gms | German Medical Science

Introduction: Muscle health is a fundamental aspect of overall health, functionality, and longevity. Skeletal muscle contributes to maintaining strength, balance and mobility, resulting in improved functionality in daily activities and reducing the risk of falls and injuries [1]. Particularly in older adults, associations between inadequate nutrient intake and muscle fat mass and strength have been shown [2], often in the context of sarcopenia [3]. Fatty infiltration is a sign of decreased muscle quality. Given the importance of maintaining muscle health for healthy aging, it is especially relevant to study the impact of nutrition on muscle size and fat. We thus aim to investigate the association of habitual dietary intake of energy-providing nutrients (carbohydrates, fat, protein, alcohol) and essential amino acids (phenylalanine, valine, tryptophan, threonine, isoleucine, methionine, histidine, leucine, lysine) on muscle size and fat, as derived by MRI, in a sample from a population-based cohort.

Methods: The analysis is based on the KORA-MRI study, a sample from a population-based cohort including N=400 individuals who underwent 3T whole-body MRI [4]. Skeletal muscle was assessed on multi-echo Dixon sequences by a standardized, anatomical landmark-based segmentation. Muscle size was quantified as area in cm² and muscle fat as proton density fat fraction in % [5]. Habitual dietary intake was calculated based on repeated 24h recalls and a food frequency questionnaire. Multiple adjusted regression analyses were performed for exposure habitual intake and outcome muscle parameters, for the whole sample and sex-stratified.

Results: The final sample included N=294 participants (132 women) with a mean age of 56.5±9.0 years, and a mean BMI of 27.8±4.8 kg/m². Average MRI-derived skeletal muscle fat was 16.3±6.9% in women and 12.5±5.2% in men, and average muscle area was 69.7±12.1cm² in women and 98.1±14.6cm² in men. After scaling nutrients to % of total energy intake and adjustment for age, sex, BMI, physical activity and glycemia, there was no association of any nutrient with muscle area in the whole sample or in sex-stratified analyses. For outcome muscle fat, there was no association of carbohydrate intake or fat intake, in the overall sample or in sex-stratified analyses. Increased protein intake was associated with lower muscle fat in the overall sample (β=-0.34%, 95%-CI [-0.69%, 0.00%], p=0.052), but associations were attenuated in sex-stratified analyses. Increased alcohol intake was associated with higher muscle fat in the overall sample (β=0.31%, 95%-CI [0.14%, 0.48%], p<0.001) and in men (β=0.28%, 95%-CI [0.10%, 0.45%], p<0.001), but there was no significant association in women. There were tentative associations of increased intake of methionine (β=-0.50%, 95%-CI [-1.09%, 0.09%], p=0.096) and leucine (β=-0.63%, 95%-CI [-1.27, 0.01%], p=0.054) with decreased muscle fat in the overall sample.

Conclusion: In a sample from a population-based cohort, there was no association between habitual diet and imaging-derived muscle area. However, increased protein intake and increased intake of specific essential amino acids were associated with lower muscle fat, indicating better muscle quality. Increased alcohol intake was associated with higher muscle fat, particularly in men. Personalized diet adaptations with adequate protein intake might improve muscle health on a population-based level.

The authors declare that they have no competing interests.

The authors declare that a positive ethics committee vote has been obtained.