Efficacy of Bifidobacterium animalis subsp. lactis BL-99 in the treatment of functional dyspepsia: a randomized placebo-controlled clinical trial

Randomized, placebo-controlled trial in adults 18-60 years with functional dyspepsia diagnosed by Rome IV criteria and no organic lesions on recent upper endoscopy. Participants were recruited from outpatient clinics in Beijing, China and randomized 1:1:1:1 to placebo, positive control, BL-99 low dose, or BL-99 high dose; for the BL-99 low-dose arm, 50 were randomized and 47 completed, and for the BL-99 high-dose arm, 50 were randomized and 45 completed.

Bifidobacterium animalis subsp. lactis BL-99 was taken orally as a solid beverage once daily for 8 weeks. The low-dose arm received 1 x 10^10 CFU/day and the high-dose arm received 5 x 10^10 CFU/day, compared with placebo and a proton pump inhibitor positive control.

High-dose BL-99 improved functional dyspepsia symptoms more than placebo and the proton pump inhibitor after 8 weeks, and the benefit persisted for 2 weeks after treatment stopped. The 8-week complete response rate for FD score was 90.0% with BL-99_high versus 58.0% with placebo, 74.0% with BL-99_low, and 70.0% with positive control (p = 0.001, p = 0.044, and p = 0.017, respectively). At 2-week follow-up, the complete response rate remained higher with BL-99_high (84.0%) than placebo (62.0%) and positive control (66.0%) (p = 0.016 and p = 0.041). Serum gastrin G17 increased more with BL-99_high (mean change 4.11 +/- 4.73) than placebo (0.14 +/- 1.60), positive control (0.78 +/- 3.06), and BL-99_low (1.87 +/- 2.96), with p < 0.001, p < 0.001, and p = 0.003. Treatment was well tolerated, with adverse events in 1/50 in each BL-99 arm versus 2/50 placebo and 1/50 positive control.

The trial was short, with follow-up limited to 2 weeks after stopping treatment, and the overview notes that benefit did not persist at 8 weeks post-treatment. The sample came from Beijing, China, which limits generalizability to other populations and ethnicities. Diet and physical activity were not formally measured, and the study provides limited evidence for long-term efficacy.