Effect of Protein Intake on Lean Body Mass in Functionally Limited Older Men

Abstract

set the recommended dietary allowance (RDA) for protein at 0.8 g/kg/d for the entire adult population. It remains controversial whether protein intake greater than the RDA is needed to maintain protein anabolism in older adults. OBJECTIVE To investigate whether increasing protein intake to 1.3 g/kg/d in older adults with physical function limitations and usual protein intake within the RDA improves lean body mass (LBM), muscle performance, physical function, fatigue, and well-being and augments LBM response to a muscle anabolic drug. DESIGN, SETTING, AND PARTICIPANTS This randomized clinical trial with a 2 × 2 factorial design was conducted in a research center. A modified intent-to-treat analytic strategy was used. Participants were 92 functionally limited men 65 years or older with usual protein intake less thanor equal to 0.83 g/kg/d within the RDA. The first participant was randomized on September 21, 2011, and the last participant completed the study on January 19, 2017. INTERVENTIONS Participants were randomized for 6 months to controlled diets with 0.8 g/kg/d of protein plus placebo, 1.3 g/kg/d of protein plus placebo, 0.8 g/kg/d of protein plus testosterone enanthate (100 mg weekly), or 1.3 g/kg/d of protein plus testosterone. Prespecified energy and protein contents were provided through custom-prepared meals and supplements. MAIN OUTCOMES AND MEASURES The primary outcome was change in LBM. Secondary outcomes were muscle strength, power, physical function, health-related quality of life, fatigue, affect balance, and well-being. RESULTS Among 92 men (mean [SD] age, 73.0 [5.8] years), the 4 study groups did not differ in baseline characteristics. Changes from baseline in LBM (0.31 kg; 95% CI, −0.46 to 1.08 kg; P = .43) and appendicular (0.04 kg; 95% CI, −0.48 to 0.55 kg; P = .89) and trunk (0.24 kg; 95% CI, −0.17 to 0.66 kg; P = .24) lean mass, as well as muscle strength and power, walking speed and stair-climbing power, health-related quality of life, fatigue, and well-being, did not differ between men assigned to 0.8 vs 1.3 g/kg/d of protein regardless of whether they received testosterone or placebo. Fat mass decreased in participants given higher protein but did not change in those given the RDA: between-group differences were significant (difference, −1.12 kg; 95% CI, −2.04 to −0.21; P = .02). CONCLUSIONS AND RELEVANCE Protein intake exceeding the RDA did not increase LBM, muscle performance, physical function, or well-being measures or augment anabolic response to testosterone in older men with physical function limitations whose usual protein intakes were within the RDA. The RDA for protein is sufficient to maintain LBM, and protein intake exceeding the RDA does not promote LBM accretion or augment anabolic response to testosterone. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT01275365

Differential effects of testosterone on circulating neutrophils, monocytes, and platelets in men: Findings from two trials

“…These findings were verified in another trial in which testosterone treatment was administered to functionally limited older men. 23…”

“…The randomized trials from which these data were derived have been published. 22,23 Both trials were approved by institutional review boards of Boston University Medical Center and Brigham and Women's Hospital. All participants gave written informed consent.…”

“…The primary aim of the OPTIMEN trial was to determine whether increasing protein intake to 1.3 g kg −1 day −1 in functionally limited, older adults with usual protein intake < 0.83 g kg −1 day −1 improves lean body mass (LBM) and augments LBM response to testosterone. 23 Briefly, community-dwelling men, 65 years or older, with moderate degree of functional limitation as indicated by Short Physical Performance Battery score 3-10, whose average daily usual protein intake was ≤ 0.83 g kg −1 day −1 , were randomized for 6 months to one of four intervention arms: 0.8 g kg −1 day −1 protein plus placebo weekly, 1.3 g kg −1 day −1 protein plus placebo, 0.8 g kg −1 day −1 protein plus 100 mg/week TE, or 1.3 g kg −1 day −1 protein plus TE. Men with a history of prostate cancer, severe LUTS, untreated sleep apnea, heart failure, myocardial infarction, or stroke within 6 months, as well as those having glycated hemoglobin levels > 8% or those with erythrocytosis were excluded.…”

“…Similarly, in the OPTIMEN trial, protein intake level had no effect on hematocrit 23 ; therefore, men who received testosterone treatment were combined and the men randomized to placebo were combined regardless of protein intake level; sensitivity analyses were performed to assess potential effect of protein level on hematopoietic variables. Participants who had baseline and at least one post-randomization complete blood count were included in the analyses.…”

AGS and NIA Bench‐to Bedside Conference Summary: Osteoporosis and Soft Tissue (Muscle and Fat) Disorders

“…High dietary protein intakes have no adverse effects on bone health, and moderate evidence supports a protective effect on lumbar spine BMD . However, protein's effects on lean body mass and physical performance diminish with age . The protein recommended daily allowance is based on nitrogen balance studies, an inadequate outcome for older adults at risk of sarcopenia.…”