Weight reduction effect of alginate associated with gut microbiota and bile acids: A double-blind and randomized trial

Being overweight is a risk for various chronic diseases. Alginate, a soluble dietary fiber extracted from seaweed, has been linked to weight loss with unclear mechanisms. We conducted a double-blind, randomized trial in overweight or normal-weight adults to explore alginate’s weight loss effect and mechanism. Normal-weight or overweight participants were randomized to receive either alginate (15 g/day) or maltodextrin (13.8 g/day) for 14 weeks. Compared to maltodextrin (−0.91 kg; 95% CI, −1.91 to 0.10), alginate helped overweight subjects lose weight (−2.67 kg; 95% CI, −3.89 to −1.46) (P = 0.0017) after 14 weeks. In overweight subjects, alginate increased fecal-conjugated bile acids (taurocholate acid and taurochenodeoxycholic acid) and reduced bile acid-related bacteria (Bacteroides, Oscillibacter and Eubacterium). Our results indicate that alginate decreases weight and increases bile acid excretion in overweight subjects, related to gut microbiota alterations and inhibited intestinal bile acid absorption.