Effects of pre-meal dashi consumption on food preferences and sweet taste sensitivity in patients with type 2 diabetes: a pilot randomized controlled trial

Background & Aims Impaired sweet taste sensitivity and preferences for energy-dense foods have been reported in patients with type 2 diabetes, although practical strategies to modify these preferences remain limited. We investigated whether consuming dashi, a soup stock rich in umami, before meals could alter food preferences and sweet taste sensitivity in patients with type 2 diabetes. Methods We conducted an open-label randomized controlled trial with an initial 4-week parallel-group period followed by an exploratory 4-week period in which participants received the alternate intervention without a washout interval. Twenty patients with type 2 diabetes were randomly assigned to consume either dashi (dashi group) or hot water (water group) before breakfast and dinner during the initial phase. The primary outcome was the between-group difference in the change in sweet taste threshold from baseline to week 4. Secondary outcomes included the feasibility of pre-meal dashi intake, food preferences, biomarkers, anthropometric parameters, and dietary intake. Second-period outcomes were summarized descriptively. Results Eighteen participants (90%) completed the week 4 assessment, and adherence to the dashi intervention was 97%. The adjusted between-group difference in sweet taste threshold was −5.2 g/L (95% CI, −13.1 to 2.9; p = 0.19). In exploratory within-group analyses, preference for non-sweet fatty foods and sweet carbohydrate foods decreased in the dashi group; however, the corresponding adjusted between-group differences were −11 points (95% CI, −28 to 7; p = 0.22) and −8 points (95% CI, −22 to 7; p = 0.29), respectively. Among participants with impaired sweet taste sensitivity at baseline, 3 of 5 (60%) in the dashi group and 0 of 4 (0%) in the water group improved to normal sensitivity ( p = 0.17). Conclusions In this pilot randomized controlled trial, pre-meal dashi intake was feasible, but superiority over hot water was not demonstrated. Exploratory findings on food preferences and sweet taste sensitivity are hypothesis-generating and warrant confirmation in further large-scale, independently conducted trials. Trial registration This study was registered with the University Hospital Medical Information Network (UMIN000050054).