Cross-sectional associations of dietary and circulating magnesium with skeletal muscle mass in the EPIC-Norfolk cohort

Background: Maintenance of skeletal muscle in older age is critical to reducing frailty and the risk of falls and fractures. Nutrition has established importance for muscle health in general, but less research has looked at associations of dietary intake of specific micronutrients on skeletal muscle mass in older adults. Aims: This study aimed to investigate the influence of dietary and circulating magnesium on skeletal muscle mass in a UK population of 14,340 middle to older-aged men and women participating in the EPIC-Norfolk cohort study. Methods: Dietary nutrient intakes were estimated from 7-day food diaries and fat-free mass (FFM) by bioelectrical impedance analysis. Multivariable regression was used to investigate associations of FFM-based indices of muscle mass with quintiles of dietary magnesium intake or serum magnesium concentration groups. All analyses were stratified by sex, and regression models were adjusted for relevant covariates. Results: Significant positive trends in FFM measures were evident across magnesium dietary intake quintiles for both sexes (all p < 0.001; n = 6350 men; n = 7990 women) and both <60 and >= 60 year olds, with all-age quintile 5 versus quintile 1 maximal differences of 4.6% in men and 6.3% in women; highly relevant compared to the estimated 1% decline per year after 40 years of age. These observations were not reflected in serum magnesium analyses, where no consistent trends were found across the skeletal muscle mass indices tested. Conclusion: Further investigation will be required to improve our understanding of the relationship between serum magnesium concentration and skeletal muscle mass. However, this study has demonstrated strong associations between dietary magnesium intake and indices of skeletal muscle mass in a UK population of middle to older-aged adults, highlighting the likely importance of dietary magnesium for optimal muscle health in this population. (C) 2018 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.