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Vitamin A

 

Natural Standard Monograph, Copyright © 2013 (www.naturalstandard.com). Commercial distribution prohibited. This monograph is intended for informational purposes only, and should not be interpreted as specific medical advice. You should consult with a qualified health care professional before making decisions about therapies and/or health conditions.

Related Terms

  • 3,7-Dimethyl-9-(2,6,6,trimethyl-1-cyclohexen-1-yl)-2,4,6,8-natetraen-1-ol, 3-dehydroretinol, Accutane®, acitretin, adapalene, all-trans retinoic acid, Altinac®, Amnesteem®, antixerophthalmic vitamin, Aquasol A®, Avita®, axerophtholum, beta-carotene, beta-carotene oleovitamin A, bexarotene, Differin®, etretinate, isotretinoin, Palmitate-A®, Renova®, Retin-A®, Retin-A Micro®, retinaldehyde (RAL), retinyl acetate, retinyl N-formyl aspartamate, retinyl palmitate, retinoic acid, retinol, Solatene®, Soriatane®, SourceCF®, Targretin®, tazarotene, Tazorac®, Tegison®, topical retinoids, tretinoin, Vesabiod®, Vesanoid®, Vitamax®, vitamin A USP, vitamin A1, vitaminum A.

Background

  • Vitamin A is a fat-soluble vitamin that is derived from two sources: preformed retinoids and provitamin carotenoids. Retinoids, such as retinal and retinoic acid, are found in animal sources such as liver, kidney, eggs, and dairy produce. Carotenoids, such as beta-carotene (which has the highest vitamin A activity), are found in plants such as dark or yellow vegetables and carrots.
  • Natural retinoids are present in all living organisms, either as preformed vitamin A or as carotenoids, and are required for biological processes such as vision and cellular growth. A major biologic function of vitamin A (as the metabolite retinal) is in the visual cycle. Research also suggests that vitamin A may reduce the mortality rate from measles, prevent some types of cancer, aid in growth and development, and improve immune function.
  • Recommended dietary allowance (RDA) levels for vitamin A oral intake have been established by the U.S. Institute for Medicine of the National Academy of Sciences to prevent deficiencies in vitamin A. At recommended doses, vitamin A is generally considered nontoxic. Excess dosing may lead to acute or chronic toxicity.
  • Vitamin A deficiency is rare in industrialized nations but remains a concern in developing countries, particularly in areas where malnutrition is common. Prolonged deficiency can lead to xerophthalmia (dry eye) and ultimately to night blindness or total blindness, as well as to skin disorders, infections (such as measles), diarrhea, and respiratory disorders.

Evidence

 

Uses based on scientific evidence 

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare professional.

Grade* 

Acne 

Topical retinoids are considered among the best treatments for acne. Tretinoin (all-trans retinoic acid) Avita®, Renova®, Retin-A®, Retin-A Micro®) and derivatives of vitamin A, retinoids, and oral prescription medications, such as isotretinoin (Accutane®), are available for treatment. Isotretinoin may cause severe side effects, such as burning, erythema, and pruritus, and should be used only for severe resistant acne. Adapalene (Differin®), a naphthoic acid derivative and retinoid, is also effective and reported to have fewer side effects. Another retinoid, tazarotene (Tazorac®), has shown superior either tretinoin or adapalene. In general, supplementation with any retinoid (including tretinoin) must not be used in women who are pregnant, plan to become pregnant, or have a chance of being pregnant, due to a risk of severe birth defects. These medications should be prescribed and coordinated by a qualified licensed healthcare professional. Retinoids should not be used simultaneously, due to a risk of increased toxicity.

A 

Acute promyelocytic leukemia (treatment, all-trans retinoic acid) 

The prescription drug all-trans retinoic acid (ATRA, Vesanoid®) is a vitamin A derivative that is an established treatment for acute promyelocytic leukemia that improves median survival in this disease. Treatment should be under strict medical supervision. Vitamin A supplements should not be used simultaneously with ATRA, due to a risk of increased toxicity.

A 

Anemia 

Vitamin A deficiency has been shown to impair the mobilization of iron status, impair erythropoiesis, and increase susceptibility to infection. Vitamin A supplementation has been shown to raise hemoglobin levels and serum iron concentrations, particularly in children and pregnant women. It has also been shown to enhance the efficacy of iron supplementation in patients with vitamin A deficiency and iron deficiency anemia.

A 

Malaria (supportive agent) 

Limited research suggests that vitamin A may reduce fever, morbidity, and parasite blood levels in patients with malaria (Plasmodium falciparum infection). However, there is a lack of evidence suggesting that vitamin A is equivalent or superior to well-established drug therapies used for the prevention or treatment of malaria. Patients with malaria or those who are living or traveling in endemic areas should speak with a physician about appropriate measures.

A 

Measles (supportive agent) 

Vitamin A should be administered to children diagnosed with measles in areas where vitamin A deficiency may be present. Measles is a viral disease that can lead to serious complications, such as diarrhea, pneumonia, and encephalitis. Supplementation with vitamin A in children with measles has been shown to be beneficial, by decreasing the length and impact of the disease. Side effects such as diarrhea, pneumonia, and death have been reduced with the use of vitamin A. Management of measles should be under strict medical supervision.

A 

Mortality reduction (childhood; all-cause) 

Vitamin A is necessary for healthy growth and development, and recommended dietary allowances (RDAs) should be assured, particularly in children. Major causes of vitamin A deficiency in children are maternal vitamin A deficiency (thus low concentrations of vitamin A in breast milk), inadequate vitamin A intake upon weaning, and prevalent illness. Experts have maintained that in developing countries, diet alone is insufficient to main adequate vitamin A levels in children. Vitamin A is associated with a reduced risk of mortality in children.

A 

Retinitis pigmentosa 

Retinitis pigmentosa is a genetic disorder that affects night vision. Early symptoms include night blindness and progressive loss of vision over time. Based on recent findings, vitamin A in the palmitate form has been recommended in patients with retinitis pigmentosa.

A 

Skin damage caused by the sun 

Some studies suggest that topical tretinoin (all-trans retinoic acid, the acid form of vitamin A) may improve the appearance and integrity of photodamaged skin. Common adverse effects are skin pain and redness.

A 

Vitamin A deficiency 

Vitamin A deficiency is generally rare in industrialized nations. In developing countries, diet alone may be insufficient to maintain adequate vitamin A levels, especially in children. Vitamin A supplementation can help prevent or treat vitamin A deficiency.

A 

Xerophthalmia (dry eye) 

Prolonged vitamin A deficiency can lead to xerophthalmia (dry eye). It is most prevalent in rural, underdeveloped areas, such as India and Southeast Asia. Oral vitamin A is the treatment of choice for xerophthalmia caused by prolonged vitamin A deficiency, and it should be given immediately once the disorder is established. Bitot's spot, or the buildup of keratin debris in the conjunctiva, is a sign of xerophthalmia and may also be treated with vitamin A supplementation.

A 

Healing after photorefractive keratectomy (adjunct therapy) 

Photorefractive keratectomy is a type of laser eye surgery used to correct nearsightedness. High-dose vitamin A supplementation in addition to vitamin E has been suggested to help improve ocular healing after surgery and to improve visual acuity, although additional evidence is necessary before a definitive conclusion can be reached.

B 

HIV (supportive treatment) 

The role of vitamin A in the prevention, transmission, or treatment of HIV is controversial and not well established. A clear conclusion cannot be formed based on the available scientific research.

B 

Oral leukoplakia 

Vitamin A may improve clinical resolution of oral leukoplakia (white patches or plaque in the mouth), although relapse is common. Further research is required.

B 

Age-related macular degeneration 

Although this has not been well studied in humans, the use of vitamin A and carotenoids may be useful in the prevention of age-related macular degeneration. Further research is required.

C 

Asthma 

Vitamin A intake is inversely associated with asthma risk and severity. A clear conclusion cannot be formed based on the available scientific research.

C 

Breast feeding (nipple pain) 

Vitamin A and D ointment may be useful for sore and cracked nipples that occur during breastfeeding. However, available studies have not shown vitamin A or any other topical therapy to relieve the pain of breastfeeding.

C 

Bronchiolitis 

Vitamin A is thought to be important in immune function. A clear conclusion cannot be formed on the effects of vitamin A on bronchiolitis (inflammation of the bronchioles) based on the available scientific research.

C 

Bronchopulmonary dysplasia in premature infants 

Research results are not clear as to whether vitamin A is beneficial for bronchopulmonary dysplasia in premature infants (chronic lung condition). Further research is needed.

C 

Chemotherapy adverse effects 

The effect of vitamin A supplementation on chemotherapy-related side effects, including nausea, vomiting, diarrhea, or mouth sores, is unclear. Also, it is unclear if vitamin A interacts with chemotherapy agents. Further research is needed.

C 

Colorectal cancer 

Alpha-carotene and vitamin A may protect against recurrence of colorectal cancer in nonsmokers and nondrinkers or be indicative of compliance or another healthy lifestyle factor that reduces risk. Further research is needed before a conclusion can be drawn.

C 

Cystic fibrosis 

Human research is lacking, and further research is needed in this field.

C 

Esophageal cancer 

Higher intakes of beta-carotene and vitamin A were associated with reduced risk of esophageal adenocarcinoma. There is not sufficient evidence to form a clear conclusion at this time.

C 

Liver disease 

There is insufficient evidence to support or refute the benefits or adverse effects of antioxidant supplements (including vitamin A) in patients with liver disease.

C 

Lung cancer 

Vitamin A has been studied as a possible treatment for lung cancer, without evidence of benefits. The available evidence suggests that high-dose vitamin A and beta-carotene may actually increase the risk of adverse effects, especially among alcohol users and smokers.

C 

Miscarriage (prevention) 

Poor nutrition is associated with an increased risk of miscarriage. However, excess intake of vitamin A has been reported to increase the risks of some birth defects. Vitamin A supplementation above the RDA is therefore not recommended in pregnancy.

C 

Mortality reduction 

Adequate vitamin A (either through diet or supplementation) appears to have a major role in the prevention of morbidity and mortality. Further research is needed.

C 

Mortality reduction (maternal; maternal supplementation postpartum) 

Maternal supplementation of vitamin A postpartum provides limited number of benefits to maternal health status. A clear conclusion cannot be formed based on the available scientific research.

C 

Mortality reduction (maternal; supplementation during pregnancy) 

Vitamin A supplementation during pregnancy and lactation does not appear to reduce infant morbidity and mortality; however, it does appear to reduce maternal morbidity. A clear conclusion cannot be formed based on the available scientific research.

C 

Parasite infection (Ascaris reinfection) 

After deworming, children supplemented with vitamin A may be less prone to Ascaris parasite reinfection. These benefits may be less in children with stunted growth.

C 

Prostate cancer (prevention) 

It is unclear whether dietary vitamin A affects prostate cancer risk. Interventional studies are lacking. More research is needed in this area.

C 

Skin cancer 

It is not clear if vitamin A or beta-carotene, taken by mouth or used on the skin with sunscreen, is beneficial in the prevention or treatment of skin cancers or wrinkles.

C 

Tuberculosis 

There is insufficient evidence to assess vitamin A for tuberculosis. Further research is needed before a conclusion can be drawn

C 

Viral infection (Norovirus (NoV) infection) 

Vitamin A supplementation has been suggested to help prevent NoV infection in children and reduce the symptoms associated with NoV infections.

C 

Weight loss 

Daily vitamin A with calcium has been suggested for weight loss. In one study, an average loss of two pounds was reported after two years of supplementation in young women.

C 

Wound healing 

In preliminary research, retinol palmitate significantly reduced rectal symptoms of radiation proctopathy, perhaps because of wound-healing effects. Further research is needed to confirm these results.

C 

Arthritis 

The available evidence does not support the effectiveness of vitamin A (or combination products containing vitamin A) for the treatment of any form of arthritis. Further research is needed to confirm these results.

D 

Childhood growth promotion 

Vitamin A is necessary for healthy growth and development, and recommended dietary allowances (RDA) should be assured, particularly in children. Overall, the available evidence has not shown significant changes in growth in children with respect to height and weight due to vitamin A.

D 

HIV (mother-to-child transmission) 

Overall evidence does not support the use of vitamin A supplementation in HIV-infected pregnant women to reduce mother-to-child transmission of HIV.

D 

Infant mortality (maternal postpartum supplementation) 

Overall, studies suggest a lack of effect of postnatal vitamin A supplementation on infant mortality.

D 

Infant mortality (maternal supplementation during pregnancy) 

Overall, studies suggest a lack of effect of prenatal vitamin A supplementation on perinatal or neonatal infant mortality.

D 

Respiratory tract infections 

Overall evidence is not sufficient to support the reduction of pneumonia incidence or mortality in children without measles.

D 

Cancer (gastrointestinal; prevention) 

The overall evidence not only suggests that vitamin A does not reduce the rates of gastric cancer or precancerous gastric lesions but also links vitamin A supplementation with increased mortality.

F 

 

*Key to grades: 

A: Strong scientific evidence for this use;
B: Good scientific evidence for this use;
C: Unclear scientific evidence for this use;
D: Fair scientific evidence against this use (it may not work);
F: Strong scientific evidence against this use (it likely does not work).

For full grading rationale, click here.

Uses based on tradition or theory 

The below uses are based on tradition or scientific theories. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified health care professional

Aging, AIDS (adjunct), allergic rhinitis, autism, burns, cancer (treatment), candidiasis, cataracts, cervical cancer, chemical sensitivities (pollutant protection), chronic diseases (prevention), conjunctivitis, Crohn's disease, deafness, deficiency (protein), diabetes, diarrhea, dysentery (shigellosis), dysmenorrhea, eczema, epilepsy, fibrocystic breast disease, gastric ulcers, glaucoma, hay fever, headache (persistent), heart disease, hepatocellular carcinoma (chemoprevention), herpes (cold sores), hyperthyroidism, immune enhancement, increasing sperm count, infections (general, nose), kidney stones, lichen planus pigmentosus, menorrhagia (heavy menstruation), metabolic disorders (Hurler syndrome), mouth cancer, neurodegenerative diseases, nutritional supplement, pancreatic cancer, pancreatitis, periodontal disease, pityriasis rubra pilaris, premenstrual syndrome (PMS), psoriasis, respiratory disorders, sebaceous cysts, sinus infections, sinusitis, skin disorders (Darier's disease, ichthyosis), sleep (regulation), smell disorders, stroke, sunburn, tinnitus, tumors (neoplasms), ulcers (stress ulcers in severely ill hospitalized patients), urinary tract infection, vaginal atrophy, vaginal infections, vaginitis, vascular diseases (prevention), vision enhancement (nearsightedness, blurred vision), warts, yeast infection.


Safety

The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare professional before starting a new therapy. Consult a healthcare professional immediately if you experience side effects.

Allergies

  • Avoid in individuals with a known hypersensitivity or allergy to vitamin A or any component of the formulation.

Side Effects and Warnings

  • Vitamin A is considered safe when consumed in recommended dietary allowances (RDAs). Adults who eat fortified foods with vitamin A, such as low-fat dairy products and a lot of fruits and vegetables, generally do not require supplements or multivitamins that contain vitamin A.
  • Adverse effects from vitamin A may include mouth ulcers, cracked lips, psoriasis flare-ups, cracked fingernails, sore eyes, scaling skin, hair loss, skin irritation, skin dryness, pain, and redness (topical analogs), as well as diarrhea, dyspepsia, steatosis (fatty change), perisinusoidal fibrosis (in the liver), chronic hepatitis, cirrhosis, transient fullness and bulging of the anterior fontanelle, cough, fever, respiratory infection, and increased risk of lung cancer, HIV transmission (through breastfeeding), and mortality.
  • Vitamin A toxicity, or hypervitaminosis A, is rare in the general population. Vitamin A toxicity can occur with excessive amounts of vitamin A taken over short or long periods of time. Consequently, toxicity can be acute or chronic. Symptoms of acute (short-term) toxicity include nausea, headache, fatigue, loss of appetite, dizziness, dry skin, desquamation (loss of skin), and cerebral edema (swelling in the brain). Symptoms of chronic (longer-term) toxicity include dry itchy and cracking skin, desquamation, dry lips, scaling anorexia, headache, psychiatric changes, cerebral edema, bone and joint pain, osteoporosis, and hip fracture. Severe toxicity can lead to eye damage, high levels of calcium, and liver damage. In children, signs of toxicity include irritability, drowsiness, dizziness, delirium, coma, vomiting, diarrhea, increased intracranial pressure with bulging fontanelles in infants, headache, swelling of the optic (eye) disk, bulging eyeballs, visual disturbances, and skin redness and peeling.
  • Persons with liver disease and high alcohol intake may be at risk for hepatotoxicity from vitamin A supplementation. Vitamin A toxicity may lead to intrahepatic cholestasis, a condition where bile cannot flow from the liver into the intestines. Treatment with ursodeoxycholic acid has been shown to greatly improve the symptoms of cholestasis.
  • Use cautiously in children and infants, as high-dose vitamin A has been shown to increase the risk of respiratory infection in preschool-aged children and infants less than one month of age.
  • Use cautiously in combination with bile acid sequestrants, mineral oil, neomycin, or orlistat, due to reduced absorption of vitamin A.
  • Use cautiously in combination with contraceptives taken by mouth, due to increased levels of vitamin A.
  • Use cautiously in combination with alcohol or anticancer agents, due to the potential for increased risk of adverse effects.
  • Vitamin A may increase the risk of bleeding. Avoid in patients with bleeding disorders or those taking drugs that may increase the risk of bleeding.
  • Avoid in combination with tetracycline antibiotics, hepatotoxic agents, or retinoids, due to the increased risk of toxic effects.
  • Avoid in patients with fat malabsorption syndromes, intestinal infections, severe protein energy malnutrition, liver disease, or type V hyperlipoproteinemia (a genetic disorder).
  • Smokers who consume alcohol and beta-carotene may be at an increased risk for lung cancer or cardiovascular disease. High-dose vitamin A and beta-carotene should be avoided in patients at high risk of lung cancer.
  • Avoid in individuals with a known hypersensitivity or allergy to vitamin A or any component of the formulation.

Pregnancy and Breastfeeding

  • Vitamin A should only be used within the recommended dietary allowance, because vitamin A excess, as well as deficiency, has been associated with birth defects. Excessive doses of vitamin A have been associated with central nervous system malformations.
  • Vitamin A is excreted in human breast milk. The benefits or dangers to nursing infants have not been clearly established.

Interactions

Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare professional before starting a new therapy.

Interactions with Drugs

  • Vitamin A may increase the risk of bleeding when taken with drugs that increase the risk of bleeding. Some examples include aspirin, anticoagulants (blood thinners) such as warfarin (Coumadin®) or heparin, antiplatelet drugs such as clopidogrel (Plavix®), and nonsteroidal anti-inflammatory drugs such as ibuprofen (Motrin®, Advil®) or naproxen (Naprosyn®, Aleve®).
  • Vitamin A may interfere with the way the body processes certain drugs using the liver's cytochrome P450 enzyme system. As a result, the levels of these drugs may be increased or decreased in the blood and may cause increased or decreased effects or potentially serious adverse reactions. Patients using any medications should check the package insert and speak with a qualified healthcare professional, including a pharmacist, about possible interactions.
  • The bile acid sequestrants cholestyramine (Questran®) and colestipol (Colestid®) may decrease the effectiveness of vitamin A by reducing absorption of this fat-soluble vitamin.
  • Neomycin may interfere with the absorption of vitamin A, although this interaction has not been found to be clinically significant.
  • Oral contraceptives (birth control pills) may increase plasma vitamin A levels.
  • Vitamin A may reduce seroconversion rates to the measles virus or vaccine, rendering the vaccine less effective. Other vaccines may be enhanced by vitamin A, including the Haemophilus influenzae type b vaccine and the diphtheria vaccine. Other vaccines have been demonstrated to be unaffected by vitamin A supplementation. These include the oral polio vaccine (OPV) and the tetanus toxoid, pertussis, and hepatitis B vaccines. Vitamin A may also alter the immune response to the Bacille Calmette-Guérin (BCG) vaccine, but this interaction is unclear.
  • Mineral oil has been reported to reduce absorption of all fat-soluble vitamins. With occasional use, the effect on vitamin A levels does not appear to be significant.
  • Alcohol, particularly chronic use, may induce vitamin A deficiency.
  • Orlistat (an obesity drug) decreases the absorption of fat-soluble vitamins, although studies suggest that vitamin A is not affected as much by orlistat as other fat-soluble vitamins are. Nonetheless, the manufacturer of orlistat recommends that all patients take a multivitamin supplement containing all the fat-soluble vitamins (including vitamins A, D, E, and K), unless otherwise contraindicated, separating the dosing time by at least two hours from orlistat.
  • Patients who take tetracycline antibiotics, specifically minocycline (Minocin®), plus vitamin A are at a risk for developing benign intracranial hypertension (pseudotumor cerebri), which can occur with tetracyclines and vitamin A intoxication. Therefore, high doses of vitamin A should be avoided in people taking chromic tetracyclines. Other examples of tetracyclines include demeclocycline (Declomycin®) and Achromycin®.
  • Increased toxicity with concurrent use of vitamin A and chemotherapy, retinoids (such as acitretin (Soriatane®), all-trans-retinoic acid or tretinoin (ATRA, Vesanoid®, Vesabiod®, Avita®, Renova®, Retin-A®, Retin-A® Micro, Altinac®), bexarotene (Targretin®), etretinate (Tegison®), and isotretinoin (Accutane®, Amnesteem®)), or agents toxic to the liver, may occur.
  • Vitamin A may improve iron status in people who are deficient in iron and vitamin A. There is likely no benefit in people who are not vitamin A deficient.
  • Vitamin A may inhibit vitamin K absorption, although this has not been well studied.
  • Vitamin A may also interact with folic acid, folate analogs, or valproic acid.

Interactions with Herbs and Dietary Supplements

  • Vitamin A may increase the risk of bleeding when taken with herbs or supplements that increase the risk of bleeding. Multiple cases of bleeding have been reported with the use of Ginkgo biloba, and fewer cases with garlic and saw palmetto. Numerous other agents may theoretically increase the risk of bleeding, although this has not been proven in most cases.
  • Vitamin A may interfere with the way the body processes certain herbs or supplements using the liver's cytochrome P450 enzyme system. As a result, the levels of other herbs or supplements may become too high or too low in the blood. It may also alter the effects that other herbs or supplements possibly have on the cytochrome P450 system.
  • Oral contraceptives (birth control pills) may increase plasma vitamin A levels.
  • Increased toxicity with concurrent use of vitamin A and agents toxic to the liver may occur.
  • Vitamin A may improve iron status in people who are deficient in iron and vitamin A. There is likely no benefit in people who are not vitamin A deficient.
  • Vitamin A may inhibit vitamin K absorption, although this has not been well studied.
  • Apple pectin, carob, carrageenan, fiber, guar, microcrystalline cellulose, multiple micronutrient supplements, wheat bran, and vitamin E may increase levels of vitamin A in the blood or absorption of vitamin A.
  • Zinc deficiency may alter vitamin A status, although the mechanism is unclear.
  • Vitamin A may also interact with antibacterials, blood lipid-lowering agents, anticancer agents, folic acid, and plant stanols and sterols.

Authors

Selected References

Natural Standard developed the above evidence-based information based on a systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to www.naturalstandard.com. Selected references are listed below.

  1. Becker P, Maurer B, Schirmacher P, et al. Vitamin A-induced cholestatic hepatitis: a case report. Z Gastroenterol 2007 Oct;45(10):1063-6.
  2. Bjelakovic G, Nikolova D, Simonetti RG, et al. Antioxidant supplements for preventing gastrointestinal cancers. Cochrane Database Syst Rev 2008 Jul 16;(3):CD004183.
  3. Block KI, Koch AC, Mead MN, et al. Impact of antioxidant supplementation on chemotherapeutic toxicity: a systematic review of the evidence from randomized controlled trials. Int J Cancer 2008 Sep 15;123(6):1227-39.
  4. Cooney TM, Johnson CS, Elner VM. Keratomalacia caused by psychiatric-induced dietary restrictions. Cornea 2007 Sep;26(8):995-7.
  5. Cox SE, Arthur P, Kirkwood BR, et al. Vitamin A supplementation increases ratios of proinflammatory to anti-inflammatory cytokine responses in pregnancy and lactation. Clin Exp Immunol 2006 Jun;144(3):392-400.
  6. Darboe MK, Thurnham DI, Morgan G, et al. Effectiveness of an early supplementation scheme of high-dose vitamin A versus standard WHO protocol in Gambian mothers and infants: a randomised controlled trial. Lancet 2007 Jun 23;369(9579):2088-96.
  7. Diness BR, Fisker AB, Roth A, et al. Effect of high-dose vitamin A supplementation on the immune response to Bacille Calmette-Guerin vaccine. Am J Clin Nutr 2007 Oct;86(4):1152-9.
  8. Kafi R, Kwak HS, Schumacher WE, et al. Improvement of naturally aged skin with vitamin A (retinol). Arch Dermatol 2007 May;143(5):606-12.
  9. Klemm RD, Labrique AB, Christian P, et al. Newborn vitamin A supplementation reduced infant mortality in rural Bangladesh. Pediatrics 2008 Jul;122(1):e242-50.
  10. Long KZ, Rosado JL, DuPont HL, et al. Supplementation with vitamin A reduces watery diarrhoea and respiratory infections in Mexican children. Br J Nutr 2007 Feb;97(2):337-43.
  11. Newton S, Owusu-Agyei S, Ampofo W, et al. Vitamin A supplementation enhances infants' immune responses to hepatitis B vaccine but does not affect responses to Haemophilus influenzae type b vaccine. J Nutr 2007 May;137(5):1272-7.
  12. Payne LG, Koski KG, Ortega-Barria E, et al. Benefit of vitamin A supplementation on ascaris reinfection is less evident in stunted children. J Nutr 2007 Jun;137(6):1455-9.
  13. Saltzman MD, King EC. Central physeal arrests as a manifestation of hypervitaminosis A. J Pediatr Orthop 2007 Apr-May;27(3):351-3.
  14. Swami HM, Thakur JS, Bhatia SP. Impact of mass supplementation of vitamin A. Indian J Pediatr. 2007 May;74(5):443-7.
  15. Tielsch JM, Rahmathullah L, Katz J, et al. Maternal night blindness during pregnancy is associated with low birthweight, morbidity, and poor growth in South India J Nutr 2008 Apr;138(4):787-92.
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