Dietary animal protein intake:: Association with muscle mass index in older women

Background: Aging is associated with reductions in muscle mass and strength, so-called sarcopenia, and is generally characterized using muscle mass index (MMI = FFM (kg) / height (M)(2)). It is believed that adequate nutrition especially regarding protein intake, can delay this progression and enhance the quality of life of elders. Objectives: We examined whether the predominant source of protein consumed (animal or vegetal) by older women was associated with MMI. Design: Thirty-eight healthy, normal weight, sedentary women, aged between 57-75 years (mean age: 66 +/- 5 years old), and taking no medication that could influence metabolism were recruited. Body composition was measured by dual-energy X-ray absorptiometry; muscle protein content was measured by the use of creatinine excretion. Physical activity metabolism was obtained by the use of acceterometry, and indirect calorimetry. Finally, protein intake was measured with a 3-day dietary record. Results: Significant correlations were observed between MMI and body mass index, fat-free mass, muscle protein content, total protein intake, animal protein intake, fat mass, visceral fat and daily energy expenditure. However, a stepwise regression analysis showed animal protein intake to be the only independent predictor of MMI (r(2)=0. 19; p=0.008). Conclusions: Our results suggest that protein intake, especially from animal sources, may be associated with a better preservation of MMI. However, more research is needed to confirm our results.