Vitamin A (retinoid)

Vitamin A is also known as retinol. The NHS says it has several important functions from strengthening immunity against infections to helping vision in dim light as well as maintaining cell growth in some parts of the body. There are two types of Vitamin A. This article is primarily about the active form of vitamin A -- retinoids -- which come from animal products. Beta-carotene is among the second type of vitamin A - carotenoids - which come from plants.

Vitamin A uses

Topical and oral retinoids are common prescription treatments for acne and other skin problems, including wrinkles. For instance, one recent Cochrane review published in the journal Dermatologic Therapy argues, "Retinoids are capable not only of repairing photoaged skin at both the clinical and biochemical levels but their use may prevent photoaging."

Vitamin A has also been studied as a treatment for many other conditions, including some types of cancer, cataracts and HIV. However, the results for these are inconclusive and more research is needed.

Most people get enough vitamin A from their diets. However, a doctor might suggest vitamin A supplements for people who have vitamin A deficiencies. People most likely to have vitamin A deficiency are those with certain diseases (such as digestive disorders) or very poor diets.

Vitamin A doses and instructions for use

The NHS says that men need 0.7mg of vitamin A a day, and women need 0.6mg a day, and that a person should be able to get all the vitamin A they need from a healthy diet.

It also advises that having a total of 1.5mg or less of vitamin A per day, on average, from diet and supplements is unlikely to cause adults any harm. Higher doses might be used to treat vitamin A deficiencies, but you should never take more unless instructed to by your doctor.

Vitamin A food sources

Good food sources of retinoid vitamin A include:

• eggs
• whole milk
• liver
• fortified skim milk and cereals

Plant sources of vitamin A (from beta-carotene) include carrots, spinach, and apricots.

Vitamin A supplement information

Vitamin A, often in the form of beta-carotene, is standard in multivitamins (it is omitted from pregnancy multivitamins). Vitamin A is also available as a prescription cream. As with any supplement, keep vitamin A supplements in a cool, dry place, away from humidity and direct sunlight.

Vitamin A warnings

• Side-effects. Symptoms of vitamin A toxicity include dry skin, jointpain, vomiting, headaches and confusion.
• Interactions. If you take any medicines, ask your doctor if vitamin A supplements are safe. Vitamin A supplements may interact with some oral contraceptives, blood thinners, acne medicines, cancer treatments and many other drugs.
• Risks. Do not take more than the RDA of vitamin A unless your doctor recommends it. High doses of vitamin A have been associated with birth defects, lower bone density and liver problems. People who drink too much alcohol or have kidney or liver disease should not take vitamin A supplements without talking to a doctor.   If you are pregnant or planning to have a baby, the Department of Health advises avoiding taking supplements containing vitamin A, including fish liver oil (unless instructed otherwise by your doctor) and avoid eating liver, or liver products like pâté, as these are very rich in vitamin A.