Effect of prebiotic fiber on physical function and gut microbiota in adults, mostly women, with knee osteoarthritis and obesity: a randomized controlled trial

Fortuna R, Wang W, Mayengbam S, Tuplin EWN, Sampsell K, Sharkey KA, Hart DA, Reimer RA · European Journal of Nutrition

The only randomized trial of a fibre intervention with joint outcomes, and the endpoints that separated are performance-based rather than self-reported: timed-up-and-go, 40 m fast-paced walk and hand-grip strength all favoured prebiotic over placebo. Trunk fat mass fell at 6 months and trunk fat percentage at 3 months. Knee pain showed a trend only (p = 0.059). Thirty-seven amplicon sequence variants differed between groups, and *Bifidobacterium* abundance correlated positively with 6-minute walk distance and grip strength.

Population

Adults with BMI over 30 and unilateral or bilateral knee OA, mostly women

Intervention

16 g/day oligofructose-enriched inulin for 6 months

Comparator

Isocaloric maltodextrin placebo

Limitations

n=54 with unequal allocation (31 vs 21), mostly women, single centre, and the pain endpoint — the one most people care about — missed significance. Grip strength improving alongside walking speed raises the possibility of a general conditioning or motivation effect rather than a knee-specific one. Trunk fat fell, so weight change is not separated from the fibre. Registered NCT04172688.