Protein or Amino Acid Intake at Breakfast for Muscle Mass Gain in Older Adults: A Systematic Review and Meta-Analysis

Preventing sarcopenia is a major goal for older adults. High protein breakfast, while maintaining overall daily intake, has been proposed as a promising approach to support muscle health. However, the optimal timing of protein consumption remains uncertain. Therefore, the specific effects of breakfast protein intake are therefore important for refining nutritional recommendations. The methodology of this review is as follows: which included randomized controlled trials (RCTs) comparing morning protein intake with no intake in healthy and frail adults aged ≥ 60 years. A trained librarian developed comprehensive search strategies for MEDLINE, CENTRAL, EMBASE, and ClinicalTrials.gov. Two reviewers independently screened the studies, extracted data, and assessed the risk of bias using Cochrane's RoB tool 1.0. Standardized mean differences (SMD) were calculated using Review Manager. Seven RCTs involving 305 participants were included. Five studies (n = 181) reported lean mass with an SMD of -0.11 (95% CI, -0.41 to 0.18). Six studies (n = 274) measured grip strength (SMD -0.01; 95% CI, -0.25 to 0.23). Three studies (n = 157) evaluated lower limb strength (SMD -0.11; 95% CI, -0.41 to 0.18), showing similar results. Morning protein intake had a marginal reduction in total daily energy intake (SMD -0.35; 95% CI, -0.70 to 0.00), and had a significant reduction in trials without exercise (SMD, -0.47; 95% CI, -0.82 to -0.11). As a conclusion, morning protein intake may not improve muscle mass, strength, or physical performance among older adults and may reduce little food intake without exercise. But the evidence is very uncertain. Further high-quality RCTs are needed for the effects of morning protein intake on muscle health in older adults.