Sunday, February 17, 2008

Understanding Vitamin A

Everyone knows that vitamins are important for good health. Of the 13 essential vitamins, the human body can only manufacture a small portion of these. The rest must come from the diet or, in some cases, supplementation. But what exactly are the benefits of these vitamins and how much of it do we need to be healthy? In particular, what are the benefits of Vitamin A, and what are its sources?

As an antioxidant, vitamin A prevents cell damage caused by free radials and may be helpful in preventing some types of cancer. It is believed that vitamin A may help protect against lung cancer. Vitamin A has also played a part in helping heal and prevent acne. The potent acne medication, Accutane (isotretinoin), is a derivative of vitamin A.

Good sources of the retinol form of vitamin A in the diet include the following:

Egg yolks
Fortified whole milk

Retinol plays many important roles in the body. It prevents night blindness and is essential for good eye health. Without retinol, cell division and cell growth cannot proceed normally. Bones and teeth need the proper amounts of vitamin A in order to develop properly. Other parts of the body, such as the tissue that lines intestines and airways also require retinol.

Vitamin A is a fat soluble vitamin that exists in multiple forms. Retinol, retinoic acid, and retinyl esters are stand-alone forms. This means that they are readily available in foods in their current form, and do not need to be combined with other minerals in order to be effective. The two types of vitamin a are retinols and beta carotene. Most of the time Vitamin A is referred to interchangeably with either of these terms. Vitamin A in the diet comes from two main sources: animal products and plants. Retinols are obtained from animal products, whereas the form beta carotene comes from plants such as yellow and orange vegetables.

Beta carotene is abundant in the following plant sources:

Yellow squash

Healthy adults only need 800-1000 micrograms of vitamin A on a daily basis. Too much vitamin A can cause headaches and vision problems, joint aches, loss of appetite, and skin problems. Women who are pregnant should not take vitamin A supplements, since excessive amounts of retinol have been linked to birth defects.

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