The goal of this cohort-based cluster-randomized controlled trial is to investigate the effect of the combined intervention of exercise, fruit, and vitamin supplementation on frailty among older adults. Older individuals aged 65~80 years old with low physical activity levels and low fruit intake will be recruited. 14 clusters will be randomized into 2 arms with 1:1 ratio. Participants in the intervention arm will receive the combined intervention of physical activity, fruit, and vitamin supplementation 3 times a week for 2 months (the 1st and 6th months). They will also be given group interventions, such as self-management group activity or health education, at least once a week. Participants in the control arm will not receive any intervention.

Objectives Primary objectives

• To evaluate the effect of the combined intervention of exercise, fruit, and vitamin supplementation on preventing muscle loss among older adults over the 12-month period.

Secondary objectives

• To evaluate the effect of the combined intervention of exercise, fruit, and vitamin supplementation on preventing muscle loss in older adults over 6 months.
• To evaluate the effect of the combined intervention of exercise, fruit, and vitamin supplementation on ameliorating frailty in older adults over 6 and 12 months.
• To evaluate the effect of the combined intervention of exercise, fruit, and vitamin supplementation on improving healthy behavior of physical activity and fruit intake in older adults over 12 months.
• To evaluate the effect of the combined intervention of exercise, fruit, and vitamin supplementation on lower the risk of all-cause hospitalization in the older adults over 12 months.
• To evaluate the effect of the combined intervention of exercise, fruit, and vitamin supplementation on lower the risk of all-cause death, cardiovascular and cerebrovascular disease in the older adults over 12 and 24 months.
• To evaluate the effect of the combined intervention of exercise, fruit, and vitamin supplementation on regulating blood lipids in the older adults over 12 and 24 months.
• To evaluate the effect of the combined intervention of exercise, fruit, and vitamin supplementation on regulating blood glucose in the older adults over 12 and 24 months.
• To evaluate the health economic effectiveness of the combined intervention of exercise, fruit, and vitamin supplementation.

Sample size

Sample size was estimated using the Power Analysis and Sample Size (PASS) software (version 15.0.5) based on data from published research. Previous studies showed that the Cohens' d value was between 0.18~1.78. With these data, we estimated effect size of Cohen' d = 0.45, considering probabilities of 5% for type I error, 20% for type II error, and 0.05 for intraclass correlation coefficient (ICC). We randomized all 14 clusters (villages) into two arms with 1:1 ratio, and the total sample size was calculated to be 700 (50 participates per cluster). A conservative estimate of 25% loss to follow-up or drop-out indicates a total of 934 participates is needed.

Inclusion Criteria:

1. Permanent resident population aged 65~80 years;
2. Able to walk independently indoors and outdoors;
3. Physical activity less than 1400 metabolic equivalent task (MET)-min/week and fruit intake less than 50 g/day；
4. Have not taken vitamin B and vitamin C supplementation in the past 3 months.

Exclusion Criteria:

1. Presence of a history of fracture;
2. Patients with severe impairment of renal or hepatic fuction. Severe hepatic impairment is defined as serum alanine aminotransferase and aspartate aminotransferase levels above 100 U/L, while severe renal impairment is defined as estimated glomerular filtration rate (eGFR) < 45 mL/min, calculated according to the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations.