Q. Your May 8 article said that vitamin E, A and beta carotene may shorten life, but I read the study was flawed because it included lots of critically ill patients yet attempted to apply its conclusions to healthy folks, and it excluded hundreds of studies, thereby including only a tiny fraction of available evidence. What's the scoop?

If you had a fine food restaurant, would you serve beer or fine wine? The highly regarded Cochrane group wanted to use only the finest, most accurate studies — randomized controlled trials (RCTs) — in determining the exact effect vitamin E, A and beta carotene had on health.

They therefore excluded hundreds of weaker observational studies from their meta-analysis, as such studies are prone to bias and often reach the wrong conclusions. Observational studies are like beer, and RCTs the vintage wine. To learn about RCTs and why wine may not be as heart healthy as everyone says, google "Landis Lum wine" to read my March 27 article.

And the ill patients were not critically ill. Their health problems ranged from cataracts and macular degeneration to stable heart disease and skin cancers. But when Cochrane excluded these patients, healthy folks still had an increased risk of dying if they took extra vitamin E, A or beta carotene, alone or in combination. And Cochrane's not alone in its conclusions. In a cancer prevention meta-analysis in the Mayo Clinic Proceedings in January, Aditya Bardia and others said, "With the compelling evidence already available, it's very unlikely that additional randomized trials of beta carotene and vitamin E as chemopreventive agents will yield positive results."

Taking antioxidants such as vitamin E, A and beta carotene reduces free radicals, but the body uses free radicals for detoxification as well as to destroy germs, aged and damaged cells, pre-cancers and cancers.

In the Journal of Nutrition in 2004, Dr. Craig Albright reported that he had fed mice prone to getting cancers a diet with no vitamin A or E so they'd have more free radicals to use to destroy tumors. Amazingly, mice fed this diet had less breast cancers with less metastasis to their lungs than mice fed a normal diet.

And if natural vitamins are even better at reducing free radicals than synthetic ones, perhaps they'd even be better at weakening the immune system, increasing cancers.

There's such heavy marketing of vitamins and anti-oxidants that we unquestioningly accept their benefits as gospel truth. They're natural, so they can't possibly harm and can only do good. Well, plants and mushrooms are natural, but many are also toxic.

Indeed, in response to my May 8 article titled "Some vitamins do more harm than good," one reader noted that vitamin E caused his dizzy spells.

Alternative medicine and vitamins are multibillion dollar businesses just as eager to turn a profit as anyone else. So could their health claims regarding their products be just a bit biased?

Landis Lum is a family-practice physician for Kaiser Permanente and an associate clinical professor at the University of Hawai'i's John A. Burns School of Medicine. Send your questions to: Prescriptions, Island Life, The Advertiser, P.O. Box 3110, Honolulu, HI 96802; islandlife@honoluluadvertiser.com; or fax 535-8170. This column is not intended to provide medical advice.