A new Yale study has shown that sweetness, as opposed to calories alone, has an impact on how carbohydrates are processed by our body’s metabolism.

Researchers at the Yale School of Medicine have identified a novel relationship between sugar and carbohydrates in our brains, discovering that sugar gives our brain part of the signal for how food is to be processed and converted into energy. The finding provides backing for hypothesized links between artificial sweeteners and diabetes. The study was published in the journal Current Biology on Aug. 21.

“We found something unexpected in that sweet taste regulates carbohydrate metabolism,” said senior author and Yale professor of psychiatry Dana Small. “The gut is controlling the brain.”

The study made use of functional MRI machines, which allowed researchers to pinpoint areas of brain activation in the participants.

The researchers prepared two different drinks with the same amount of sugar: one with low calories and one with high calories. Holding the sugar level constant, the researchers looked at the fMRI results, and found to their surprise that the drink with fewer calories but the same sugar level generated a greater brain — and thus metabolic — response.

In nature, sweetness is typically correlated with the caloric content of the food, allowing it to serve as a signal for the brain and dictate the metabolic response, Small said, adding that it notifies the body of the food’s energy content.

However, processed foods foil this. Now, Small explained, sweetness does not mean there will be more calories. This altered metabolic response due to misleading sugar content subsequently affects how the carbohydrates are used in the gut as energy.

In addition, the researchers discovered that sweetness and caloric load cause a nonlinear relationship between caloric load and the body’s metabolic response.

“Collectively, these studies from humans and rodents suggest that the reinforcing effects of sugar derive not from the perceived pleasantness of sweet taste but rather from a post-ingestive signal that regulates neural circuits that control feeding,” the researchers wrote in the research paper. In other words, in a low calorie beverage, the presence of sugar may trick the body into believing that the beverage contains a high caloric load.

Artificial sweeteners, which were used in this study and have become increasingly popular, contribute significantly to this effect.

Small explained that in a modern food environment, processed foods are made to be more pleasurable without regard for their nutritional content. In place of naturally occurring glucose, the synthesized sugars are used to make common foods tastier.

The study shows that this manipulation may actually have a detrimental effect on human health. Though the relationship should be studied more, Small said that this study may provide a potential mechanism behind the link between sweetened beverages and the diabetes epidemic.

Further defining the link may be instrumental in bettering public education and health with regard to artificial sweeteners and sweetened beverages, she added.

Although the study was a good starting point, Small said, it needs to be generalized with other sugars. Splenda, a well-known artificial sweetener, was used in the study. Many other artificial sweeteners exist, however, meaning that the significance of the study will be determined by the consistency of its results across sweeteners.

Additionally, Small said that another study looking at the long-term effects of using the artificial sweeteners will provide information on how long-term alteration of the metabolic system affects human health.

According to the Centers for Disease Control and Prevention, as of 2014, 29 million people in the United States, or 9.3 percent of the population, were diabetic and a further 86 million were prediabetic.

Vikram Shaw | vikram.shaw@yale.edu