LeBron James has a cramp. It’s the final minutes of a 2014 playoff game between the San Antonio Spurs and the Miami Heat. With his team down by four points, James takes a quick step, beats his defender, and jumps, sending the ball in a high arc toward the basket. It’s a beautiful shot, but the glory is short-lived: On landing, James can’t run. In fact, he can barely walk. After much whistle-blowing, the game stops and a flurry of players, trainers, and coaches escort the limping James off the court, eventually carrying him to the bench.

That fateful cramp took him out of the game, but it also thrust the biggest NBA star into a new entrepreneurial venture—sports supplements. Not satisfied with the options on the market, James set about developing his own line of specialized products; last fall, with celebrity partners Arnold Schwarzenegger, Lindsey Vonn, and Cindy Crawford, he launched Ladder. The company makes four workout supplements, promising better results through its high-quality ingredients and scientifically backed blends of superfoods, probiotics, and protein powders. “Supplements are only going to make a small difference but an important difference,” says Adam Bornstein, Ladder’s chief of nutrition. “If it works for LeBron, imagine the impact it would have on the average person.”

Dietary supplements are a more than $45 billion industry, and they got that way by promising outsize results in nearly every aspect of your physical well-being, from bigger muscles to better heart health. More than half of US adults regularly take some kind of supplement, whether fish oil, vitamin E, vitamin D, or protein powders. On the whole, these products are barely regulated. The US Food and Drug Administration treats dietary supplements like foods, not like drugs. That means the agency isn't authorized to approve a supplement's safety or effectiveness before it is marketed to consumers. To get a product off the market, the FDA must prove that it isn't safe or that its label is misleading.

Ladder says it’s in the 1 percent of manufacturers that voluntarily submit their products for independent testing by the nonprofit NSF International, whose “Certified for Sport” label verifies the supplements aren't contaminated with any illegal steroids, hormones, stimulants, or toxins.

Although dietary supplements are presumed safe until government regulators hear otherwise, the Centers for Disease Control and Prevention estimates that they cause some 23,000 visits to the emergency room every year, many due to cardiovascular problems. With booming demand and no premarket regulation, the industry has been flooded in recent years with a wide variety of products, many sporting their own proprietary blends.

Paul Thomas, a nutrition consultant at the National Institutes of Health, describes these products like snowflakes: “No two are alike.” That makes their effectiveness extremely difficult to study. Nutrients don’t work in a vacuum. Different combinations affect your body differently. Those special mixtures of amino acids and protein powders could have varying dosages and results. Blends are also frequently spiked with extra caffeine, sugars, steroids, or other ingredients that haven’t been tested at all.

“There have just been increasingly more products on the market with multiple combinations of ingredients that haven’t been assessed for safety,” says Patricia Deuster, director of the Human Performance Laboratory at Uniformed Services University. She estimates that between 60 and 80 percent of armed services members use some kind of supplement. “They think that the more ingredients, the better, when in fact we have no idea how these ingredients interact,” says Deuster. “It’s a public health risk.” (In 2012, after several deaths related to dietary supplements, the Department of Defense set up an education campaign called Operation Supplement Safety.)