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Vitamin A (retinol)

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Also listed as: Retinol, Carotenoids
Related terms
Background
Evidencetable
Tradition
Dosing
Safety
Interactions
Attribution
Bibliography

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 Table

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 provider. GRADE *


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


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


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


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


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


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 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


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


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


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


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


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


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


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

C


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


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


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


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


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


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

C


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


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


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


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


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


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


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


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


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

C


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


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

C


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

C


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


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


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


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


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


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

D


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

D


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

D


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 for this use (it may not work)
F: Strong scientific evidence against this use (it likley does not work)


Tradition / Theory

The below uses are based on tradition, scientific theories, or limited research. 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 healthcare provider. There may be other proposed uses that are not listed below.

  • 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.

Dosing

Adults (18 years and older)

  • Vitamin A is found in dairy products, fish, and darkly colored fruits and vegetables. Consumption of five servings of fruits and vegetables daily supplies 5-6 milligrams daily of provitamin A carotenoids, which provides about 50-65% of the adult recommended dietary allowance (RDA) for vitamin A.
  • Vitamin A is included in most multivitamins, often in 5,000 IU doses as softgels, capsules, tablets, or liquid. U.S. RDAs for adults have been established by the U.S. Institute of Medicine of the National Academy of Sciences. The recommendations are as follows: 900 micrograms daily (3,000 IU) for men and 700 micrograms daily (2,300 IU) for women. For pregnant women 19 years old and older, 770 micrograms daily (2,600 IU) is recommended. For lactating women 19 years old and older, 1,300 micrograms daily (4,300 IU) is recommended.
  • For vitamin A deficiency not involving xerophthalmia, the following has been used: 100,000 IU by mouth or injected into the muscle daily for three days, followed by 50,000 IU daily for two weeks. A maintenance dose of 10,000-20,000 IU daily for two months has been recommended.
  • For community-based in intervention, 200,000 IU has been taken as a single dose by mouth monthly for six months.
  • For acute promyelocytic leukemia (treatment), all-trans retinoic acid (Vesanoid® (tretinoin)) has been administered as follows: 45 milligrams per square meter of body surface area daily by mouth, as two evenly divided doses until complete remission; therapy should be discontinued 30 days after the achievement of complete remission or after 90 days of treatment, whichever occurs first.
  • For HIV, vitamin A (400,000 IU in adults and 50,000 IU in infants) has been given to women and infants by mouth during the postpartum period for two years.
  • For mortality reduction, 1,333-200,000 IU has been taken by mouth daily or on alternate days for 28 days to 12 years.
  • For oral leukoplakia, 300,000 IU has been taken by mouth weekly for 12 months or 200,000 IU has been taken by mouth weekly for six months or 1-2 milligrams of 13-cis-retinoic acid per kilogram of body weight has been taken by mouth daily for three months. Topical 0.1% isotretinoin gel three times daily for four months or a topical formulation of 20 milligrams of acitretin daily in a two-layer mucoadhesive tablet has been used.
  • For retinitis pigmentosa, the National Eye Institute (NEI) recommends that patients with typical forms receive 15,000 IU of supplemental vitamin A palmitate daily under medical supervision.
  • For tuberculosis, 5,000-200,000 IU has been taken three times by mouth prior to antituberculosis medication.
  • For UV-induced skin damage, topical all-trans retinoic acid (tretinoin, the acid form of vitamin A), at a concentration of 0.02% or higher, has been used over a period of 4-11 months.
  • Supporting care following chemotherapy may include weekly injections of 100,000 IU of vitamin A. Patients receiving vitamin A should be observed carefully for liver toxicity.
  • Injections should always be performed by a licensed healthcare provider.

Children (under 18 years old)

  • Recommended dietary allowances (RDAs) have been established by the U.S. Institute of Medicine of the National Academy of Sciences. The recommendations are as follows: for children 1-3 years old, 300 micrograms (1,000 IU) daily; for children 4-8 years old, 400 micrograms (1,300 IU) daily; and for children 9-13 years old, 600 micrograms (2,000 IU) daily. For pregnant women 14-18 years old, 750 micrograms (2,500 IU) daily is recommended. For lactating women 14-18 years old, 1,200 micrograms (4,000 IU) daily is recommended.
  • The World Health Organization (WHO) has established dosage guidelines for children 6-11 months old to receive 100,000 IU of vitamin A. This increases to 200,000 IU every six months from 12 to 59 months of age.
  • For anemia, 3,000 micrograms of vitamin A has been taken by mouth daily for two months.
  • For bronchopulmonary dysplasia in premature infants, 2,000 IU on alternate days to 4,000 IU three times weekly by mouth has been taken.
  • For childhood growth promotion, 60 milligrams of vitamin A has been taken for up to six months.
  • For cystic fibrosis, the 2002 cystic fibrosis guidelines recommend vitamin A supplements for all children with cystic fibrosis and pancreatic insufficiency, specifically 3,000 micrograms of retinol activity equivalents (RAEs) daily for children over the age of eight years.
  • For infant mortality, the following has been taken: three milligrams by mouth daily from 18 to 28 weeks' gestation; 7,000 micrograms by mouth once weekly during gestation; 5,000-10,000 IU daily by mouth from 12-24 weeks' gestation; 200,000 IU weekly, or 200,000 IU at time of delivery; and 200,000-400,000 IU daily by mouth postpartum. A dose of 2,000 IU has been taken every two days for 28 days, injected into the muscle of infants. Also injected into the muscle, 4,000 IU every two days or 3,750 IU every two days for 16 days has been used. Doses between 1,500 and 5,000 IU, by mouth or injected into the muscle of the infant, have been used every other day or three times weekly. Doses from 8,333 IU weekly to 200,000 IU every six months by mouth have been used.
  • For malaria, children aged 6-60 months were given one capsule (or half a capsule if younger than 12 months) of 200,000 IU of vitamin A (in 200 microliters of peanut oil with 10 micrograms of vitamin E as a preservative) every three months for 13 months.
  • For measles, the World Health Organization (WHO) recommends 200,000 IU daily by mouth for two days for children with measles who live in areas of vitamin A deficiency. For infants with measles, the WHO recommends 100,000 IU daily by mouth for two days.
  • For childhood mortality, does from 8,333 IU weekly to 200,000 IU every six months by mouth have been used. Doses from 10,000 IU weekly for 40 weeks to 206,000 IU once very four months, for up to six doses, have been used.
  • For HIV, a large dose of vitamin A (400,000 IU in adults and 50,000 IU in infants) has been given to women and infants during the postpartum period for two years.
  • For xerophthalmia (dry eye), the World Health Organization (WHO) recommends 200,000 IU daily by mouth immediately on diagnosis, 200,000 IU on the following day, and then 200,000 IU prior to discharge, or if clinical deterioration occurs, or 2-4 weeks later. Infants under 12 months of age and very small and very-low-weight children should be given half the dosage.

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 provider before starting a new therapy. Consult a healthcare provider 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, oral contraceptives, mineral oil, neomycin, or orlistat, due to reduced absorption 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

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 reduce 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 tetracycline (Achromycin®).
  • Increased toxicity with concurrent use of vitamin A and chemotherapy, retinoids, 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 may reduce 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.

Attribution
  • This information is based on a systematic review of scientific literature edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

Bibliography
  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.

Copyright © 2011 Natural Standard (www.naturalstandard.com)


The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.

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