Large doses of vitamin A can cure cancer

This is not true but vitamin A or vitamin A-like compounds may have a role in the prevention of cancer. The latter conclusion has been reached from experimental studies on animal cells and also from studies in people. These studies suggest that vitamin A protects the 'lining tissues of the body (called epithelial tissues) like skin or the linings of the bowel, airways of the lungs, uterus or prostate glands. This does not mean, however, that vitamin A can cure cancer. It is not even certain that it can prevent some cancers.

Vitamin A can be toxic if taken in excessive quantities. Usually if a vitamin is obtained from food, rather than pills, it can be regarded as safe. However, some foods that contain large quantities of vitamin A, such as liver from marine or polar animals, can also be potentially toxic.

The body can convert a number of other dietary constituents into vitamin A. These are known as provitamins A and include a number of orange to yellow compounds called carotenes. As long as vitamin A is obtained from food in the provitamin A forms it is not even toxic. So the safest forms of vitamin A are the provitamins A in plants such as green leafy and yellow vegetables.