The effect of gastrointestinal bitter sensing on appetite regulation and energy intake: A systematic review

Taste receptors are located on the epithelial surface throughout the alimentary canal to identify nutrients and potential toxins. In the oral cavity, the role of taste is to encourage or discourage ingestion, while in the gastrointestinal (GI) tract, the taste receptors help the body prepare for an appropriate response to the ingested foods. The GI sensing of bitter compounds may alter the secretion of appetite-related hormones thereby reducing food intake, which may have potential use for managing health outcomes. This systematic literature review investigated the acute effects of administering different bitter tasting compounds on circulating levels of selected GI hormones, subjective appetite, and energy intake in humans. A literature search was conducted using Medline, CINAHL and Web of Science databases. Of 290 articles identified, 16 met the inclusion criteria. Twelve studies assessed food intake; four of these found bitter administration decreased food intake and eight did not. Fourteen studies assessed subjective appetite; seven found bitter administration affected at least one measure of appetite and seven detected no significant changes. Nine studies included measures of GI hormones; no significant effects were found for changes in GLP-1, CCK or PYY. Four studies measured motilin and ghrelin and found mostly consistent changes in either food intake or subjective appetite. Overall, the data on food intake and subjective appetite were inconsistent, with only motilin and ghrelin responsive to post-oral bitter administration. There is limited consistent conclusive evidence that bitter compounds influence food intake, appetite or hormones with the reasons for this discussed within. Systematic review registration: CRD42021226102.