Bifidobacterium animalis subsp. lactis HN019 (HN019) ameliorates chronic idiopathic constipation. Our aim was to determine the efficacy and safety of 28-day supplementation with 1 × 10 9 or 1 × 10 10 CFU of HN019/day for constipation. A total of 228 adults who were diagnosed with functional constipation according to the Rome III criteria were randomized in a double-blind and placebo-controlled trial. Colonic transit time (CTT), the primary outcome, and secondary outcomes that were measured using inventories—patient assessment of constipation symptoms (PAC-SYM) and quality of life (PAC-QoL), bowel function index (BFI), bowel movement frequency (BMF), stool consistency, degree of straining, bowel emptying, bloating, and pain severity—were assessed. Ancillary parameters and harms were also evaluated.
There were no statistically significant differences in the primary or secondary outcomes between interventions. A post hoc analysis of 65 participants with fewer than 3 bowel movements per week (BMF ≤ 3/week) showed a physiologically relevant increase in weekly BMF in the high- (+2.0) and low-dose (+1.7) HN019 groups—by RMANOVA, the HN019 groups with BMF ≤ 3/week, pooled together, had a higher BMF versus placebo ( P value = 0.01). Thus, improving low stool frequency could be a target of future interventions with HN019. High-dose HN019 also decreased the degree of straining at Day 28 versus placebo in those with BMF ≤ 3/week ( P value = 0.02). Three unlikely related AEs—2 with low-dose HN019 and 1 with placebo—were followed until full recovery. In conclusion, although there were no differences in the primary analysis, HN019 is well tolerated and improves BMF in adults with low stool frequency.