The effects of intermittent vitamin D3 supplementation on muscle strength and metabolic parameters in postmenopausal women with type 2 diabetes: a randomized controlled study.

Abstract

The aim of this study was to evaluate the effect of weekly vitamin D3 supplementation on metabolic parameters and muscle strength of postmenopausal women with type 2 diabetes. A total of 38 patients with serum 25-hydroxy vitamin D [25(OH)D] below 30 ng/ml and hand strength below 20 kg were randomly assigned to oral vitamin D3 (6600 IU/week in 2 cc oil preparation) or 2 cc olive oil weekly for 3 months. There were nonsignificant increases in serum 25(OH)D in the intervention group to 22.98 ± 4.23 ng/ml and nonsignificant decreases in the control group to 22.84 ± 3.88 (26% of the intervention and 48% of the control groups had 25(OH)D < 20 ng/ml). Handgrip strength improved significantly in the intervention group (right arm 17.4 ± 2.68 to 19.9 ± 3.53 kg, p = 0.002; left arm 16.31 ± 2.6 to 18.46 ± 3.2 kg, p < 0.001) but not in the control group (right arm 16.87 ± 3.99 to 17.93 ± 4.91 kg, p = 0.1; left arm 16.13 ± 4.29 to 16.86 ± 4.79 kg, p < 0.2). More patients in the control group became obese at the end of the study period (p = 0.014). There were no significant changes in mean fasting glucose, glycated haemoglobin (HbA1c), serum triglycerides and blood pressure with vitamin D supplementation. Systolic blood pressure increased significantly in the control group from 136.6 ± 18.6 to 141.4 ± 17.6 mmHg, p = 0.04). Vitamin D3 supplementation in doses equivalent to 942 IU/day improved isometric handgrip strength, but had no effect on glycaemic control in postmenopausal women with longstanding type 2 diabetes.