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vitamin A

What Is It?
Health Benefits
Forms
Recommended Intake
If You Get Too Little
If You Get Too Much
General Dosage Information
Guidelines for Use
General Interaction
Cautions
References
Evidence Based Rating Scale


What Is It?

This famed vision-enhancing nutrient was isolated in 1930, the first Fat-soluble Vitamin to be discovered. The body acquires some of its vitamin A through animal fats. The rest it synthesizes in the intestines from the beta-carotene and other carotenoids abundant in many fruits and vegetables.

Vitamin A is stored in the liver. Small amounts are also found in most human tissues in chemical forms called retinoids, a name related to the vitamin's critical effect on vision (and particularly on the retina of the eye). (1)

Health Benefits

Although vitamin A is probably best known for promoting and maintaining healthy eyesight, it has other important functions as well. One of its major contributions is to improve the body's resistance to infection. It does this in part by maintaining the health of the skin, mucous membranes, and other surface linings (intestinal tract, urinary tract, respiratory tract) so that harmful bacteria and viruses can't get into your body.

Another way that vitamin A boosts immunity is by enhancing the infection-fighting actions of the white blood cells called lymphocytes. Vitamin A is also vital to the growth of bones, the division of cells in your body, and to human reproduction.

Specifically, vitamin A may help to:

  • Promote healthy vision. This nutrient is involved in the proper functioning of the retina of the eye and is essential for the integrity of the mucous membranes surrounding the eyes. It is invaluable in preventing night blindness, and assisting the eye in adapting from bright light to darkness. Vitamin A eyedrops (available over-the-counter) are also effective in treating a disorder known as dry eye, caused by a failure of the tear glands to produce sufficient fluid. (3) And a study of nearly 3000 persons in Sydney, Australia showed that those getting higher amounts of vitamin A in their diets were half as likely to develop nuclear cataracts. (33)
  • Ward off infections such as colds, flu, sore throat, and bronchitis. By supporting the healthy maintenance of mucous membranes, vitamin A may be useful for fighting colds and other common infections. In the case of chronic bronchitis, the nutrient encourages healing of damaged lung tissue and may even help to prevent recurrences. In a 1996 Brazilian study, male smokers with mild chronic obstructive pulmonary disease (COPD) were found to have improved pulmonary function after being given 5000 IU of vitamin A daily for 30 days. (4)

  • Fight cancer. This immune-system booster may be of value in reducing the risk of breast cancer (5) and reducing the number of new tumors in smokers with lung cancer. (6) Vitamin A in combination with chemotherapy has been found to increase  the survival rate of leukemia patients.(7,8) It may also protect against the development of a melanoma (a form of skin cancer that is often highly malignant).(9,10) In addition, some research indicates that cancer patients with high vitamin A levels respond particularly well to chemotherapy treatment.(11)
  • Treat skin disorders, such as acne, eczema, psoriasis, and rosacea. Research has shown that vitamin A is vital for healthy skin. (12) In the l940s, high doses were prescribed for conditions such as psoriasis and acne. This practice ended abruptly with the realization that such high doses are toxic. (13) Today, doctors commonly prescribe safer medications made from derivatives of vitamin A, such as retinoic acid (Retin A, a popular prescription cream for acne and wrinkles) and isotretinoin (Accutane, an oral drug prescribed for severe acne and rosacea). Short of prescription medications, however, careful use of moderate oral doses--see the Dosage Recommendations Chart--may be key to promoting skin health.
  • Control cold sores. Vitamin A has well-known antiviral properties, and it may be worth trying orally to boost immunity. Liquid forms can even be applied directly to cold sores, also known as fever blisters, which develop as a result of a herpes simplex viral infection.
  • Correct hair and scalp problems. One of the signs of a vitamin A deficiency (albeit a severe one) is flakiness of the scalp. Correcting the deficiency may eliminate this often itchy and embarrassing condition. Vitamin A provides relief from folliculitis, a scalp condition where itchy bumps surround inflamed hair bumps. In addition, vitamin A in combination with minoxidil may accelerate hair growth. (14,15) But keep in mind that more isn't always better when it comes to vitamins: Too much vitamin A (more than 100,000 IU a day) taken over a long time can actually cause hair loss (among other problems).
  • Encourage healing of minor burns, cuts, and scrapes. When applied to the skin, vitamin A cream or ointment can accelerate the healing of minor cuts, burns, and scrapes. (16,17) It’s often combined with vitamin D for this use.
  • Protect against certain gastrointestinal problems. Because it is helpful in protecting the lining of the digestive tract, vitamin A may ease symptoms of Inflammatory Bowel Disease (IBD) and ulcers. (18) A large study of men ages 40-75 showed that those who were least likely to suffer from ulcers of the duodenum (a part of the small intestine) were the ones who had the highest intake of vitamin A, mainly from a combination of diet, multivitamins, and supplements. (19)
  • Increase testosterone levels. Early studies indicate retinol increased testosterone levels in male rats and low testosterone levels were linked with vitamin A deficiency. (20,21)
  • Reduce swelling from sprains and strains. The anti-inflammatory properties of vitamin A may reduce swelling in sprains and strains. In addition, the supplement may help repair damaged tissue.(22)
  • Thyroid disease. Animal studies indicate vitamin A affects the production of the thyroid hormone triiodothyronine (T3), and protects the body from damage in hyperthyroidism. More studies are needed in humans. (23)
  • Replace deficiency in Crohn's disease. Vitamin A deficiency is often seen in patients with Crohn's disease due to malabsorption. This puts them at a high risk for developing night blindness. (27)
Forms
  • tablet
  • suppository
  • softgel
  • ointment
  • liquid
  • cream
  • capsule

Recommended Intake

The RDA for vitamin A is 5,000 IU daily for men, and 4,000 IU daily for women.

If You Get Too Little

Few people in the United States suffer from a deficiency of vitamin A, although those with vitamin-poor diets are at risk (indeed, some elderly individuals fall into this category). Low levels can significantly reduce resistance to infection, cause a flaky scalp, and contribute to heavy or prolonged menstrual periods. And very low levels of this nutrient can cause night blindness or even complete blindness.

If You Get Too Much

Excessive vitamin A from supplements can cause serious health problems. It's virtually impossible to get too much of this nutrient from foods; the body makes only what it needs from carotenoid-rich fruits and vegetables. But care is needed when taking supplements containing "preformed" vitamin A, meaning it has already been synthesized for you during the manufacturing process.

Symptoms of vitamin A toxicity include irritability, headache, double vision, dry and cracking skin, brittle nails, excessive hair loss, nausea and vomiting, weight loss, bone and joint pain, liver damage, fatigue, bleeding gums, hemorrhage, and coma. Women who are pregnant or may become pregnant should be especially cautious, as excess doses are known to cause fetal abnormalities. 

General Dosage Information

Special tips:
--Some sources measure vitamin A in retinol equivalents (RE) reported as μg/day rather than as international units (IU); one RE is equivalent to 3.3 IU.

--Most multivitamins offer vitamin A as beta-carotene, an Antioxidant that the body can convert to vitamin A. However, the amount of vitamin A produced during this conversion is small and inadequate for those conditions in which vitamin A itself was shown to be therapeutic.

Be sure to check out our Dosage Recommendations Chart for Vitamin A, which lists therapeutic dosages for specific ailments at a glance. Note: the doses listed are for adults. Dosage recommendations for children and youth under 18 should be guided by your pediatrician.

Guidelines for Use

  • Make sure to take vitamin A supplements with food; some fat in the diet will enhance absorption. 

  • Both vitamin E and zinc aid the body in using vitamin A. Research has shown that zinc aids the body in using vitamin A for restoring night vision. (24) In turn, vitamin A facilitates the absorption of iron from foods. A good daily multiple vitamin/Mineral will provide the necessary amounts.

    • General Interaction

  • Don't take vitamin A in addition to isotretinoin or other acne drugs. Together, they may cause high blood levels of vitamin A, which can lead to unwanted side effects. 

  • Mineral oil (sometimes used for constipation) and cholesterol-adsorbing resins such as cholestyramine used for reducing cholesterol, may interfere with vitamin A absorption.

    Note: For information on interactions with specific generic drugs, see our WholeHealthMD Drug/Nutrient Interactions Chart.

    • Cautions

  • Don't exceed recommended doses of vitamin A. Large doses of preformed vitamin A can build up to toxic levels. Because vitamin A is stored in the liver, the risk for developing hypervitaminosis A is related to total cumulative dose of vitamin A rather than a specific daily dose.

  • However, if you're pregnant or may become pregnant, don't take more than 5,000 IU of vitamin A daily as a supplement. Pregnant women should add up doses of vitamin A intake from all sources. Forms of vitamin A are found in several foods including animal products, primarily liver, some fortified breakfast cereals and other dietary supplements. There may also be absorption from skin care products. Amounts over 10,000 IU/day may result in birth defects. A good combination prenatal vitamin is your best source. Practice birth control if consuming doses greater than 5,000 IU, and for a month after stopping.

    References 

    1. Wolf George. A History of Vitamin A and Retinoids. FASEB J. July 1996;10:1102-1107
    2. Guven M, Aladag I, Eyibilen A, Filiz NO, Ozyurt H, Yelken K. Experimentally induced acute sinusitis and efficacy of vitamin A. Acta Otolaryngol. 2007 Aug;127(8):855-60.
    3. Kim EC, Choi JS, Joo CK. A Comparison of Vitamin A and Cyclosporine A 0.05% Eye Drops for Treatment of Dry Eye Syndrome. Am J Ophthalmol. 2008 Oct 8.
    4. Paiva SA, Godoy I, Vannucchi H, Fávaro RM, Geraldo RR, Campana AO. Assessment of vitamin A status in chronic obstructive pulmonary disease patients and healthy smokers. Am J Clin Nutr. 1996 Dec;64(6):928-34.
    5. Zhang S, Hunter DJ, Forman MR, Rosner BA, Speizer FE, Colditz GA, Manson JE, Hankinson SE, Willett WC. Dietary carotenoids and vitamins A, C, and E and risk of breast cancer. J Natl Cancer Inst. 1999 Mar 17;91(6):547-56.
    6. Pastorino U, Infante M, Maioli M, Chiesa G, Buyse M, Firket P, Rosmentz N, Clerici M, Soresi E, Valente M, et al. Adjuvant treatment of stage I lung cancer with high-dose vitamin A. J Clin Oncol. 1993 Jul;11(7):1216-22.
    7. Di Febo A, Laurenti L, Falcucci P, Tosti ME, Fianchi L, Pagano L, Leone G. All-trans retinoic acid in association with low dose cytosine arabinoside in the treatment of acute myeoid leukemia in elderly patients. Am J Ther. 2007 Jul-Aug;14(4):351-5.
    8. Xin L, Wan-jun S, Zeng-jun L, Yao-zhong Z, Yun-tao L, Yan L, Chang-chun W, Qiao-chuan L, Ren-chi Y, Ming-zhe H, Jian-xiang W, Lu-gui Q. A survival study and prognostic factors analysis on acute promyelocytic leukemia at a single center. Leuk Res. 2007 Jun;31(6):765-71. Epub 2006 Sep 27
    9. Lens M, Medenica L. Systemic retinoids in chemoprevention of non-melanoma skin cancer. Expert Opin Pharmacother. 2008 Jun;9(8):1363-74.
    10. Alberts D, Ranger-Moore J, Einspahr J, Saboda K, Bozzo P, Liu Y, Xu XC, Lotan R, Warneke J, Salasche S, Stratton S, Levine N, Goldman R, Islas M, Duckett L, Thompson D, Bartels P, Foote J. Safety and efficacy of dose-intensive oral vitamin A in subjects with sun-damaged skin. Clin Cancer Res. 2004 Mar 15;10(6):1875-80
    11. Block KI, Koch AC, Mead MN, Tothy PK, Newman RA, Gyllenhaal Impact of antioxidant supplementation on chemotherapeutic efficacy: a systematic review of the evidence from randomized controlled trials. Cancer Treat Rev. 2007 Aug;33(5):407-18.
    12. Brelsford M, Beute TC. Preventing and managing the side effects of isotretinoin. Semin Cutan Med Surg. 2008 Sep;27(3):197-206
    13. Kowalski TE, Falestiny M, Furth E, Malet PF Vitamin A hepatotoxicity: a cautionary note regarding 25,000 IU supplements. Am J Med. 1994 Dec;97(6):523-8.
    14.Kwon OS, Pyo HK, Oh YJ, Han JH, Lee SR, Chung JH, Eun HC, Kim KH Promotive effect of minoxidil combined with all-trans retinoic acid (tretinoin) on human hair growth in vitro J Korean Med Sci. 2007 Apr;22(2):283-9
    15. [No authors listed] Promising treatment for folliculitis. Posit Aware. 1996 Jan-Feb;7(1):6
    16. Wicke C, Halliday B, Allen D, Roche NS, Scheuenstuhl H, Spencer MM, Roberts AB, Hunt TK. Effects of steroids and retinoids on wound healing. Arch Surg. 2000 Nov;135(11):1265-70.
    17. Hunt TK. Vitamin A and wound healing. J Am Acad Dermatol. 1986 Oct;15(4 Pt 2):817-21.
    18. Kasper H, Brodersen M, Schedel R Concentration of vitamin A, retinol-binding protein and prealbumin in serum in response to stress: A contribution to the prevention of stress ulcers by means of vitamin A. Acta Hepatogastroenterol (Stuttg). 1975 Dec;22(6):403-8.
    19.Katsambas A, Dessinioti C. New and emerging treatments in dermatology: acne. Dermatol Ther. 2008 Mar-Apr;21(2):86-95
    20. Chaudhary LR, Hutson JC, Stocco DM. Effect of retinol and retinoic acid on testosterone production by rat Leydig cells in primary culture. Biochem Biophys Res Commun 1989 Jan 31;158(2):400-6.
    21.Appling DR, Chytil F. Evidence of a role for retinoic acid (vitamin A-acid) in the maintenance of testosterone production in male rats. Endocrinology 1981 Jun;108(6):2120-4.
    22. Reifen R. Vitamin A as an anti-inflammatory agent. Proc Nutr Soc. 2002 Aug;61(3):397-400.
    23. Higueret P, Pailler I, Garcin H Vitamin A deficiency and tri-iodothyronine action at the cellular level in the rat. J Endocrinol. 1989 Apr;121(1):75-9
    24. Christian P, Khatry SK, Yamini S, Stallings R, LeClerq SC, Shrestha SR, Pradhan EK, West KP Jr Zinc supplementation might potentiate the effect of vitamin A in restoring night vision in pregnant Nepalese women. Am J Clin Nutr. 2001 Jun;73(6):1045-51.
    25. Aldoori WH, Giovannucci EL, Stampfer MJ, et al. Prospective study of diet and the risk of duodenal ulcer in men. Am J Epidemiol. 1997 Jan 1;145(1):42-50.
    26.Chytil F. Function of vitamin A in the respiratory tract. Acta Vitaminol Enzymol. 1985;7 Suppl:27-31.
    27. A N Main, P R Mills, R I Russell, J Bronte-Stewart, L M Nelson, A McLelland, and A Shenkin. Vitamin A deficiency in Crohn's disease. Gut. 1983 December; 24(12): 1169–1175.
    28. Romand R, Dollé P, Hashino E. Retinoid signaling in inner ear development. J Neurobiol. 2006 Jun;66(7):687-704
    29. Verfaille CJ, Borgers M, van Steensel MA. Retinoic acid metabolism blocking agents (RAMBAs): a new paradigm in the treatment of hyperkeratotic disorders J Dtsch Dermatol Ges. 2008 May;6(5):355-64.
    30. Turjanmaa K, Reunala T Isotretinoin treatment of rosacea. Acta Derm Venereol. 1987;67(1):89-91
    31. High KP, Legault C, Sinclair JA, et al. Low plasma concentrations of retinol and alpha-tocopherol in hematopoietic stem cell transplant recipients: the effect of mucositis and the risk of infection. Am J Clin Nutr. 2002;76:1358-66
    32. Wolf JS Jr, Soble JJ, Ratliff TL, Clayman RV. Ureteral cell cultures II: Collagen production and response to pharmacologic agents. J Urol. 1996 Dec;156(6):2067-72.
    33. Cumming RG, Mitchell P, Smith W. Diet and cataract: the Blue Mountains Eye Study. Ophthalmology 2000;10:450-6. 

    Evidence Based Rating Scale    

    The Evidence Based Rating Scale is a tool that helps consumers translate the findings of medical research studies with what our clinical advisors have found to be efficacious in their personal practice. This tool is meant to simplify which supplements and therapies demonstrate promise in the treatment of certain conditions. This scale does not take into account any possible interactions with any medication/ condition/ or therapy which you may be currently undertaking. It is therefore advisable to ask your doctor before starting any new treatment regimen.

    Condition

    Rating

    Explanation

     

      

     

     

    Acid-Related Stomach Disorders: Ulcers, GERD

     

     

     

     

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