When you start eating chocolate, it’s hard to stop. The same goes for ice cream or cakes. But why is sugar so addictive in humans?
Eating sugar activates the brain’s reward system and makes us feel good. However, everyone also knows that eating too much sugar is very unhealthy. In a new study published in the journal Nature, researchers show that in addition to the reward system, sugar triggers a separate neurological pathway that begins in the intestines.
From the intestines, signals announcing the arrival of sugar travel to the brain, where they feed an appetite for even more sugar, which would explain why we are so addicted to this magical molecule.
Previously, Charles Zuker, a researcher at the Howard Hughes Medical Institute, and his team had demonstrated that sugar and artificial sweeteners activate the same system of perception of taste. Once in the mouth, these molecules activate the sweet taste receptors on the taste buds, which trigger signals that travel to the part of the brain that processes sweetness. However, sweeteners don’t cause the same addiction in people like sugar.
In order to understand the difference between the two, Zuker and his team carried out a test opposing sugar to the acesulfame K sweetener, used in diet sodas, sachets of sweeteners, and other products. By offering mice water with sweeteners and water with sugar, they realized that the mice preferred sweetened water. “We thought that the animal’s unquenchable motivation to consume sugar, rather than the artificial sweetener, could have a neural basis,” says Zuker.
By studying the brain activity of rodents when they were consuming sugar versus an artificial sweetener, the researchers first identified the region of the brain that only interacts with sugar: the caudal nucleus of the solitary tract (cNST). Located in the brainstem, away from where the mice process tastes in general, the cNST is an information center on the state of the body. The path to cNST begins in the wall of the gut. There, the sensor molecules trigger a signal that goes through the vagus nerve. The latter then provides a direct line of information from the intestines to the brain.
This circuit promotes a form of sugar: glucose and similar molecules and ignores artificial sweeteners. It also neglects certain other types of sugar, such as fructose, found in fruits.
“The discovery of this circuit helps explain how sugar directly influences our brain to stimulate consumption,” explains Zuker, convinced that the same way of detecting glucose exists in humans. It also exposes new potential targets and strategy opportunities to help reduce our insatiable appetite for sugar. ”
In order to better understand how the brain’s strong preference for sugar develops, scientists are now studying the connections between this sweet intestine-brain circuit and other brain systems, such as those involved in reward, food, and emotions.
The risks linked to overconsumption of sugar are very numerous. This can in particular lead to dental caries problems, cardiovascular diseases, digestive disorders, etc. If you experience a barbell during the day, this may be because your sugar intake is too high. Eating too much sugar also increases the risk of obesity due to insulin production. You can also exhaust your pancreas by making it insulin resistant, hence the risk of type 2 diabetes, and ultimately obesity.