Vitamin A (or beta carotine) is necessary for the function of light-sensitive nerve cells (photoreceptors) in the eye’s retina. It also helps keep the skin and the lining of the lungs, intestine, and urinary tract healthy and protects against infections. Carotenoids, such as beta-carotine, are pigments in vegetables that give them their yellow, orange or red color. Once consumed, carotenoids are slowly converted to vitamin A in the body. Carotenoids are best absorbed from cooked or homogenized vegetables served with some fat or oil.

Vitamin A Deficiency

Night blindness is one of the early signs of vitamin A deficiency. Blindness can eventually develop.Bacterial invasion and permanent scarring of the cornea of the eye (xerophthalmia) is a symptom of more profound deficiency. Profound vitamin A deficiency also results in altered appearance and function of skin, lung, and intestinal tissues. Children are most at risk of vitamin A deficiency because they have not yet developed adequate vitamin A stores. It has been estimated that 0.5 million children in the world become blind each year, 70% of these due to vitamin A deficiency.

The diagnosis is based on symptoms and blood tests.

Recommendation:

Taking high doses of vitamin A for several days corrects the deficiency. Vitamin A deficiency is common in areas of the world where people do not eat enough of certain foods:

• Animal and fish liver
• Orange, yellow and green vegetables
• Eggs
• Milk products

For example, the deficiency occurs in southern and eastern Asia, where rice is the main food. Disorders that impair the intestine’s absorption of fats can reduce the absorption of vitamin A and increase the risk of vitamin A deficiency. Surgery on the intestine or pancreas can have the same effect. Liver disorders can interfere with the storage of vitamin A.People with an increased risk of vitamin A deficiency:

• Drinkers
• Smokers
• Women on the pills
• Most multiple vitamins contain little or no vitamin A.

Vitamin A Excess

Consuming too much vitamin A causes:

• hair loss
• cracked lips
• dry skin
• weakened bones and muscle pain
• headaches
• increased pressure in the brain

The diagnosis is based on symptoms and blood tests.

Most people recover completely when they stop taking vitamin A supplements.

Remember !!!

• Too much vitamin A can cause toxicity. For example, taking daily doses 10 times the RDA (recommended daily allowance) or greater for a period of months can cause toxicity. Special formulations of high dose vitamin A may be taken to treat severe acne or other skin disorders. A smaller dose can cause toxicity in infants, sometimes within a few weeks. Sometimes children accidentally take a very high dose, and toxicity occurs quickly.

• Carotenoids can be consumed in foods without causing toxicity because their conversion to vitamin A is very slow. However, when large amounts are consumed, the skin turns a deep yellow (carotenosis), especially on the palms and soles. High-dose supplements of beta-carotene may increase the risk of cancer.

Clinical uses of vitamin A

Some derivatives are used to treat acne and skin wrinkling (trade name Accutane, also known as isotretinoin).

Other derivatives are used to treat breast cancer (4-HPR, Fenretinide). No one should consume vitamin A in quantities exceeding the RDA without a doctor’s advice because of the dangers of toxicity.

Approxiately 20% of vitamin A which is not absorbed is excreted within one or two days into the faeces. Of the 80% absorbed, about 20% to 50% either combines with or burns down into products that are excreted within about one week in the faeces or urine. The remainder 30% to 60% of the absorbed vitamin A is stored.

Recommended Daily Allowance - Vitamin A

Men 600 mcg Women 600 mcg Children 600 mcg Infants 350 mcg Lactating Women 950 mcg

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Tags | beta carotine, deficiency, excess, retinol, Vitamins