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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.
Common Uses
• 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.
Major Benefits
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.
Additional Benefits
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.
Other Sources
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.
Caution!
• 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.
Latest Findings
• 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.
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