Sure, on a recent episode of Running Wild With Bear Grylls, President Obama may have decided against drinking his own urine (he did snack on fish discarded by a bear, to give him credit), but it turns out that sipping on pee is a thing that some people regularly do—and recommend.

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Esther Sullivan, a retiree living in the London borough of Brent, was suffering from kidney malfunction, swollen ankles, and diabetes. She was taking five pills a day and facing the possibility of a kidney transplant. Then she began drinking her own urine.

Now, she says that she’s no longer diabetic, no longer takes pills, and has been able to keep her kidneys. “Blood tests have proved that I’m healthy,” she says. “I’m more energetic and well again.”

Most think of urine as a distasteful cocktail of water and waste products. But as any good recycler will tell you, “waste” is just a valuable resource. Lab analyses show that urine contains hundreds of compounds and chemicals absorbed from food, beverages, dust, and even the air we breathe. Some of these pass through us pretty much unchanged, and some have been broken down by our bodies or the billions of microorganisms that live within us.

Proponents of urine therapy, such as Sullivan, believe these compounds can actually be very beneficial when returned to the body. While this may sound strange or downright repulsive, even mainstream science has used urine to create medicines. Emmenin, the first estrogen replacement product marketed in the US, back in 1933, was made from the urine of pregnant women. The more affordable Premarin arrived a decade later and is still used today. It’s made from the urine of pregnant mares. More recently, the fertility drugs Pergonal and Metrodin were developed from urine. And Urokinase, which is used to unblock coronary arteries, comes from the same, err, wellspring. Urine is also rich in natural urea, a product found in high-end skin moisturizers, as well as in ear drops designed to remove wax. (And don’t use cotton swabs! There are much safer ways to remove ear wax.)

Urine therapy, urotherapy, urinotherapy, or auto-urine therapy has enjoyed a small but dedicated following for centuries, and those who recommend it say there are mentions of the practice found in the Bible (“If you believe in me, you will never thirst… Rivers of living water shall flow from your bellies..” John 7:38), as well as ancient Ayurvedic texts. Proponents claim that drinking or applying it externally can cure almost any ailment of the human body, from skin rashes to diabetes and even cancer.

Dr. Rakshak Mal Lodha, in Jodpur, India, has been practicing urine therapy and recommending it to his family and patients for more than 40 years. He claims it has cleared up stomach issues and helped many people avoid visits to the hospital. “We drink fresh urine in the morning, whatever we’ve passed in our daily routine,” he says. “And I apply urine to my face during the day” as a skin treatment.

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Unsurprisingly, most US medical doctors discourage the practice. Many of the nutritionists we contacted were aghast to even be asked. “This is not a therapy I support,” says registered dietician Melissa Halas-Liang, former spokesperson for the California Dietetic Association. “It’s outside my scope of practice. Sorry.” Mainstream sources like the National Institute of Health and Harvard Medical center have, as you might expect, very little information on the health effects of drinking urine.

But what about in extreme Bear Grylls-type situations? It turns out it’s not actually recommended then either. “In a survival situation it is a poor choice for hydration,” says Tod Schimelpfenig, curriculum director of the National Outdoor Leadership School’s Wilderness Medicine Institute. Things like urine, alkaline pool water, brackish pond, or swamp water, he says, “contain large amounts of solutes that would require more water to excrete than they provide.” Meaning that you’re actually hastening dehydration as opposed to delaying it.

If you’re relatively healthy and well-hydrated, is drinking urine dangerous? Probably not, though it’s pretty gross. A healthy person’s urine shouldn’t have any pathogens, and (depending on what you recently ate) it’s nontoxic. But urine therapy could be detrimental if you use it in place of traditional treatments for life-threatening conditions, or avoid following the advice of a medical doctor.