Researchers at Johns Hopkins report that use of
high-dose vitamin E supplements, in excess of 400 IU
(international units), is associated with a higher overall
risk of dying. These results should be of concern to the
millions of Americans who take vitamin E supplements for
perceived health benefits.
The Johns Hopkins team presented its findings Nov. 10
at the American Heart Association's Scientific Sessions
2004 in New Orleans, with simultaneous publication of their
study in the Annals of Internal Medicine Online.
The study results showed that people taking vitamin E
supplements of 400 IU or more per day had an increased risk
of death.
"Our study results do not support the use of high-dose
vitamin E supplements. If people are taking a multivitamin,
they should make sure it contains no more than a low dose
of vitamin E," said study lead author and internist Edgar
R. Miller III, associate professor of
medicine at the
School of Medicine. "A lot of people take vitamins
because they believe it will benefit their health in the
long term and prolong life. But our study shows that use of
high-dose vitamin E supplements certainly did not prolong
life but was associated with a higher risk of death."
Vitamin E capsules, used as supplements, typically
contain 400 IU to 800 IU. The study results indicated that
these high-dose supplements were associated with a higher
risk of death.
In the current study, the Johns Hopkins team
re-analyzed raw data from 19 major clinical trials, sorting
information by whether high- or low-dose levels of vitamin
E were taken. Nine of these studies tested vitamin E alone;
10 tested its use in combination with other vitamins.
The 19 studies took place between 1993 and 2004 and
involved more than 136,000 patients in North America,
Europe and China. All the studies involved use of a control
group taking placebo. Risk of death was estimated by
comparing the death rates in both groups. Follow-up periods
ranged from 1.4 years to 8.2 years.
When the data for these trials was re-evaluated,
through a process called a meta-analysis, nine of 11 trials
involving high-dose vitamin E (400 IU per day, or more)
showed an increased risk of death. The other eight trials
involved low-dose vitamin E users.
It was unclear whether low amounts (200 IU per day, or
less) of vitamin E supplements increased a person's risk of
death.
Because most of the patients in all the trials were
over 60, and a majority had pre-existing conditions, such
as heart disease, the study's application to younger,
healthy adults may be limited, the Johns Hopkins
researchers point out.
Current U.S. dietary guidelines do not recommend
vitamin E supplementation; however, the guidelines do set
an upper tolerable intake limit of up to 1,500 IU per
day.
"Policy-makers and government regulators should
consider lowering this level, perhaps, to an upper limit of
400 IU per day," said Eliseo Guallar, senior author of the
study and assistant professor of epidemiology at the Johns
Hopkins Bloomberg School of Public Health. "Additional
research is needed to determine the effects, if any, of
low-dose levels of vitamin E supplements. As well, there
are unresolved questions on the benefits of vitamin E when
combined with other antioxidants."
Vitamin E is one of 13 vitamins essential to body
metabolism, cell growth and function. It is also known as
tocopherol and is an antioxidant important in the formation
of red blood cells and the use of vitamin-K-mediated
clotting factors. Sources of dietary intake include wheat
germ, corn, nuts, seeds, olives, spinach, asparagus and
other green leafy vegetables, vegetable oils and products
made from vegetable oils, such as margarine. On average,
dietary intake of vitamin E is 10 IU per day. Multivitamin
pills usually contain 30 IU to 60 IU of vitamin E.
The research was conducted at Johns Hopkins. Other
researchers who participated in this study were Roberto
Pastor-Barriuso, Darshan Dalal, Rudolph Riemersma and
Lawrence Appel.
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