For many people, guzzling industrial quantities of vitamins is an insurance policy against the worst consequences of an unhealthy lifestyle.

One in three women (and a quarter of all men) now swallow some sort of dietary supplement every day. Many hope the pills will provide glowing skin, shiny hair, supercharged energy and any number of disease-preventing benefits. For others, it is simply a matter of attempting to offset the damage caused by a week of hard work, hard partying and a high alcohol intake. It is a policy based on faith, and it doesn’t come cheap – in total, we spend an estimated £330m a year on such products.

Although there are recommended daily allowances, there is no consensus about safe maximum limits. Dieticians say they regularly see people who admit taking impressive cocktails of different synthetic versions of the natural nutrients found in food.

Now a report into the effects of taking these vitamins and supplements has thrown the whole issue of pill-popping into confusion. The study, published by the Cochrane Collaboration, is the biggest analysis of its type, looking at the impact of these pills on 233,000 sick and healthy people. It showed there is no evidence that supplements reduce the risk of dying prematurely, and some of the most fashionable antioxidants may shorten rather than prolong life.

The studies specifically looked at the most popular supplements, the much-fabled antioxidants beta-carotene, vitamin A, vitamin C, vitamin E and selenium, and compared people taking them with people taking placebo pills or no supplements at all.

Antioxidants are compounds used by the body to mop up free radicals, potentially dangerous molecules produced by the body during normal cell functioning. Free radicals are believed to cause damage to cell DNA when they proliferate due to illness, other toxins in the body or normal ageing.

However, the new research raises questions about whether high levels of antioxidants may somehow disrupt the absorption of other nutrients. Goran Bjelakovic, who led the study, said: “We found no evidence to support taking antioxidant supplements to reduce the risk of dying earlier in healthy people or patients with various diseases. If anything, the findings of our review show that people in trial groups who were given the antioxidants beta-carotene, vitamin A and vitamin E had increased rates of mortality.” He also noted that while there was no evidence that vitamin C and selenium did any harm, there was no evidence they did any good, either. More trials of both were needed, but, he warned: “Such trials should be closely monitored for potential harmful effects.”

The findings add weight to the growing anxiety over the unregulated sale of dietary supplements, which are more widely available in Britain than elsewhere in western Europe. Many dieticians say the pills should be treated as medicines; they are calling for a reporting system for adverse reactions similar to the “yellow card” system used by doctors to monitor unexpected reactions to drugs.

Catherine Collins, the chief dietician at St George’s University Hospital in south London, says she has seen one patient with liver failure induced by an overdose of vitamin A, and a teacher in her early fifties who was made seriously ill by a combined overdose of magnesium and vitamin C, recommended by a naturopath.

Collins says there is a case for multivitamins for frail babies and toddlers, but the rest of us are almost certainly getting what we need from our diet, and there is no evidence that vitamin supplements make a difference for most people. She does however, agree with research evidence that folic acid supplements for pregnant women, and those seeking to become pregnant, reduces the incidence of spina bifida in babies.

Patrick Holford, one of Britain’s most high-profile nutritionists, who runs a nutritional supplement company called Biocare, points to diet surveys showing that the majority of people fail to consume anything like the recommended daily levels of essential nutrients. He believes the Cochrane review is part of a conspiracy by the medical establishment to undermine the advance of the nutritional route to better health.

It does appear, though, that the very success of this unregulated industry may also lead to its downfall. The greater the number of people taking supplements, and the higher the volume they consume, the greater likelihood of nasty things happening to some of them.