Tongue can Discern Six Tastes

by Rajashri on Aug 22 2008 4:32 PM

The human tongue might be able to taste calcium as well besides the five established tatses of sweet, sour, salty, bitter, and savory.

That's the conclusion of a new research, which has discovered rats' capability to taste calcium. With rodents and humans sharing many of the same genes, the finding suggests that people might also have such a taste.

In a report scheduled for presentation here today at the 236th National Meeting of the American Chemical Society, scientist Michael G. Tordoff, Ph.D., and colleagues with the Monell Chemical Senses Center in Philadelphia describe research they say demonstrates that a taste for calcium exists in mice.

"People don't consume as much calcium as nutritionists would like, and one reason for this is that foods high in calcium don't taste good to many people," Tordoff said.Tweaking its taste could encourage a calcium-deficient population to consume more of this key nutrient.

"By understanding how calcium is detected in the mouth, we can either make it easier to consume by reducing its bad taste or even make pharmacological agents that make it taste better," Tordoff added.

To reach the conclusion, Tordoff's team used genetic methods to pinpoint two receptors involved in tasting calcium.

A receptor is a molecule either on the surface of or inside a cell that serves as the binding or docking site for a specific substance. When that substance - calcium, for instance - attaches to the receptor, a specific effect occurs, such as a release of signals resulting in the sensation of taste.

The research shows that the taste of calcium is detected by two receptors on the tongue. One is a calcium-sensing receptor called CaSR that has been found by other researchers in the parathyroid glands, kidney, brain and gastrointestinal tract.

"We didn't know it was on the tongue before," Tordoff said.

The other is a receptor known as T1R3. This is a component of the "sweet-taste" receptor - a finding that researchers described as "very unexpected."

The researchers measured the calcium preferences of 40 different strains of mice.

"Most mice dislike calcium, but we found a very unusual strain that drinks it avidly. By comparing the genes of this strain with other strains, we were able to identify the two calcium taste genes," Tordoff said.

"It remains to be seen if what we have discovered in mice-the existence of two calcium taste genes-- holds true for humans. We know people have the

sweet-taste gene, Tas1r3, and the gene involved with the calcium-sensing receptor, CaSR. We don't know if we have the same forms of genes as the mice have, but it seems pretty likely they have the same function," Tordoff added.

Calcium is a mineral with critical roles in building and sustaining strong bones. Without it, children develop weak bones; calcium-deficient adults risk the progressive loss of bone mass known as osteoporosis, a major cause of fractures in older people. Studies also have linked low calcium intake to an increased risk of heart disease, high blood pressure, and certain cancers.