The effect of freeze dried whole raspberries on pain, joint flexibility, and inflammation in individuals with symptomatic knee osteoarthritis

Objective: The purpose of this study was to examine the effect of freeze dried whole raspberries on pain, joint flexibility, and inflammation in individuals with symptomatic knee osteoarthritis (OA).

Methods: In this double-blind and randomized trial, a total of 63 men and women were recruited and placed into either a treatment group (raspberry powder) or placebo group (powder without raspberry) for a period of 4 months. The raspberry group (n=34) was given 35 grams of freeze dried whole raspberry powder daily. Participants were instructed to mix the raspberry powder in 10-12 oz of water, and to consume it within 5 minutes. The placebo group (n=29) consumed 35 grams of placebo powder mixed with 10-12 oz of water. The placebo group was given a powder that was of similar appearance and energy content as the raspberry powder, but without the raspberry content. At baseline, midpoint (60 days), and final (120 days) visits, demographic data including height, weight, and blood pressure (systolic and diastolic) were obtained. At each study visit, participants filled out the Western Ontario McMaster Osteoarthritis Index (WOMAC) questionnaire to evaluate pain, stiffness, and difficulty in activity associated with knee OA. Range of motion testing was conducted using a goniometer during each study visit to assess joint flexibility. Additionally, an overnight fasting blood specimen was collected at each study visit to assess biomarkers of inflammation.

Results: A total of 44 participants completed the study with a drop-out rate of approximately 30%. No significant changes in weight or BMI were observed in either group. A significant decrease in systolic and diastolic blood pressure was seen among the raspberry group at final visit compared to baseline. No changes in systolic or diastolic blood pressure were noted in the placebo group. Total WOMAC score as well as its subgroups (pain, stiffness, and difficulty performing daily activities) were significantly decreased at final visit compared to baseline in the raspberry group. In the placebo group, a significant decrease in stiffness was observed at final compared to baseline. There were no significant changes in total WOMAC score or its subgroups between the two groups. There were no significant changes in overall ROM scores in the raspberry or placebo groups. At midpoint visit, right knee extension was significantly less in the raspberry group than in the placebo group. There was also a significant decrease noted in right knee extension in the raspberry group at midpoint compared to baseline. A significant decrease in left knee extension was observed in the raspberry group at midpoint compared to baseline. No differences were observed in right knee flexion. However, there was a significant increase in left knee flexion in the raspberry group at final compared to baseline. For inflammation, no significant changes were witnessed among the pro-inflammatory (TNF-α, IL1β, IL-6) or anti-inflammatory biomarkers (IL-10, IL-4, IL13). However, slight changes were noted in some of these biomarkers. There was a slight decrease in IL-6 concentrations in the raspberry group at final timepoint, although not significant. Additionally, there was a slight increase in IL-6 concentrations in the placebo group at final compared to baseline. There was a decrease in IL-10 concentration in both the raspberry and placebo group at final in comparison to baseline.

Conclusion: The findings of this study suggest that daily incorporation of whole raspberries can reduce pain, stiffness, and difficulty to perform daily activities. There was also a small, albeit not significant, improvement in joint flexibility in the knees. We did not observe any changes in the biomarkers of inflammation. Improvement in pain, stiffness, difficulty doing daily activities, and joint flexibility associated with consumption of raspberry may lead to an increase in overall quality of life in individuals with symptomatic knee OA.