Here's why you shouldn't take Mark Cuban's health advice

Earlier this week, Mark Cuban — billionaire entrepreneur, "Shark Tank" investor, NBA team owner, "Sharknado 3"star, and non-medical professional — took to Twitter to dispense some health advice.

Cuban thinks people should get quarterly blood tests so they can monitor what changes in their bodies over time.

But more frequent testing won't provide useful information for a healthy person and could actually harm people who end up getting unnecessary medical treatment. Most experts say this sort of behavior will hurt more people than it will help.

Here's what started it all:

It's easy to see why this seems appealing: We live in a time where we believe we can live better by gathering more data on everything.

And some people think that in the future, we'll all monitor our blood and body data over time. Keeping an eye on blood test results is what Elizabeth Holmes, founder of the revolutionary blood test company Theranos, thinks will transform medicine and help people find out they are sick sooner in life.

But here's the problem: right now, all the evidence we have says that getting more blood tests doesn't make you healthier. In theory, it seems like a good idea, but in practice, it's not.

Extra testing often means people notice something that prompts follow-up tests and potentially treatment, even when there is nothing wrong with them. More people are harmed by unnecessary side effects of extra treatment than are helped by what they learn from those tests.

As ProPublica healthcare reporter Charles Ornstein pointed out in a reply to Cuban, getting more tests and screenings even though you are healthy is not only unnecessary, it's dangerous.

It's especially bad for someone with as big of a platform and audience as Cuban to publicly promote ideas that could hurt people.

Medical treatment isn't a "more is better" thing. When people are treated more than is absolutely necessary, it's easy to mess something up — a widely known problem known as "overtreatment."

As Dan Diamond points out over at Forbes, a great example here is prostate cancer screening.

The United States Preventative Services Task Force — the people who make recommendations about the best way to use preventative medicine — does not recommend prostate cancer screening. That's because the false positives and unnecessary (often invasive) treatment for cancers that won't kill people actually ends up hurting more people without saving lives.

As Diamond says, "For every 1,000 men who get regularly screened for prostate cancer, about 20% of them will end up getting unneeded biopsies or even have their prostate unnecessarily removed because the data is wrong." A biopsy or an unnecessary removal is no joke and can have serious permanent consequences.

Every test comes with risks. Ornstein says that "there's this belief, and it's wrong, that screening tests can only help, not hurt." Yet "there are false positives and false negatives. There's fear that results from an abnormal result (even if it later proves normal) and there's treatment. And treatment comes with side effects."

In some cases, those side effects are riskier than the tests themselves, and as Dr. Kyle Fischer notes, that means more people will be hurt than helped.

When it comes to blood tests, which is what Cuban referred to specifically, Dr. Aaron E. Carroll explains at The Incidental Economist that at the Indiana University School of Medicine, he teaches "residents and medical students never, ever to order blood tests unless they are looking for a specific problem."

That's because interpreting blood tests is complex and there's a good chance you could often find something "abnormal" if you are just looking for any abnormalities, which aren't as clear as one might think. That would lead you or your doctor to seek treatment even though you don't need it.

"We should get tests when we have evidence that they will help. We should get them when we expect they will do more good than harm," Carroll writes. "At this time, there’s no reason to believe that for any individual, quarterly blood tests would fit these criteria."

In the future, that could be different. But for now, as Forbes reporter Matthew Herper noted, we're working within the realities of a "flawed system."

Cuban thinks that more testing is better because he claims he trusts data. But the data says that getting those tests is a bad idea.

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