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. For this reason, it should be used with caution.
It has long been assumed that beta-carotene supplements taken at nutritional doses are a safer way to get the vitamin A you need. However, while this may be true in general, beta-carotene also appears to present some risks. See the full
article for more information.
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, as follows:
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
ulcerative colitis, and cystic fibrosis.
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
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
eczema,21-24 as well as menorrhagia (heavy menstruation)4
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,
ulcerative colitis, and
One study suggests that vitamin A is
According to many
but not all
studies, people with
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
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.
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
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.
According to a double-blind study of 86 people with
Crohn's disease, vitamin A does
not help prevent flare-ups.33
Lower respiratory tract infections include conditions like pneumonia and bronchiolitis. Young children are especially susceptible to these infections. A review of 10 trials involving over 33,000 children under age 7 years found that, in the majority of cases, vitamin A did not reduce the incidence of infection or severity of symptoms.47
In two of the studies, vitamin A was beneficial for undernourished children. However, children with adequate nutrition actually faired worse.
The safe upper intake levels of vitamin A have been set as follows:38
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
In addition, relatively high intake of vitamin A (but
beta-carotene) has been associated with increased risk of
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
In addition, because vitamin A chemically resembles the drug
(Accutane), it may amplify its toxic effects.
If you are taking:
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Last reviewed September 2014 by EBSCO CAM Review Board
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