The study aim to evaluate the improvement and correlation of soluble dietary fiber (prebiotics) in the frailty of elderly people by a randomized, double-blind, placebo-controlled clinical trial.

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.

Inclusion Criteria:

• Age ≥65 years;
• Can get up from a chair and walk 6 meters
• Clearly consciousness, able to read or use words to express and communicate without difficulty
• Agree and accept the study plan

Exclusion Criteria:

• Acute and chronic inflammatory disease of the intestine within 3 months
• Use of antibiotics, probiotics, prebiotics or synthetics, laxatives or diarrhea medications, proton pump inhibitors or gastric motility drugs within 1 month
• Dementia
• mental illness or blindness
• acute infection
• cancer

We will not make individual participant data (IPD) available to other researchers in a few years.