Scientists Discover How Animals Taste, and Avoid, High Salt Concentrations

For consumers of the typical Western diet—laden with levels of salt detrimental to long-term health—it may be hard to believe that there is such a thing as an innate aversion to very high concentrations of salt.

But Charles Zuker, PhD, and colleagues at Columbia University Medical Center have discovered how the tongue detects high concentrations of salt (think seawater levels, not potato chips), the first step in a salt-avoiding behavior common to most mammals.

The findings, which were published online in the journal Nature, could serve as a springboard for the development of taste modulators to help control the appetite for a high-salt diet and reduce the ill effects of too much sodium.

The sensation of saltiness is unique among the five basic tastes. Whereas mammals are always attracted to the tastes of sweet and umami, and repelled by sour and bitter, their behavioral response to salt dramatically changes with concentration.

“Salt taste in mammals can trigger two opposing behaviors,” said Dr. Zuker, professor in the Departments of Biochemistry & Molecular Biophysics and of Neuroscience at Columbia University College of Physicians & Surgeons. “Mammals are attracted to low concentrations of salt; they will choose a salty solution over a salt-free one. But they will reject highly concentrated salt solutions, even when salt-deprived.”

Over the past 15 years, the receptors and other cells on the tongue responsible for detecting sweet, sour, bitter, and umami tastes—as well as low concentrations of salt—have been uncovered largely through the efforts of Dr. Zuker and his collaborator Nicholas Ryba from the National Institute of Dental and Craniofacial Research.

“But we didn’t understand what was behind the aversion to high concentrations of salt,” said Yuki Oka, a postdoctoral fellow in Dr. Zuker’s laboratory and the lead author of the study.

The researchers expected high-salt receptors to reside in cells committed only to detecting high salt. “Over the years our studies have shown that each taste quality—sweet, bitter, sour, umami, and low-salt—is mediated by different cells,” Dr. Ryba said. “So we thought there must be different taste receptor cells for high-salt. But unexpectedly, Dr. Oka found high salt is mediated by cells we already knew.”