Examining the Gastrointestinal Effects of Solnul®, a Prebiotic Resistant Potato Starch: A Replication Randomized, Double-Blind, Placebo-Controlled Clinical Trial in Healthy Adults

Background: A prebiotic is a substrate that is selectively utilized by host microbiota to confer a health benefit. Consumption of 3.5 g of Solnul® resistant potato starch (RPS) was previously shown to selectively increase Bifidobacterium and Akkermansia, as well as improve stool form relative to a placebo. The objective of this study was to reproduce these effects in an independent cohort. Methods: A 4-week, randomized, double-blind, placebo-controlled, parallel group trial evaluated the effects of 3.5 g RPS versus a placebo on changes in Bifidobacterium, Akkermansia, stool form, and bowel movement (BM) frequency using 16s rRNA sequencing, the Bristol Stool Form Scale, and personal diaries in healthy adults aged 18–69 years in Guelph, ON. Results: Compared to the placebo (n = 35), the relative abundance of Bifidobacterium increased (p = 0.049, Brunner–Munzel), and the number of normal stools (Type 3 or 4) was higher in the RPS group (n = 35; p = 0.0077, Chi-Square; key secondary endpoints). While differences were not observed for Akkermansia relative to the placebo (p = 0.49; primary endpoint), End-of-Study Akkermansia levels were higher than Run-In levels for RPS (p = 0.046, Wilcoxon signed-rank) but not the placebo (p = 0.14). Participants consuming RPS had higher BM frequency at the End-of-Study compared to the Run-In period, but the effect was not different from the placebo. Comparing End-of-Study and Run-In periods, the RPS group experienced fewer days without a BM relative to the placebo. No changes in the GSRS or serious adverse events were reported in the RPS group. Conclusions: This clinical trial confirmed that 3.5 g of RPS induces a bifidogenic effect and normalized stool form, consistent with the previous study. NCT06949631.