Thursday, May 15, 2008

Vision Care: Vitamin A for Your Eyes

Photograph of Cod Liver Oil capsules.Image via WikipediaDocumentation of vitamin A's benefits to the eyes goes back a long way. Ancient Egyptians ate liver to improve their vision, especially at night. Now we know that liver is one of the richest sources of vitamin A, which is essential for eye health.

Vitamin A is important for bone growth and helps maintain a healthy immune system. It preserves the integrity of the skin and mucous membranes, and is vital for a healthy reproductive system and cell division. Vitamin A is probably best known, though, for its role in eye health. Vitamin A in the diet has been linked to preventing cataracts, and may help prevent macular degeneration, the leading cause of blindness in the world.

Vitamin A deficiency may cause visual fatigue, dry eyes and sensitivity to light. Without sufficient vitamin A, your eyes recover very slowly when exposed to flashes of bright light at night and you may have difficulty seeing in dim light. Unless the vitamin A deficiency is corrected, your cornea can become damaged.

Fortunately, it’s easy to meet your daily vitamin A requirement. Cod liver oil, beef or chicken liver, whole milk and whole eggs all are excellent sources; as are carrots, pumpkin, mango, sweet potatoes, papaya and melon. Eating fresh foods is best, because heating, cooking or canning destroys vitamin A. If you don't want to eat foods that are rich in vitamin A in their raw forms, you can take a nutritional supplement. Because vitamin A is a fat-soluble vitamin (that is, the body can absorb it only with the help of fat in the diet), it’s best to take vitamin A after a meal.

Some people are particularly at risk of vitamin A deficiency, such as those with cystic fibrosis or pancreatic disorders, or if you’ve had stomach surgery or damage to the intestinal lining after diarrhea. These all cause your ability to absorb vitamin A to be adversely affected.

Vegetarians who do not consume eggs or dairy foods usually have a greater need for vitamin A supplementation, as do people who smoke or drink alcohol -- tobacco use prevents your body from absorbing vitamin A, and drinking alcoholic beverages depletes the vitamin A already stored in your body.

Remember, however, that “more” is not always “better.” To be safe, follow the NIH Institute of Medicine Daily Tolerable Upper Levels for intake of vitamin supplements to help prevent the risk of toxicity:

Recommended Dietary Allowances (RDAs) for vitamin A

Age
(years)
Children
(mcg RAE)
Males
(mcg RAE)
Females
(mcg RAE)
Pregnancy
(mcg RAE)
Lactation
(mcg RAE)
1-3300
(1,000 IU)




4-8400
(1,320 IU)




9-13600
(2,000 IU)




14-18
900
(3,000 IU)
700
(2,310 IU)
750
(2,500 IU)
1,200
(4,000 IU)
19+
900
(3,000 IU)
700
(2,310 IU)
770
(2,565 IU)
1,300
(4,300 IU)

Excerpt from the NIH Vitamin A and Carotenoids Fact Sheet:
RDAs for vitamin A are listed as micrograms (mcg) of Retinol Activity Equivalents (RAE) to account for the different biological activities of retinol and provitamin A carotenoids. This table also lists RDAs for vitamin A in International Units (IU), which are used on food and supplement labels (1 RAE = 3.3 IU)

NOTE: The information in this article about vitamin A is not meant to take the place of professional medical advice. Check with your doctor before making decisions on any vision care supplement.
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