eVitamins Schweiz: What is Vitamin A?

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Learn all about Vitamin A

Also indexed as: A Vitamin, Retinol (Vitamin A)

How to take Vitamin A

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 remains unclear.

Where to Find It

Liver, dairy products, and cod liver oil are good sources of vitamin A. Vitamin A is also available in supplement form.

Possible Deficiencies

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. 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. 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 dietary intake.

References

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75. Stephensen CB, Franchi LM, Hernandez H, et al. Adverse effects of high-dose vitamin A supplements in children hospitalized with pneumonia. Pediatrics 1998;101(5):E3 [abstract].

76. Bresee JS, Fischer M, Dowell SF, et al. Vitamin A therapy for children with respiratory syncytial virus infection: a multicenter trial in the United States. Pediatr Infect Dis J 1996;15:777–82.

77. Quinlan KP, Hayani KC. Vitamin A and respiratory syncytial virus infection. Serum levels and supplementation trial. Arch Pediatr Adolesc Med 1996;150:25–30.

78. Kjolhede CL, Chew FJ, Gadomski AM, et al. Clinical trial of vitamin A as adjuvant treatment for lower respiratory tract infections. J Pediatr 1995;126:807–12.

79. Pinnock CB, Douglas RM, Badcock NR. Vitamin A status in children who are prone to respiratory tract infections. Aust Paediatr J 1986;22:95–9.

80. Murphy S, West KP Jr, Greenough WB 3d, et al. Impact of vitamin A supplementation on the incidence of infection in elderly nursing-home residents: a randomized controlled trial. Age Ageing 1992;21:435–9.

81. 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 Pediatr 2000;137:660–7.

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93. Coutsoudis A, Broughton M, Coovadia HM. Vitamin A supplementation reduces measles morbidity in young African children: a randomized, placebo-controlled, double-blind trial. Am J Clin Nutr 1991;54:890–5.

94. Rosales FJ, Kjolhede C. A single 210-mumol oral dose of retinol does not enhance the immune response in children with measles. J Nutr 1994;124:1604–14.

95. Rahmathullah L. Effect of receiving a weekly dose of vitamin A equivalent to the recommended dietary allowances among pre school children on mortality in south India. Indian J Pediatr 1991;58:837–47.

96. Vijayaraghavan K, Rashmiah G, Suryaprakasam B, et al. Effect of massive dose of vitamin A on morbidity and mortality in Indian children. Lancet 1990;336:1342–53.

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164. Lee J, Jiang S, Levine N, Watson RR. Carotenoid supplementation reduces erythema in human skin after simulated solar radiation exposure. Proc Soc Exp Biol Med 2000;223:170–4.

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166. Aust O, Stahl W, Sies H, et al. Supplementation with tomato-based products increases lycopene, phytofluene, and phytoene levels in human serum and protects against UV-light-induced erythema. Int J Vitam Nutr Res 2005;75:54–60.

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174. Fuchs J, Kern H. Modulation of UV-light-induced skin inflammation by D-alpha-tocopherol and L-ascorbic acid: a clinical study using solar simulated radiation. Free Radic Biol Med 1998;25:1006–12.

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177. Garmyn M, Ribaya-Mercado JD, Russel RM, et al. Effect of beta-carotene supplementation on the human sunburn reaction. Exp Dermatol 1995;4:104–11.

178. Wolf C, Steiner A, Honigsmann H, et al. Do oral carotenoids protect human skin against UV erythema, psoralen phototoxicity, and UV-induced DNA damage? J Invest Dermatol 1988;90:55–57.

179. Mathews-Roth MM, Pathak MA, Parrish J, et al. A clinical trial of the effects of oral beta-carotene on the responses of human skin to solar radiation. J Invest Dermatol 1972;59:349–53.

180. Gollnick HP, Hopfenmuller W, Hemmes C, et al. Systemic B-carotene plus topical sunscreen are an optimal protection against harmful effects of natural UV-sunlight. Eur J Dermatol 1996;6:200–5.

181. Lee J, Jiang S, Levine N, Watson RR. Carotenoid supplementation reduces erythema in human skin after simulated solar radiation exposure. Proc Soc Exp Biol Med 2000;223:170–4.

182. Heinrich U, Gartner C, Wiebusch M, et al. Supplementation with beta-carotene or a similar amount of mixed carotenoids protects humans from UV-induced erythema. J Nutr 2003;133:98–101.

183. Aust O, Stahl W, Sies H, et al. Supplementation with tomato-based products increases lycopene, phytofluene, and phytoene levels in human serum and protects against UV-light-induced erythema. Int J Vitam Nutr Res 2005;75:54–60.

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186. La Ruche G, Cesarini JP. Protective effect of oral selenium plus copper associated with vitamin complex on sunburn cell formation in human skin. Photodermatol Photoimmunol Photomed 1991;8:232–5.

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Vitamin A Benefits

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