Sarcopenia is the aging loss of lean muscle, resulting from a loss of strength – dynapenia – and a related anabolic resistance – the inability to regenerate lean muscle at the same rate, as a younger individual. This degenerative process can begin without interventions, such as increased protein intake and resistance training, in the fourth decade and accelerate after the age of sixty.
New research – Dietary Protein Intake Is Positively Associated with Appendicular Lean Mass (ALM) and Handgrip Strength Among Middle-Aged US Adults - published in the December issue of the Journal of Nutrition, comments that, “protein intake predicts skeletal muscle mass and strength among older adults, but knowledge of similar associations among middle-aged adults is lacking.”
In order to determine the effect of protein intake on lean mass maintenance in middle-aged adults, researchers from Purdue University in Indiana, assessed appendicular lean mass, adjusted for BMI (body mass index), and handgrip strength data from 1209 men and women from 2011 to 2014 aged 40 to 59 years of age. ALM is the sum of lean tissue in the arms and legs.
Daily protein intake per kilogram of body weight was determined by two- 24-hour recalls. The participants protein intake was broken into three categories: less than the recommended daily allotment of 0.8 grams per kilogram (2.2 pounds) of body weight; moderate protein intake of between 0.8 to 1.2 g/kg/; and high at greater than 1.2 g/kg.
The ALM - the sum of lean tissue in the arms and legs - was assessed by DXA Scans and handgrip strength. The investigators used the National Institutes of Health criteria for the ALM to define the categories of “low lean mass and “weakness.”
The results reflected, “among middle-aged adults, 15.6% of men and 13.4% of women had low lean mass and 3.5% of men and 2.3% of women exhibited weakness.”
It was further determined that, compared with the moderate protein group, the high protein group had a higher handgrip strength and the low protein group had lower grip strength among men and women.
The researchers concluded that higher protein intakes were associated with greater ALM and handgrip strength relative to BMI. The take-away is that a protein intake above the recommended daily intake of 0.8 g/kg/day, may need to be increased after the age of 40.