A Consumer Reports survey finds more than two-thirds of american adults take a multivitamin or other dietary supplement.
In fact, we spent more than 32- billion dollars on dietary supplements last year alone - and celebrities are pushing them.
Nicole Kidman is the new face of Swisse, one of Australia's biggest brands of supplements, now entering the U.S. Market.
Media mogul Martha Stewart is getting into the act. And Katy Perry tweeted about all the supplements she takes.
Even though dietary supplements are enormously popular, Consumer Reports' Medical Advisor says there are few scientific studies to support their benefits.
"There's really very little evidence showing that supplements have a measurable positive effect on health, even in the case of fish oil, which was believed to improve cardiovascular health."
In fact, a recent study in the New England Journal of Medicine found fish-oil pills did not lower the rate of heart attacks or strokes compared to a placebo.
And multivitamins? A lot of people take them, but a study of nearly 15,000 older Americans found daily multivitamins did not reduce the risk of heart attack, stroke, or death.
As for calcium, a recent study backed by the national institutes of health showed an increased risk of death from heart disease in men taking more than 1,000 milligrams of calcium supplements a day.
"Among the most serious risks of supplements is their ability to interact with regular medications. Vitamin E, for example, can cause bleeding and should not be taken with blood thinners or aspirin. It's really important to tell your doctor which supplements you're taking."
But in Consumer Reports' survey, 26 percent of people who took a multivitamin or supplement said they hadn't told their doctor what they were taking.
"It may seem easier to meet your daily nutritional requirements from a bottle, but it's actually healthier to eat a varied diet of fruits, vegetables, fish, and other healthy foods."