They are believed by millions to be an easy way to maintain health. In the UK alone, one third of the population pops at least one vitamin pill a day, and the supplements industry is worth in excess of £330million a year.
Yet studies now suggest vitamin supplements are ineffective and may even increase the risk of illness.A recent review by Copenhagen University found 'no convincing evidence' that supplements helped keep disease at bay.
Researchers also concluded that taking supplements of Vitamins A and E 'significantly increased mortality'. Vitamin A was linked to a 16 per cent increased risk of dying, and Vitamin E to a four per cent increased risk. Taking Vitamin C or selenium didn't seem either to prolong or to diminish life.
Scientists at the University of Washington also reported this year that taking daily supplements of Vitamin E for ten years may increase the risk of lung cancer. And New Zealand researchers suggested calcium supplements, often prescribed after the menopause to counter the loss of bone density, raised the risk of a heart attack in older women.
So, just how effective are vitamin pills? To find out, we asked three devotees who spend up to £200 a year on supplements, to stop taking them for a month, while not making any changes to their diet.