Effects of vitamin D3 on glucose metabolism in patients with severe osteoarthritis: A randomized double‐blind trial comparing daily 2000 with 800 IU vitamin D3

Abstract

To investigate the effect of daily 800 versus 2000 IU of vitamin D3 supplementation over 24 months on glycaemic control in older adults after unilateral knee replacement. The Zurich Multiple Endpoint Vitamin D Trial in Knee OA Patients was a randomized, double-blind trial conducted from 2008 to 2014 in Zurich, Switzerland. Participants were randomly allocated to 800 or 2000 IU vitamin D3 daily for 24 months. This study investigates the predefined secondary endpoints of fasting blood glucose (FBG) and homeostatic model assessment for insulin resistance (HOMA-IR) using linear mixed models adjusted for age, sex, baseline vitamin D deficiency and body mass index. A total of 251 participants (age 70.2 ± 6.5 years; 55.4% women; 39% impaired glucose tolerance, mean 25-hydroxyvitamin D 27.48 ± 12.48 ng/mL, mean FBG 5.49 ± 0.71 mmol/L) were included in this analysis. There was no significant difference in FBG between the group receiving 800 versus 2000 IU after 2 years with a least square mean (95% CI) of 5.32 (5.19; 5.44) versus 5.39 (5.27; 5.51) mmol/L (ptreat = .130) and no difference in HOMA-IR (0.44 [0.37; 0.52] vs. 0.49 [0.41; 0.58]; ptreat = .162), respectively. However, FBG decreased significantly over time independent of vitamin D3 dose (800 IU: 5.54 [5.42; 5.66] to 5.32 [5.19; 5.44], ptime < .001; 2000 IU: 5.5 [5.38; 5.62] to 5.39 [5.27; 5.51] mmol/L, ptime = .019). There was no clinically meaningful difference between 800 and 2000 IU of vitamin D3 over 2 years in FBG or HOMA-IR in community-dwelling older adults. Glycaemic outcomes improved in both groups.