A new study in mice shows that a diet rich in sugar can reduce the ability to taste sweetness.
For many people, a high-sugar diet has become almost accidental. Three-quarters of the food items in the supermarket have added sugar, says Monica Doss, associate professor of molecular, cellular and developmental biology at the University of Michigan.
“This is not a subtle effect. It is really powerful, and it only took four weeks.”
In the new study, the researchers wanted to further study whether the dulled sense of taste is a physiological effect that occurs in the senses of mice consuming a high-sugar diet.
As mentioned in the magazine current biologyThe response of the nerve that transmits sweetness information from the tongue to the brain decreased by nearly 50% in mice fed a high-sugar diet.
Several years ago, a study showed that lowering sugar levels in the human diet led people to perceive sugar as more intense. But how does that happen? Doss says.
“Many of our previous papers found that sugar impairs sweet taste in fruit flies by decreasing the nerve response and reprogramming taste cells, but flies are still just flies. I really wanted to understand if and how that happens in mammals.”
Restore the taste of sugar
Doss reached out to Robert Bradley and Charlotte Mistrita, professors in the College of Dentistry, who have studied how taste works and how diet and disease can change it. The team also reached out to Cary Villario, an assistant professor of pharmacology at the College of Medicine, who studies the neurobiology of swallowing behavior in mice.
The researchers gave one group of mice their typical diet and access to sugar water. The control group of mice received their usual diet and regular water. Four weeks later, the researchers used electrodes to record nerve responses while stimulating the tongue with various solutions. This nerve carries taste information from the front of the rat’s tongue, which contains taste bud cells that sense chemicals, to the brain.
Next, the researchers gave the mice sweet, bitter, sour, salty, and umami-flavored solutions, and measured the mice’s responses to touch and cold. While they did this, they tested the response of the front of the tongue to those flavors and sensations.
The researchers found no difference in the mice’s reaction to salty, bitter, sour, and umami flavors, nor to touch or cold, but they did see a 50 percent decrease in the nerve’s response to the sweet sucrose (table sugar) solution.
“This is not a hidden effect,” Doss says. “It’s really strong, and it only took four weeks.”
At the end of the four weeks, the researchers also found that the mice had not gained weight from the sugar. Then the scientists returned the mice to their regular diet with plain water. After another four weeks, they retested the mice’s sensitivity to sweetness, and found that they recovered.
“This is potentially good news for us,” Doss says. “If you eat a lot of sugar, but decide to stop eating sugar, it shows that you can restore your taste (assuming the system works the same way).”
Sweetness on the brain
Doss says this result was somewhat predictable. Previously, Mistrita and Bradley have found the taste system to be highly plastic and can recover from drug treatments that disrupt it, such as chemotherapy.
The group then investigated why this happened. Looking at rats’ tongues, they found no change in the rats’ taste buds, the structures that house the tongue’s taste buds. This makes sense, Doss says: If they had it, they likely would have also found changes in the mice’s sensitivity to other tastes.
The researchers also found no changes in the number of taste buds on the tongue, nor in how the nerve connects to the taste buds. But by looking inside the taste buds, they found fewer cells that detected sweetness in mice on a high-sugar diet.
In future studies, Doss and Ferrari will study how these taste changes affect eating and the activity of cells deep in the brain that receive information about sweetness. For example, Dus previously found that in flies, a decreased sensation of sweetness results in reduced dopamine release, which reduces feelings of satiety and leads to overeating. Does this also happen in mice?
There is plenty of evidence that diets high in sugar and fat affect the dopamine and nutritional learning systems in the brains of humans and mammals, but the reasons for these changes remain largely unknown. Do they arise from changes in our senses, specifically the taste changes observed here?
“Because we are mammals and our taste systems are similar to rats, this is the best available evidence that a high-sugar diet alters the sensory system,” Doss says. “So this may affect your food choices. This may affect your metabolism.”
“But also, the other important implication is that if your taste system is really plastic, it is likely that if we reformulate foods so that they have less sugar, our taste buds will learn how to eat and like the food as much as we enjoyed the sugary things today. “.
source: University of Michigan
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