Sweet sensing, homeostasis and hedonics in the human gut–brain axis

Consumption of added sugars has been associated with excessive energy intake, obesity and its comorbidities, while non‐nutritive sweeteners offer caloric‐free sweet taste and might be helpful in decreasing energy intake. The importance of gut–brain nutrient signalling in the regulation of food intake has recently become a field of extensive research; however, understanding about how nutritive and non‐nutritive sweet tastants affect gut–brain crosstalk is limited. Much of the research has focused on the effects of non‐nutritive sweeteners on gut function, especially after the demonstration that sweet taste receptors are also present in enteroendocrine cells. However, the majority of human studies have not confirmed a physiologically significant biological activity of non‐nutritive sweeteners, nor a role for gut sweet taste receptors in glucose and gut peptide postprandial responses, gastric emptying or appetite. The use of functional and physiological MRI scanning has enabled the investigation of human brain responses to sweet tastants. Imaging studies have demonstrated that the human brain is able to distinguish the sweet taste of caloric sugars from non‐nutritive sweeteners, most likely as a result of nutrient detection in the gut. More studies are required to explore the comparative effects of caloric sugars and non‐nutritive sweeteners on homeostatic, neurophysiological and hedonic signals, which may interact to determine the effects of sweet sensing.