Background:The role of magnesium in maintaining muscle integrity and function in older adults is largely unknown. Objective: We aimed to investigate the relation between serum magnesium concentrations and muscle performance in older subjects. Design: Data are from the baseline examination conducted between September 1998 and March 2000 of the InCHIANTI (aging in the Chianti area) study, a prospective epidemiologic survey of risk factors for late-life disability. From among 1453 randomly selected community residents completing a home interview, 1138 men (46%) and women (aged 66.7 Ȁ 15.2 y; x Ȁ SD) with complete data on muscle performance and serum magnesium who were not severely cognitively compromised and had no evidence of kidney disease or hypercalcemia were included in the analysis. Muscle performance was evaluated by grip strength, lower-leg muscle power, knee extension torque, and ankle extension isometric strength and was normalized for age and body mass index (BMI) within each sex. Results: After adjustment for age, sex, BMI, laboratory variables, presence of chronic diseases, muscle area, muscle density, and physical activity level, serum magnesium concentrations were significantly associated with indexes of muscle performance, including grip strength (␤ ҃ 2.0 Ȁ 0.5, P ҃ 0.0002), lower-leg muscle power (␤ ҃ 8.8 Ȁ 2.7, P ҃ 0.001), knee extension torque (␤ ҃ 31.2 Ȁ 7.9, P 0.0001), and ankle extension strength (␤ ҃ 3.8 Ȁ 0.5, P 0.0001). Conclusions:The serum magnesium concentration is an independent correlate of muscle performance in older persons. Whether magnesium supplementation improves muscle function remains to be shown.Am J Clin Nutr 2006;84:419 -26.

A fast (15 min) and simple HPLC method for determination of all-trans-retinol and alpha-, gamma- and delta-tocopherols in human plasma has been developed. The assay utilized 200 microl of plasma to which 20 microl of internal standard solution (retinol acetate) was added followed by 200 microl of water, 400 microl of ethanol and 800 microl of hexane. The hexane layer was collected, evaporated, the residue dissolved in 200 microl of methanol and analyzed on a Zorbax Eclipse XDB-C18 column using a step gradient with a polar organic mobile phase composed of acetonitrile and methanol and variable wavelength fluorescence detection. The quantification limits for all-trans-retinol and gamma-tocopherol were 20 ng/ml and for alpha- and delta-tocopherols 500 ng/ml and 10 ng/ml, respectively. The procedure was validated and applied to the analysis of plasma samples from the Baltimore Longitudinal Study of Aging.

The serum magnesium concentration is an independent correlate of muscle performance in older persons. Whether magnesium supplementation improves muscle function remains to be shown.