Vitamin d supplementation and physical performance in knee osteoarthritis patients

Abstract

Osteoarthritis (OA) is a common cause of musculoskeletal disability and pain worldwide. Low vitamin D status and OA were related with an accelerated decline in muscle quality. The purpose of this study was to determine the efficacy of vitamin D supplementation on muscle mass, muscle strength, and physical performance in knee OA patients with low vitamin D status. Firstly, this study aimed to evaluate the prevalence of vitamin D deficiency and sarcopenia in knee OA patients. A total of 238 knee OA patients were enrolled. Body composition, muscle strength, physical performance, metabolic profile, serum 25-hydroxyvitamin D (25(OH)D), leptin, interleukin-6 (IL-6), parathyroid hormone (PTH), and protein carbonyl were evaluated. Our study showed that knee OA patients had highly prevalent vitamin D insufficiency (49.60%), vitamin D deficiency (33.60%) and vitamin D sufficiency (16.80%). Moreover, the prevalence of sarcopenia in knee OA patients using the Asian Working Group for Sarcopenia (AWGS) criteria demonstrated that 10.10% was sarcopenia, 12.60% and 77.40% were pre-sarcopenia, and non-sarcopenia, respectively. Knee OA patients with vitamin D deficiency were younger, lower knee extension force, higher levels of low-density lipoprotein (LDL) cholesterol, triglyceride, PTH, IL-6, and protein carbonyls than vitamin D sufficiency group but physical performance was not different among three groups.

Secondly, we further determined the efficacy of vitamin D2 supplementation in knee OA patients with low vitamin D status (< 30 ng/ml). One hundred seventy-five knee OA patients with low vitamin D status were received 40,000 IU vitamin D2 (ergocalciferol) per week for 6 months. Baseline mean serum 25(OH)D in knee OA patients was 20.73 ng/ml. After vitamin D2 supplementation for 6 months, mean serum 25(OH)D was increased to 32.14 ng/ml, while mean LDL cholesterol, protein carbonyl, and PTH were all significantly decreased. Quality of life (SF-12) and pain (visual analog scale) were both significantly improved from baseline. Knee OA patients demonstrated the significant increasing grip strength and improvement for all physical performance measurements after vitamin D2 supplementation. In conclusion, vitamin D2 supplementation for 6 months reduced oxidative protein damage and pain while improved quality of life, grip strength and physical performance in knee OA patients.