Does Magnesium Supplementation Improve Body Composition and Muscle Strength in Middle-Aged Overweight Women? A Double-Blind, Placebo-Controlled, Randomized Clinical Trial Nazanin Moslehi & Mohammadreza Vafa & Javad Sarrafzadeh & Abbas Rahimi-Foroushani Received: 19 January 2013 / Accepted: 14 April 2013 / Published online: 26 April 2013 # Springer Science+Business Media New York 2013 Abstract Muscle strength, an independent predictor of met- abolic disorders, disability, and mortality, reduces gradually with advancing age. Little is known about the influence of nutritional intervention on muscle strength in middle-aged. The aim of the present study is to examine whether magne- sium could improve body composition and muscle strength in middle-aged overweight women. In this double-blinded, placebo-controlled, randomized trial, a total of 74 healthy middle-aged overweight women (25 ≤ BMI ≤ 30 kg/m 2 ) re- ceived either 250 mg magnesium in the form of magnesium oxide or placebo daily for 8 weeks. Body composition was assessed using Bioelectrical Impedance Analysis (BIA). Handgrip strength and knee extension strength were mea- sured with isometric dynamometry. Functional mobility was assessed using Time Get Up and Go Test (TGUG). A significant increase in mean lean body mass was observed (P=0.05) accompanied with a significant decrease in fat mass (P=0.02) solely in the magnesium group at the end of 8 weeks compared to baseline values but the changes did not reach significant as compared to placebo group. Hand- grip strength and TGUG improved in the magnesium group compared to baseline but they were not significant com- pared to placebo. There were no significant differences in increasing knee extension strength in the magnesium group as compared with placebo. Baseline values of serum mag- nesium and muscle strength of participants did not indicate any influences on response to magnesium supplementation. Our findings indicate that magnesium as magnesium oxide, 250 mg/day, for 8 weeks do not lead to a significant greater gain in muscle strength and function compared to placebo. Keywords Magnesium . Muscle strength . Sarcopenia . Body composition Introduction Muscle strength is considered as an indicator of functional and nutritional status, which can predict osteoporotic frac- ture [1, 2], disability, and all-cause mortality in middle-aged and elderly [3–5]. Muscle strength has also been found to be a strong predictor of metabolic syndrome, independent of age, body size, insulin resistance, and abdominal fat [6–8], suggesting that interventions designed to prevent metabolic disorders should develop to improve muscle fitness in addi- tion to reducing fatness. Aging is generally accompanied by the gradual loss of muscle strength and muscle mass, leading to functional impairments, disability, and metabolic consequences [9, 10], which exert a significant burden on both individuals N. Moslehi : M. Vafa (*) Department of Nutrition, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran e-mail: mrvafa@tums.ac.ir M. Vafa Endocrine Research Center, Firouzgar Hospital, Tehran University of Medical Sciences, Tehran, Iran J. Sarrafzadeh Department of Physical Therapy, School of Rehabilitation Sciences, Tehran University of Medical Sciences, Tehran, Iran A. Rahimi-Foroushani Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Biol Trace Elem Res (2013) 153:111–118 DOI 10.1007/s12011-013-9672-1