There are many conflicting opinions about the benefit of vitamins to supplement diet.

Some studies conclude that vitamins may lower the risk of heart disease or lower certain cancer rates. I know many people who have a daily ritual of taking multiple tablets and powders, or take high doses of vitamin C at the earliest signs of a cold or flu.

Yet recent studies by the government-funded Women's Health Initiative, tracking 150,000 women over eight years, found no significant difference in lifespan or rates of cancer and heart disease between those who took multivitamins, and those who didn't.

Other studies have concluded that no manufactured vitamin or supplement can match the effectiveness of nutrients obtained from eating whole foods.

The fact is, different studies can give contradictory results. I have read articles in journals strongly citing the superior vision or comfort of a new contact lens or solution -- only to see the study was performed by someone representing the manufacturer.

I personally believe in the natural diet way of achieving health. But I also advise patients who believe in supplements to continue to take them, if there are no harmful side effects.