• Vitamin A promotes healthy skin and good night vision
• It  strengthens immune system
• It can help treat acne

How it works

Vitamin A is needed by the body for the production of rhodpsin, a pigment that enables us to see in the dark. It is also crucial for keeping the linings of the mouth and lungs moist, the adequate growth of body tissues, and maintaining the development of strong bones, a balanced reproductive system, and healthy skin. It also plays a role in the body's immune response, helping fight bacterial, viral, and parasitic infections.

Absorption helpers Vitamin A is best absorbed together with a little oil or fat in the diet.

Absorption inhibitors Long-term use of the drug cholestyramine, which is prescribed for the treatment of high cholesterol, can alter the natural balance of vitamin A in the body. Antacids required for indigestion may also reduce the body's vitamin A stores, and a lack of the mineral zinc in the diet may lower blood levels.

Taking vitamin A supplements

The adult RDA (800mcg) for vitamin A is equivalent to 3 grams of grilled calves' liver, or eight eggs. The body can also make vitamin A from beta-carotene, the bright pigment in vegetables and fruit. Vitamin A supplements are usually oil based and derived from fish oils. Vitamin A is also present in cod liver oil.

Precautions Vitamin A is stored in the body's fat cells, so excess intakes build up over time and can become toxic. Doses of 300mg in adults and 100mg in children are harmful, causing hair loss, vomiting, headaches, bone damage, double vision, and liver damage. Regular intakes should not exceed 9,000mcg in men and 7,500mcg in women; the best advice is to not exceed 100 per cent of the RDA. Avoid combining vitamin A sources - such as multivitamins plus cod liver oil - which together may contribute to excess intakes. Supplements should be avoided by pregnant women as intakes of 3,300mcg a day can cause birth defects in the developing foetus.

Why take this supplement?

Anyone on a long-term low-fat diet, or with poor absorption (such as people with cystic fibrosis), or taking cholestyramine may benefit from this supplement. Specialist skin doctors may prescribe a course of vitamin A supplements, and people with the following symptoms may have vitamin A deficiency:

Therapeutic uses

·         Psoriasis and acne Psoriasis and acne may improve from high doses of vitamin A by helping to change the way the skin's surface is formed. This must be done under a doctor's supervision.

·         Cancer The action of substances that trigger cancerous changes to cells in the body may be dampened down if vitamin A is in good supply. If vitamin A stores are low, supplements may help to prevent the risk of developing cancer.

·         Respiratory problems Vitamin A supplements may reduce the number of respiratory illnesses in children who regularly suffer this condition.

·         Glaucoma It is possible that vitamin A supplements may be beneficial to those with glaucoma if the vitamin is lacking in the diet.

·         Measles A course of supplements may dramatically reduce the risk of measles in children whose diets are poor in vitamin A.

RDA for adults

800mcg

Top sources of Vitamin A mcg/100g of food
 

·         Calves' liver 29,730mcg/100g

·         Butter815mcg/100g

·         Margarine780mcg/100g

·         Egg yolk 535mcg/100g

·         Cream cheese 385mcg/100g

·         Herring 45mcg/100g

·         Oysters 75mcg/100g

·         Anchovies 57mcg/100g

·         Whole milk 52mcg/100g

·         Mackerel 45mcg/100g