Peanut Protein Supplemenation to Augment Muscle Growth and Improve Markers of Muscle Quality and Health in Older Individuals

Abstract

It is generally accepted that resistance training (RT) in conjunction with protein supplementation has positive effects on strength and muscle mass in older individuals. However, to date, no study has examined the effects of a RT program in combination with a high-protein, defatted peanut powder (PP) supplement on these markers. Herein, 39 older, untrained individuals (n=17 female, n=22 male; age=58.6±8.0 years; body mass index =28.7±5.8) completed a 6-week (n=22) or 10-week (n=17) RT program, where full-body training was implemented twice weekly. Participants were randomly assigned to consume either a PP supplement shake once per day (35 g protein, 315 kcal; n=20) or no supplement (CTL; n=19). Right leg vastus lateralis (VL) muscle biopsies were obtained prior to and 24 hours following the first training bout in all participants to assess changes in myofibrillar protein synthetic rates (MyoPS) as measured via the deuterium-oxide (D2O) tracer method. All participants also completed PRE- and POST-intervention testing including dual energy x-ray absorptiometry (DXA), VL ultrasound, mid-thigh peripheral quantitative computed tomography (pQCT) scan, and right leg strength assessment using an isokinetic dynamometer. There was a significant group-by-time interaction for protein consumption when cohorts were pooled (p=0.008), and a trend toward significance when cohorts were examined individually as a 10-week (p=0.086) and 6-week (p=0.072) cohort. MyoPS rates were not significantly different between supplement groups following the first workout bout. Regarding chronic changes, there were no significant group-by-time interactions (p<0.05) in DXA-derived fat mass, lean soft tissue mass (LSTM) or percent body fat between supplementation groups. There was, however, a significant increase in VL thickness for PP versus CTL participants when the 6- and 10-week cohorts were pooled (interaction p=0.041). There was also a significant increase in knee flexion torque in the 10-week PP group versus the CTL group (interaction p=0.032). In conclusion, a high-protein, defatted peanut powder supplement in combination with RT may have beneficial effects on select indices of muscle hypertrophy and strength in an untrained, older adult population.