(P04-011-25) Subjective Gastrointestinal and Mood Responses to a 4-week High-Fiber Diet

Objectives: High-fiber diets are known for their metabolic advantages and their role in reducing chronic disease risks. Yet, their impact on subjective mood and gastrointestinal (GI) symptoms remains underexplored. We aimed to investigate the effect of consuming a high-fiber (HiFi) versus low-fiber (LowFi) dietary intervention on subjective mood and gastrointestinal (GI) responses.

Methods: total of 29 adult participants (HiFi (25 g/d of dietary fiber): n = 13 [7 men, 6 women]; LowFi (5 g/d of dietary fiber): n = 16 [9 men, 7 women]), who had at least one characteristic of metabolic syndrome, completed the study over a 4-week period. At baseline and after 4 weeks, participants completed a meal test challenge lasting 4 hours, during which fasting and postprandial GI symptoms and mood responses were evaluated using a 100 mm visual analogue scale. Total area under the curve (AUC) values were calculated using the Trapezoidal rule. Based on normality, paired t-tests and Wilcoxon Signed-Rank tests were used for within-group, and Welch’s t-tests and Mann-Whitney U tests for between-group comparisons.

Results: The mean ± SD BMI and age were 30.1 ± 2.8 kg/m² and 30.7 ± 9.6 years for the HiFi group and 30.1 ± 2.6 kg/m² and 32.2 ± 9.4 years for the LowFi group. Within-group analyses for the LowFi group revealed significant reductions after week 4 in the total AUC for nausea (1765.1 ± 586.7 vs 788.0 ± 240.1; P = 0.0219), concentration (14881.4 ± 471.7 vs 12931.9 ± 840.3; P = 0.0294), boredom (7830.2 ± 1300.5 vs 5986.4 ± 1080.2, P = 0.0421) and overall mood (16103.9 ± 954.3 vs 14815.3 ± 975.5; P = 0.0446). Within the HiFi group there were significant reductions in constipation (4749.5 ± 1825.2 vs 1144.6 ± 390.9; P = 0.0144), cramps (2100.0 ± 614.0 vs 908.7 ± 361.6; P = 0.0053), bloating (3395.8 ± 1090.3 vs 1135.7 ± 345.1; P = 0.0253), anxiety (4760.5 ± 1043.3 vs 1994.7 ± 714.0; P = 0.0253), irritability (4770.3 ± 1302.9 vs 1710.0 ± 453.3; P = 0.0427) and boredom (6999.5 ± 1683.1 vs 3109.9 ± 744.0, P = 0.0119) after 4 weeks. Between-group comparisons of changes revealed significant differences in anxiety (HiFi: -2765.8 ± 1264.2 vs LowFi: 351.8. ± 1270.4; P = 0.0226).

Conclusions: This study suggests that both HiFi and LowFi diets can significantly affect GI symptoms and mood after 4 weeks, with HiFi diets having a particularly notable impact on anxiety reduction.

Funding Sources: University of Missouri and NIH-K01- NHLBI