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Vitamin A helps maintain healthy skin and eyesight
Vitamin A supports normal growth and development, promotes healthy skin, builds strong nails, and maintains good eyesight. Beta-carotene, found in foods such as carrots and tomatoes, is converted to vitamin A in the body.
Other vitamin A sources are carotenoids, such as alpha-carotene, and the preformed vitamin A compounds, the retinoids. Vitamin A is a fat-soluble vitamin. Its precursors, such as alpha and beta-carotene, are antioxidants that protect cell membranes by absorbing harmful free-radical molecules before they can cause damage.
Quick Facts About Vitamin A (and Carotenoids)
- RDA is 800 to 1,000 RE (1 RE is equal to 1 mcg retinol, or 6 mcg beta-carotene) per day for healthy adults.
- Some foods rich in vitamin A are fish liver oil, whole eggs, and whole milk.
- Foods rich in beta-carotene are yellow and orange fruits, and leafy green vegetables.
- Some signs of Vitamin A deficiency are eye disorders, night blindness, and skin problems.
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You May Need More Vitamin A if You Have (or Have Had)
- A history of excessive alcohol or drug use/abuse
- Chronic malnutrition
- A portion of your gastrointestinal tract removed
- Recent injury or severe burns
- Recent surgery
- Kidney disease, liver disease, cystic fibrosis, or chronic diarrhea
- Zinc or magnesium deficiency
Or if You're
- Pregnant or breastfeeding (But consult your doctor because too much vitamin A can cause birth defects.)
- Over age 55
- A smoker
- Recovering from an infection
- Under excessive stress: mental, physical, environmental
- Taking bile-sequestering drugs or the drug methotrexate
- Suffering from cystic fibrosis because of fat absorption problems
What Works Best -- and Worst -- with Vitamin A
- Palmitate is a water soluble form of vitamin A and might be useful if you have problems absorbing fats.
- When taken with a normal amount of vitamin E, both vitamins enhance each others' absorption and utilization.
- High intake of vitamin A with vitamin E can interfere with beta-carotene absorption.
- Zinc assists in the transportation of vitamin A.
- Antioxidants (like vitamin C and selenium) and complements the antioxidant effects of beta-carotene.
Forms Available
- Individual supplements, with or without beta-carotene, as extended-release capsules or tablets
- An oral solution
- A multivitamin/mineral supplement
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Chemical Forms
- Retinol
- Retinyl palmitate
- Beta-carotene
- Other carotenoids
Comments on Vitamin A
- The precursor A compounds are the carotenoids -- alpha-carotene and beta-carotene -- which get converted in your body into active vitamin A.
- There are over 600 carotenoids, including beta-carotene (the most popular), alpha-carotene, canthaxanthin, cyptoxanthin, lutein, lycopene, and zeaxanthin.
- Regardless of where it comes from, the active form of vitamin A is retinol.
- Not all carotenoids have vitamin A activity, but many have antioxidant properties, plus specific anticancer and cardiovascular-protective effects.
- Precursor vitamin A compounds, such as beta-carotene, have added health benefits, plus reduced toxicity so they can be taken in larger quantities without the danger of vitamin A overdose.
- Remember that 6 mcg of beta-carotene are equivalent to 1 mcg of retinol (active vitamin A), which equals 1 RE (retinol equivalent).
- Active vitamin A and beta-carotene have different functions, so you should take a combination of each for best results.
- Your body easily converts beta-carotene into vitamin A in your small intestine, where special enzymes split each beta carotene molecule into two vitamin A molecules.
- Unused vitamin A circulates in your blood and enters your cells. The remainder is stored in your fatty tissues and your liver (which normally holds between 300 to 900 mcg).
- Because of readily available beta-carotene supplements, there may be no reason for you to use only preformed vitamin A.
- A good mixed carotenoid supplement should contain beta carotene, at least 20% alpha carotene, xanthophylls, and lycopene.
- Retinyl palmitate may be a better choice for those having difficulty absorbing fats. It is a water-soluble form of vitamin A.
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Known Benefits of Vitamin A
- Aids in the development of keratin, a hard protein in hair and nails.
- As an antioxidant, it protects from free radical damage.
- Helps maintain healthy mucous membranes, the body's first line of defense against germs.
- Helps preserve your eyesight, hinders cataracts, and aids color vision.
- Prevents night blindness.
- Essential to proper growth and cellular differentiation.
- Promotes the formation of smooth, healthy skin.
Unproven Claims
- May reduce the risk of developing esophageal, stomach, colon, breast, and cervical cancer.
- Builds your resistance to colds and sore throats.
- Enhances the fight against infections.
- Helps wounds heal faster.
- Boosts the immune system.
- Protects against cardiovascular disease.
- May protect against blindness due to macular degeneration.
Vitamin A May Prevent These Signs of Deficiency
- Eye damage that may become permanent if untreated
- Drying and keratinization of the eye
- Eye disorders and night blindness
- Increased susceptibility to infection especially respiratory infections
- Patches of rough or dry skin
- Susceptibility to respiratory infections
- Weak tooth enamel
Recommended Dosage Range for Vitamin A
- Healthy adults may safely take between 1,000 to 6,000 RE. The dose may be higher if beta-carotene is used.
- RDA values were set as the minimum needed to offset deficiency or disease, not as an actual value needed for optimum health.
- In the United States, the average consumption of vitamin A is:
- 1,419 RE per day for men
- 1,170 RE per day for women
- 1,049 RE per day for children (ages 1 to 5)
- Consult your physician before starting any high-dose supplement regimen.
Dietary Sources
Food Tips
- Too much heat destroys vitamin A and beta-carotene in foods, but cooked vegetables release more beta-carotene because the cell walls are broken down.
- Light, air, and humidity degrade vitamin A.
- Frozen foods preserve most of the vitamin A found in certain foods, while canned and prepared foods have lost most of their vitamin A.
- The color intensity of foods does not indicate how much vitamin A is in it.
| Foods High in Vitamin A | Serving Size | Amount of Vitamin A | Units |
|---|
Beef liver
Chicken liver
Apricots, fresh
Asparagus, cooked
Beet greens
Broccoli, cooked
Cantaloupe
Carrot, raw
Collard greens, cooked
Kale, cooked
Orange
Peach
Pepper, sweet red
Prunes, stewed
Spinach, cooked
Squash, winter
Sweet potato, cooked
Tomato
Tomato juice
Turnip greens, cooked
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3 ounces
3 1/2 ounces
3
1 cup
1/2 cup
1/2 cup
1 cup
1 medium
1/2 cup
1/2 cup
1 medium
1 large
1/2 cup
1/2 cup
1/2 cup
1/2 cup
1 medium
1 medium
6 ounces
1/2 cup
|
9000
4913
289
122
370
194
272
810
741
456
40
203
222.5
106.5
729
656
923
111
146
457
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RE
RE
RE
RE
RE
RE
RE
RE
RE
RE
RE
RE
RE
RE
RE
RE
RE
RE
RE
RE
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When and How to Take Vitamin A
- Take with food or after meals to enhance absorption.
- Large daily doses should be divided into three to four smaller doses throughout the day for better absorption.
- Swallow tablets whole with a full glass of liquid.
What to Take with Vitamin A
- When taken with a normal amount of vitamin E, both vitamins enhance one another's absorption and utilization.
- Zinc aids in the transportation (metabolism) of vitamin A.
- Antioxidants like vitamin C and selenium complement the antioxidant effects of beta-carotene.
- Dietary fat helps vitamin A and beta-carotene absorption.
What Not to Take with Vitamin A
- High doses of vitamin E interfere with beta-carotene absorption.
- Tobacco products decrease absorption of beta-carotene and vitamin A.
- Excess alcohol combined with excess beta-carotene may cause liver damage.
- Alcohol reduces bodily stores of vitamin A and beta-carotene.
- Tobacco products combined with high levels of beta-carotene may increase chances of developing lung cancer.
Storage
- Keep vitamin A in a cool, dry place away from direct sunlight and air.
- Don't store it in your bathroom medicine cabinet. Heat and moisture may make it less effective.
- Store safely out of children's reach.
Recommended Daily Allowance
| AGE/GROUP | RDA |
|---|
Infants
0 to 6 months
6 to 12 months
1 to 3 years
4 to 6 years
7 to 10 years
Males
11 to 14 years
15 to 18 years
19 to 24 years
25 to 50 years
51+ years
Females
11 to 14 years
15 to 18 years
19 to 24 years
25 to 50 years
51+ years
Pregnant
Lactating
1 to 6 months
6 to 12 months
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Retinol Equivalents (RE)*
375
375
400
500
700
1000
1000
1000
1000
1000
800
800
800
800
800
800
1300
1200
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* 1 RE is equivalent to 1 mcg retinol or 6 mcg beta-carotene, and 1 RE is equivalent to 3.3 International Unit (IU) for animal products (preformed vitamin A) or 10 IU for plant products (beta-carotene) |
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Warnings
Consult a physician before use or do not use vitamin A if:- You're about to start a high-dose supplement program. A dose of 7,600 RE (25,000IU) may produce toxic effects.
- You're pregnant or intend to be. Birth defects are possible with doses greater than 6,000 RE (20,000 IU) per day.
- You're a smoker. Studies show that beta-carotene supplements may increase the risk of lung cancer.
Vitamin A May Have Interactions with the Following
- Alcohol: increases risk of liver damage from vitamin A and reduces vitamin A reserves.
- Antacids containing aluminum: decreases absorption of fat soluble vitamins A, D, E, and K.
- Caffeine: reduces vitamin A reserves.
- Cholestyramine: decreases vitamin A absorption.
- Cortisone: reduces liver stores of vitamin A.
- Isotretinoin: increases the risk of vitamin A toxicity.
- Mineral oil: decreases absorption of all fat soluble vitamins, including vitamins A, D, E, and K.
- Oral contraceptives: increase vitamin A levels.
- Phenobarbital and other barbiturates: reduce vitamin A reserves.
- Sucrafate: increases the risk of vitamin A toxicity.
- Tobacco: plasma levels of vitamin A in non-drinkers vary inversely with amount of smoking.
- Vitamin E: in normal amounts facilitates absorption, utilization and storage in the liver and protects vitamin A from oxidation during digestion.
- Vitamin E: taken in large amounts may deplete stores of vitamin A in the liver.
- Zinc deficiency: causes a fall in vitamin A plasma levels.
Side Effects
- Carotenemia -- a non-life-threatening yellowing of the skin and eyes from over-ingestion of carotenoids
- While beta-carotene is safer, vitamin A (retinol) can be toxic in large doses.
- Side effects usually appear when repeated daily doses exceed 50,000 IU (15,000 mcg) retinol in adults and 20,000 IU (6,000 mcg) in infants and children or if single dose exceeds 1 million IU (300 mg) in adults and 200,000 IU (60 mg) in children.
- If you are pregnant or intend to be, you should take beta-carotene instead of vitamin A. Doses over 6,000 RE (20,000 IU) of vitamin A may cause birth defects.
Signs of Overdose
- Abdominal pain
- Appetite loss
- Blurred vision
- Bone pain and sensitivity
- Confusion or unusual excitement
- Diarrhea
- Dizziness
- Double vision
- Enlarged liver and spleen
- Fatigue
- Gastrointestinal problems
- Hair loss
- Headache
- Hydrocephalus -- increased fluid pressure on the brain
- Irritability
- Joint or bone pain
- Menstruation disturbances
- Peeling skin on lips and palms
- Skin lesions
- Soft spot on a baby's head bulges
- Vomiting
- Weight loss
- Symptoms may develop gradually if overdose is milder and takes place over a longer time period. A minimum toxic dose of vitamin A is 7,600 RE (25,000 IU).
- Toxicity symptoms usually appear about 6 hours after ingestion of overdose of vitamin A; symptoms usually disappear a few weeks after cessation of supplements.
What to Do in Case of Overdose
- Stop use and contact your physician immediately.
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Sources & Further Reading
Books
- 1. Basu, TK and Dickerson, JW.Vitamins in Human Health and Disease. CAB INTL, UK 1996.
2. Bendich, A and Deckelbaum, RJ.Preventive Nutrition: The Comprehensive Guide for Health Professionals. Humana Press. Totowa, NJ 1997.
3. Fauci et al. Harrison's Principles of Internal Medicine, Fourteenth Ed. McGraw-Hill Co., Inc. 1998.
4. Groff, JL, Gropper, SS, Hunt, SM.Advanced Nutrition and Human Metabolism, Second Ed. West Pub. Co. St. Paul, MN 1995.
5. Kastrup EK et al. Drug Facts and Comparisons. Facts and Comparisons.
6. Machlin, LJ.Handbook of Vitamins, Second Ed. Marcel Dekker, Inc. New York, NY 1991.
7. Meletis, CD and Jacobs, T.The Practitioner's Guide to Drug-Nutrient and Nutrient-Nutrient Interactions. 1996.
8. Papas, AM et al. Antioxidant Status, Diet, Nutrition and Health. CRC Press, LLC. Boca Raton, FL 1999.
9. Pence, BC and Dunn, DM.Nutrition & Women's Cancers. CRC Press, LLC. Boca Raton, FL 1998.
10. Werbach, MR.Nutritional Influences on Illness, Second Ed. Third Line Press. Tarzana, CA 1996.
Find more books on health and wellness at  barnesandnoble.com.
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- 2. Bendich A.Carotenoids and the immune response. Journal of Nutrition. 119(1):112-115, 1989.
- 3. Bendich A.The safety of beta-carotene. Nutr Cancer 11(4): 207-214, 1988.
- 4. Bendich A, Langseth L.Safety of vitamin A. American Journal of Clinical Nutrition. 49(2):358-371, 1989.
- 5. Boyd AS.An overview of the retinoids. American Journal of Medicine. 86(5) 568-574, 1989.
- 6. Christian P, West KP Jr.Interactions between zinc and vitamin A: an update. Am J Clin Nutr 1998 Aug 68:2 Suppl 435S-441S.
- 7. Czeizel AE, Rockenbauer M.Prevention of congenital abnormalities by vitamin A. Int J Vitam Nutr Res 1998 68:4 219-31.
- 8. Dudley L, Hussey G, Huskissen J, Kessow G.Vitamin A status, other risk factors and acute respiratory infection morbidity in children. S Afr Med J 1997 Jan 87:1 65-70.
- 9. Jane M Love, Lorraine J Gudas.Vitamin A, differentiation and cancer [Review article]. Current Opinion in Cell Biology 1994, 6:825-831.
- 10. Lindblad A, Diczfalusy U, Hultcrantz R, Thorell A, Strandvik B.Vitamin A concentration in the liver decreases with age in patients with cystic fibrosis. J Pediatr Gastroenterol Nutr 1997 Mar 24:3 264-70.
- 11. Macsai MS, Agarwal S, Gamponia E.Bilateral corneal ulcers in primary vitamin A deficiency. Cornea 1998 Mar 17:2 227-9.
- 12. Miller RK, Hendrickx AG, Mills JL, Hummler H, Wiegand UW.Periconceptional vitamin A use: how much is teratogenic?. Reprod Toxicol 1998 Jan-Feb 12:1 75-88.
- 13. Tomoko Kuno, Masatoshi Hozumi, Takao Morinobu, Takuji Murata, Zheng Mingci, Hiroshi Tamai, E. Niki.Antioxidant Vitamin Levels in Plasma and Low Density Lipoprotein of Obese Girls [Original Paper]. Free Radical Research 1997.
- 14. Urayama S, Lissoos TW, Fishman GA, Grover S, Schiano TD, Conjeevaram H, Baker AL.Night blindness secondary to vitamin A deficiency in a patient with bile duct strictures after liver transplantation. Transplantation 1998 Aug 27 66:4 537-9.
- 15. Yong LC, Brown CC, Schatzkin A, Dresser CM, Slesinski MJ, Cox CS, Taylor PR.Intake of vitamins E, C, and A and risk of lung cancer. The NHANES I epidemiologic followup study. First National Health and Nutrition Examination Survey. Am J Epidemiol 1997 Aug 1 146:3 231-43.
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