CRN pours cold water on new vitamin E research
do more harm than good is simply an attempt to grab headlines, says
the US supplements industry association the CRN, writes Philippa
Nuttall.
The research that was simultaneously released on the website of the Annals of Internal Medicine and reported at the American Heart Association's Scientific Sessions states that daily vitamin E doses of 400 international units (IU) or more can increase the risk of death and should be avoided.
The researchers noted that "in animal and observational studies, vitamin E supplementation was shown to prevent cardiovascular disease and cancer. However, other studies suggested that high doses could be harmful".
In order to investigate these findings and determine if there is a 'dose-dependant response', researchers studied death rates in published clinical trials comparing vitamin E supplementation to placebo and included findings from 14 studies undertaken between 1993 and 2004. "Doses ranged from 15 to 2000 IU/day, and average intake was about 400 IU a day," said the researchers.
"Increasing doses of vitamin E were linked to an increase in death," said lead author Edgar Miller, associate professor of medicine at Johns Hopkins University in Baltimore.
He qualified this statement by noting that there was no increased risk of death with a dose of 200 IU per day or less, "and there may even be some benefit". However, there was an increased risk at amounts above 200 IU per day and significant risk of death was found at 400 IU and above a day.
"Those who take greater than 400 IU of vitamin E a day are about 10 percent more likely to die than those who do not," researchers said, adding that many people who take vitamin E supplements take between 400 and 800 IU in a single capsule.
"Typically, we get about 6-10 IU per day of vitamin E in our diets. Vegetable oils, nuts and green leafy vegetables are the main dietary sources of vitamin E. Supplementation can increase intake by 100-fold," said Miller.
Researchers said the current US dietary guidelines do not recommend vitamin E supplementation, but indicate that the upper tolerable limit of intake is 1000 IU per day.
Vitamin E is currently growing faster than traditional food ingredients at around 5-7 per cent on a global basis. Natural vitamin E is growing slightly faster, based on its use in health products.
However new research can cause spikes in demand for vitamins.
US trade association the Council for Reponsible Nutrition says that this meta-analysis "inappropriately tries to draw conclusions for the whole population based on a combination of studies of people who were already at grave risk with existing diseases including cancer, heart disease, Alzheimer's, Parkinson's and kidney failure".
The trade body said that even though the researchers noted limitations in their meta-analysis, they continue to "make sweeping generalizations about the use of vitamin E and all-cause mortality for the whole population, although they provide no evidence that these kinds of effects would occur in healthy populations".
"This is an unfortunate misdirection of science in an attempt to make something out of nothing for the sake of headlines," said John Hathcock, vice president of scientific and international affairs at the CRN.
He added : "The overall conclusion of this meta-analysis is driven by the results from a few of these clinical trials, some of which are suspect and/or dated. For example, the WAVE trial (Waters et al., 2002) made no correction for multiple comparisons, and found one of 22 comparisons 'significant.' This is 1/22 whereas 1/20 would have been expected on a random basis. In other words, they found nothing."
Hathcock concluded that as far as the CRN was concerned, vitamin E supplements are safe at levels of at least up to 1,000 mg (1,600 IU) for normal, healthy adults.
