One of the first vitamins to be discovered, this essential nutrient keeps your eyesight keen, your skin healthy and your immune system strong. It follows that an extra dose of vitamin A may help to remedy various eye problems, a number do skin disorders and a wide range of infections.
What it is?
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 contained 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 the health of the retina of the eye.
What it does?
This vitamin prevents night blindness; maintains the skin and cells that line the respiratory and gastrointestinal tracts; and helps to 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 production of immune cells that line the airways and digestive tract and form an important line of defense against 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 to combat breast and lung cancers and improve survival rates in those with leukaemia; in addition, animal studies suggest that 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 anti-wrinkle cream Retin-A. Lower doses of vitamin A (25000 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 recovery from sprains and strains. The therapeutic effects of vitamin A extend to the lining of the digestive tract, where it helps to 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.
- Fights colds, flu and other types of infections.
- Treats skin disorders.
- Heals wounds, burns and ulcers.
- Maintains eye health.
- Enhances the effectiveness of chemotherapy treatment.
- Eases inflammatory bowel disease.
- Soft gel.
- 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 2500 IU of vitamin A daily; higher doses may cause birth defects. Use birth control when taking more than 2500 IU and for at least a month afterwards.
- Reminder: If you have a medical condition, talk to your doctor before taking supplements.
How much you need?
The RDI for vitamin A is 2500 IU (750 mcg) a day for men and women; women who are breast-feeding benefit from 4000 IU (1200 mcg). Higher doses are typically given for specific ailments.
If you get too little:
Although quite rare in Australia and New Zealand, 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 500000 IU may induce weakness and vomiting. And as little as 25000 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?
Multivitamins supply vitamin A, sometimes in the form of beta-carotene. For specific complaints in adults, up to 10000 IU a day is generally safe for long-term use (except for pregnant women and those considering pregnancy, who should not exceed 2500 IU a day). As a broad guideline, it's safe to take 25000 IU a day for up to a month or 100000 IU for up to a week, though in some cases higher doses may be needed.
Guidelines for use:
Take vitamin A supplements with food; a little fat in the diet aids absorption. Vitamin E and zinc help the boy to use vitamin A, which in turn boosts absorption of iron from foods.
Vitamin A is plentiful in fish (particularly fish liver), egg yolks, butter and organ meats such as liver (85 g provides more than 9000 IU). 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 as needed.
- You can't overdose on vitamin A by eating carotenoid-rich fruits and vegetables, such as apricots, leafy greens or rockmelon. Your body does convert some carotenoids into vitamin A, but it makes only as much as it needs. Unless you eat a lot of liver or oily fish, it's almost impossible to get too much vitamin A from your diet.
- If you're heading for the North Pole, watch what you eat: 125 g of polar bear liver contains more than 2 million IU of vitamin A – an acutely toxic dose.
- Vitamin A has been shown to be effective in repairing lung membrane and reducing asthma attacks. Dosages of up to 20000 IU can be taken by adult asthmatics, as long as these are supplemented by 30 mg of zinc.
- Vitamin A shows promise in the treatment of diabetes. In two recent studies, up to 25000 IU of vitamin A daily improved insulin's ability to control blood sugar.
- A Brazilian study found that vitamin A may combat chronic lung diseases. After 30 days of taking supplements, men who received 5000 IU a day could breathe better than those given a placebo.
Did you know?
You'd have to eat about 10 eggs to meet the daily RDI for vitamin A. Most people get enough from other animal sources and from carotenoid-rich fruits and vegetables.