Vitamin A

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 ³⁸]]> are expressed in international units (IUs) or retinol activity equivalents (RAE), which are measured in micrograms, as follows:

• Infants
  • 0-6 months: 400 mcg RAE or 1,330 IU
  • 7-12 months: 500 mcg RAE or 1,665 IU
• Children
  • 1-3 years: 300 mcg RAE or 1,000 IU
  • 4-8 years: 400 mcg RAE or 1,330 IU
• Males
  • 9-13 years: 600 mcg RAE or 2,000 IU
  • 14 years and older: 900 mcg RAE or 3,000 IU
• Females
  • 9-13 years: 600 mcg RAE or 2,000 IU
  • 14 years and older: 700 mcg RAE or 2,330 IU
• Pregnant Women
  • 18 years or younger: 750 mcg RAE or 2,500 IUs
  • 19 years and older: 770 mcg RAE or 2,560 IU
• Nursing Women
  • 18 years or younger: 1,200 mcg RAE or 4,000 IUs
  • 19 years and older: 1,300 mcg RAE or 4,300 IU

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. However, certain diseases can 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.

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 infectious illnesses among children in developing countries, ^3,39]]> 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 might improve blood sugar control in people with ]]>diabetes]]> . Unfortunately, people with diabetes may also 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 shown some potential for preventing one type of skin cancer (squamous cell cancer). ]]>^41,42]]> However, in these studies, doses above the standard safe upper limits have been used. With proper monitoring, this may be safe, but we do not recommend trying it without physician supervision. High-dose vitamin A has been tried for a variety of other skin diseases, including ]]>acne]]> , ]]>psoriasis]]> , ]]>rosacea]]> , ]]>seborrhea]]> , and ]]>eczema]]> , ]]>^21-24]]> as well as menorrhagia (heavy menstruation) ]]>⁴]]> and ]]>retinitis pigmentosa]]> (a chronic disease of the eyes). ]]>^43-44]]> However, the benefits seen have been modest at best, and again the recommended dosages of vitamin A are so high as to raise concerns about toxic risk.

Vitamin A might be beneficial for people with HIV; however, results of studies have been contradictory, and some evidence even suggests that vitamin A supplements might increase transmission of the disease from a pregnant mother to her newborn. ]]>⁴⁵]]>

Topical vitamin A may be helpful for treatment of aging skin. One double-blind, placebo-controlled study found that a 0.4% vitamin A lotion applied three times a week significantly reduced the number of “fine” wrinkles in seniors. ]]>⁴⁶]]> Benefits were also seen in terms of some biochemical measures of skin health.

On the basis of very weak evidence, too weak to be relied upon at all, vitamin A has been proposed as a treatment for a wide variety of other conditions, including Down's syndrome, ]]>ear infections]]> , ]]>eating disorders]]> , ]]>glaucoma]]> , ]]>gout]]> , impaired ]]>night vision]]> , ]]>kidney stones]]> , ]]>lupus]]> , ]]>multiple sclerosis]]> , ]]>ulcerative colitis]]> , and ]]>ulcers]]> .

One study suggests that vitamin A is not effective for ]]>Crohn's disease]]> . ]]>¹²]]>

What Is the Scientific Evidence for Vitamin A?

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]]> ).

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 fairly 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, 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 2,000 IU
• Children
  • 1-3 years: 600 mcg RAE or 2,000 IU
  • 4-8 years: 900 mcg RAE or 3,000 IU
• Males and Females
  • 9-13 years: 1,700 mcg RAE or 5,660 IUs
  • 14-18 years: 2,800 mcg RAE or 9,320 IUs
  • 19 years and older: 3,000 mcg RAE or 10,000 IU
• Pregnant Women
  • 18 years old or younger: 2,800 mcg RAE or 9,320 IU
  • 19 years and older: 3,000 mcg RAE or 10,000 IU
• Nursing Women
  • 18 years old or younger: 2,800 mcg RAE or 9,320 IU
  • 19 years and older: 3,000 mcg RAE or 10,000 IU

It is thought that 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. However, one recent study found no harm with dosages as high as 75,000 IU taken for 1 year. ]]>⁴²]]> Nonetheless, we do not recommend using vitamin A at doses over the upper levels, except under close physician supervision. Some people may be more likely to develop toxic symptoms than others.

If you already have liver disease, check with your doctor before taking vitamin A supplements, because even small doses may be harmful.

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.

Excessive intake of vitamin A (or ]]>beta-carotene]]> ) appears to accelerate liver injury in people with ]]>alcoholism]]> . ]]>³⁴]]> In addition, relatively high intake of vitamin A (but not beta-carotene) has been associated with increased risk of ]]>osteoporosis]]> . ]]>^35,40]]>

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]]> medications (Depakote, Depacon, or Depakene) may be even more at risk of vitamin A toxicity. ]]>³⁶]]>

Vitamin A may increase the anticoagulant effects of ]]>warfarin]]> (Coumadin). ]]>³⁷]]> In addition, because vitamin A chemically resembles the drug ]]>isotretinoin]]> (Accutane), it may amplify its toxic effects.

Interactions You Should Know About

If you are taking:

• Isotretinoin (Accutane)]]> : Don't take vitamin A, as the two might enhance each other's toxicity.
• ]]>Valproic acid (Depakote, Depacon, or Depakene)]]>and you are pregnant : Do not take vitamin A supplements unless advised to do so by a physician.
• ]]>Warfarin]]> (Coumadin): Do not take vitamin A supplements unless advised to do so by a physician.