So, does Michael Phelps believe in flossing?

Story highlights

  • Ford Vox: Michael Phelps, others using untraditional treatments like "cupping." And benefits of flossing now questioned
  • Vox: We know the mind has the capacity to palliate itself, so are cupping and flossing just features of a healthy imagination?

Ford Vox is a physician specializing in rehabilitation medicine and a journalist. He is a medical analyst for NPR station WABE-FM 90.1 in Atlanta. He writes frequently for CNN Opinion. Follow him on Twitter @FordVox. The opinions expressed in this commentary are solely those of the author.

(CNN)No, those purple spots viewers first noticed on Michael Phelps' back last weekend weren't telltale signs of Zika, or hickeys from the night before. As the media zoomed in, the world soon learned they were the result of a traditional Chinese technique called cupping, and as you might have heard by now, it's got quite a following among Olympic athletes.

As an American physician trained in the standard "allopathic" (that is, mainstream) regime, I'm inclined to roll my eyes. I'm skeptical, but open-minded enough to know not everything I do comes with a sterling base of, uh, evidence.
    You see, all the Olympic excitement about cupping, which has me rubbing my chin, comes directly after a wave of news headlines calling into question another funny-looking health routine Westerners have dutifully performed since the early 1800s: flossing. Did these two treatments get to where they are in 2016, despite faults, due to valuable evidence or simple belief? We know the mind has the capacity to palliate itself, so are cupping and flossing just features of a healthy imagination?
    Cupping is practiced outside the mainstream, but flossing is part of the American oral health pantheon, touted for years by the dentists and hygienists we've long thanked for setting our nation's smiles apart from others.
    Yet now the Departments of Agriculture and Health and Human Services have dropped flossing from the country's dietary guidelines. The president of the American Academy of Periodontology actually admitted to a reporter that the scientific evidence is "weak" and studies examining flossing are inadequate.
    It's enough to make a doctor dizzy.
    Let's look a little closer at the moving ground beneath us. Cupping is not the only untraditional treatment US Olympic athletes are taking up in Rio. The wrestling team has a newfound appreciation for brainwave-synching sleep music, according to Coach Matt Lindland. He thinks the Brain.fm app (artificial-intelligence-generated tunes for "focus, relaxation, meditation, naps and sleep") is giving his athletes an edge as they accomplish their power lifts.
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    STAT News's Sharon Begley notes that the product's core claim, that its music syncs with your brain's own waves, is tough to believe when everyone's EEG is unique at any given time, and the app does no processing and matching of music to your EEG pattern.
    Wacky? Maybe not entirely, when you consider that elite level athleticism is as much a mind game as a physical game -- and athletes will do just about anything (sexual abstinence, lucky underwear) to get into the zone. There's also plenty of medical evidence that one's attitude and outlook can make quite a difference in one's performance.
    For example, when we ask people soon after an injury how long they think symptoms will last, people who think their symptoms will linger do indeed have more persistent symptoms compared with those who expect they'll recover quickly.
    What about cupping, a therapy that has been around for 2,000 years and is mostly associated with traditional Chinese medicine? It's a simple enough physical process: Cups are heated with a flame, typically from burning off an alcohol coating, and then the cups are placed, opening-down, on the body part(s) that needs treatment. As the cup and the air within cool off, a resulting vacuum pulls up the skin, soft tissue, and even the muscle underneath. A new-wave version many Olympic athletes are using involves a mechanical suction pump, so no heat is involved.
    Why might this relieve pain and help sports injuries heal? We know the suction force is great enough to break small capillaries in the skin, which causes the bruising, and this trauma to the soft tissue generates more local blood flow, bringing with it immune-system-signaling molecules that can kick off repair processes. I suspect simple distraction from pain is a major factor.
    There have been hundreds of studies on cupping in the past decade, but much of the research finds a home in alternative medicine journals that aren't too popular among medical doctors.
    Cupping did find its way into the American Pain Society's Journal of Pain in 2009, however, where it demonstrated superiority in a randomized trial to a sham treatment people would expect to work: heat. Subjects in that German study, who all had carpal tunnel syndrome, either got "wet cupping" (the above-described dry cupping but also pricking the skin with a lancet to provoke bleeding) or a heating pad. The group who got cupping reported less pain and more function than those who just got heat.
    But a suction cup that leaves a dramatic circular bruise (and causes bleeding) should make a bigger psychological impact than a simple heating pad. One can see lasting evidence of the treatment with one's own eyes. That's a bigger placebo.
    Another study addressed that problem by comparing dry cupping to a cup with a tiny air leak so it couldn't form a proper suction. Both cups relieved fibromyalgia pain better than "usual care," with no significant difference between them.
    Think about that: People who got the leaky cup experienced no possible physiological change whatsoever from the actual cupping. There's no tugging at the skin, no broken capillaries, no change in circulation, and yet they felt better. They had one aspect in common with the real cupping group, though. Both groups, whether they knew it or not, were in the grips of positive thinking.
    But even as I give the Olympic hopefuls a hard a time for their cupping and brain music, the news about flossing sets me back.
    If you didn't see the headlines, a wily AP reporter, tipped off by his son's orthodontist, started asking dentists, periodontists and the US government thorny questions about flossing. Turns out there have not been rigorous randomized controlled trials to back up the commonly made claims that the practice helps prevent gum disease and cavities.
    This has been openly discussed in dental journals, but much of the general public didn't know dentists don't have too much to go on beyond their clinical experiences when they're telling you you better floss.
    But it's quite difficult to study flossing properly: You'd have to get a large group of people to avoid flossing for many years, enough time so that cavities and gingivitis can gradually develop, and compare their disease rate to another group that flosses religiously.
    And the group that doesn't floss would have to brush their teeth for the same amount of time, and in the same way, using the similar toothbrushes and toothpaste as the group that isn't flossing.
    Oh, and the two groups need to be of very similar age, socioeconomic background, keep to similar diets and maintain a similar general health status. Good luck conducting this multimillion-dollar enterprise. Industry has no motivation to fund it, subjects have no desire to join such a study, and I'd be thoroughly disgusted if the National Institutes of Health, with all of the more pressing problems out there, spent a dime on it. The same goes for cupping.
    I trust the dentists and their experience comparing the mouths of their patients who floss regularly to those who don't floss in their own clinics.
    And while I think that flossing is more important to the health of far more people — that is, pretty much everyone -- than cupping is to an elite group of athletes, both are relatively low risk activities even if they're not doing everything that's claimed.
    One thing, though: Cupping can cause burns, so maybe you're better off with a mechanical vacuum method if you're going to do it, and flossing can send bacteria into the bloodstream, so discuss it with your doctor if you're immunocompromised.
    But whatever you do, stay positive.