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Vitamin A

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The forms

The two main forms of vitamin A are:

Retinol is the naturally occurring form of vitamin A found in animal products.

Beta-carotene is also called the 'plant' vitamin A. It is a carotenoid which is converted into vitamin A in the liver. Beta-carotene is found in brightly colored fruit and vegetables, such as carrots from which carotene is named.

The functions of vitamin A

Vitamin A plays an important role in many of our body's functions, including:

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The symptoms and signs of vitamin A deficiency

The symptoms of a vitamin A deficiency include:

Vitamin A deficiency can occur:

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Food sources of vitamin A

Vitamin A is found in animal foods such as whole eggs, whole milk and liver.

Carotenoids are found in darkly colored fruits and vegetables.

What Destroys Vitamin A?

Vitamin A can be destroyed by:

To retain vitamin A in food:

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How much vitamin A do we need?

Recommended Dietary Allowances for vitamin A in micrograms (mcg) Retinol Activity Equivalents (RAE) and International Units (IUs) for children and adults

Recommended Dietary Allowances
Age (years) Children Men Women Pregnancy Lactation
1-3 300 mcg or 1000 IU        
4-8 400 mcg or 1333 IU        
9-13 600 mcg or 2000 IU        
14-18   900 mcg or
3000 IU
700 mcg or
2330 IU
750 mcg or
2500 IU
1200 mcg or
4000 IU
19 +   900 mcg or
3000 IU
700 mcg or
2330 IU
770 mcg or
2565 IU
1300 mcg or
4335 IU

For infants, Adequate Intake for vitamin A in micrograms (mcg) and International Units (IU) is shown in the small table below.

Note that there is insufficient information to establish a RDA for vitamin A for infants. An adequate intake (AI) has been established that is based on the amount of vitamin A consumed by healthy infants who are fed breast milk.

Adequate Intake For Infants
Age (months) Males and Females
0 to 6 400 mcg or 1330 IU
7 to 12 500 mcg or 1665 IU

It is very important for anyone who consumes excessive amounts of alcohol to include good sources of dietary vitamin A. However, Vitamin A supplementation may not be recommended for individuals who abuse alcohol because alcohol may increase any liver toxicity associated with the excess intakes of vitamin A.

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Who may need extra vitamin A to prevent a deficiency?

The World Health Organization (WHO) and the United Nations International Children's Emergency Fund (UNICEF) have issued a joint statement about vitamin A and children's health. Both agencies recommend vitamin A supplements for:

In 1994, the American Academy of Pediatrics recommended vitamin A supplementation for:

Other people who may need vitamin A supplements include people with:

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Vitamin A, beta carotene and cancer

Vitamin A (and in particular beta carotene) has recently been identified as a powerful antioxidant and therefore anti-carcinogen.

There is evidence that a higher intake of green and yellow vegetables or other food sources of beta-carotene and/or vitamin A may decrease the risk of lung cancer, bladder cancer and skin cancers associated with excessive exposure to sunlight. However, the studies on this are still not entirely conclusive.

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Vitamin A toxicity

Questions have been raised concerning the toxicity of vitamin A, which is known to be concentrated in the liver.

Symptoms of vitamin A excess include:

Toxic symptoms can also arise after consuming very large amounts of vitamin A over a short period of time.

Beta-carotene does not cause toxicity.

Pregnant women and those planning pregnancy should not take in excess of 7,500 IU of vitamin A per day because of the risk of birth defects. Also avoid eating animal livers because of the high concentration of vitamin A in livers.

Over the past 15 years, synthetic retinoid has been prescribed for acne, psoriasis, and other skin disorders and is considered an effective anti-acne therapy. At very high doses, however, it can be toxic, which is why this medication is usually saved for the most severe forms of acne.

The most serious consequence of this medication is birth defects. It is extremely important for sexually active females who may become pregnant and who take these medications to use an effective method of birth control. Women of childbearing age who take these medications are advised to undergo monthly pregnancy tests to make sure they are not pregnant.

More of this vitamin is required when:

It may also be indicated if you suffer from diabetes or have an under-active thyroid gland. Be careful using vitamin A in pregnancy.

It is a good idea to take vitamin A with vitamins E, B group and C, choline, essential fatty acids, calcium, phosphorus and zinc for the best results.

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Bland, J. 1996, Contemporary Nutrition. J & B Associates.

Davies, S. and A. Stewart., 1997, Nutritional Medicine. Pan.

Holden, S., Hudson, K., Tilman, J. & D. Wolf, 2003, The Ultimate Guide to Health from Nature. Asrolog Publication.

Pressman, A. and S. Buff, 2000, The Complete Idiot's Guide to Vitamins and Minerals. (2nd Ed.) Alpha Books.

Soothill, R. 1996, The Choice Guide to Vitamins and Minerals. A Choice Book Publication.

Sullivan, K. 2002, Vitamins and Minerals: A Practical Approach to a Health Diet and Safe Supplementation. Harper Collins.

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In 1990, 39% of the vitamin A (including carotenes) in the diets of Americans came from fruits and vegetables. Dark-green vegetables and deep-yellow fruits and vegetables provided about half of the vitamin A.

Meats and dairy products each supplied about 20% of the vitamin A consumed.