Turmeric and Curcumin: Evidence Review

Short answer: Turmeric is a spice, and curcumin is the main compound studied in its supplements. The best evidence is for short-term relief of knee osteoarthritis pain, where a 2022 review of 15 trials found curcumin extracts beat placebo, but the trials were low quality and varied widely. [S02] For almost everything else, the evidence is early or inconsistent, and NIH's National Center for Complementary and Integrative Health (NCCIH) says there isn't enough evidence to conclude turmeric or curcumin helps any health condition. [S01] Regular-strength products are likely safe for 2 to 3 months, but enhanced-absorption products have been linked to rare liver injury. [S01] [S03]

This review covers what turmeric and curcumin are, what the trials show, why absorption matters and who should be careful.

Turmeric vs curcumin

Turmeric is the root-like stem of a plant in the ginger family, long used in cooking and in Ayurvedic, Chinese and other traditional medicine. [S01] Curcumin gives the spice its yellow color, and the effects of turmeric are usually attributed to curcumin and related compounds called curcuminoids. [S01] Curcumin makes up only up to about 5% of turmeric. [S06]

That difference matters. Most trials tested concentrated curcumin or curcuminoid extracts, not turmeric as a spice. NCCIH notes that products vary in how much curcumin they actually contain, and often include other plant compounds such as piperine from black pepper, which makes studies hard to compare. [S01]

Knee osteoarthritis: the strongest evidence

Knee osteoarthritis is the most-studied use. A 2022 systematic review pooled 15 randomized trials with 1,670 people that tested curcuminoids on their own. [S02] Compared with placebo, people taking curcuminoids reported less pain, 1.77 points lower on a visual analog pain scale, and better scores for stiffness and function. [S02] In the trials that compared curcuminoids with NSAID pain relievers, results were not worse, and side effects were not more common than with placebo. [S02]

The authors still recommended caution: the studies were low quality, differed a lot from each other and were short term. [S02] NCCIH reaches a similar view. The initial evidence for knee osteoarthritis is positive, but higher-quality studies are needed, and it isn't clear whether curcumin ointment on the skin helps knee pain. [S01]

Other uses: early or mixed evidence

NCCIH summarizes the research on other common uses like this: [S01]

A 2022 review of 31 randomized trials across 10 autoimmune diseases found signs of benefit in some conditions, including psoriasis, ulcerative colitis and rheumatoid arthritis, but no benefit in its pooled analysis for oral lichen planus. [S05] Most diseases had only one to a few small trials, and the authors called for larger, multicenter studies. [S05]

The case for skepticism

Not all researchers read this literature the same way. A 2017 review by medicinal chemists argued that curcumin is unstable, reactive and poorly absorbed, and that it often gives misleading results in lab tests. [S06] Its authors said that, despite more than 120 clinical trials, no double-blind, placebo-controlled trial of curcumin had succeeded at that point. [S06]

Later meta-analyses, such as the 2022 knee osteoarthritis review, did report benefits over placebo, so that statement is contested. [S02] Still, the critique is a useful reminder: positive results from small or low-quality trials can shrink once larger, better-designed studies are done.

Why absorption matters

Curcumin taken by mouth is poorly absorbed. In a 1998 study in healthy volunteers, 2 grams of curcumin alone produced blood levels that were undetectable or very low. [S07] Adding 20 milligrams of piperine, a compound from black pepper, raised curcumin's bioavailability by 2000%. [S07] This was a small, short pharmacokinetic study that measured blood levels, not health outcomes.

That's why many products add black pepper extract or use special formulations. NCCIH says combining curcumin with piperine is one way to increase absorption. [S01] It also warns that highly bioavailable curcumin formulations may harm the liver. [S01] Better absorption may increase effects, wanted and unwanted.

Side effects and liver injury

NCCIH says conventional oral turmeric or curcumin, not modified to boost absorption, is likely safe in recommended amounts for up to 2 or 3 months. [S01] Common side effects include nausea, vomiting, acid reflux, stomach upset, diarrhea and constipation. Curcumin applied to the skin can cause hives or itching. [S01]

Liver injury is rare but serious. The US Drug-Induced Liver Injury Network described 10 cases linked to turmeric products enrolled between 2004 and 2022, all since 2011. [S03] Five people were hospitalized and one died of acute liver failure. [S03] Turmeric was confirmed in all 7 products tested, and 3 of them also contained piperine. [S03] Injury usually showed up 1 to 4 months after starting, and 7 of the 10 people carried the same immune gene variant, HLA-B\*35:01. [S03] A case series like this shows the harm is real but can't tell you how often it happens.

Turmeric is widely used. A national survey of US adults from 2017 to early 2020 found turmeric products were the most commonly used of six botanicals linked to liver injury, and the authors estimated 15.6 million US adults had taken at least one of the six in the past 30 days. [S04]

If you notice fatigue, nausea, poor appetite, dark urine or yellowing of the skin or eyes, NCCIH advises stopping turmeric or curcumin right away and contacting your health care provider. [S01]

Who should be careful

• Pregnancy: NCCIH says turmeric supplements may be unsafe during pregnancy. [S01]
• Breastfeeding: little is known about amounts larger than those in food. [S01]
• People taking medicines: NCCIH advises talking with a provider before using any herbal product, because some herbs and medicines interact in harmful ways. [S01] Our herb-drug interactions guide explains how to check.

Supplements are not approved by the FDA before they are sold, and manufacturers are responsible for their safety and labeling. [S01] For a comparison with other popular supplements, see our reviews of ashwagandha and berberine.

How strong is the evidence?

• Knee osteoarthritis pain: limited. Many trials point the same way, but they are low quality, varied and short. [S01] [S02]
• Fatty liver, mouth sores, autoimmune conditions: early. Small or few trials. [S01] [S05]
• Most other claims: not enough evidence. [S01]
• Safety: likely safe short term in regular forms; rare but serious liver injury with some products. [S01] [S03]

Cooking with turmeric is a different question from taking concentrated extracts, and the studies above are about supplements.