Scientists find 'fat' is the sixth human taste
For generations, scientists thought the human tongue could detect only four basic tastes: sweet, sour, salt and bitter.
Then a fifth was discovered, "umami" or savoury. Now, researchers have identified a previously-unrecognised "sixth taste" – fat.
A team in the United States has located a chemical receptor in the taste buds on the tongue that recognises fat molecules, and found that its sensitivity varies between individuals.
The finding may help to explain why some people consume more fatty foods, as they are less aware of the taste as they eat.
The researchers hope their discovery can be exploited to combat obesity by increasing people's sensitivity to fat in their food.
Apart from the basic tastes, other aspects of food flavour actually come from the smell and are detected in the nose.
The research team, from the school of medicine at Washington University, St Louis, showed that people with more of a receptor called CD36 were better at detecting the presence of fat in food.
They found that variations in a gene that produces CD36 makes people more or less sensitive to the presence of fat.
"The ultimate goal is to understand how our perception of fat in food might influence what foods we eat and the qualities of fat that we consume," said Professor Nada Abumrad, who led the research.
"We've found one potential reason for individual variability in how people sense fat. What we will need to determine in the future is whether our ability to detect fat in foods influences our fat intake, which clearly would have an impact on obesity."
The study, which is published in the Journal of Lipid Research, found that those with half as much CD36 were eight times less sensitive to the presence of fat.
Up to 20 per cent of people are believed to have a variant of the CD36 gene that is associated with producing lower levels of the receptor, which could mean they are less sensitive to the presence of fat in food. This may make them more prone to obesity.
Dr Yanina Pepino, who also conducted the research, added: "If we follow the results in animals, a high-fat diet would lead to less production of CD36, and that, in turn, could make a person less sensitive to fat.
"From our results in this study, we would hypothesise that people with obesity may make less of the CD36 protein.
"So it would seem logical that the amounts of the protein we make can be modified, both by a person's genetics and by the diet they eat."