Some years ago studies of diet suggested that taking large amounts of food rich in vitamin A might reduce the risk of some cancers, particularly lung cancer.

As a result of these reports several large clinical trials were started in which people who were thought to be at risk of getting lung cancer (mainly smokers) where either given vitamin A supplements (or a substance called beta-carotene, which the body converts into vitamin A) or placebo tablet with no vitamin content.

To everyone's surprise the first two of these trials, which involved large numbers of people in Scandinavia and the USA, actually showed that the group taking the vitamin A or beta-carotene actually developed more lung cancers than those taking the inactive placebo.

As result of these findings the other trials were stopped because of the risk that the vitamin supplements might actually be causing rather than preventing the cancers.

These trials only looked at vitamin A and beta-carotene and so don't tell us anything about other vitamin supplements and lung cancer.

Also, these results do not tell us anything about the effects of vitamin A supplements on non-smokers but they do suggest that smokers should avoid them.

At the end of the day the best way for a smoker to reduce their risk of getting lung cancer is to stop smoking!