Curcumin is the main curcuminoid in turmeric, the rhizome that colors curry, and one of the most researched natural compounds there is. Supplements range from plain turmeric powder through standardized curcuminoid extracts to formulations engineered for absorption, with piperine from black pepper, with phospholipids, or as nanoparticles.

Two facts organize the literature. First, the trials for knee osteoarthritis are numerous enough that someone has now meta-analyzed the meta-analyses, and the result favors curcumin for pain and function. Second, curcumin on its own is barely absorbed, which means a trial result belongs to the formulation that produced it, and a cheap powder does not inherit it.

Curcumin inhibits NF-kappa-B and the inflammatory signaling downstream of it, including COX-2 and the cytokines TNF-alpha and IL-6, and acts as an antioxidant and a modulator of several kinases. The 66-trial meta-analysis of inflammatory markers measures the downstream end of that: CRP, TNF-alpha and IL-6 all fell with supplementation. The problem is delivery. A 2007 review summarized why plasma and tissue levels stay low, poor absorption, rapid metabolism and rapid elimination, and the approaches to get around it: piperine to block glucuronidation, liposomes, nanoparticles and phospholipid complexes. The approach that improves absorption most, piperine, is also the one the liver-injury cases keep turning up with.

Knee osteoarthritis. The 2024 umbrella meta-analysis pooled 11 meta-analyses and found curcumin reduced pain on a visual analog scale and improved WOMAC total, function, pain and stiffness scores, all significant, and shortened use of other medication. A 2022 meta-analysis of 29 trials in 2,396 people across five types of arthritis, at 120 to 1,500 mg for 4 to 36 weeks, found improved pain and inflammation with low-quality trials flagged.

Inflammation. The 2023 GRADE-assessed meta-analysis of 66 randomized trials found CRP 0.58 mg/L lower, TNF-alpha 3.48 pg/mL lower and IL-6 1.31 pg/mL lower, with total antioxidant capacity up and malondialdehyde down. IL-1 beta did not change.

Muscle damage. A 2021 meta-analysis found curcumin lowered creatine kinase by 48.5 IU/L and reduced a muscle soreness index after exercise-induced muscle damage; a 2024 systematic review of 11 studies in athletes agreed, with post-exercise dosing looking more useful than pre-exercise.

Depression. A 2020 meta-analysis of ten studies in 531 people found a large effect on depressive symptoms (Hedges' g minus 0.75) and on anxiety, mostly as an add-on in major depression, with the authors urging caution over small samples.

Across all of it, the formulation varies from trial to trial and the dose range is wide, so the pooled numbers describe a family of products rather than one.

Phase I trials found curcumin safe at up to 12 g a day, and the arthritis trials report safety across the board. The signal that has changed since those reviews is the liver.

The US Drug-Induced Liver Injury Network reported ten adjudicated cases of turmeric-associated liver injury in 2023, all since 2011 and six since 2017, with hepatocellular injury, five hospitalizations and one death from acute liver failure. Three of seven tested products also contained piperine. Seven of ten patients carried HLA-B*35:01, an allele frequency of 0.45 against 0.06 in the population, which points to a genetic susceptibility. Latency was one to four months. The network's authors think the rise reflects usage and the combination with black pepper.

The practical reading: a rare, idiosyncratic, potentially severe reaction, more likely with absorption-enhanced products, in people who cannot know in advance that they carry the risk allele. Anyone taking it should know what jaundice and dark urine mean. It also has mild antiplatelet effects, so caution with anticoagulants, and it can cause stomach upset at gram doses.

A food, a food coloring (E100 in the European Union) and a dietary supplement in the United States, the United Kingdom and the European Union, with no claims reviewed. The osteoarthritis and inflammation findings are not claims a supplement label may make. No regulator has licensed a curcumin product as a medicine for any of the conditions on this page.