"It's rather few cases ... where multivitamins have been put to test in a clinical trial to date. None have really shown benefits for any clinical outcome like cancer or heart disease," said Ross L. Prentice, a biostatistician with the Fred Hutchinson Cancer Research Center and the University of Washington who has been involved in some long-term studies of the effects of multivitamins on the risk of disease.
"There may be some short-term benefits people report but, in terms of chronic diseases, I don't think so," Prentice said.
Prentice said he is skeptical of the vitamin-based approach to improving health, despite the number of primary care physicians -- including his own -- who have recommended taking more vitamins.
"I think it's a large, expensive industry without convincing data. Billions of dollars in expensive urine so far," he said.
"I think we should be looking into commonplace things like how many calories we consume ... how much physical activity we get," he said. "Those are difficult topics to study reliably, but they're likely the keys to our obesity epidemic and obesity-related diseases."
Do you want to know more about strength training, sports nutrition, healthy eating and more positive lifestyle changes for men? Visit the ABCNews.com OnCall+ Men's Health Center to get all your questions answered.