Common vitamin pills may "significantly" increase the risk of death, a new study has found.

Vitamin A, vitamin E and beta carotene taken singly or with other supplements "significantly increase mortality", according to scientists from Copenhagen University Hospital in Denmark.

The researchers found no evidence that Vitamin C could increase longevity, while selenium tended to reduce the risk of death.

The study, published in the Journal of the American Medical Association, involved analysis of 68 previous trials of the five antioxidant supplements, involving 232,606 participants.

The Copenhagen team singled out 47 "low-bias risk" trials, with 180,938 participants, as being the best quality.

Based on these low-bias studies, the supplements were found to be associated with a 5% increased risk of mortality.

Taking beta carotene was associated with a 7% risk, vitamin A with a 16% risk and vitamin E with a 4% risk, while there was no increased mortality risk with vitamin C or selenium.

The authors wrote: "Our findings contradict the findings of observational studies, claiming that antioxidants improve health.

"Considering that 10-20% of the adult population (80-160 million people) in North America and Europe may consume the assessed supplements, the public health consequences may be substantial."