Effects of oral creatine supplementation on body composition and objective physical function in rheumatoid arthritis patients. A randomised controlled trial

Objective: Muscle wasting (‘rheumatoid cachexia’) is evident in most rheumatoid arthritis (RA) patients, including those with well-controlled disease, and contributes substantially to the reductions in strength and physical function that are characteristic of this disease. The aim of this randomized controlled trial was to investigate the efficacy of oral creatine (Cr) supplementation on improving muscle mass, strength and function in stable RA patients. Method: Forty RA patients were randomized to 12 weeks supplementation of Cr or placebo, in a double-blind fashion. Body composition (by whole-body dual-energy X-ray absorptiometry, DXA, and bioelectrical impedance spectroscopy, BIS), strength and objectively-assessed physical function measures were taken at baseline, week 12, and week 24 (i.e. after 12 weeks of treatment withdrawal). Data was analyzed by ANCOVA. Results: Cr supplementation increased appendicular lean mass (ALM; a surrogate DXA measure of muscle mass) by (mean±SE) 0.52±0.13kg (P=0.004 vs placebo), and total LM by 0.60±0.37kg (P=0.158 vs placebo). The increment in LM by DXA corresponded with the elevation in intracellular water (ICW) estimated by BIS (0.64±0.22 L, P=0.035 vs placebo). However, the observed increases in ALM, total LM and ICW were not accompanied by improvements in isometric knee extensor strength (P=0.408), hand-grip strength (P=0.833), or objectively assessed function (30s sit-to-stand, 50’ walk, 8’ up-&-go, estimated VO2max; P’s=0.335-0.764) Conclusion: Twelve weeks of Cr supplementation improved muscle mass, but not strength or objectively-measured physical function in RA patients. As no adverse treatment-related effects occurred, Cr supplementation appears to be a safe and acceptable adjunct treatment for attenuating muscle loss in RA patients. This treatment may be especially suitable for patients with severe rheumatoid cachexia.