The evidence that vitamin supplements are useful in preventing cancer or heart disease is not conclusive, the US Preventive Services Task Force, an influential US government advisory panel, has said.

Moreover, β carotene supplementation may do more harm than good in patients with lung cancer, the panel found (Annals of Internal Medicine 2003;139:51-5).

A separate meta-analysis reported by researchers at Oregon Health and Science University who are affiliated with the Preventive Services Task Force also found no evidence that vitamins are useful in preventing cardiovascular disease (Annals of Internal Medicine 2003;139:56-70).

In reaching these findings the task force researchers searched medical reports from 1966 to September 2001, using the Cochrane controlled trials register and …