Antioxidant Pills Questioned, Again(was: bloated feeling)

[Guest guest]

Jun wrote:

" i also need to get over that " feeling " because i've backed off taking my

multi-vitamins, which i know are an important part of CRON. " ........

____________________________________

Actually vitamins are becoming more controversial: at worst causing harm,

at best a waste of money. Just today this article (and also scientific

studies that have been posted here) came out in the Washington Post:

By January W. Payne

A new analysis of published studies concludes that antioxidant supplements

may not provide protection against several cancers -- and could increase the

risk of death.

While some experts say the report adds to the growing case against the use

of antioxidant supplements, once thought to be widely beneficial in fighting

disease and promoting health, others question the researchers' methods and

conclusions. They say the supplements have benefits not reflected in this

report.

The findings, published in the Oct. 2 issue of The Lancet, are based on an

analysis of 14 randomized trials involving more than 170,000 patients taking

antioxidant supplements or placebos. The trials -- about half of which the

authors deemed " high quality " by virtue of their design and controls --

reported on patients who developed esophageal, gastric, colorectal,

pancreatic or liver cancer.

There is " no convincing evidence that beta carotene, vitamin A, vitamin C

and vitamin E or their combinations may prevent gastrointestinal cancers. .

.. . These antioxidant supplements may even increase mortality, " study

co-author Goran Bjelakovic, a professor in gastroenterology and hepatology

at the University of Nis in Yugoslavia, stated in an e-mail interview.

The analysis looked at antioxidant pills, not at antioxidant vitamins found

in foods. Nutrition experts remain in nearly universal agreement that

antioxidants found in fresh fruit, vegetables and other whole foods have

important benefits. Vitamin-rich whole foods should form the core of a

healthy diet, they say.

Some experts said the report sheds new light on an existing concern. " What

it does is confirm what we're already learning about antioxidants and heart

disease, and that is that they don't provide the protection that we once

thought they would, " said Schardt, a nutritionist at the Center for

Science in the Public Interest, a Washington-based advocacy group.

Limburg, director of the Mayo Clinic's gastrointestinal neoplasia

clinic, said " antioxidants have demonstrated lots of appeal " in other types

of research, such as studies based on self-reports of previous supplement

use. But data derived from clinical trials -- studies that follow over

extended periods people who take either supplements or an inert placebo --

" have been strikingly unremarkable, " he said.

Still, Limburg says, the study is not definitive. " It shows, on a

best-case scenario, there's no benefit. I think we still need to do further

analysis " into the question of harm, Limburg said.

Other experts caution against drawing broad conclusions.

Forman, a University of Leeds cancer epidemiologist who co-authored

an editorial in the same issue of The Lancet, said he " would be very

reluctant to draw any conclusions regarding mortality from the evidence

that's been presented. What they've got as a result is just on the threshold

of being statistically significant. "

The Council for Responsible Nutrition, a trade association representing

dietary supplement suppliers and manufacturers, questioned the researchers'

decision to do a meta-analysis of studies that investigated a variety of

antioxidants, rather than analyzing them as individual nutrients.

" They're violating one of the basic tenets [of meta-analysis] by combining

things that shouldn't be combined, " said Hathcock, vice president of

scientific and international affairs at the council. Some antioxidants are

known to have opposing effects, so in a study population taking two

supplements, the benefits of one may be masked by the negative effects of

the second, he said.

In addition, participants in the studies took high doses of antioxidants,

which the authors said might contribute to the negative findings.

Researchers said that the antioxidant levels that provide protective

effects are not known and probably differ between individuals. Some

nutrients may have benefits at lower levels but negative effects at higher

ones.

Participants in the studied trials took doses considerably higher than

those found in multivitamins and some antioxidant supplements. For instance,

every one to two days they took between 1,500 and 15,000 micrograms of

vitamin A, compared with the recommended intake (known as a Dietary

Reference Intake, published by the Food and Nutrition Board of the Institute

of Medicine) of 700 micrograms for most women and 900 micrograms for most

men. Study participants took 30 to 600 milligrams of vitamin E, compared

with a recommended intake of 15 milligrams daily for most adults. (The

labeling on many bottles of over-the-counter supplements measures some pill

contents in international units; some use the metric scale.)

Not all antioxidant supplements were found to be without benefit or

potentially risky. Selenium appears to be an exception, Bjelakovic said,

potentially leading to a reduction of gastrointestinal cancers.In four

trials, selenium supplements reduced the incidence of gastrointestinal

cancers, according to the study. The reductions occurred within two to four

years after beginning supplementation.

Selenium has been found to offer other potential benefits, leading the

National Cancer Institute (NCI) to sponsor further study into its effects.

NCI is funding a clinical trial to see if selenium and vitamin E reduce the

risk of prostate cancer.

Two trials of beta carotene included in the analysis drew criticism from

some experts. The trials, which found that beta carotene had harmful

effects, included participants who were smokers or had been exposed to

asbestos and were therefore at higher risk for cardiovascular disease and

lung cancer.

" No one can tell what was responsible for their increased risk, " said

Blumberg, a nutrition professor at Tufts University. " Basically this

[beta carotene research] is driving the entire conclusion of this report. "

Blumberg sits on advisory boards for several nutritional pharmaceutical

companies and receives honoraria for attending some meetings.

But other previous reports conclude that antioxidant supplements are of

limited value. A meta-analysis in the July issue of the Archives of Internal

Medicine looked at seven trials involving vitamin E supplementation. It

found that the supplements did not help prevent cardiovascular disease and

that patients' assumptions about unproven benefits may keep them from

developing a healthy lifestyle.

The U. S. Preventive Services Task Force last year said there is

insufficient evidence to recommend for or against the use of supplements of

vitamins A, C or E; multivitamins with folic acid; or antioxidant

combinations for the prevention of cancer or cardiovascular disease.

The task force also recommended against the use of beta carotene

supplements, alone or in combination, for prevention of those diseases.

Parnes, chief of NCI's prostate group in the division of cancer

prevention, said that, regardless of the infighting about this new analysis,

it's clear that consumers should focus more on eating healthy diets and less

on taking supplements. With studies showing harm to some populations, and

others showing no benefit, there are good reasons to be a cautious consumer

of vitamin pills beyond doses found in a multivitamin.

" I really don't think people should be going out and taking large amounts

of antioxidants, " said Parnes, who said he doesn't take supplements but does

eat a " colorful " diet rich in vegetables and fruit. " Eating a good diet is

the number one way [to stay healthy]. If people for whatever reason can't or

don't eat a good diet, a multivitamin is a good alternative. " •