A study published in Gastroenterology shows that carbonation in soft drinks may alter the brain’s perception of sweetness and make it difficult to distinguish between sugar and artificial sweeteners.
Taste is the main sensory modality influencing food preferences and dietary behavior and affecting body weight, risk of chronic disease, and health. The acceptance of a sweet taste signals calories, while the rejection of a strongly bitter taste warns against toxins. These are brain stem reflexes that appear prenatally in humans and are modified during life but are never removed by experience. Knowledge of the central neural processing of taste is still largely incomplete. It involves the anterior insula (AI) and frontal operculum (human primary taste cortex), opercular cortex and orbitofrontal cortex (OFC), amygdala (Amy), and prefrontal cortex.
In addition to basic tastes (sweet, salty, sour, bitter, and umami), the gustatory system appears to be responsive to carbon dioxide (CO2), which modulates gustatory processing of basic tastes and of their combination in beverages. Given the widespread use of CO2 in sweet beverages, the modulation of sweet perception is particularly interesting. CO2 may affect the neural processing of various sweet substances differently, affecting the liking of beverages containing sucrose or sugar substitutes.
The researchers investigated the interference between CO2 and perception of sweetness and the differential effects of CO2 on sucrose and artificial sweeteners (aspartame-acesulfame, a common combination used in diet beverages) by monitoring the changes in regional brain activity using functional magnetic resonance imaging.
The researchers found that the presence of carbonation in sweet solutions, independently of the sweetening agent, reduced neural activity in the anterior insula, orbitofrontal cortex, and posterior pons parts of the brain. Carbonation also reduces the perception of sweetness and the differences between the sensory profiles of sucrose and aspartame-acesulfame. “Although this effect may increase intake of sucrose, it is also favorable to the formulation of diet beverages, designed to reduce caloric intake, being perceived as similar to that of regular beverages,” wrote the authors.
The researchers concluded that, “Our data suggest that CO2 modulates the perception of sweetness, reducing the global neural processing of sweetness, the processing of sucrose more than of As-Ac, and the processing difference between sweetening agents.”