2007年VOA标准英语-Study: Antioxidant Vitamins May Increase Health

According to the results of a new study, antioxidant vitamin supplements taken by people to promote their health may actually shorten their life.  The findings were based on a review of dozens of studies on the health effects of vitamin supplements.  VOA's Jessica Berman reports.

The study by Danish researchers analyzed 1 the data of 68 anti-oxidant studies involving almost a quarter of a million people.  About half took beta carotene, and vitamins A, E and C supplements, thinking the vitamin pills improved their health.

The supplement-takers in the studies were compared to groups of participants who did not take antioxidants.

The Danish investigators 2 found that on average, those taking vitamin A increased their risk of death by 16 percent; beta-carotene supplements taken regularly increased the risk of premature 3 death by seven percent and vitamin E supplements increased the risk by four percent.  The researchers found that vitamin C did not have an effect one way or the other.

The results of the study were published in the Journal of the American Medical Association (JAMA).

Edgar Miller 4 is a professor of medicine at Hopkins University School of Public Health in Baltimore, Maryland.  Miller called the study extremely well done and one that would be hard to replicate 5 given its size and scope. 

The study looked at the effects of supplements that can be purchased in the average health food store, like vitamin E, which Miller says can be up to 50 times the amount found in a healthy diet.

Those kinds of mega-doses, says Miller, might do more harm than good.

"The emerging evidence that giving high dose supplements like this can actually displace other natural antioxidants," he said.  "It can affect your normal cell signaling where if you have a damaged cell that is maybe is pre-cancerous typically what happens it sends out these signals that it needs to be taken care of by your own immune system.  But perhaps these anti-oxidants [from supplements] are blocking that signal."

Natural anti-oxidants neutralize 6 free radicals 7, cell-damaging molecules 8 that are produced in the body as a result of the energy producing process. 

Balz Frei is director of the Linus Pauling Institute at Oregon State University, which studies the role of vitamins and minerals in preventing disease.  Frei says the study was flawed.

"This study really does nothing to advance the knowledge in the field.  It does not do anything to help consumers decide what they should do," he said.  "And it does not reveal the true health effects of anti-oxidants, whether beneficial or otherwise."

Frei says additional, large scale studies need to be done that measure the benefits of vitamin supplements, and they should be compared head to head to studies such as the one that was just published. 

In the meantime, Miller thinks people ought to proceed with caution if they are taking vitamin supplements or are thinking about it.

"If it is anecdotal reports or if it is a nutraceutical or pharmaceutical 9 company that is promoting the use of it, you really need to look at the evidence whether it would benefit or not.  I think this study in JAMA shows that in this large number of trials it does not prolong life.  In fact, it may actually shorten life."

Miller believes there will now be medical research into why anti-oxidant supplements appear to cause harm.