Vitamin D and omega-3 unwarranted for pain reduction in knee osteoarthritis
medwireNews: Vitamin D and marine omega-3 fatty acid supplements are unlikely to improve chronic knee pain associated with osteoarthritis (OA), suggests an analysis of the randomized VITAL trial.
As reported in Arthritis & Rheumatology, the analysis included 1398 trial participants (mean age 67.7 years) with chronic knee pain, considered “highly likely” to have knee OA, who had received vitamin D (cholecalciferol 2000 IU/day), omega-3 (Omacor® 1 g/day and 840 mg eicosapentaenoic acid and docosahexaenoic acid in a 1.3:1.0 ratio), or placebo as per the random assignment.
During a mean 5.3 years of follow-up, there were no significant differences in WOMAC pain scores at any timepoint between the 674 patients in the vitamin D group and the 724 in the placebo group. This was also the case for the 695 patients given omega-3 and their 703 counterparts who were instead given placebo.
WOMAC pain scores decreased slightly over the follow-up period, but this occurred in all groups, and “may reflect regression to the mean and some loss of participants to [total knee replacement],” according to Lindsey Macfarlane (Brigham and Women’s Hospital, Boston, Massachusetts, USA) and team.
They note that men (44% of the study participants) taking vitamin D derived “a nominally statistically significant” benefit of the supplement over time, but the least squared mean WOMAC pain scores differed only at the last follow-up, being 4.5 points lower in the vitamin D than placebo group.
Moreover, Macfarlane and colleagues say that “this difference is unlikely to be clinically meaningful” and point out that there was no association between pain score and sex overall.
Further analysis of WOMAC scores revealed that neither vitamin D nor omega-3 significantly improved knee function or stiffness compared with placebo. And total knee replacements, indicative of severely symptomatic knee OA, were no less likely to occur among patients taking vitamin D or omega-3 as they were among those taking placebo.
Macfarlane et al conclude: “These results are in agreement with past smaller randomized [controlled] trials and suggest that supplementation of vitamin D or [omega-3 fatty acid] does not have a role in the management of symptomatic knee pain due to osteoarthritis.”
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