Effects of Peanut Butter Supplementation on Older Adults' Physical Function: A 6-Month Randomised Controlled Trial

Abstract

Background: Nut consumption has been associated with a reduced risk of functional decline, but evidence from randomised controlled trials to support functional benefit is lacking. Therefore, this study aimed to investigate whether daily supplementation of peanut butter over 6 months, relative to usual care, can improve physical function in community-dwelling older adults. Methods: One hundred and twenty older adults (aged ≥ 65 years) at risk of falls were randomly assigned to receive peanut butter (43 g/day, n = 60) or maintain usual care (control, n = 60) for 6 months. Outcomes assessed at baseline and 6 months included physical function (4-m gait speed [primary outcome], standing balance test, four-square step test [FSST], five times sit-to-stand [5STS] test time and muscle power, 30-s sit-to-stand (30-s STS) and timed up and go [TUG] tests), muscle strength (handgrip [HGS] and isometric knee extensor strength tests [KES]) and anthropometry/body composition (weight, body mass index [BMI], total lean and fat mass and appendicular lean mass). Linear regression models, adjusting for age, sex, baseline value of the dependent variable, BMI, physical activity and diet quality, estimated intention-to-treat intervention effects. Results: A total of 108 (90%) participants completed the study. At baseline, 70% were female, and the mean ± SD age and BMI were 76.1 ± 4.6 years and 27.5 ± 4.2 kg/m2, respectively. At 6 months, there were no significant treatment effects on the primary outcome of gait speed or other measures of physical function (p > 0.05), with the exception that 5STS time and muscle power improved significantly more in the peanut butter compared to control group (estimated treatment effect: time, −1.23 s [95% CI, −2.09, −0.37], p = 0.006; absolute power, 22.0 W [95% CI: 7.1 to 36.9], p = 0.004; relative power, 0.27 W/kg [95% CI: 0.10 to 0.45], p = 0.002). Changes in HGS, KES, weight, BMI, total fat mass, total lean mass or appendicular lean mass did not differ between groups. In the peanut butter group, among those who completed the follow-up, the mean (SD) adherence was 86.0 (13.8) %. Conclusion: In community-dwelling older adults at risk for falls, daily peanut butter consumption for 6 months improved 5STS time and muscle power based on 5STS, but not gait speed, muscle strength or body composition. Trial Registration: Australian New Zealand Clinical Trials: ACTRN12622001291774.