In a study published in PLOS ONE, scientists report the identification of a new human sensory ability to detect sugars in the mouth with a kind of a molecular ‘calorie detector’. It could help explain why artificially sweetened beverages just don’t have the same appeal as ones containing sugar.
“Our mouth can identify when a sweetener has the potential to deliver calories versus a non-caloric sweetener, which cannot,” said first author Paul Breslin, PhD, a Monell investigator and a professor of Nutritional Sciences at Rutgers University.
The paper describes the first-in-human demonstration of a signaling pathway that uses the sugar glucose, a component of table sugar and high fructose corn syrup, to signal the presence of calories, in addition to the well-studied sweet-taste receptor in taste buds. Glucose is present in many foods, and has been consumed by humans in the form of honey, fruit and other sugar-rich foods.
“Humans love fruit and sugar, as do many other apes, which obtain most of their calories from sugar,” said Prof Breslin.
Recent findings from Monell showed taste bud cells in mice could identify when a sweetener has calories to burn, which prompted the researchers to see whether the ability to sense glucose in the human mouth may also involve this additional pathway. The team wanted to know if the calorie detector is functional, and if it could affect our responses to dietary sugar.
“Now that we know this calorie-detecting taste system is operating in humans, it could help explain the overall preference for sugared beverages over non-caloric sweetener beverages,” said Prof Breslin.
In a series of three human-taste experiments, the team compared oral glucose sensitivity to the ability to sense the artificial sweetener sucralose and to a special form of glucose that cannot be metabolised. “Overall, there are two sweet-sensing pathways in the mouth: one for sweet taste, and another for detecting potential energy-burning sugars,” said coauthor Linda J. Flammer, PhD, a senior research associate at Monell.
The fact that diet fizzy drinks never captured a major share of the beverage market always puzzled Prof Breslin, but he now has a hint: “Diet drinks are not as satisfying as sugared beverages. As a public health initiative, might we get beverages and foods with lower sugar levels to be more rewarding? Now that we know there is this second glucose-sensing system in the mouth, maybe we can tap into it to make healthier beverages that people enjoy drinking.”
Sugar calories are sensed in the gut and blood after swallowing, but this study shows that sugars are identified as different from non-caloric sweeteners in the mouth. “It is remarkable that we evolved a mechanism not only to taste oral sugars as sweet, but also to sense that they have a metabolic or caloric signal,” said Breslin. “This means that the mouth is much smarter than we realised and that it will be difficult to trick it by simply providing non-caloric sweeteners.”
Source: Monell Chemical Senses Center