Vitamin D, fish oil supplementation of no benefit to adults with chronic knee pain

Long-term supplementation of vitamin D and marine omega‐3 fatty acids (n‐3 FA) in adults with chronic knee pain turns out to be fruitless, yielding no favourable effect on knee pain, function, or stiffness, as shown in a study.

The study involved adults who self-reported knee pain symptoms in walking 2–3 blocks and experienced pain >1 day/week for more than a year. They were randomized to vitamin D3 (cholecalciferol; 2,000 IU/day), n-3 FA (1g/d, 840 mg eicosapentaenoic acid and docosahexaenoic acid), or placebo in a two-by-two factorial design. Researchers administered follow-up questionnaires at 6 months and then annually.

A total of 1,398 participants (mean age, 67.7 years; 66 percent were female) completed at least one knee pain questionnaire and were included in the analysis. Mean Western Ontario and McMaster Universities Arthritis Index (WOMAC; 0–100; 100 indicated worst) pain score was 37. Mean follow‐up time was 5.3 years.

WOMAC pain scores did not differ between vitamin D or n‐3 FA and placebo at any time point during follow‐up. No significant treatment interaction was observed for either supplement (vitamin D, p=0.41; n‐3 FA, p=0.77), and neither did WOMAC function and stiffness scores improve over time.

Finally, supplementation with either vitamin D or n-3 FA did not reduce the incidence of total knee replacement compared with placebo, and there were no changes observed in the use patterns of analgesics including opioids.