Turmeric/curcumin

Abstract

Curcumin is the primary curcuminoid present in the turmeric plant, Curcuma longa, and gives turmeric its orange-yellow color. The names “turmeric” and “curcumin” are often used interchangeably, especially for the spice used in cooking. Turmeric extracts and curcumin are used primarily for osteoarthritis (OA) and inflammatory conditions. They also may have activity in diabetes, obesity, and cardiovascular diseases. Curcumin has anti-inflammatory activity via inhibition of arachidonic acid, lipoxygenase, COX, nuclear factor-kappa B, tumor necrosis factor-alpha, and interleukins. In a study of knee OA, 30 mg of curcumin extract three times daily decreased COX-2 secretion into synovial fluid, similar to the effect of 25 mg of diclofenac three times daily. In another study of knee OA, serum levels of Coll2-1, a cartilage-specific biomarker, were significantly reduced. Clinical trials demonstrating benefit have used 1,000–1,500 mg per day in divided doses. The oral bioavailability of turmeric/curcumin may be low, so products that contain black pepper extracts or other compounds as absorption enhancers are preferred. The most common adverse effects are GI discomfort and nausea. Human studies have shown good tolerance even with higher dosages. Curcumin inhibits platelet aggregation in vitro and in vivo, so patients taking antithrombotic agents such as warfarin or clopidogrel should use this botanical cautiously. Multiple small studies have evaluated curcumin and related compounds for treatment of OA and rheumatoid arthritis (RA), alone or in combination with other natural products. Although some studies were placebo controlled, others compared curcumin with NSAIDs. An Iranian study of 40 participants with knee OA compared treatment with 1,500 mg of curcuminoids per day in three divided doses with placebo for 6 weeks. Treatment with curcuminoids resulted in greater improvements on standard OA assessment tools, including the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Lequesne’s pain functional index, and visual analogue scale (VAS), with few adverse effects. Pain and physical function also improved, but not stiffness. An Indian trial1Amalraj A. et al.J Med Food. 2017; 20: 1022-1030Crossref PubMed Scopus (62) Google Scholar randomized 36 participants with RA into three groups to receive 250 mg or 500 mg of curcumin or placebo twice daily for 90 days. The active treatment groups had significant improvement in their clinical symptoms at study end. Favorable changes in disease markers also occurred, including the erythrocyte sedimentation rate, C-reactive protein levels, and rheumatoid factor values. A 2018 Indian study2Karlapudi V. et al.J Med Food. 2018; 21: 511-520Crossref PubMed Scopus (9) Google Scholar of 105 patients with OA evaluated a combination curcumin product versus placebo in a 90-day trial that demonstrated improvements in pain, physical function, and quality of life. A noninferiority trial of 367 participants with OA compared 1,500 mg of curcumin extract daily to 1,200 mg of ibuprofen daily for 4 weeks. The WOMAC total, pain, stiffness, and function scores were similar between the curcumin and ibuprofen groups, with about two-thirds of participants rating themselves as “improved” on the global assessment. Curcumin-treated patients had less abdominal pain. An OA trial of 120 participants evaluated several natural products. Patients were randomized to receive 500 mg of curcumin extract, 750 mg of glucosamine sulfate, curcumin extract/glucosamine sulfate, or placebo twice daily for 42 days. The VAS pain scores were reduced from baseline, with the greatest reduction in the curcumin extract group. The WOMAC scores were also improved in the curcumin extract group. Improvements from baseline were noted with glucosamine, but less than those with curcumin. Evidence for curcumin/turmeric is promising given its safety, and it may be an option for patients with mild OA symptoms. Inform patients that the curcumin formulations used in studies may not be widely available. Products containing compounds such as black pepper extract are recommended and should be taken with meals with fats or oils to enhance absorption.