According to new research from the Monell Center, sensitivity to sweet taste varies widely across school-aged children and is in part genetically determined. The findings may inform efforts to reduce sugar consumption and improve nutritional health of children.
In the study, published online ahead of print in Nursing Research, the researchers determined the sweet taste threshold, defined as the lowest detectable level of sucrose, of 216 healthy children aged 7–14. Each child was given two cups, one containing distilled water and the other containing a sugar solution and asked to indicate which contained a taste. This procedure was repeated across a wide range of sugar concentrations: the lowest concentration that the child could reliably distinguish from water was designated as that child’s sweet detection threshold (a lower taste threshold means the child is more sensitive to that taste).
Detection thresholds varied across a large range. The most sensitive child required the equivalent of only 0.005 teaspoon of sugar dissolved in a cup of water to detect sweetness, whereas the least sensitive needed three teaspoons to get the same sensation.
To explore genetic influences on sweet taste perception, DNA from 168 of the children was analyzed to identify variation in two sweet taste genes known to be related to sweet sensitivity in adults: the TAS1R3 G-coupled protein sweet receptor gene and the GNAT3 sweet receptor signaling gene. An additional analysis identified variation in the TAS2R38 bitter receptor gene, which is known to be related to individual differences in sweet preferences among children. Small changes in each of these genes are associated with differential sensitivity of the respective receptor to its activating taste stimuli.
Genotype analyses revealed that sucrose thresholds and sensitivity were related to variation in the bitter receptor gene, but not in the two sweet receptor genes. Specifically, children whose TAS2R38 receptor gene variants make them more bitter-sensitive were also more sensitive to sucrose.
Dietary records revealed that children having this same bitter-sensitive gene variant consume a higher percentage of their daily calories as added sugar. Using bioelectrical impedance to measure body composition, the researchers also asked whether sweet sensitivity might relate to measures of obesity and were surprised to find that increased body fat was associated with greater sensitivity to sweet taste.
“Our assumption was that the more obese children would be insensitive to sugar and therefore would need higher concentrations to get the same pleasing effect as leaner children,” said lead author Paule Valery Joseph, who was a doctoral student at the University of Pennsylvania School of Nursing and Visiting Fellow at Monell at the time the paper was written. “This was not the case and to our surprise, children having more body fat were more sensitive to sugar and were able to detect a sweet taste at lower concentrations of sucrose.”
