Supplementation of Protein at Breakfast Rather Than at Dinner and Lunch Is Effective on Skeletal Muscle Mass in Older Adults

Abstract

<b>Background:</b> The effects of different intake patterns of meal protein on muscle mass have not been clarified. We cross-sectionally and longitudinally examined the effect of different timing of protein intake on sarcopenia-related factors in older adults. <b>Methods:</b> This cross-sectional study 1 included 219 (male, <i>n</i> = 69, female, <i>n</i> = 150) elderly subjects aged ≥65 years. Subjects who consumed more protein at breakfast than at dinner were grouped into the morning group (MG, <i>n</i> = 76; male, <i>n</i> = 26; female, <i>n</i> = 50), and those who consumed more protein at dinner than at breakfast were grouped into the evening group (EG, <i>n</i> = 143; male, <i>n</i> = 43; female, <i>n</i> = 100). In cross-sectional study 2-1 (female, <i>n</i> = 125), the subjects were classified into four groups according to the number of meals with sufficient protein intake. In cross-sectional studies 2-2 (female, <i>n</i> = 125) and 2-3 (female, <i>n</i> = 27), the subjects were classified into eight groups and three groups according to whether they had consumed sufficient protein at three meals; sarcopenia-related factors were compared. The intervention study was a placebo-controlled, double-blind, randomized controlled trial that included 40 elderly women with low daily breakfast protein intake. The subjects were divided into four groups: morning protein and placebo intake groups and evening protein and placebo intake groups. Each group consumed the test food (containing 10 g milk protein) or placebo in the morning or evening for 12 weeks. Blood indices and physical function were assessed before and after the intervention. <b>Results:</b> Comparing all subjects, MG showed significantly higher handgrip strength than did EG (<i>P</i> < 0.05). The higher ratio of morning protein intake relative to the total protein intake, the better the muscle mass (<i>r</i> = 0.452, <i>P</i> < 0.05) and handgrip strength (<i>r</i> = 0.383, <i>P</i> < 0.05). The intervention study showed an increase in muscle mass with the intake of milk protein in the morning rather than in the evening (<i>P</i> < 0.05). <b>Conclusions:</b> Protein intake at breakfast might have relatively stronger effects on skeletal muscle mass than at lunch and dinner.