Habitual protein intake, protein distribution patterns and dietary sources in Irish adults with stratification by sex and age

Background: Given the importance of habitual dietary protein intake, distribution patterns and dietary sources in the etiology of age-related declines of muscle mass and function, this study examined these factors as a function of sex and age in Irish adults aged 18-90 years comprising The National Adult Nutrition Survey (NANS). Methods: n=1051 (males, n=523; females, n=528) undertook a four-day semi-weighed food diary. Total, body mass relative intake, and percentage contribution to total energy intake of dietary protein were determined in addition to protein distribution scores (PDS), and contribution of food groups, animal- and plant-based foods to total protein intake. Results: Total and relative protein intake were highest in those aged 18-35 y (96±3g per day, 1.32±0.40g/kg/d), with lower protein intakes with increasing age i.e. in adults aged ≥65 y (82±22g, 1.15±0.34g/kg/d, P<0.001 for both). Differences in protein intake between age groups were more pronounced in males compared to females. Protein distribution followed a skewed pattern for all age groups (breakfast, 15±10g; lunch, 30±15g; dinner, 44±17g). Animal-based foods were the dominant protein source within the diet (63±11% vs. 37±11% plant protein, P<0.001). Conclusions: Protein intake and the number of meals reaching the purported threshold for maximising postprandial anabolism were highest in young, and lower with increasing age. For main meals, breakfast provided the lowest quantity of protein across all age categories, and may represent an opportunity for improving protein distribution, whereas in older adults, increasing the number of meals reaching the anabolic threshold regardless of distribution pattern may be more appropriate.