What Is It
Vitamin A, a fat-soluble nutrient, is stored in the liver. The body gets part of its vitamin A from animal fats and makes part in the intestine from beta-carotene and other carotenoids in fruits and vegetables. Vitamin A is present in the body in various chemical forms called retinoids - so named because the vitamin is essential to health of the retina of the eye.
What Does It Do
This vitamin prevents night blindness; maintains the skin and cells that line the respiratory and gastrointestinal tracts; and helps build teeth and bones. It is vital for normal reproduction, growth, and development too. In addition, vitamin A is crucial to the immune system, including the plentiful supply of immune cells that line the airways and digestive tract and form an important line of defense against disease.
• Fights colds, flu, and other types of infections.
• Treats skin disorders.
• Heals wounds, burns, and ulcers.
• Maintains eye health.
• Enhances chemotherapy.
• Eases inflammatory bowel disease.
Vitamin A is perhaps best known for its ability to maintain vision, especially night vision, assisting the eye in adjusting from bright light to darkness. It can also alleviate such specific eye complaints as "dry eye," in addition to its many other benefits.
By boosting immunity, vitamin A greatly strengthens resistance to infections, including sore throat, colds, flu, and bronchitis. It may also combat cold sores and shingles (caused by a herpes virus), warts (a viral skin infection), eye infections, and vaginal yeast infections -and perhaps even control allergies. The vitamin may help the immune system battle against breast and lung cancers and improve survival rates in those with leukemia; in addition, animal studies suggest it inhibits melanoma, a deadly form of skin cancer. Another benefit for cancer patients is that vitamin A may enhance the effectiveness of chemotherapy.
Vitamin A was first used in the 1940s to treat skin disorders, including acne and psoriasis, but the doses were high and toxic. Scientists later developed safer vitamin A derivatives (notably retinoic acid); now sold as prescription drugs, these include the acne and antiwrinkle cream Retin-A. Lower doses of vitamin A (25,000 IU a day) can be used to treat a range of skin conditions, including acne, dry skin, eczema, rosacea, and psoriasis. Vitamin A also promotes healing of skin wounds and can be applied to cuts, scrapes, and burns; it may hasten recover from sprains and strains. The therapeutic effects of vitamin A extend to the lining of the digestive tract, where it helps treat inflammatory bowel disease and ulcers. In addition, getting enough of this vitamin will speed recovery in people who have had a stroke .Women with heavy or prolonged menstrual periods are sometimes deficient in this vitamin, so supplements may be of value in treating this condition as well.
How Much You Need
The RDA for vitamin A is 4,000 IU a day for women, and 5,000 IU a day for men. Higher doses are typically given for specific ailments.
If You Get Too Little: Although quite rare in the United States, a vitamin A deficiency can cause night blindness (even total blindness) and a greatly lowered resistance to infection. Milder cases of deficiency do occur, especially in the elderly, who often have vitamin-poor diets. Infections such as pneumonia can deplete vitamin A stores.
If You Get Too Much: An overabundance of vitamin A can be a real problem. A single dose of 500,000 IU may induce weakness and vomiting. And as little as 25,000 IU a day for six years has been reported to cause serious liver disease (cirrhosis).Signs of toxicity include dry, cracking skin and brittle nails, hair that falls out easily, bleeding gums, weight loss, irritability, fatigue, and nausea.
How To Take It
Dosage: Multivitamins supply vitamin A, sometimes in the form of beta-carotene. For specific complaints in adults, up to 10,000 IU a day is generally safe for long-term use (except for pregnant women and those considering pregnancy, who should not exceed 5,000 IU a day). As a broad guideline, it's safe to take 25,000 IU a day for up to a month or 100,000 IU for up to a week, though in some cases higher doses may be needed.
Guidelines For Use: Take supplements with food; a little fat in the diet aids absorption. Vitamin E and zinc help the body use vitamin A, which in turn boosts absorption of iron from foods.
Vitamin A is richly represented in fish, egg yolks, butter, organ meats such as liver (3 ounces provide more than 9,000 IU), and fortified milk (check the label to be sure). Dark green, yellow, orange, and red fruits and vegetables have large amounts of beta-carotene and many other carotenoids, which the body makes into vitamin A on an as-needed basis.
• Like vitamin D (another fat soluble vitamin), vitamin A can build up to toxic levels, so be careful not to get too much.
• If you're pregnant or considering pregnancy, don't take more than 5,000 IU of vitamin A daily; higher doses may cause birth defects. Practice effective birth control when taking doses higher than 5,000 IU and for at least a month afterward.
• Vitamin A shows promise in the treatment of diabetes. In two recent studies, up to 25,000 IU of vitamin A daily improved insulin's ability to control blood sugar. (Poor blood sugar control is a prime problem in people with diabetes.)
• A Brazilian study found that vitamin A may combat chronic lung diseases. After 30 days of taking supplements, men who received 5,000 IU a day could breathe better than those who were given a placebo.