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Vitamins 'increase death risk'
01/03/2007 12:20 - (SA)
Cape Town - Some vitamin supplements could do you more harm than good, according to research published on Wednesday in the Journal of the American Medical Association (JAMA).
"Beta carotene, vitamin A, and vitamin E seem to increase the risk of death," said the researchers, operating under the umbrella of the internationally-respected Cochrane Collaboration.
The findings were however immediately rejected by British nutrition guru Patrick Holford, currently on tour in South Africa.
"I suspect it's an attempt to demote vitamin therapy so we keep taking the drugs," he said in a statement.
Holford has been under fire in South Africa for a statement that the antiretroviral AZT was "proving less effective than vitamin C" in treating Aids.
The researchers included doctors from Denmark, Serbia and Italy, a number of them members of the highly-respected Cochrane Collaboration, a network whose methods are regarded as the epitome of evidence-based medicine.
They probed the effect "antioxidant supplements" had on death rates from all causes when those supplements were being tested for preventing gastrointestinal cancer.
Data analysed from clinical trials
To do this, they analysed data from 47 clinical trials conducted since October 2005 comparing beta carotene, vitamin A, vitamin C, vitamin E and selenium.
Those trials involved over 180 000 participants, some of whom were completely healthy, and some of whom already had a specific disease.
"Our systematic review contains a number of findings," said the researchers, who were led by Dr Goran Bjelakovic of the Copenhagen University Hospital.
"Beta carotene, vitamin A and vitamin E given singly or combined with other antioxidant supplements significantly increase mortality.
"There is no evidence that vitamin C may increase longevity. We lack evidence to refute a potential negative effect of vitamin C on survival."
They said the potential effect of vitamin C and selenium on mortality needed further study.
Study fails the test - Holford
Holford however said the study failed "the four key tests of 'publication bias'."
He said the summary of the study did not correlate with the actual results, and failed to note the study's own finding that vitamins given in combination either reduced, or did not increase, mortality.
"If you can have one take-home message it is that antioxidants are team players and reduce mortality in combination, and that vitamin C and selenium are more beneficial than beta-carotene or vitamin A," he said.
In addition, two "classic primary prevention studies", where vitamin E resulted in major drop in the heart attack rates, were excluded from the JAMA study.
"In conclusion, I will keep doing what I've always been doing, because this study confirms it - and that is to supplement a combination of antioxidants, including selenium and high dose vitamin C, because, as this study says, it seems to make you live longer and reduce your risk of premature death."
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