Vitamin D or fish oil supplementation failed to relieve chronic knee pain in older adults. This was the result of a secondary analysis of the data from the large randomized VITAL trial.
At baseline, the Universities of Western Ontario and McMaster (WOMAC) 100-point arthritis index pain scores were 35.4 for patients receiving vitamin D and 36.5 for those receiving placebo. At the time of the last follow-up visit after more than 5 years, the mean WOMAC pain scores in both groups were 32.7 and 34.6, respectively, and at no point during the study was there a statistically significant difference in pain scores between vitamin D. and placebo -Groups, reported Dr. Lindsey Adair MacFarlane of Brigham and Women’s Hospital in Boston and colleagues.
As shown in their online study on Arthritis & Rheumatology, WOMAC pain scores in patients randomized to receive marine omega-3s or placebo were 36.5 and 35.4 at baseline. At the last follow-up, the pain scores were 33.6 in the fish oil group and 33.7 in the placebo group, and at no time were there any significant differences in pain scores between the two groups.
“A small decrease in reported knee pain was observed over the 5.3 year follow-up period. However, this occurred in both the treatment and placebo groups and may indicate regression of the mean and some loss of total knee replacement participants be due. ” The researchers wrote.
An estimated a quarter of older adults experience knee pain, which is usually related to osteoarthritis. However, current treatment options only include exercise, weight loss, and analgesics, which are often associated with side effects, explained MacFarlane and co-authors. “Identifying safer and more cost-effective therapies that reduce pain could greatly improve the management of chronic knee pain.”
Two promising candidates were vitamin D due to its anti-inflammatory effects and its role in muscle strength and bone resorption, and fish oils, which also have anti-inflammatory properties and protect against cartilage loss. However, previous studies have shown conflicting and confusing results.
For example, in a 2-year study of patients with symptomatic knee osteoarthritis and low vitamin D levels, there was no difference between vitamin D supplementation or placebo in WOMAC pain scores, but post hoc analysis found benefits on the subscale of the WOMAC function.
Another study compared high-dose and low-dose fish oil in symptomatic knee osteoarthritis over a period of 24 months and found improvements in WOMAC pain and function scores for the low-dose group. However, the fish oil supplement used also contained sunola oil, which may skew the results.
To further answer the question of the potential benefits of these treatments, the MacFarlane group analyzed data from VITAL (VITamin D and OmegA-3 study), a large population-based study that assessed the effects of vitamin D and omega fatty acids were. 3 fatty acids in primary prevention of cancer and cardiovascular diseases.
VITAL enrolled and randomized more than 25,000 US adults aged 50 and over as of 2011 to receive vitamin D3, 2,000 IU / day; Omega-3 fatty acids (Omacor), 1 g / day; or placebo. The study was completed in late 2017. The primary results were published in late 2018.
Within the larger cohort there was a subgroup of 1,398 participants who reported frequent chronic knee pain at the start of the study and who were “very likely” to suffer from knee osteoarthritis and who filled out an annual questionnaire on knee pain at the start of the study and thereafter.
In addition to the pain scores, participants also rated the stiffness and function of these WOMAC subscales and reported the type and frequency of drugs used.
At the start of the study, the average age of the participants was 68 years, two thirds were women and the average body mass index (BMI) was 31.8 years. The majority reported daily knee pain, unilateral symptoms, and daily or occasional use of nonsteroidal anti-inflammatory drugs (NSAIDs). About 15% also used analgesics, including opioids, occasionally or daily.
As with pain scores, no differences in WOMAC stiffness or functional scores for vitamin D or fish oil were found during follow-up. In addition, the hazard rates compared to placebo were 0.97 (95% CI 0.78-1.22) for vitamin D and 0.99 (95% CI 0.79-1.24) for fish oil. There was also no change in the use of analgesics or NSAIDs during the study.
Subgroup analyzes based on the baseline vitamin D value and omega-3 fatty acid index had no influence on the effect of the treatment on knee pain, or on breed, BMI or demersal fish consumption.
This analysis suggests “that supplementation with vitamin D or omega-3 fatty acids has no role in treating symptomatic knee pain due to osteoarthritis,” the authors concluded.
One limitation of the study is the lack of radiological data.
Last updated on June 26, 2020
The authors reported on financial relationships with Flexion Therapeutics, Samumed, Amgen, Janssen, Pharmavite and the Swedish Rheumatism Foundation.