Background: It has been hypothesized that for older adults evenly distributing consumption of protein at 30-40 g per meal throughout the day may result in more favorable retention of lean mass and muscular strength. Such a thesis has not, to our knowledge, been tested outside of short-term studies or acute measures of muscle protein synthesis.
Aims: To examine whether the number of times an individual consumed a minimum of 30 g of protein at a meal is associated with leg lean mass and knee extensor strength.
Methods: Data from the 1999-2002 NHANES were used, with 1081 adults (50-85 y) constituting the analytic sample. A "multiple pass" 24-h dietary interview format was used to collect detailed information about the participants' dietary intake. Knee extensor strength was assessed objectively using the Kin Com MP dynamometer. Leg lean mass was estimated from whole-body dual-energy X-ray absorptiometry (DXA) scans.
Results: Participants with 1 vs. 0 (βadjusted = 23.6, p = 0.002) and 2 vs. 0 (βadjusted = 51.1, p = 0.001) meals of ≥30 g protein/meal had greater strength and leg lean mass (1 vs. 0, βadjusted = 1160, p < 0.05 and 2 vs. 0, βadjusted = 2389, p < 0.05). The association of protein frequency with leg lean mass and strength plateaued at ∼45 g protein/meal for those consuming 2 vs. 0 meals above the evaluated protein/meal threshold. However, for those with only 1 meal at or above the evaluated threshold, the response plateaued at 30 g/meal. Leg lean mass mediated the relationship between protein frequency and strength, with the proportion of the total effect mediated being 64%.
Conclusions: We found that more frequent consumption of meals containing between 30 and 45 g protein/meal produced the greatest association with leg lean mass and strength. Thus, the consumption of 1-2 daily meals with protein content from 30 to 45 g may be an important strategy for increasing and/or maintaining lean body mass and muscle strength with aging.
Keywords: Epidemiology; Muscle mass; Muscle strength; Protein distribution; Sarcopenia.
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