Herbs & Supplements:
Vitamin A

Supplement Forms / Alternate Names:
  • Retinol
Principal Proposed Uses
  • Viral Infections in Children in Developing Countries
Other Proposed Uses
  • Diabetes, Skin Disorders, Acne, Psoriasis, Menorrhagia (Heavy Menstruation), HIV Support, Down's Syndrome, Ear Infections, Eating Disorders, Glaucoma, Gout, Impaired Night Vision, Kidney Stones, Lupus, Multiple Sclerosis, Ulcerative Colitis, Ulcers, Crohn's Disease

Note: Beta-carotene is sometimes used interchangeably with vitamin A, because the body can turn beta-carotene into vitamin A.

Vitamin A is a fat-soluble antioxidant that protects your cells against damaging free radicals and plays other vital roles in the body. However, it is potentially more dangerous than most other vitamins because it can build up to toxic levels, causing liver damage and birth defects. For this reason, it should be used with caution.

In general, beta-carotene supplements taken at nutritional doses are a safer way to get the vitamin A you need. Sometimes called "provitamin A," beta-carotene is transformed into vitamin A as your body needs it, and presents much less risk of toxicity.

Requirements/Sources

Vitamin A is an essential nutrient—meaning you must get it in the diet. The official U.S. recommendations for daily intake of vitamin A are expressed in international units (IUs) or retinol activity equivalents (RAE), which are measured in micrograms (mcg), as follows:³⁸

• Infants 0–6 months, 400 mcg RAE or 1330 IU
  7–12 months, 500 mcg RAE or 1665 IU
• Children 1–3 years, 300 mcg RAE or 1000 IU
  4–8 years, 400 mcg RAE or 1330 IU
• Males 9–13 years, 600 mcg RAE or 2000 IU
  14 years and older, 900 mcg RAE or 3000 IU
• Females 9–13 years, 600 mcg RAE or 2000 IU
  14 years and older, 700 mcg RAE or 2330 IU
• Pregnant women, 770 mcg RAE or 2560 IU (750 mcg RAE or 2500 IUs if 18 years old or younger)
• Nursing women, 1,300 mcg RAE or 4300 IU (1,200 mcg RAE or 4000 IUs if 18 years old or younger)

Beta-carotene supplements can be used to provide vitamin A, but they are only half as potent. To make interpretation easier, the amount of beta carotene in a supplement is usually stated in terms of equivalent vitamin A activity.

Warning: Pregnant women should not take vitamin A supplements. Instead they should take beta-carotene.

We get vitamin A from many foods, in the form of either vitamin A or beta-carotene. Liver and dairy products are excellent sources of vitamin A. Carrots, apricots, collard greens, kale, sweet potatoes, parsley, and spinach are good sources as well.

Deficiency in vitamin A is common in developing countries.¹ In the developed world, deficiency is relatively rare, except among teenagers and those in lower socioeconomic groups. Certain diseases can also cause vitamin A deficiency, by impairing the ability of the digestive tract to absorb nutrients. These include Crohn’s disease, ulcerative colitis, and cystic fibrosis. Finally, the older cholesterol-lowering drugs cholestyramine and colestipol can reduce vitamin A levels; however, the effect is slight and probably not significant.²

Therapeutic Dosages

Although some studies have used high doses of vitamin A, intake above the safe upper limit level is not recommended except on physician advice (see Safety Issues).

Therapeutic Uses

There is some evidence that vitamin A supplements reduce deaths from measles and other causes among children in developing countries,³ presumably because they correct a deficiency in the children's diets. This doesn't mean that vitamin A supplements above and beyond the basic nutritional requirement are a useful treatment for measles or any other childhood disease.

Vitamin A may be helpful for diabetes. However, there are concerns that people with diabetes may be especially vulnerable to liver damage from excessive amounts of vitamin A (see Safety Issues). Therefore, if you have diabetes, you should take vitamin A only on the advice of a physician.

Vitamin A has been used in the past for a variety of skin diseases such as acne and psoriasis, but since you need to use large amounts (which could cause toxicity) to achieve benefits, standard medications are safer. High-dose vitamin A may also be helpful for menorrhagia (heavy menstruation),⁴ but again it is not safe.

Vitamin A deficiency may be linked to lower immune cell counts as well as higher death rates among people infected with HIV.⁵ A few preliminary studies have raised hopes that beta-carotene supplements (a source of vitamin A) might increase or preserve immune function or decrease symptoms among people with HIV.^6–9 However, not all studies have had positive results.^10,11

In addition, vitamin A has been proposed as a treatment for a wide variety of other conditions, some of them quite serious, including AIDS, Down's syndrome, ear infections, eating disorders, glaucoma, gout, impaired night vision, kidney stones, lupus, multiple sclerosis, ulcerative colitis, and ulcers. There is little to no evidence that it is effective for any of these conditions. One study suggests that vitamin A is not effective for Crohn's disease.¹²

What Is the Scientific Evidence for Vitamin A?

Viral Infections (in Children Living in Developing Countries)

Vitamin A has been tried as a treatment for various viral infections, including measles, respiratory syncytial virus (RSV, a common childhood viral disease of the respiratory tract), chicken pox, and AIDS.

Most of the research on vitamin A has concentrated on children in developing countries. A review article examining 12 studies suggested that vitamin A supplements can protect such children from dying, and should be used more widely.¹³

Success with measles led researchers to study its use in respiratory syncytial virus.^14,15 However, the results were not impressive.

Diabetes

According to many^16,17 but not all^18,19 studies, people with diabetes tend to be deficient in vitamin A.

An observational study suggests that vitamin A supplements may improve blood sugar control in people with diabetes.²⁰ However, due to safety concerns, they should not supplement with vitamin A except under medical supervision (see Safety Issues).

Skin Disorders

Vitamin A has been tried for various skin disorders, including acne, psoriasis, rosacea, seborrhea, and eczema.^21–24 However, the benefits have not been great, and generally vitamin A has to be taken in potentially toxic dosages to produce good effects.

Menorrhagia (Heavy Menstruation)

One study suggests that women with heavy menstrual bleeding can benefit from taking 25,000 IU daily of vitamin A.²⁵ But vitamin A cannot be recommended as an ongoing treatment for menorrhagia, since women who menstruate can become pregnant, and even low doses of supplemental vitamin A may cause birth defects.

HIV Support

One small double-blind study suggested that taking beta-carotene might raise white blood cell count in people with HIV.²⁶ However, two subsequent larger controlled trials found no significant differences between those taking beta-carotene or placebo in white blood cell count, CD4+ count, or other measures of immune function.^27,28

Two observational studies lasting 6 to 8 years suggest that higher intakes of vitamin A or beta-carotene may be helpful, but they also found that caution is in order with regard to dosage.^29,30 This group of researchers generally linked higher intake of vitamin A or beta-carotene to lower risk of AIDS and lower death rates, with an important exception: people with the highest intake of either nutrient (more than 11,179 IU per day of beta-carotene; or more than 20,268 IU per day of vitamin A) did worse than those who took somewhat less.

Despite hopes that vitamin A given to pregnant, HIV-positive women might decrease the infection rate of their babies, two double-blind studies have found no significant differences between babies whose mothers took vitamin A compared to those whose mothers took placebo.^31,32 In any case, vitamin A is not considered safe in pregnancy; beta-carotene is preferred.

Crohn's Disease

According to a double-blind study of 86 people with Crohn's disease, vitamin A does not help prevent flare-ups.³³

Safety Issues

The safe upper intake levels of vitamin A have been set as follows:³⁸

• Infants 0–12 months, 600 mcg RAE or 2000 IU
• Children 1–3 years, 600 mcg RAE or 2000 IU
  4–8 years, 900 mcg RAE or 3000 IU
• Males and females 9–13 years, 1,700 mcg RAE or 5660 IUs
  14–18 years, 2,800 mcg RAE or 9320 IUs
  19 years and older, 3,000 mcg RAE or 10,000 IU
• Pregnant women, 3,000 mcg RAE or 10,000 IU (2,800 mcg RAE or 9320 IU if 18 years old or younger)
• Nursing women, 3,000 mcg RAE or 10,000 IU (2,800 mcg RAE or 9320 IU if 18 years old or younger)

Dosages of vitamin A above 50,000 IU per day taken for several years can cause liver injury, bone problems, fatigue, hair loss, headaches, and dry skin. If you already have liver disease, check with your doctor before taking vitamin A supplements, because even small doses may be harmful for you. Also, it is thought that people with diabetes may have trouble releasing vitamin A stored in the liver. This may mean that they are at greater risk for vitamin A toxicity. For different reasons, individuals who consume too much alcohol may also be at higher risk of vitamin A toxicity.³⁴ In addition, excessive intake of vitamin A may increase the risk of osteoporosis.³⁵

Women should avoid supplementing with vitamin A during pregnancy, because at toxic levels it might increase the risk of birth defects. Pregnant women taking valproic acid may be even more at risk of vitamin A toxicity.³⁶

Vitamin A may also increase the anticoagulant effects of warfarin.³⁷ You should not take supplementary vitamin A unless under a physician's supervision.

Interactions You Should Know About

If you are taking

• The older cholesterol-lowering drugs cholestyramine or colestipol: You may need more vitamin A (preferably as beta-carotene).
• Isotretinoin (Accutane): Don't take vitamin A as they might enhance each other's toxicity.
• Valproic acid or other anticonvulsants: Do not take vitamin A if you are pregnant unless on the advice of a physician.
• Warfarin: You should not take vitamin A unless under a doctor's supervision.

Last reviewed July 2002 by Medical Review Board

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