Literature Review of Scientific Evidence to Determine the Efficacy of the Use of Curcumin in Treating the Symptoms of Osteoarthritis

by Katie Pinnick

Introduction

This literature review compiles and evaluates scientific evidence of the historical and modern therapeutic use of curcumin to assist in answering the question – Is curcumin effective in treating osteoarthritis?

Osteoarthritis (OA) is a degenerative condition affecting the weight-bearing joints, which results in inflammation of the joint cartilage and ultimately destroys the cartilage. The condition can be painful and debilitating (Australian Bureau of Statistics). In 2015 arthritis (including osteoarthritis, rheumatoid arthritis and gout) cost the health system in Australia $5.5 billion. It is estimated that this will rise to $7.6 billion by 2030 (Arthritis Australia). As Australia has an ageing population, there is a need to source evidence-based natural therapies to be used in it’s treatment.

Curcumin is the naturally occurring chemical compound found in the rhizomes of the turmeric plant (curcuma longa). It has been shown to have an anti-inflammatory effect on the body due to it’s ability to modulate multiple cell signalling pathways (Tomoko K, Shinsuke II, Hiroshi S, Hidehiko K, and Haruo S, 2014). Curcumin has a long history of therapeutic use and wide use in traditional medicine in China and India (Patwardhan B, Warude D, Pushpangadan P, and Bhatt N, 2015). Gosh at al (2015) highlight the fact that curcumin has been used therapeutically for thousands of years and over 7000 articles have been published discussing it’s applications. One limitation of curcumin to be considered is it’s low bioavailability. Suggestions by Gosh et al (2015) for enhancing the bioavailability include conjugation and encapsulation with lipid particles.

Five scientific studies published between 2009 and 2018 will be used to determine the efficacy of curcumin in the treatment of osteoarthritis. A literature search was conducted on PubMed, Cochrane and Google Scholar using the key search terms turmeric, curcumin, curcuma, curcuma longa and osteoarthritis and inflammation. Articles had to be in peer-reviewed scientific journals and published in English. The majority of articles were excluded because they either not peer-reviewed, full text was not available, they did not assess efficacy or they were animal studies.

Table 1. Summary of Reviewed Articles

Main Body

The studies evaluated fall into 5 categories which limits the ability to draw conclusions regarding comparative efficacy:

• Pharmaceutical formulation vs placebo
• Herbal extract vs pharmaceutical drug (conventional medicine)
• Nutraceutical formation vs placebo
• Nutraceutical formulation vs pharmaceutical drug
• Pharmaceutical formulation vs nutraceutical formulation

Four out of the five studies assessed reported a positive result for the use of curcumin or a curcumin formulation, however one (Kizhakkededath, R. 2013) needs to be discounted as the author’s conclusion was contradictory to the actual findings of the study. Only two of the studies used the WOMAC (Western Ontario and McMaster universities osteoarthritis) Index. A more accurate comparison could have been made if this had been used for all studies.

The most thorough study evaluated by this author was that by Haroyan, A., et al (2018). It involved a well organised and measured research design. This study highlights the potential of increasing curcumin’s effectiveness when combined with other herbs – in this case boswellic acid and suggest it is due to the synergistic effects of curcumin and boswellic acid. The thoroughness of this study is highlighted by the fact that it tested for both reductions in pain and reductions in inflammation. When reporting on the participant eligibility the authors state that participants were recruited from patients who visited two listed medical centres. This fact could affect the randomisation of the group. The study states that boswellic acid has itself got anti-inflammatory properties so it is hard to assess how much influence that herb has on the overall effect of the formulation compared to curcumin alone.

Although the study by Kuptniratsaikul, V., et al. 2009 reported similar efficacy for both it is noted that this study was only conducted for 6 weeks. The safety aspect of long-term use of ibuprofen would need to be considered if a longer trial were to be undertaken. Also to be noted is the reported fact that compliance of drug intake in the ibuprofen group was higher than in the curcuma domestica group. That was attributed to the twice daily dose for ibuprofen compared with the four times daily for the curcuma domestica. This highlights the need for consistent dosages to enable exact comparisons. Although the findings reported similar efficacy for both groups, the study also stated that more subjects evaluated themselves with moderate to high satisfaction in the curcuma domestica group than in the ibuprofen group. This is a finding that should bear more weight as a perception of an improvement of symptoms has merit. Although a relatively thorough study, a larger sample size would be more useful. In addition, the study had an extensive exclusion criteria which in turn decreases the external validity of the trial.

The study by Nakagawa, Y., et al 2016 had a significant positive outcome but involved a small sample size and allowed combined relief therapy of pain patches, making it difficult to draw any scientific conclusions about the merits of curcumin.

The study conducted by Kizhakkededath, R., et al. 2013 involved a very small sample size and the authors conclusion was contradicting the findings, rendering it difficult to make conclusions from. The external validity of the trial is decreased here also, due to the extensive exclusion criteria.

In comparison to these two above mentioned studies, the one conducted by Belcaro, G., et al. 2014 used a more relevant sample size of 124 but then lacked randomisation of this sample. In addition, this study was observational (although the WOMAC index was applied, its results were used in conjunction with evaluations from both the investigator and the patient) which leads to less methodological control over results.

Conclusion

Despite the overall poor quality of most of the studies assessed, three out of five studies reviewed suggest that curcumin has potential for reducing the symptoms of osteoarthritis.  They all also suggest that further thorough studies are required to correctly assess efficacy. The studies assessed indicate that curcumin is well tolerated, there is no dose related toxicity and patients are unlikely to suffer adverse effects. Although it is well documented that curcumin has anti-inflammatory effects on the body (Gosh et al 2015), further independent research involving large sample groups and follow ups would be useful in understanding its therapeutic potential in treating osteoarthritis. A number of the studies made reference to the challenges and imitations of the bioavailability of curcumin and suggested further study is also needed in this area.

Additional research uncovered the details of some ongoing clinical trials, but even when these results are released they will have to be rigidly analysed as many are sponsored by pharmaceutical companies.

As the condition of osteoarthritis is degenerative and is most often suffered long-term (Australian Bureau of Statistics), it is likely that any therapeutic use would correspondingly be of a long-term nature. An assessment of current research in the area of curcumin’s potential therapeutic use in treating the symptoms of osteoarthritis highlights the need for more and larger studies, but in particular long-term clinical trials.