by Erich Rosenberger M.D.

Created on: January 12, 2008

Vitamin A is a fat soluble vitamin which is part of a family of chemicals known as the retinoids. The retinoids are present in many types of food and are commonly found attached to the fatty acids. Vitamin A is an essential vitamin that your body needs for many of its metabolic functions. However, because it is fat-soluble is important to have not have too much or too little. As extremes on either side can have significant effects on your health.

Vitamin A is found in many sources of food. It is commonly found in large amounts in liver. It can also be found in many dairy products such as milk, butter, cheese, and eggs. Many fish oils also contain a significant amount of vitamin A. Many vegetables, such as carrots and broccoli also have high levels of vitamin A.

Vitamin A is stored in the liver when it is not needed. It is then attached to a protein known as an "alpha globulin" and stored until it needs to be transported to tissues, as it is required. Vitamin A has several roles to play in the metabolism of the body. One of the most important functions of vitamin A, is its use in the rods and cones of your retina. It is an essential vitamin in the proper functioning of your vision.

Vitamin A deficiencies

Deficiencies in vitamin A can be a very serious health issue. It is one of the leading causes of blindness in young children throughout the world. It is estimated by the World Health Organization that approximately 6 to 7 million new cases of blindness due to vitamin A deficiency occur each year. Up to 20% of these will be completely blind, with 50% of the remaining having partial blindness.

Blindness related to vitamin A deficiency most commonly begins as an impaired ability to see in low light or nighttime conditions. The eyes will often become very dry as the cornea becomes thickened. White plaques are often seen around the eye in children with vitamin A deficiencies. The cornea can also develop ulcerations, and infections become more common in the eye due to the generalized damage done by vitamin A deficiency.

Prevention of vitamin A deficiency

Vitamin A deficiency is uncommon in a Western diet. There is enough vitamin A found in typical dairy products, and green vegetables such that vitamin A deficiency is rare in those who are properly fed. The vitamin A is not destroyed by cooking or damaged in any way during food preparation.

In developing countries, vitamin A supplements are often given to prevent a vitamin A deficiency.

Vitamin A overdose

Being a fat soluble vitamin which is stored in high quantities in the liver, it is also possible to have too much vitamin A in your body. Although this is rare it can cause a significant health problems. Heavy doses of vitamin A over a long period of time can cause damage to the liver. It can also cause damage to bone. Hair loss, headaches, and even vomiting are possible in severe cases. If you were to take more than 300 mg of vitamin A at one time in a tablet form, it is possible that you could suffer some side effects.

It should be noted that these effects are very uncommon, and not typically seen in a person eating a normal diet. There is some evidence that high levels of vitamin A during pregnancy can potentially lead to birth defects. Therefore it is not recommended to take vitamin A supplements while you are pregnant. A healthy balanced diet is the best way to get the proper amount of vitamin A you need for yourself and the growing baby.

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