Vitamin A is one of those vitally important nutrients that we hardly notice unless we have either too little, or too much. In a generally healthy diet, with plenty of locally-grown (and preferably organic) fruit and vegetables, and dairy products in moderation, we are unlikely to be lacking in this vitamin. However, if your diet is limited in these products, you might need to take a supplement.
What is Vitamin A for?
This vitamin is best known for its role in night vision, and a good indication that someone is low in Vitamin A may be difficulty in seeing at night. If, in addition, you find bright sunshine or even bright artificial light to be painful, you may also be low in this vitamin. Severe lack of Vitamin A in the developing world has led to blindness in some children; a slight lack may be responsible for the increase in macular degeneration in the elderly.
If you are very low in Vitamin A, you may find that your skin becomes dry, and your hair seems lifeless. More seriously, you will be likely to catch any infection that is going around, and may become anaemic. Cancer can develop more readily, too, when there is little or no Vitamin A in the body.
Dangers of too much Vitamin A
While too little Vitamin A has many health risks, an excess can cause different, equally serious problems. So it's not a good idea to take Vitamin A tablets 'just in case', and you should never exceed the recommended daily dose. An excess of this vitamin is stored in the body rather than being excreted, and too much over a long period can lead to dizziness, headaches, joint pains, even coma. Long-term over-use of Vitamin A can lead to irreversible liver damage.
It is therefore important to limit intake of liver, fish-liver oils, which have the highest concentration of pre-formed Vitamin A, and also to be careful about Vitamin A supplements. The current recommended daily intake per individual is between 1000 and 3000 International Units (IU), with rather more required for women who are pregnant or breastfeeding. It used to be recommended that pregnant women ate liver daily: this is no longer considered wise.
There is some pre-formed Vitamin A in eggs and milk products such as cheese or yogurt, but not enough to worry about. A large egg, for instance, contains approximately 260 IU.
Vitamin A from carotenoids
Thankfully, there is a much safer way to get Vitamin A in our diets. Many vegetables, and some orange coloured fruits (such as apricots and some melons) contain carotenoids; micro-nutrients which are converted into Vitamin A by the body. The best-known carotenoid is probably beta-caroteine which has a high concentration in carrots, sweet potatoes and red or orange bell peppers. There is no need to limit intake of fruits and vegetables containing caroteinoids; the only known side effect of eating a vast excess of these is a slight orange tint to the skin.
Further reading