Twin study finds sweetness in the genes

A study at QIMR Berghofer Medical Research Institute involving hundreds of sets of Queensland twins (Q-Twin) has suggested that having a “sweet tooth” might be a matter of genetics.

Daniel Hwang from QIMR Berghofer’s Genetic Epidemiology group said the research – in collaboration with the Monell Chemical Senses Center in Philadelphia – has found a single set of genes affects a person’s perception of sweet taste, regardless of whether it is a natural sugar or a substitute.

“The data we collected from participants in the Q-Twin study provide the first solid evidence that approximately 30% of variation in the perception of sweet taste can be attributed to genetic factors,” Mr Hwang said.

“It may be that people who need that extra teaspoon of sugar in their tea or coffee may have been born with a weaker perception of sweet taste.”

The research involved 243 pairs of identical twins, 452 pairs of fraternal twins, and 511 individuals, who tasted and then rated the intensity of four sweet solutions – fructose, glucose and two calorie-free synthetic sweeteners.

Participants were asked to mark a line on a scale ranging from no sweet sensation, to the strongest imaginable sweetness.

Mr Hwang said the research could provide a clue to solving taste disorders, which can have a significant impact on peoples’ eating patterns and can be a risk factor for heart disease, diabetes and stroke.

“Some people lose their sense of taste or can be affected by unpleasant taste sensations due to illness or injury and people who are undergoing radiation for cancer are particularly susceptible,” Mr Hwang said.

Behavioural geneticist Danielle Reed from Monell said the next big question is if and how genes and early experiences interact to affect food choice.

“Even though almost everyone – consumers, physicians and public health officials – wants to decrease the amount of sugar in our diets, right now we have no tool that has the sensory equivalence of sugar,” Dr Reed said.

“However, if we can understand why some people have weaker sweetness perception, we might be able to adjust this attribute so we could reduce the amount of sugar in foods.”

Mr Hwang said the study suggests 70% of sweet taste perception could be related to environmental factors, so it is still possible for people to change their dietary habits.

“Our next steps are to identify key genomic regions shared by people who are weak sweet tasters, in the hopes of understanding their weaker perception.”

Mr Hwang said the genetics of bitterness have been widely studied in past decades, but there is much less genetic information on sweetness.

The study was funded by the NHMRC in Australia and the National Institutes of Health in the United States.

It has been published in the journal Twin Research and Human Genetics.