Vitamin A : Safety

by MedlinePlus

(Page 3 of 3)

Allergies

Known hypersensitivity/allergy to vitamin A.

Side Effects and Warnings

Toxicity (hypervitaminosis A): 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. An infant with acute toxicity can develop a bulging fontalle (the soft spot on the head) and symptoms similar to a brain tumor. Adults experience less specific symptoms such as headache, dizziness, fatigue, malaise, blurry vision, bone pain and swelling, nausea, and/or vomiting. Severe toxicity can lead to eye damage, high levels of calcium, and liver damage. Persons with liver disease and high alcohol intake may be at risk for hepatotoxicity from vitamin A supplementation. Smokers who consume alcohol and beta-carotene may be at an increased risk for lung cancer or cardiovascular disease.

Pregnancy and Breastfeeding

U.S. Recommended Daily Allowance (RDA) for adults: RDAs have been established by the U.S. Institute of Medicine of the National Academy of Sciences. For pregnant women between 14-18 years-old, 750mcg/day (2500 IU) is recommended; for pregnant women 19 years and older, 770mcg/day (2600 IU) is recommended. For lactating women between 14-18 years-old, 1200mcg/day (4000 IU) is recommended; for lactating women 19 years and older, 1300mcg/day (4300 IU) is recommended.

Pregnancy: Vitamin A should only be used within the recommended dietary allowance, because Vitamin A excess as well as deficiency have been associated with birth defects. Excessive doses of vitamin A have been associated with central nervous system malformations.

Lactation: Vitamin A is excreted in human breast milk. Benefits or dangers to nursing infants are not 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 provider before starting a new therapy.

Interactions with Drugs

Acitretin (Soriatane®): Increased risk of vitamin A toxicity.

All- Trans -Retinoic Acid (ATRA, Vesanoid®): Vitamin A supplements should not be taken simultaneously due to the risk of toxicity.

Anticoagulants: Increased risk of vitamin A toxicity may occur with warfarin (Coumadin®).

Bexarotene (Targentin®): Increased risk of vitamin A toxicity.

Bile Acid Sequestrants: Cholestyramine (Questran®) and colestipol (Colestid®) may decrease the effectiveness of vitamin A by reducing absorption of this fat-soluble vitamin.

Oral Contraceptives, Estrogens: Oral contraceptives increase plasma vitamin A levels.

Etretinate (Tegison®): Increased risk of vitamin A toxicity.

Isotretinoin (Accutane®, Amnesteen®): Vitamin A supplements should not be taken simultaneously due to the risk of toxicity.

Measles Vaccine: Vitamin A may reduce seroconversion rates to the measles virus/vaccine.

Mineral Oil: 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.

Neomycin(Mycifradin®, Neo-Fradin®): Neomycin may interfere with the absorption of vitamin A, although this interaction has not been found to be clinically significant.

Orlistat (Xenical®):Orlistat 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. 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 2 hours from orlistat.

Tetracyclines: Patients who take tetracyclines, 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®).

Tretinoin (Vesabiod®, Avita®, Renova®, Retin-A®, Retin-A®Micro, Altinac®): Vitamin A supplements should not be taken simultaneously due to the risk of toxicity.

Interactions with Herbs and Dietary Supplements

Carob: Increased risk of vitamin A toxicity.

Zinc: Zinc deficiency may alter vitamin A status, although the mechanism is unclear.

Iron: Vitamin A may improve anemia in people who are deficient in iron and vitamin A. There is likely no benefit in people who are not vitamin A deficient.

Interactions with Food

Olestra: High intake of olestra reduces vitamin A Daily intake of multivitamins during long-term intake of olestra in men has been shown to prevent declines in serum vitamins A and E but not carotenoids.

Sweet potato: Orange-fleshed sweet potato has been shown to improve vitamin A status.

Interactions with Lab tests

Bilirubin: Vitamin A can cause a false increase in bilirubin test results using Ehrlich's reagent.

Cholesterol: Vitamin A may produce false increases in serum cholesterol test results measured by the Zlatkis-Zak reaction, although this interaction has not been firmly established.

About the Author

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