The Correlation and Intervention of Intestinal Flora and Frailty in the Elderly

100 healthy controls, 100 pre‐frailty and 100 frailty elderly will be included. the healthy controls will be received no intervention. The pre‐frailty will be randomized at a 1：1 ratio to receive prebiotics (inulin) or placebo (maltodextrin) . The degree of improvements and correlation in frailty will be evaluated three months later.Similarly,the frailty also will be randomized at a 1：1 ratio to receive prebiotics (inulin) or placebo (maltodextrin). The degree of improvements and correlation in frailty will be evaluated three months later.