Garlic Relieves Joint Stiffness in Knee Osteoarthritis in 12-week Study
Osteoarthritis (OA) is the most common joint disease worldwide. It causes considerable pain and debility. There is a need for low-cost, safe, effective therapies. The commonly prescribed medications do not provide adequate relief. The chronic nature of OA makes the costs and adverse effects of these medications particularly problematic. The mechanisms of pain and dysfunction in OA are multifactorial. Natural products, therefore, have the possibility of affecting multiple aspects of the disease process. Garlic (Allium sativum, Amaryllidaceae) has a long history of use for many conditions. There is a robust body of evidence supporting its use as an anti-inflammatory therapy. Constituents of garlic have several known bioactivities, including cytokine modulation, immune cell stimulation, antioxidant action, and analgesic effects, that could affect OA. However, research on the use of garlic in OA has been limited. This paper investigates the use of garlic in overweight or obese women with knee OA; obesity increases the risk of OA, and increased weight is associated with greater OA pain.
This single-center, randomized, double-blind, placebo-controlled, parallel-design study involved eighty female patients with mild or moderate knee OA who were recruited from the Sina Hospital Rheumatology Clinic in Tehran, Iran. The included patients were 50-75 years old, postmenopausal, and had a body mass index (BMI) between 25 and 40. Exclusion criteria were severe pain; scheduled for surgery; receiving intra-articular therapies in previous three months; allergic to garlic; diabetes or other endocrine or chronic disorder; on a weight-loss protocol; smoker; or using hormone replacement therapy, non-steroidal anti-inflammatory drugs (NSAIDs), other analgesics, chondroitin sulfate, omega-3 fatty acids, warfarin, or other anticoagulants.
Patients were randomly assigned to one of two groups. The intervention group received 12 weeks of 1,000 mg odorless garlic tablets (500 mg twice daily), containing 2.5 mg allicin. The placebo group received identically shaped lactose tablets. To check compliance, patients were asked to return the tablet boxes at monthly clinic visits for pill counting.
The primary outcome was the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain subscale score. The WOMAC is a questionnaire with the three following subscales: pain, stiffness, and physical function. Anthropometric indices were also quantified and analyzed. These measures included height, weight, waist circumference, hip circumference, BMI, fat mass, fat percentage, and fat-free mass. Mean dietary energy and protein intake were obtained using three-day dietary recall. Patients were asked to maintain their usual diet and physical activity, but to exclude garlic from the diet during the study period. The researchers explain that garlic is not commonly consumed in food in the region of the study, due to cultural and odor issues.
All statistical tests used to analyze the collected data were two-sided, and a P value of < 0.05 was considered statistically significant. The normal distribution of variables was assessed using the Kolmogorov-Smirnov test. Baseline differences between the two groups were assessed by t-test, Mann-Whitney, or chi-square tests, as appropriate. Analysis of covariance (ANCOVA) was used at the end of the study to assess differences between the two groups, and within-group change over time with t-tests or Wilcoxon signed rank test, as appropriate…
Seventy-six patients completed the study. One patient in the garlic group withdrew due to gastrointestinal symptoms. Three patients in the placebo group were excluded – two used NSAIDs during the study, and one did not attend laboratory tests.
Mean and median values for the anthropometric and body composition means did not significantly differ between groups either before or after the intervention. Weight and BMI declined significantly during the study period (all P values <0.05) in both the placebo and garlic groups and fat-free mass in the garlic group. However, the average weight and BMI losses were quite small and the researchers consider them to be clinically insignificant.
WOMAC total score and all three subscale scores improved numerically in both groups. Some of these improvements over baseline were statistically significant within both groups, more so in the garlic group. The only statistically significant difference between the two groups was in the final WOMAC stiffness subscale, for which the garlic group had a lower score (P = 0.023). Additionally, scores in the stiffness subscale significantly declined only in the garlic group. However, the change in mean stiffness subscale score during the study (1.0 in the garlic group, 0.2 in the placebo group) was not significantly different between the two groups. The WOMAC pain subscale actually decreased slightly more in the placebo group than in the garlic group (difference not statistically significant). A post hoc analysis showed that the study had a 64% power to detect a clinically significant 2-point difference between the two groups.
OA pain is very responsive to placebo, with a reported effect size of 0.51. Its symptoms are also affected by psychological distress, a factor for which this study did not control. The researchers state that there is a need for further research on garlic for OA, as well as into the role of the placebo effect in the management of OA symptoms.
In summary, 12-week garlic supplementation may have improved knee OA symptoms in overweight or obese women, but the results were for the most part not statistically different from placebo.
The authors report no conflicts of interest.
Salimzadeh A, Alipoor E, Dehghani S, et al. The effect of 12‐week garlic supplementation on symptom relief in overweight or obese women with knee osteoarthritis. Int J Clin Pract. December 2018;pii: S1063-4584(18)31582-6. doi:10.1111/ijcp.13208.