Associations of dietary protein intake with fat free mass and grip strength: cross-sectional study in 146,816 UK Biobank participants

Adequate dietary protein intake is important for the maintenance of fat-free mass (FFM) and muscle strength: optimal requirements remain unknown. The aim of the current study was to explore the associations of protein intake with FFM and grip strength. We used baseline data from the UK Biobank (146,816 participants aged 40-69 years with data collected 2007-2010 across the UK) to examine the associations of protein intake with FFM and grip strength. Protein intake was positively associated with FFM (men 5.1% [95% CI: 5.0; 5.2] and women 7.7% [95% CI: 7.7; 7.8]) and grip strength (men 0.076 kg/kg [95% CI: 0.074; 0.078] and women 0.074 kg/kg [95% CI: 0.073; 0.076]) per 0.5 grams per kg body mass per day (g/kg/day) increment in protein intake. FFM and grip strength were higher with higher intakes across the full range of intakes, i.e. highest in those reporting consuming > 2.0 g/grams per kg/day independently of socio-demographics, other dietary measures, physical activity and comorbidities. FFM and grip strength were lower with age, but this association did not differ by protein intake categories (P > 0.05). Current recommendation for all adults (40-69 years) for protein intake (0.8 grams per kg body mass per day) may need to be increased to optimise FFM and grip strength