Metabolic effects of colour- and odour-induced sweetness enhancement

Abstract

Can the mere expectation of drinking a sweeter beverage induce changes in taste perception and blood metabolism? Recent evidence has shown that sweetness perception can be altered by other senses, such as vision, audition, and olfaction. However, it is still unclear whether such crossmodal influences have a physiological basis. The present study examined how subjective mental states, such as the expectation of drinking a sweeter beverage due to colour and odour associations, may influence taste perception and metabolism. Twenty-seven healthy participants consumed two beverages containing identical sucrose and citric acid concentrations but altered in colour and aroma, namely a green, lemon-flavoured beverage and a red, strawberry-flavoured beverage. On average, the strawberry manipulation resulted in significantly higher sweetness ratings and lower sourness ratings compared to the lemon manipulation, although there were clear individual differences in the direction of sweetness enhancement. Blood glucose and insulin levels measured at −15, 0, 10, 20, 30, 45, 60 and 90 min after consumption showed no direct difference between the two beverage conditions. However, we found a significant indirect effect of perceived sweetness on insulin release, whereby consuming the beverage perceived to be sweeter resulted in higher overall levels of insulin release compared to the beverage that was less sweet. These results show a partial role of subjective sweetness perception influencing metabolism in accordance with an anticipatory budging model, suggesting that psychological intervention programs may be important for diabetes and metabolic syndrome management.