Creatine — yes, the favorite of gym rats everywhere, a supplement many of us have taken ourselves — is a naturally occurring compound that is already found inside each person. Scientists have been studying creatine since the 1830s and, for more than a century, we have known that it was pivotal for producing energy in our muscles.

That, as anybody who was alive in the ’90s may remember, is how creatine first exploded as a consumer product. Swedish researchers published influential research in 1992 demonstrating creatine supplementation’s effectiveness in improving stamina and recovery during the short bursts of physical exercise. It didn’t take long after that for creatine supplements to hit the shelves of drugstores and workout gyms nationwide. And it was popular. Not only was it cheap — a 10-ounce jar of creatine costs $17 on Amazon — but it was also an easy way for bodybuilders and exercise enthusiasts to improve their performance. Today, as many as one in four adults say they have used creatine; $400 million worth of it is sold in the US every year.

And this was a supplement that really worked: A 2018 meta-analysis of the available research concluded that creatine is “the most effective nutritional supplement available to athletes to increase high intensity exercise capacity and muscle mass during training.” Across years of studies, no dangerous side effects have been detected.

But the most surprising use of creatine........

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