A Guide to Vitamin A

Like many vitamins, Vitamin A is an essential ingredient in the recipe for human health, and is used by our bodies for many cellular processes and functions. Vitamin A particularly affects eye health, as well as aiding in skin health, cell growth and in boosting our immune systems (see below for comprehensive list). Vitamin A is essntial for both color vision and scotopic vision, which involves how well we see in low light conditions. Other functions involving Vitamin A include:

• Immune function
• Embryonic development and reproduction
• Bone metabolism
• Gene transcription
• Haematopoiesis
• Skin health
• Antioxidant activity

Vitamin A can be absorbed via food sources, and the absorption and use depends upon whether the source is animal (eggs, milk, liver, meat) or vegetable (fruits and vegetables, especially red, orange and green). For instance, Vitamin A sourced from animals is called retinol, and is a fat-soluble substabce found in tissues. Vegetable sources such as carrots contain carotenes, which must be converted to useful substances. Recent studies suggest that vegetable-sourced Vitamin A may be less useful to us, having implications for vegetarians who must ensure they receive adequate supply.

However, the most common problem with Vitamin A is not deficiency, but toxicity, meaning excess. Because this vitamin is fat-soluble, our bodies do not rid themselves of excess as easily as with water-soluble vitamins. This can lead to nausea, jaundice, irritability, anorexia, (not to be confused with anorexia nervosa, the eating disorder [pre wikipedia]), vomiting, blurry vision, headaches, hairloss, muscle and abdominal pain and weakness, drowsiness and altered mental status. This is far less applicable to vegetable sources, as our bodies will use the excess for other purposes.*

You may have been told as a child that eating lots of carrots will help you to see in the dark, and that is partially true: due to the vitamin A our bodies produce from high levels of beta carotene that are found in such vegetables, our quality of vision can theoretically be enhanced with high consumption. Other foods which have high levels of beta carotene that can be converted to vitamin A include tomatoes and dark green leafy vegetables, such as spinach. Beta carotene is not only used to form vitamin A, but it is also a powerful antioxidant in itself. *None of the beta carotene that is absorbed is wasted as any excess after conversion to vitamin A has taken place is used to fight the harmful free radicals within the body.

Vitamin A also helps fight infections and illnesses by helping tissues that line various parts of the body, including the eyes, mouth, nose, throat and lungs, to grow and also to repair them if they are damaged to prevent infection. Children also need plenty of vitamin A to help their bones and teeth to develop properly.

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