Also indexed as: Retinol (A)
Vitamin A is a fat-soluble vitamin with four major functions in the body: (1) It helps
cells reproduce normally—a process called differentiation (cells that have not properly
differentiated are more likely to undergo pre-cancerous changes). (2) It is required for
vision; vitamin A maintains healthy cells in various structures of the eye and is required for
the transduction of light into nerve signals in the retina. (3) It is required for normal
growth and development of the embryo and fetus, influencing genes that determine the
sequential development of organs in embryonic development. (4) It may be required for normal
reproductive function, with influences on the function and development of sperm, ovaries and
Vitamin A has been used in
connection with the following conditions (refer to the individual
health concern for complete information):
Who is likely to be deficient?
People who limit their consumption of
liver, dairy foods, and beta-carotene-containing vegetables can develop a vitamin A deficiency.
Extremely low birth weight babies (2.2 pounds or less) are at high risk of being born with a
deficiency, and vitamin A shots given to these infants have been reported in double-blind
research to reduce the risk of lung disease.1 The earliest deficiency sign is poor
night vision. Deficiency symptoms can also
include dry skin, increased risk of
infections, and metaplasia (a precancerous condition). Severe deficiencies causing
blindness are extremely rare in Western societies.
Less severe deficiencies are more likely to occur with a variety of conditions causing malabsorption. A high incidence of vitamin A
deficiency in people infected with HIV has
also been reported. People with hypothyroidism
have an impaired ability to convert
beta-carotene to vitamin A.2 3 For this reason, some doctors suggest
taking supplemental vitamin A (perhaps 5,000–10,000 IU per day) if they are not
consuming adequate amounts in their diet.
Very old people with type 2 diabetes have
shown a significant age-related decline in blood levels of vitamin A, irrespective of their
How much is usually taken?
For most people, up to 25,000 IU (7,500 mcg) of vitamin A per day is considered safe.
However, people over age 65 and those with liver disease should probably not supplement with
more than 15,000 IU per day, unless supervised by a doctor. In women who could become pregnant, the maximum safe intake is being
re-evaluated. However, less than 10,000 IU (3,000 mcg) per day is generally accepted as safe.
There is concern that larger intakes could cause
birth defects. Whether the average person would benefit from vitamin A supplementation
Are there any side effects or interactions?
Since a 1995 report from the New England Journal of Medicine,5 women
who are or could become pregnant have been
told by doctors to take less than 10,000 IU (3,000 mcg) per day of vitamin A to avoid the risk
of birth defect. A recent report studied
several hundred women exposed to 10,000–300,000 IU (median exposure of 50,000 IU) per
day.6 Three major malformations occurred in this study, but all could have happened
in the absence of vitamin A supplementation. Surprisingly, no congenital malformations
happened in any of the 120 infants exposed to maternal intakes of vitamin A that exceeded
50,000 IU per day. In fact, the high-exposure group had a 50% decreased risk for malformations
compared with infants not exposed to vitamin A. The authors noted that some previous studies
found no link between vitamin A and birth defects, and argued the studies that did find such a
link suffered from various weaknesses. A closer look at the recent study reveals a 32% higher
than expected risk of birth defects in infants exposed to 10,000–40,000 IU of vitamin A
per day, but paradoxically a 37% decreased risk for those exposed to even higher levels. This
suggests that both “higher” and “lower” risks may have been due to
Excessive dietary intake of vitamin A has been associated with birth defects in humans in
fewer than 20 reported cases over the past 30 years.7 8 Presently, the
level at which vitamin A supplementation may cause birth defects is not known, though combined
human and animal data suggest that 30,000 IU per day should be considered safe.9
Women who are or who could become pregnant should consult with a doctor before supplementing
with more than 10,000 IU per day.
Vitamin A supplements can both help and hurt children. Many people have heard that vitamin
A supplements support immune function and
prevent infections. This is true under some
circumstances. However, vitamin A can also increase the risk of infections, according
to the findings of a double-blind trial.10 In a study of African children between
six months and five years old, a 44% reduction in the risk of severe diarrhea was seen in those children given four
100,000–200,000 IU applications of vitamin A (the lower amount for those less than a
year old) during an eight-month period. On further investigation, the researchers discovered
that the reduction in diarrhea occurred only in children who were very malnourished. For
children who were not starving, vitamin A supplementation actually increased the risk
of diarrhea compared with the placebo group. The vitamin A-supplemented children also had a
67% increased risk of coughing and rapid breathing, signs of further lung infection,
although this problem did not appear in children infected with AIDS. These findings should be
of concern to American parents, whose children are not usually infected with AIDS or severely
malnourished. Such relatively healthy children fared poorly in the African trial in terms of
both the risk of diarrhea and the risk of continued lung problems. Vitamin A provided no
benefit to the well-nourished kids. Therefore, it makes sense to not give vitamin A
supplements to children unless there is a special reason to do so, such as the presence of a
condition causing malabsorption (e.g., celiac disease).
In a study of people with retinitis pigmentosa (a degenerative condition of the eye),
participants received 15,000 IU of vitamin A per day for 12 years with no signs of adverse
effects or toxicity.11 For other adults, intake above 25,000 IU (7,500 mcg) per day
can—in rare cases—cause headaches, dry skin, hair loss, fatigue, bone problems,
and liver damage.12 At higher levels (for example 100,000 IU per day) these
problems become more common.
A controlled clinical trial showed that people who took 25,000 IU of vitamin A per day for
a median of 3.8 years had an 11% increase in
triglycerides, a 3% increase in total
cholesterol and a 1% decrease in HDL cholesterol compared to those who did not take
vitamin A.13 Although the significance of these findings is not clear, people at
risk for cardiovascular disease should use
caution when considering long-term vitamin A supplementation.
One study found that increasing the intake of vitamin A in the diet was associated with
bone loss and risk of hip fracture, possibly due to a vitamin A-induced stimulation of cells
that break down bone.14 In this study, a vitamin A intake greater than 5,000 IU per
day, when compared to a lower intake, was associated with a reduction in bone mineral density
that approximately doubles the risk of hip fracture. Beta-carotene (which can be used by the body to make
vitamin A) has not been linked to reduced bone mass. Until more is known, people concerned
about osteoporosis may consider taking
beta-carotene supplements rather than supplementing with vitamin A.
Data from test tube, animal, and human studies show that excessive vitamin A intake can
accelerate bone loss and inhibit formation of new bone, increasing the risk of
osteoporosis.15 In humans, small studies have found these effects at about
85,000–125,000 IU per day. 16 17
Taking vitamin A and iron together helps
overcome iron deficiency more effectively than
iron supplementation alone.18 Supplementation with zinc, iron, or the combination has been found to
improve vitamin A status among children at high risk for deficiency of the three
Are there any drug
Certain medicines may interact with vitamin A. Refer to drug interactions for a list of those medicines.
1. Tyson JE, Wright LL, Oh W, et al. Vitamin A supplementation for
extremely-low-birth-weight infants. N Engl J Med 1999;340:1962–8.
2. Smolle J, Wawschinek O, Hayn H, Eber O. Vitamin A and carotene in
thyroid disease. Acta Med Austriaca 1983;10:71–3 [in German].
3. Aktuna D, Buchinger W, Langsteger W, et al. Beta-carotene, vitamin A
and carrier proteins in thyroid diseases. Acta Med Austriaca 1993;20:17–20 [in
4. Polidori MC, Mecocci P, Stahl W, et al. Plasma levels of lipophilic
antioxidants in very old patients with type 2 diabetes. Diabetes Metab Res Rev
5. Rothman KJ, Moore LL, Singer MR, et al. Teratogenicity of high vitamin
A intake. N Engl J Med 1995;333:1369–73.
6. Mastroiacovo P, Mazzone T, Addis A, et al. High vitamin A intake in
early pregnancy and major malformations: a multicenter prospective controlled study.
7. Biesalski HK. Comparative assessment of the toxicology of vitamin A
and retinoids in man. Toxicology 1989;57:117–61.
8. Azais-Braesco V, Pascal G. Vitamin A in pregnancy: requirements and
safety limits. Am J Clin Nutr 2000;71(5 Suppl):1325S–33S [review].
9. Wiegand UW, Hartmann S, Hummler H. Safety of vitamin A: recent
results. Int J Vitam Nutr Res 1998;68:411–6 [review].
10. Fawzi WW, Mbise R, Spiegelman D, et al. Vitamin A supplements and
diarrheal and respiratory tract infections among children in Dar es Salaam, Tanzania. J
11. Sibulesky L, Hayes KC, Pronczuk A, et al. Safety of <7500 RE
(<25000 IU) vitamin A daily in adults with retinitis pigmentosa. Am J Clin Nutr
12. Bendich A, Langseth L. Safety of vitamin A. Am J Clin Nutr
13. Cartmel B, Moon TE, Levine N. Effects of long-term intake of retinol
on selected clinical and laboratory indexes. Am J Clin Nutr 1999;69:937–43.
14. Melhus H, Michaelsson K, Kindmark A, et al. Excessive dietary intake
of vitamin A is associated with reduced bone mineral density and increased risk for hip
fracture. Ann Int Med 1998;129:770–8.
15. Binkley N, Krueger D. Hypervitaminosis A and bone. Nutr Rev
16. Frame B, Jackson CE, Reynolds WA, Umphrey JE. Hypercalcemia and
skeletal effects in chronic hypervitaminosis A. Ann Intern Med
17. Patel P, Hanning RM, Atkinson SA, et al. Intoxication from vitamin A
in an asthmatic child. CMAJ 1988;139:755–6.
18. Mejia LA, Chew F. Hematological effect of supplementing anemic
children with vitamin A alone and in combination with iron. Am J Clin Nutr
19. Muñoz EC, Rosado JL, Lopez P, et al. Iron and zinc
supplementation improves indicators of vitamin A status of Mexican preschoolers. Am J Clin