Despite studies questioning whether dietary supplements provide any benefit, they remain as popular as ever, with more than half of all Americans reporting they are regular users.

Some individual supplements are fading, but others are rapidly gaining steam, according to a recent study in the Journal of the American Medical Association (JAMA).

Vitamin D and fish oil supplements have become much more common, while the use of multivitamins is falling.

Researchers sought to examine the use of dietary supplements in recent years, at a time when there has been both an explosion of supplement products marketed and increased scrutiny over the effectiveness and safety of supplements.

The study was led by Elizabeth Kantor of the Memorial Sloan Kettering Cancer Center in New York. Researchers examined patterns of supplement use from 1999 to 2012. In all, 37,958 adults were surveyed about their use of supplements. The average age of participants was about 46 years old.

Researchers found the percentage of supplement users has not budged — holding steady at 52 percent — during the course of the study period.

Yet there were winners and losers among the various kinds of supplements available. The percentage of multivitamin users dropped from 37 percent to 31 percent, but vitamin D use grew from 5 percent to 19 percent. And consumption of fish oil supplements soared from 1.3 percent to 12 percent.

Use of supplements — including vitamins, minerals and herbs — has become a $32 billion industry.

A 2013 review of 27 studies on vitamin and mineral supplements found no evidence that supplements protect against heart disease or that those who take them live longer.

Supplements only slightly reduced the risk of cancer, according to the review conducted for the U.S. Preventive Services Task Force.

But not all supplements have unproven benefits, wrote Harvard Medical School's Dr. Pieter Cohen, in an opinion piece that accompanied the JAMA study.

"Many supplements including vitamins, minerals and probiotics, are important components of modern health care," he stated in his commentary. But for the majority of adults, he concluded, "supplements likely provide little, if any, benefit."

"Future efforts should focus on developing regulatory reforms that provide consumers with accurate information about the efficacy and safety of supplements and on improving mechanisms for identifying products that are causing more harm than good," Cohen advised.

"To Your Health" offers quick doses of health news several times a week.

Allie Shah • 612-673-4488

@allieshah