Blois Olson’s ankles hurt so much that the pain made him walk “like an old man.”

The St. Louis Park man consulted his doctor, who told Olson he had early arthritis and recommended a supplement — glucosamine — for relief. For the next six months, Olson downed glucosamine tablets every day.

These days, Olson, 42, no longer feels that throbbing pain in his ankles. And he’s become a believer in the healing power of nutritional supplements.

“Once one of them worked, then I trusted others. I was more open to taking them,” said Olson, who has since added fish oil to his daily intake.

He’s among the more than half of American adults who take dietary supplements to prevent or treat health problems.

Use of supplements — including vitamins, minerals and herbs — has become a $32 billion industry, despite scant evidence of their effectiveness.

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.

Yet people continue to embrace them — believing that supplements are “natural” and therefore safe. In fact, some patients who are hesitant to take prescribed medications show little or no skepticism about taking supplements, doctors say.

Dr. Donald Hensrud, a Mayo Clinic physician who specializes in preventive medicine, chalks it up to our belief that there’s a quick fix.

“Humans are optimistic and they want to believe in things,” he said. “They want to look for an easy way to improve their health.”

The increased use of supplements also reflects dramatic changes in health trends, including the rise of alternative medicine and the empowerment of patients, who want to have a say in — or take charge of — their own treatments.

“People are taking their personal health more into their own hands,” said Jeannemarie Beiseigel, who teaches nutrition at the University of St. Thomas.

Doctors’ take

While consumers may be hot on everything from echinacea to Ginkgo biloba to St. John’s wort, many doctors give them mixed reviews.

A recent probe by New York state officials added to existing concerns about supplements. Last month, Target, Wal-Mart, GNC and Walgreens pulled some herbal products off shelves after DNA testing found that the products didn’t contain the key ingredients listed on the labels.

That’s added to Hensrud’s skepticism about the widespread use of supplements.

“From the big picture standpoint, there are a minority that are beneficial,” he said. “There are a small amount that are detrimental and have sometimes serious side effects. And there are a whole lot that have no proven benefit and a lot of marketing, hope and hype.”

Hensrud, however, doesn’t write off all supplements. For example, if an elderly person has a documented vitamin deficiency — such as B12 vitamin — then taking a supplement might help.

At the Penny George Institute for Health and Healing in Minneapolis, supplements are included in many treatment plans. The institute’s philosophy: People want to use supplements, so doctors need to provide guidance.

“We encourage people to always come in for some sort of provider consultation first,” said Dr. Courtney Baechler, cardiologist and vice president of the institute.

Many of her patients have heard success stories about supplements and want something that will have as few side effects as possible, Baechler said. She also pointed out that some supplements are becoming part of mainstream medicine.

“We certainly try to use supplements if we can instead of a medication,” she said, citing fish oil as an example. “While not all fish oil is created equal and you need to find a good product, fish oil is actually part of the American Health Association’s guidelines for triglyceride management.”

For a patient with high cholesterol, for example, a “therapeutic dose” of fish oil plus a new diet plan might be prescribed instead of a standard medication that might trigger unwanted side effects, she said.

Natural appeal

But Beiseigel advises caution when it comes to using supplements.

“One of my big concerns is that even if a label is credible, the amount you get in supplements can vary hugely from a quantity which could do nothing to mega doses which can be highly toxic,” she said.

Gretchen Chapman, a psychology professor at Rutgers University, suggests our theories of how our bodies work have played into the assumption that supplements are safe and effective.

“If we know that one of the things that makes healthy foods healthy is that they have vitamins in them, that’s one of the reasons why vegetables are considered healthy foods and cheese curls aren’t,” Chapman said. “So this seems like a natural extension that taking a multivitamin tablet would be a healthy thing to do. It’s sort of close to eating a vegetable.”

Supplements also appeal to people looking for an easy fix.

“It’s just swallowing a pill. It’s not like you have to go jogging or go to Pilates class or actually eat kale, or something that’s actually onerous to do,” Chapman said.

Still, as people become increasingly involved in their personal health — turning to Google or friends for advice — doctors aren’t the only trusted sources of medical information anymore.

“People talk to each other and they’ll say, ‘My sister went on this and had great relief in her back pain. And gosh, [with] the narcotics that my doctor prescribed, I’m not able to drive my car, and I’m having constipation and feel out of it all the time. So what else [is there?]. There’s got to be something else?’ ” Baechler said.

Although Olson took glucosamine on his doctor’s advice, he also asked his friends about it.

“It’s one of those things that 40-year-old guys compare — ‘Are you taking glucosamine?’ ”

That’s when he started to think, “This really does work.”