An Australian study has revealed that humans have a sixth taste by which they can detect fat.
Using a series of taste-testing experiments, researchers from Deakin University have found that humans can identify the taste of fat by its chemical composition, rather than by its texture.
They say it appears that those people who are highly sensitive to the taste of fat tend to eat less of it, and hence have significantly lower body mass indexes.
"Fat has a very nice mouth feel to it [but it] appears that fat is activating something in the oral cavity independent of texture," the Sydney Morning Herald quoted lead researcher, Russell Keast, as saying.
Dr Keast and his team had a group of people sample various types of fatty acids found in common foods, mixed in with non-fat milk to disguise the texture. Of the 33 people tested, all could detect the taste of fat to a varying degree, he said. The findings could lead to new ways of treating obesity.
Fat flavour can now be added to the other known tastes: sweet, salt, sour, bitter, and umami - a taste for protein-rich foods.
Just like the other tastes, Dr Keast said, the degree of sensitivity to fat differed between individuals. "I may be very sensitive to sweet tastes, while somebody else may be insensitive, this is common throughout the tastes, and it's exactly what we're finding with fat," he said.
After the research group had established that humans could taste fat, they wanted to know if the ability to taste fat had any influence on what people ate.
Study participants were divided into two groups, those who were hyper or very sensitive to the fat taste, and those who were not. "People who are very sensitive to fat can taste very low concentrations of it," he described.
Dr Keast then compared the daily diets of both groups and found those people who were hypersensitive to fat ate less of it in their daily diet. They also had lower body mass indexes.
"It appears (hypersensitive) people have a mechanism that is telling them to stop eating it," he said.
The reverse was happening in people who were not sensitive to the taste. "They are over-consuming and this is creating an energy imbalance, which is leading to higher BMI or development of overweight or obesity," he added.
Dr Keast is now looking into why some people are sensitive and others are not.