WTF ??? 'High doses of vitamin E may hasten death'

[Guest guest]

High

doses of vitamin E may hasten death

15:00 10 November 04

NewScientist.com

news service

Taking high doses of

vitamin E may increase a person's overall risk of dying in any given

year, according to a controversial new analysis. The US researchers say

the finding - whose cause is unknown - suggests people should stop

taking high doses of the popular supplement.

Earlier studies suggest

vitamin E, an antioxidant, has either no effect on mortality rates or

lowers the risk of dying from cardiovascular disease. And unlike some

other antioxidants, such as vitamin A, vitamin E does not accumulate in

the body, potentially becoming toxic.

So US dietary

guidelines, while not recommending vitamin E supplements, set a high

upper limit of 1500 international units (IU) for their daily intake.

Most of the 25% of US adults who take vitamin E supplements take them

in large doses - greater than 400 IU per day.

"People take high doses

because they think they're going to live longer," says lead author

Edgar R. , a physician at s Hopkins University School of

Medicine in Baltimore, land. "But this research doesn't support

that. The death rate is higher with high doses."

Vitamin overdose

says previous

studies have been small and not taken dosage into account. But he and

his colleagues analysed the dosage levels and death rates of about

136,000 people in 19 clinical trials conducted around the world.

They found that the

risk of dying within five years rose by about 5% in the 11 trials with

vitamin E doses of at least 400 IU per day. The effect of low-dose

supplements, however, lowered the risk of death by less than 1%. The

researchers presented their results on Wednesday at a meeting of the

American Heart Association in New Orleans, Louisiana. They will publish

the work in the ls of Internal Medicine.

But the authors caution

that the results may not apply to the population at large because the

high-dose trials were small and their participants tended to have

chronic health problems such as heart disease. And because most of the

studies did not note the cause of death, the authors say they cannot

conclude anything about the underlying mechanism.

But they list four

possible causes. Vitamin E is an anti-coagulant, so it may increase the

risk of bleeding - which contributes to strokes - in people already

taking blood-thinning drugs. Or it could be down to the irregular way

people take the supplement. Withdrawal symptoms, such as chest pain,

may start when people stop their daily regime.

Rogue compound

Or, say the

researchers, vitamin E could become a “turncoat†free radical at high

doses, damaging the very proteins and fats it usually protects.

Maret Traber, a

nutritionist at Oregon State University in Corvallis, who helped

develop the US guidelines for vitamin E, says the turncoat effect has

been seen in test tubes. But she notes that the human body may contain

enough other antioxidants to neutralise a rogue vitamin compound

immediately

"It's kind of like a little spark flying out of the fireplace

- the vitamin E radical never stays around long enough to actually do

any damage," Traber told New Scientist.

Finally, the researchers say the type of vitamin E in

supplements could displace other antioxidants - including another form

of vitamin E found in many foods, disrupting the balance of antioxidant

systems.

"It's difficult to figure out why vitamin E should cause

death," says Traber, who points out that the new analysis looked only

at studies in which people died.

But Bent, a physician who studies herbal supplements

at the University of California in San Francisco, says: "Most of the

evidence really hasn't panned out that vitamin E is a very beneficial

supplement. So to think that high doses might be harmful is not that

surprising."

Maggie McKee