Coconut water now joins the ranks of miracle drinks, debunked. At least some brands of coconut water are impostors, find researchers at ConsumerLab.com, an independent health-product testing firm. After testing three top label coconut water drinks that claim to contain high quantities of nutrients and electrolytes--making them the perfect post-workout beverage--ConsumerLab found that only one, Zico Natural, contained the ingredients its label advertised.

Coconut water beverages, which claim to contain potassium and magnesium, "nutrients key to hydration," actually contain 82% and 35% less than the listed amounts, reports CNN's Alyssa Sparacino.

This certainly isn't the first fad beverage to sweep gyms until skeptics did their homework. Acai had a similar trajectory, endorsed by both Oprah Winfrey and Dr. Mehmet Oz, until some questioned its supposed health benefits, reports The New Yorker's John Colapinto.

Coconut water was supposed to be "filled with electrolytes like sodium and magnesium," CNN's Sparacino reports, but it turns out most of the drinks don't contain these. Furthermore, though, unless you're doing a really intense workout, like training for a marathon, you probably don't even need a sports drink containing sodium and magnesium, Taub-Dix, the author of Read It Before You Eat It, told Sparacino. And nutritionist Monical Reinegal seconded that sentiment. "If you're a marathoner, if you're doing Bikram yoga--and if this is really about sweat replacement, relying on coconut water to replenish your lost sodium is not a good idea," she told the Huffington Post's Catherine Pierson, explaining that unless you've been working out hard for an hour or more, water is just fine.