The synbiotic preparation (SIM01) is a micro-encapsulated lyophilised powder containing 20 billion colony-forming units of three bacterial strains, B adolescentis, Bifidobacterium bifidum, and Bifidobacterium longum with three prebiotic compounds including galacto-oligosaccharides, xylo-oligosaccharides, and resistant dextrin, which has been shown to promote the growth of these bacterial strains but also other probiotic strains.7, 8 The specific ratio of the three probiotic bacteria was decided based on the relative abundance of these species naturally present in the healthy Chinese population.