef liver and fortified breakfast cereals, whereas major contributors of provitamin A carotenoids are carrots, cantaloupes, sweet potatoes, and spinach.

			Night blindness is one of the first signs of vitamin A deficiency. In ancient Egypt, it was known that night blindness could be cured by eating liver, which was later found to be a rich source of the vitamin. Vitamin A deficiency contributes to blindness by making the cornea very dry and damaging the retina and cornea.

			Healthy adults usually have a reserve of vitamin A stored in their livers and should not be at risk of deficiency during periods of temporary or short-term fat malabsorption. Long-term problems absorbing fat, however, may result in deficiency. In these instances physicians may recommend additional vitamin A.

			Vegetarians who do not consume eggs and dairy foods need provitamin A carotenoids to meet their need for vitamin A. They should include a minimum of five servings of fruits and vegetables in their daily diet and regularly choose dark green leafy vegetables and orange and yellow fruits to consume recommended amounts of vitamin A.

			Take one capsule daily that contains 10,000 International Units of Vitamin A and 400 IU of Vitamin D (preferably as fish liver oil). If you are allergic to fish take a capsule or tablet with 10,000 IU of fish-free, dry Vitamin A.

			Fish Liver Oil Softgels (A-10,000 IU/D-400 IU), 100 Softgels (6 Bottles) NLF

			Caution: Do not take more than 10,000 IU of Vitamin A per day.

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