Taking vitamin supplements does not improve health and may increase the risk of premature death, according to media reports.
A review of 67 randomised trials found that taking the supplements vitamin A, vitamin E and beta-carotene could lead to premature death.
The evidence for vitamin C and selenium suggested that the pills did not increase the risk of death, but there was no benefit in taking the pills compared with a placebo.
The researchers concluded that the current evidence does not support the use of antioxidant supplements in a healthy population.
There is no suggestion from the review, however, that a diet rich in natural sources of antioxidants could be damaging to health, say the papers.
Around 12 million people in Britain are taking vitamin supplements fuelling a £330 million industry.
What is the research?
The reports are based on the findings of a Danish study into the impact of antioxidant supplements on mortality rates.
A search of published literature and other studies held by manufacturers identified 815 trials. But only 67 were considered to be adequately run randomised controlled trials. These included 232,550 people aged an average of 62 years.
Twenty-one of the trials focused on the use of supplements in healthy individuals, while the rest tested patients with a range of diseases. Trials including children, pregnant women or patients with acute conditions, such as cancer, were excluded.
Antioxidant supplements were found to increase the risk of premature death in 47 trials.
Overall, antioxidant supplements were linked to a 4 per cent increased risk of death compared with placebo.
But when antioxidants were assessed separately, the researchers found that vitamin A was linked to a 16 per cent increased risk of premature death. For beta-carotene there was a 7 per cent increased risk of death and for vitamin E a 4 per cent increased risk of death.
The use of vitamin C or selenium did not increase the risk of death but showed no beneficial health effects compared with placebo.
Antioxidant supplements could lead to early death by eliminating too many free radicals, suggest the researchers. This could interfere with some essential defensive mechanisms such as apoptosis and detoxification, they say.
What do the researchers say?
Lead author Dr Christian Gluud, from the centre for clinical intervention research at Copenhagen University, called for better regulation of antioxidant supplements.
‘If a patient can eat a healthy, varied diet, then there is no need to take vitamin supplements. According to our results this may even be harmful.
‘Based on our results, as well as the results from other studies, it seems that these supplements might increase the progression of cardiovascular diseases and certain cancers.
‘It seems that the increased mortality comes from an acceleration of disease progression rather than from the development of new diseases.’
The team has not looked at whether a diet rich in natural antioxidants could be harmful to health but it would be good to conduct some large scale trials into this, said Dr Gluud.
What do other experts say?
Anne Sidnell, nutrition scientist at the British Nutrition Foundation, said: ‘The findings of this study are in line with other studies that have shown that antioxidants have no health benefits when consumed as supplements rather than through food.
‘Our bodies are designed to take in the correct amounts of nutrients from food, but there is a danger of overdosing when using supplements.’
There may be occasions when supplements are needed, such as vitamin D supplements for the elderly or folic acid for pregnant women, but overall a balanced diet is the best way to stay healthy, she added.
But Pamela Mason, nutritionist and spokeswomen for the Health Supplements Information Service, said: ‘Trials using antioxidant supplements have shown inconsistent findings and yet another review or meta-analysis is not going to tell us anything at this stage.
‘Antioxidants, including these noted in the Cochrane review, are essential for health and UK national dietary surveys have shown that some people have poor intakes of such nutrients.’
Antioxidants are not ‘magic bullets’ and were never intended for the prevention of chronic disease and mortality but for health maintenance, she added.
Tags: acute conditions, antioxidant supplements, Beta Carotene, cancer, controlled trials, danish study, diseases, health effects, literature, mortality rates, natural sources, placebo, pregnant women, premature death, randomised trials, Selenium, taking the pills, vitamin c, vitamin e, vitamin supplements