I seem to take a lot of contrarian views in this column, at one time or another disputing the health benefits of wine, fish oils, vitamin E, and drinking eight glasses of water a day. How do I decide what the truth really is?

To know whether vitamin E or fish oil really improves health, you want to look at all studies ever done on the subject rather than just two or three, or the latest one. To do this, look at a so-called systematic review or meta-analysis. Furthermore, you should only look at much more accurate randomized controlled studies rather than weaker observational ones, even though the latter may have enrolled thousands more subjects than the former. No matter how much you try to mathematically correct observational studies to make them more accurate (you'll see the words "adjusted for cholesterol, diabetes ... "), they still often reach the wrong conclusions.

The highly regarded Cochrane group does just this, producing systematic reviews using only more accurate randomized studies on topics from earwax removal to strokes. Experts consider Cochrane to be even better than the New England Journal of Medicine, UpToDate and Harrison's Principles of Internal Medicine. Try this yourself — google "cochrane review omega 3" and you'll find that it is not clear whether omega-3 fats reduce heart attacks, strokes, dementia or cancers.

And hot off the presses, on April 16 the Cochrane group published a systematic review of antioxidant supplements, analyzing 67 studies involving almost a quarter of a million subjects. They found that beta-carotene, vitamin A and vitamin E, whether taken alone or combined with other antioxidants, actually shortens life and increases the risk of dying, likely from cancers and heart disease.

Furthermore, vitamin C did not lengthen life, and there was no guarantee it did not shorten it. Indeed, vitamin C may at times act as a pro-oxidant.

Taking antioxidants reduces free radicals, but your body uses free radicals in biochemical reactions to destroy unwanted cells like germs, aged and damaged cells, pre-cancers and cancers. In an effort to boost their immunity, Dr. Craig Albright in the Journal of Nutrition in 2004 fed mice prone to getting cancers a diet with no vitamin E or vitamin A so they'd have more free radicals to use to destroy tumors and pre-cancerous cells. Amazingly, mice fed this diet had smaller breast cancers with less metastasis to their lungs than mice fed a normal diet — their tumors had more free radicals that killed more cancer cells.

So taking extra antioxidants may actually weaken the immune system. Kaiser no longer sells beta carotene or vitamin A, or vitamin E in doses above 100 IU. But I'd avoid vitamin E pills, period.

Dr. 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.