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 of 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 defence 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 (25 000 IU a day) can be used to treat a rangeof 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 hsten 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.
- Treat skin disorders.
- Heals wounds, burns and ulcers.
- Maintains eye health.
- Enhances the effectiveness of chemotherapy treatment.
- Eases inflammatory bowel disease.
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 amounts.
If you get too little: Although quite rare in Australia and New Zealand, a vitamin A deficiency can cause night blindness (even total blindness) an 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 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
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 2500 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 vitamin A supplements with food; a little fat in the diet aids absorption. Vitamin E and zinc helps the body 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.
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 getting pregnant, don’t take more than 2500 IU of vitamin A daily; higher doses may cause birth defects. Use birth control when taking more that 2500 IU and for at least a month afterwards.
Reminder: If you have a medical condition, talk to your doctor before taking supplements.
In the first world (developed countries) deficiencies of Vitamin A are rare and most often associated with stict dietary regimes or poor diet due to excessive drug or alcohol intake.
In the third world (developing countries) , however, it is a different story. Vitamin A deficiency diminishes the body's ability to fight infections. Approximately 250,000 to 500,000 malnourished children in the developing world go blind or die each year from complications of infectious diseases that are endemic to their environment because of poverty or social conflict.
Night blindness is one of the first signs of Vitamin A deficiency because the cornea becomes very dry, damaging the retina and cornea.. Before it was known why if worked, it was noticed that night blindness could be cured by eating liver. Now it is established that liver is a rich source of Vitamin A.