Science Story

02 December 2008 22:06 BST

Humans 'could be made to like calcium'

More people could enjoy the health benefits of calcium if new research showing its distinctive taste can be cancelled out is to be believed.

American scientists say studies on mice have shown there are taste receptors on the tongue for calcium, an essential mineral for building and sustaining strong bones.

The US team used genetic methods to pinpoint two receptors involved in tasting calcium.

With mice and humans sharing many of the same genes, the findings suggest that people also may have such a taste, which could have a range of practical applications.

The research, from Philadelphia's Monell Chemical Senses Centre (MCSC), is due to be presented at the annual meeting of the American Chemical Society.

Michael Tordoff from the MCSC explained that many people were put off from eating calcium-rich foodstuffs such as collard greens, bok choy, kale and bitter melon because of their "calciumy" taste.

"There isn't a better word for it," he said. It is bitter, perhaps even a little sour. But it's much more because there are actual receptors for calcium, not just bitter or sour compounds," he said.

Mr Tordoff said a potential modification of the sense of taste using genetic research could be an indispensable and widespread tool to increase nutrition.

"I'm not saying people can't take tablets to get enough calcium, but eating real food is a great pleasure. With salt, sweet and fat, the problem is to reduce intake without reducing palatability. For calcium, it's a problem of being not palatable enough," he said.

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," Mr 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," Mr Tordoff added. "By comparing the genes of this strain with other strains, we were able to identify the two calcium taste genes."

"It remains to be seen if what we have discovered in mice - the existence of two calcium taste genes - holds true for humans," he continued said. "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."

Without calcium children develop weak bones and 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.

The recommended daily intake of calcium, which varies with age and gender, is 1,200 milligrams for young adults.