Solving this dilemma would be simple, if not necessarily easy—persuade doctors and patients to use modern medicines instead of bear bile—except for one thing: Bear bile works. Specifically, UDCA works. This naturally occurring bile acid was first isolated from the gallbladders of polar bears by Swedish researchers at the beginning of the 20th century. It is found in the bodies of many vertebrates, including humans, usually at concentrations of 1 percent to 5 percent (of all biliary acids).

Most species of bears, however, have much more, from the sun bear, with 8 percent UDCA on average, to the brown bear (Ursus arctos), with 19 percent. The American black bear (Ursus americanus) has a bile acid composition of nearly 40 percent UDCA, more than twice as much as any other animal.

Recent studies have shown that UDCA’s therapeutic powers may be nothing short of astonishing. “It truly is one of nature’s great molecules,” says Clifford Steer of the University of Minnesota Medical School, who has either authored or coauthored more than two dozen papers on the subject. In a 2002 study, Steer and colleagues found that rats treated with tauroursodeoxycholic acid (TUDCA), a soluble form of UDCA, emerged from mechanically induced strokes with roughly half as much brain damage as rats that hadn’t received the molecule. A difference of 10 percent is striking; 50 percent is enough to give a researcher palpitations.

In a study in 2006, Steer and another group showed that TUDCA greatly slowed retinal degeneration in mice exposed to high light levels. (It’s no surprise, the authors noted, that among the 28 types of Chinese patent medicines that contain bear bile, 15 are ophthalmologic.)

UDCA’s effects come from its ability to keep cells alive, Steer says. Most cells, when they are damaged or reach the end of their preprogrammed lifespan, selfdestruct through a process called apoptosis. The molecule’s anti-apoptotic effects are so pronounced, Steer says, that it could potentially be used to treat degenerative disorders—such as glaucoma, Huntington’s disease, Parkinson’s, and Alzheimer’s—that affect millions of people worldwide.

This may also explain why bears have so much of it. Months of hibernation would leave most animals near death from muscle atrophy and other kinds of cell loss, yet bears emerge from dens every spring missing little more than excess fat. UDCA may make this possible, and Steer says he has considered suggesting to NASA that they give supplements to astronauts to help prevent the wasting effects of weightlessness. Preliminary data suggests that UDCA could also help victims of spinal cord injuries, and it may even have antiaging properties, since senescence is at some levels a form of cell death. If that’s true, then someday “people might reach for their coffee, vitamins, and a UDCA pill every morning,” Steer says. “I would.”

The molecule is nontoxic and has already been used in the United States for decades, with FDA approval, to treat gallstones and primary biliary cirrhosis in humans. Since the original patent from the early 1990s has run out, it is currently available in the inexpensive generic form ursodiol.

Best of all, UDCA doesn’t have to come from bears. Researchers like Steer rely on established commercial vendors, who in turn get their molecules and compounds from sources such as slaughterhouses. Compared with black market prices, the cost of UDCA derived from the gallbladders of cows, pigs, and turkeys is a steal; the purified form is available online for as little as $13.50 per gram. (It’s also possible to synthesize UDCA from scratch, but the process is complicated and expensive.)

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