Sweet-toothed Europeans now have another reason to gorge on a few more pieces of chocolate cake, for they are among the most sugar-sensitive people in the world, concludes a new genetic analysis.
People in the UK, France, Italy and Russia have a tandem of genetic variations in a sugar-sensing gene, which makes them detect trace levels of sweetness.
Dennis Drayna, a geneticist at the National Institute on Deafness and Other Communication Disorders in Bethesda, Maryland, said that all over the world, people living at northern latitudes carry these genetic variations at far higher frequencies than tropical-living peoples
For the study, the researchers presented 144 Europeans, Asians and Africans with nine solutions containing varying amounts of table sugar - sucrose - in amounts varying from 0 to 4 per cent.
"Four-per-cent sucrose is very sweet to everyone, and to me it's intensely sweet. Imagine some cloyingly sweet desert," New Scientist quoted Drayna as saying.
Volunteers arranged the solutions in order of their perceived sweetness numerous times.
Using this arrangement, the researchers calculated a sucrose sensitivity score for each person.
The researchers correlated the scores with variations in two sugar-sensing genes, TAS1R3 and TAS1R2, and found two variants just outside of the TAS1R3 gene that seemed to predict their volunteer's scores.
However, this was puzzling because TAS1R2 is chock-full of single DNA letter differences between people.
In addition, research on bitter taste genes suggested that such mutations - which change the shape of the receptor - underlie these differences.
Drayna said that instead, the two variations near TAS1R3 probably determine how much of a receptor protein is produced by the taste buds.
Tests showed that the variations most common in Europeans crank up the expression of TAS1R3.
Although the gene variants were commonest in Europeans, they were also widespread in Japanese, Palestinian, Han Chinese and other Middle Eastern and Asian populations.
Low-sensitivity variations were most prevalent among the several different African populations examined by the team.
The study is published in Current Biology.