The effects of ​Laminaria digitata​ fibres on the gut microbiota: An ​in vitro​ and ​in vivo​ investigation.

Seaweeds, rich in atypical polysaccharides, are habitually consumed in South East Asian populations and their consumption has been linked with a reduction in disease risk of non-communicable diseases. One of the mechanisms attributed to the health benefits of consuming seaweed is the non-digestible fibre component’s effects on the gut microbiome. The fibre component of the brown seaweed ​Laminiaria digitat​a (LD) was extracted and the potential effects on the GM were assessed employing both ​in vitro human faecal fermentations as well as long term supplementation studies in mice. Human faecal fermentation experiments revealed that the fibres from LD stimulated the production of butyrate, propionate and total SCFA as well as altering a number of bacterial genera as assessed by 16S rDNA gene sequence analysis. The fibres were also found to reduce serum cholesterol in both a standard chow (-9.05%; P=0.025) and diet induced obese mouse (-20.77%; P=0.003) models. In addition, LD was found to significantly increase the relative abundance of Akkermansia (150 fold, P=0.006) and decrease the Firmicutes/Bacteroidetes ratio, increased caecal and colonic butyrate pools, increase energy expenditure and reduce fat mass and metabolic endotoxemia in a diet induced obese mouse model. This study provides initial indications that the consumption of LD fibre may confer health benefits associated with fat metabolism/storage which is associated with alterations to the composition and metabolic activity of the GM.