Sugar in soda is a known culprit in promoting diabetes and obesity. But a new study takes a look at another potential player in the soda-obesity equation: carbonation.
New research published in the journal Gastroenterology suggests that carbonation in sugary drinks can affect the brain's perception of sugar, making it think sugar consumption is less than it actually is.
The Italian researchers also found that a certain amount of carbonation seems to keep the brain from being able to tell the difference between sweet from sugar and sweet from artificial sweeteners.
The finding could potentially be good for people looking to lose weight by consuming diet drinks because "it facilitates the consumption of low-calorie drinks because their taste is perceived as pleasant as the sugary, calorie-laden drink," study researcher Rosario Cuomo, an associate professor of gastroenterology in the department of clinical medicine and surgery at "Federico II" University in Italy, said in a statement.
However, it's important to note that the link between artificial sweeteners and weight is still not clear: It's unknown whether obese people drink diet drinks in an effort to lose weight, or if obesity is spurred by consumption of diet drinks. Some research has suggested artificial sweeteners can prime the brain to want more sweet, thereby theoretically promoting weight gain through added sugar consumption.
The new study is based on two functional neuroimaging experiments. In the first experiment, study participants underwent brain scans while tasting four altered types of Sprite. The first kind was just carbonated and sweetened with sucrose (sugar), the second was non-carbonated and sweetened with sucrose, the third was carbonated and sweetened with aspartame (artificial sweetener), and the fourth was non-carbonated and sweetened with aspartame.
The second part of the study involved using brain imaging to see where neural effects in the insular cortex brain region were strongest when tasting carbon dioxide and sour taste (sour-sensing cells are responsible for detecting carbon dioxide) versus water. In addition to this element of the experiment, study participants also reported their perceptions of sweetness from the different kinds of Sprite used in the first experiment, as well as carbon dioxide added to a 10 percent glucose solution.
Researchers found that across the board, the presence of carbonation seemed to decrease the perception of sweet in the brains of the study participants.
Catia Sternini, of the David Geffen School of Medicine at the University of California, Los Angeles, who wrote a commentary in the same journal on the new study, noted that "making the perception of noncaloric sweetener similar to the caloric sweetener, carbonation might then favor the consumption of low-calorie, diet beverages. However, the reduced sweetness perception due to carbonation might be a double-edged sword in that it could also stimulate sucrose and food consumption because the brain perceives less sugar intake, and because energy balance is impaired."
Carbonation's effect on the gastrointestinal tract could also potentially play a role in the soda-obesity link, Sternini wrote:
Consumption of carbonated beverages induces gastric distension, eliciting a sense of fullness and thus affecting food intake. In addition, the sense of taste in the mouth, together with the sight and the smell of food and drink, initiates physiologic reflexes beyond the oral cavity, such as the secretion of digestive enzymes, hormones, and other signaling molecules from the gastrointestinal tract and its associated glands, which prepare the gut to digest and absorb nutrients or to reject and neutralize potentially dangerous non-nutritive chemicals.