Men and women differ in gastric fluid retention and neural activation after consumption of carbonated beverages

Abstract

Background: The most commonly consumed carbonated beverages are soda and beer. Carbon dioxide increases gastric volume, which can lead to epigastric discomfort. Women are more susceptible to this; however, correlations with neural activity and gastric distention are unknown. Objective: This study sought to determine the subjective, gastric, and neural correlates of epigastric discomfort in men and women. Methods: Thirty-four healthy, normal-weight adults [17 women; mean ± SD body mass index (BMI; kg/m 2 ): 22.3 ± 1.9; 17 men; BMI: 22.8 ± 1.8] participated in a randomized crossover study with 2 treatments: ingestion of 500 mL beer or soda. Before and after consumption, gastric content and brain activity were measured with magnetic resonance imaging (MRI). Participants rated fullness, bloating, hunger, and nausea at baseline and at t = 0, 10, 20, and 30 min together with gastric MRI. Brain activity [cerebral blood flow (CBF)] was measured at baseline and at t = 5 and 35 min. Liquid, gas, and total gastric volume (TGV) were segmented from gastric MRI. Ratings and gastric content areas under the curve (AUCs) were tested with a mixed model with sex and drink as factors. Results: For subjective ratings, only nausea in the beer condition scored significantly greater for women (9.4-point increase; P = 0.045). Liquid stomach content was significantly greater for women (2525 mL × min increase; P = 0.019). In both men and women, the strongest correlation for bloating was with TGV (r = 0.45, P < 0.01) and for nausea was with the liquid fraction AUC (r = 0.45, P < 0.01). CBF changes did not differ between the drinks. Men showed greater CBF than women in the left precentral and postcentral gyri at t = 5 min. Conclusions: There are differences between sexes when it comes to appetite ratings, gastric fluid retention, and neural activation. Discomfort in women may be related to fluid rather than gas in the stomach, because they retain more fluid than men. Differences between men and women should be considered when studying digestion.