Hardly a day goes by that people don’t tell me that one or more dietary supplement has cured or prevented an ailment of theirs or suggest that I try one to treat a problem of my own. And I am not immune to wishful thinking that an over-the-counter vitamin, mineral or herb may help to keep me healthy or relieve some distress without having to see a doctor.

I have succumbed to several popular suggestions, including melatonin and magnesium to improve my sleep, glucosamine-chondroitin to counter arthritic pain and fish oil to protect my brain and heart. I take these even knowing that irrefutable, scientifically established evidence for such benefits is lacking and I may be paying mightily for a placebo effect.

But as a scientifically trained journalist, I feel obliged to help others make rational decisions about which, if any, dietary supplements may be worth their hard-earned dollars. I’ll start with the bottom line on the most popular of these, the daily multivitamin/mineral combo: If you are a healthy adult with no known nutritional deficiencies, save your money.

An independent panel convened by the National Institutes of Health concluded that evidence is lacking for or against the ability of a multivitamin to prevent chronic disease. The American Cancer Society, the American Heart Association and the United States Preventive Services Task Force, among others, have found no role for a one-a-day supplement to prevent cancer or heart disease; they recommend instead a balanced diet with a variety of foods as likely to be more effective than any capsule.