Zeng L, Yang T, Yang K, et al. Efficacy and safety of curcumin and Curcuma longa extract in the treatment of arthritis: A systematic review and meta-analysis of randomized controlled trial. Front Immunol. July 22, 2022;13:891822. doi: 10.3389/fimmu.2022.891822.
Arthritis is characterized by chronic inflammation of one or more joints, causing pain that is often disabling. It is related to degenerative diseases and autoimmunity. More than 100 different forms of arthritis have been identified. Of those, osteoarthritis (OA) and rheumatoid arthritis (RA) are most common. These have different etiologies but share common symptoms including pain and limited mobility resulting from joint inflammation. RA is a systemic inflammatory and destructive autoimmune disease. Without intervention, it can lead to joint deformity and loss of function. Analgesics, steroids, non-steroidal anti-inflammatory drugs (NSAIDs), and biologically targeted drugs are used as standard treatment to reduce pain and inflammation. However, side effects from these interventions prevent sustained relief. Turmeric (Curcuma longa, Zingiberaceae) has a rich history in traditional medicine with demonstrated benefits against arthritis. Curcumin is the main constituent in turmeric. Studies have shown curcumin to have anti-inflammatory, immunosuppressive, and anticancer properties. Some evidence has shown that curcumin may reduce subjective pain in patients diagnosed with muscle-related disease. The purpose of this systematic review and meta-analysis was to determine the efficacy of turmeric and curcumin for symptoms management in patients diagnosed with arthritis.
Preferred reporting items for systematic reviews and meta-analysis (PRISMA) guidelines were followed. A literature search was performed using Web of Science, Cochrane Library, PubMed, ClinicalTrials.gov, China Biology Medicine (CBM), VIP Database, China National Knowledge Infrastructure (CNKI), MEDLINE Complete, Wanfang Database, and Embase. Randomized controlled trials (RCTs) were included from inception through February 2022. Studies were included that were conducted on patients diagnosed with any type of arthritis that used curcumin as the intervention. No restrictions were placed on dosage, form, and usage. Control groups that used a placebo or conventional therapy were included. Studies were required to evaluate one or more of the following outcomes: efficacy indicators, inflammatory indicators, and adverse events.
Titles and abstracts of 1982 articles were screened following removal of duplicates. Of those, 1944 were excluded. The remaining 37 full-text articles were assessed for eligibility. Seven were excluded with reasons (not disclosed). Thirty were included in this review and meta-analysis. Five types of arthritis were evaluated including RA, OA, ankylosing spondylitis (AS), juvenile idiopathic arthritis (JIA), and gout/hyperuricemia. Studies were conducted in Iran, India, China, Australia, Belgium, Armenia, Indonesia, Thailand, Japan, Italy, and Romania. The interventions included curcumin, curcuminoids, and turmeric. Preparations, doses, and extracts were different. Three studies evaluated high-dose and low-dose groups. One study evaluated curcumin (500 mg) and curcumin (500 mg) plus diclofenac sodium (50 mg). Samples sizes ranged from 20 to 200 patients (pooled sample size was not disclosed).
Nine studies showed an unclear risk of selection bias. Eight had an unclear risk of allocation concealment bias. Eleven were shown to have an unclear risk of performance bias, and four had a high risk. One study was shown to have a low risk for detection bias, but high risk for performance bias. Another study showed the opposite: low risk for performance bias and high risk for detection bias. Only two articles were shown to have an unclear risk of reporting bias. Finally, nine studies were rated with a high risk of bias due to competing conflicts of interest.
The RCTs evaluating RA showed significant benefits of curcumin for disease activity score (DAS28; P < 0.0001), erythrocyte sedimentation rate (ESR; P < 0.0001), C-reactive protein (CRP; P = 0.0005), and rheumatoid factor (RF; P < 0.00001). Significant differences were not observed for tender joint count and swollen joint count. There were no significant differences in adverse events between the experimental group and control group.
Efficacy of treatment for OA included pain indicators, physical function, and stiffness. The visual analogue scale (VAS) and Western Ontario and McMaster University Arthritis Index (WOMAC) were used. Curcumin was shown to significantly decrease pain compared to the control (VAS: P < 0.0001; WOMAC: P < 0.00001). Curcumin significantly improved physical function (WOMAC: P = 0.001) and stiffness (P = 0.0007). A significant difference was observed for ESR (P < 0.0001), minimal disease activity (MDA; P = 0.02), and superoxide dismutases (SOD; P < 0.001). No adverse events were observed in either group.
One study reported on AS in a study with 12 patients. The treatment group received nanocurcumin. A significant increase in Treg cells, and interleukin (IL)-10 and transforming growth factor-beta (TFG-ß) levels, as well as a significant decrease in IL-6 levels were observed in the experimental group compared to the control group. Nanocurcumin significantly decreased expression of microRNA (miR)-17 and miR-27 (P < 0.05).
Two studies evaluated curcumin for JIA. One study compared patients between the ages of 8 and 16 years who received 600 mg of curcumin three times a day to a control. Significant improvements in American College of Rheumatology Pediatric 30 (ACR Pedi 30), ACR Pedi 50, ACR Pedi 70, and ACR Pedi 90 were observed (P < 0.05 for all). The other study compared curcumin (1200 mg) plus blue laser and found a decrease in the Disease Activity Score (JADAS-71) and an increase in their functional activities of daily living using the childhood health assessment questionnaire (CHAQ) when compared to a placebo. Only one study examined the effects of curcumin on gout/hyperuricemia. The results were not significant.
Limitations of this review include limited sample size and that only articles in English and Chinese were included. Some studies showed a high risk of bias, and the review did not account for omissions in the collection of documents and data extraction by the researchers. Curcumin and Curcuma longa extract showed safety in all studies, and the authors conclude that curcumin and turmeric “may improve symptoms and inflammation levels in people with arthritis.” They caution that while the data show significant improvements in outcome measures, the results should be interpreted carefully. Further investigations are needed to verify the claims of this systematic review and meta-analysis.
There was statistical heterogeneity.
The authors declare no conflict of interest.