Turmeric and curcumin

What it is

Turmeric is the ground root (rhizome) of Curcuma longa, a perennial plant in the ginger family native to India. Curcumin is the best-known of its yellow pigments (curcuminoids) and makes up only a few percent of turmeric. Supplements range from ground turmeric to purified curcumin extracts, often combined with piperine or other delivery systems to raise absorption.

What the research says

The claim is that curcumin is anti-inflammatory and helps joints, mood and blood sugar. The trial literature is large but mostly low quality. Pooled trials report modest improvements in knee osteoarthritis pain, depression scores and blood sugar, but the reviews that grade the evidence rate most of it low or very low certainty, and a well-run 12-month trial in inherited colon polyps found no effect. Medicinal chemists argue curcumin is unstable, poorly absorbed and gives false positives in lab tests, so much of the early laboratory promise may not be real. High-absorption products are now the most common cause of herbal liver injury reported in the United States, strongly linked to the immune gene HLA-B*35:01.

Evidence grade: Disputed.

What goes wrong

A US Drug-Induced Liver Injury Network case series found ten cases of turmeric-associated liver injury, one fatal, with a strong link to the immune gene HLA-B*35:01. (Source 1)

• Case series, Low certainty.
• Size: 10 cases.
• Who: Adults enrolled in the US Drug-Induced Liver Injury Network, 2004-2022.
• How long: Latency typically 1 to 4 months.
• Result: 5 hospitalised, 1 death from acute liver failure; HLA-B*35:01 allele frequency 0.450 vs 0.056-0.069 in population controls; 3 of 7 tested products also contained piperine.
• Funding: not stated.

HLA typing demonstrated that 7 patients carried HLA-B*35:01, 2 of whom were homozygous, yielding an allele frequency of 0.450 compared with population controls of 0.056-0.069.

The DILIN authors concluded turmeric can cause potentially severe hepatocellular liver injury and that cases appear to be increasing, possibly with more combination with black pepper. (Source 1)

• Case series, Low certainty.
• Size: 10 cases.
• Who: Adults enrolled in DILIN.
• How long: 2004-2022.
• Result: Qualitative conclusion.
• Funding: not stated.

Liver injury due to turmeric appears to be increasing in the United States, perhaps reflecting usage patterns or increased combination with black pepper.

The NIH LiverTox summary (a position) states turmeric has become the most common cause of clinically apparent herbal liver injury in the United States, estimating incidence at roughly 1 in 10,000 to 1 in 100,000 people exposed. (Source 2)

• Official position, Certainty not rated.
• Size: Not applicable.
• Who: People taking turmeric or curcumin products.
• How long: Not applicable.
• Result: Estimated incidence 1:10,000 to 1:100,000 exposed.
• Funding: independent (NIH)

Turmeric appears to have become the most common cause of clinically apparent, herbal-related liver injury in the United States.

Turmeric sold in Bangladesh has been adulterated with lead chromate pigment and was a primary source of lead exposure; enforcement cut detectable lead in market samples from 47% to 0%. (Source 3)

• Survey study, Low certainty.
• Size: 631 market samples; 15 workers with blood lead.
• Who: Turmeric markets and polishing mills in Bangladesh.
• How long: 2017-2021.
• Result: Samples with detectable lead 47% (2019) to 0% (2021), p < 0.0001; worker blood lead median drop 30%.
• Funding: not stated.

Turmeric adulterated with lead chromate pigment has been previously identified as a primary source of lead exposure in Bangladesh.

What the evidence supports

A meta-analysis restricted to curcuminoids alone found short-term reductions in knee osteoarthritis pain and improved function versus placebo, but the authors called the included studies low quality and heterogeneous. (Source 4)

• Meta-analysis, Low certainty.
• Size: 1,670 patients in 15 RCTs.
• Who: Adults with symptomatic knee osteoarthritis.
• How long: Short term (trial durations varied)
• Result: VAS pain WMD -1.77 (95% CI -2.44 to -1.09) versus placebo; WOMAC total WMD -7.06 (95% CI -12.27 to -1.84); adverse events versus placebo RR 1.03 (95% CI 0.69 to 1.53)
• Funding: not stated.

However, considering the low quality and substantial heterogeneity of present studies, a cautious and conservative recommendation for broader clinical use of CURs should still be made.

A dose-response meta-analysis found curcumin or turmeric lowered fasting glucose and HbA1c in adults with prediabetes or type 2 diabetes, with significant heterogeneity between trials. (Source 5)

• Meta-analysis, Low certainty.
• Size: 34 RCTs (39 treatment arms)
• Who: Adults with prediabetes or type 2 diabetes.
• How long: Trial durations varied.
• Result: Fasting glucose WMD -10.15 mg/dL (95% CI -12.59 to -7.72); HbA1c WMD -0.32% (95% CI -0.43 to -0.21); HOMA-IR WMD -0.46.
• Funding: not stated.

hemoglobin A1c (HbA1c) (WMD = -0.32%; 95% CI: -0.43, -0.21)

What the evidence does not support

The same glycaemic meta-analysis found no significant change in a measure of insulin-producing (beta-cell) function. (Source 5)

• Meta-analysis, Low certainty.
• Size: 34 RCTs.
• Who: Adults with prediabetes or type 2 diabetes.
• How long: Trial durations varied.
• Result: No significant alteration in HOMA-B.
• Funding: not stated.

However, no significant alteration in homeostatic model assessment of β-cell function (HOMA-B) levels was detected

In a double-blind randomised trial in familial adenomatous polyposis, pure curcumin 3,000 mg/day did not reduce the number or size of intestinal polyps compared with placebo. (Source 6)

• Randomized trial, Moderate certainty.
• Size: 44 patients.
• Who: Adults aged 18-85 with familial adenomatous polyposis in Puerto Rico and the United States.
• How long: Randomised to 12 months of treatment; the published abstract reports the polyp outcome 'After 12 weeks' and concludes '12 weeks' (an internal contradiction in the journal abstract)
• Result: Mean polyps: placebo 18.6 (95% CI 9.3-27.8) vs curcumin 22.6 (95% CI 12.1-33.1), P = .58; polyp size P = .76.
• Funding: not stated.

Limit of this finding: The published abstract of this trial contradicts itself on duration: it says patients were randomised to curcumin or placebo 'for 12 months', then reports the result 'After 12 weeks' and concludes 'for 12 weeks'. The trial was designed and run as a 12-month course. The quotation here is faithful to what the journal printed, so do not read the '12 weeks' in it as the real length of treatment.

After 12 weeks, there was no significant difference in the mean number of polyps between the placebo group (18.6; 95% CI, 9.3-27.8) and the curcumin group (22.6; 95% CI, 12.1-33.1; P = .58).

A medicinal chemistry review argued that curcumin is a pan-assay interference compound (PAINS) and an invalid metabolic panacea (IMPS): unstable, reactive and poorly absorbed, so many positive laboratory results are likely false. (Source 7)

• Lab study in cells, Certainty not rated.
• Size: Review of chemistry, assay and clinical literature.
• Who: Not applicable.
• How long: Not applicable.
• Result: Qualitative; notes >120 clinical trials.
• Funding: not stated.

This manuscript reviews the essential medicinal chemistry of curcumin and provides evidence that curcumin is an unstable, reactive, nonbioavailable compound and, therefore, a highly improbable lead.

The same review stated that no double-blind placebo-controlled trial of curcumin had been successful as of 2017. (Source 7)

• Lab study in cells, Certainty not rated.
• Size: Review of >120 clinical trials.
• Who: Not applicable.
• How long: Not applicable.
• Result: Qualitative.
• Funding: not stated.

No double-blinded, placebo controlled clinical trial of curcumin has been successful.

Where the evidence is mixed

An overview of the seven systematic reviews of curcumin for knee osteoarthritis found the reviews themselves were of extremely low methodological quality and that most of the evidence behind their results was low or extremely low quality. (Source 8)

• Review of reviews, Very low certainty.
• Size: 7 systematic reviews, 48 outcomes.
• Who: Adults with knee osteoarthritis (trials within the included reviews)
• How long: Literature to 11 January 2025.
• Result: Of 48 outcomes: 5 medium-quality, 6 low-quality, 37 extremely low-quality evidence; high risk of bias in 4 of 7 reviews.
• Funding: not stated.

Among 48 outcomes assessed, evidence quality was mostly low, with 5 medium-quality, 6 low-quality, and 37 extremely low-quality evidences.

A 2026 meta-analysis of randomised trials found curcumin lowered depression scores, but the effect was very heterogeneous and did not survive sensitivity analysis, so the authors called it fragile. (Source 9)

• Meta-analysis, Low certainty.
• Size: 19 RCTs (8 pooled for depression, 11 for depressive symptoms)
• Who: Adults with depression or depressive symptoms.
• How long: Trial durations varied.
• Result: Depression SMD -0.76 (95% CI -1.22 to -0.30; I2 94.5%); depressive symptoms SMD -0.53 (95% CI -0.97 to -0.09; I2 85.7%)
• Funding: not stated.

This meta-analysis suggests that curcumin supplementation may improve depression and depressive symptoms significantly; however, due to sensitivity analysis the observed effect was fragile.

An umbrella review of 25 meta-analyses across many conditions found possible benefits but rated overall methodological quality as relatively poor and many conclusions uncertain. (Source 10)

• Review of reviews, Low certainty.
• Size: 25 meta-analyses.
• Who: Adults across many conditions.
• How long: Literature to 18 June 2024.
• Result: Narrative summary; GRADE and AMSTAR-2 applied.
• Funding: not stated.

The overall methodological quality was relatively poor, and there is considerable room for improvement.

Where the research disagrees

Whether curcumin's clinical results are real

• Xu et al., umbrella review, Frontiers in Pharmacology 2025, Umbrella review of 25 meta-analyses: The available evidence suggests that curcumin is a safe medicinal agent that improves multiple clinical outcomes; however, the scientific quality of published studies needs to be improved. (Source 10)
• Nelson et al., Journal of Medicinal Chemistry 2017, Medicinal chemistry review: No double-blinded, placebo controlled clinical trial of curcumin has been successful. (Source 7)

Whether curcumin is safe

• Xu et al., umbrella review 2025, Umbrella review: The available evidence suggests that curcumin is a safe medicinal agent that improves multiple clinical outcomes (Source 10)
• US Drug-Induced Liver Injury Network, American Journal of Medicine 2023, Case series of 10 adjudicated cases: Turmeric causes potentially severe liver injury that is typically hepatocellular, with a latency of 1 to 4 months and strong linkage to HLA-B*35:01. (Source 1)

How much

• Reference intake: No recommended intake exists; turmeric and curcumin are not essential nutrients. LiverTox (NIH, 2025) notes rigorous proof of efficacy in any medical condition is lacking. (Source 2)
• Upper limit: No tolerable upper limit was found in the sources reviewed. LiverTox (NIH, 2025) estimates clinically apparent liver injury at about 1:10,000 to 1:100,000 persons exposed. (Source 2)
• Studied: A 12-month familial adenomatous polyposis trial gave 1,500 mg pure curcumin twice daily (3,000 mg/day). (Source 6)
• Studied: A human pharmacokinetic study gave 2 g curcumin with or without 20 mg piperine. (Source 11)

A common belief, and what the research shows

The belief: Turmeric is a natural spice, so turmeric supplements cannot hurt the liver.

What the research shows: Turmeric products are now the most commonly reported cause of herbal liver injury in the US. LiverTox states 'Turmeric appears to have become the most common cause of clinically apparent, herbal-related liver injury in the United States.' and DILIN found 'Five patients were hospitalized, and 1 patient died of acute liver failure.'

Questions and answers

What is it?

Turmeric is the root of Curcuma longa, a plant in the ginger family native to India. Curcumin is its main yellow compound and makes up a small percentage of the root. (Source 2)

What does it do in the body?

Curcumin is claimed to reduce inflammation. Human trials show modest possible effects on joint pain, mood and blood sugar, but most of the evidence is low quality, and chemists argue much of the laboratory activity is an artefact of an unstable compound. (Source 7)

Is it good or bad for you?

As a cooking spice it has a long record of safe use. As a concentrated supplement the benefits are uncertain and there is a rare but real risk of serious liver injury, especially with high-absorption products and in people carrying HLA-B*35:01. (Source 1)

How do you get more of it?

In food, turmeric is eaten as a spice. Studies have raised blood curcumin by pairing it with piperine from black pepper; curcumin alone is barely absorbed. That same absorption boost is linked to the liver injury reports. (Source 11)

If it is harmful, what reduces it?

When turmeric-associated liver injury occurs, it usually resolves after the product is stopped. Where turmeric is contaminated with lead chromate, enforcement and testing sharply reduced lead in market samples and in workers' blood. (Source 3)

Why might someone be low in it or missing it?

Does not apply in the nutritional sense. Curcumin is not an essential nutrient, so the body cannot be deficient in it; people simply get more or less from their diet. (Source 2)

Which whole foods contain it or feed it?

Turmeric root and ground turmeric (as in curry dishes) are the food sources. Curcumin makes up only a few percent of the root. (Source 7)

What happens if you do not have it?

Nothing is known to happen. Curcumin is not essential, and trials of added curcumin have not consistently shown benefit, so not eating it is not known to cause harm. (Source 7)

How can you test for it?

No clinical test for curcumin status exists in the literature we searched. Blood curcumin is barely detectable after oral doses. Laboratory assay results for curcumin are themselves unreliable because it interferes with many assays. (Source 11)

References

1. The American Journal of Medicine. Liver Injury Associated with Turmeric-A Growing Problem: Ten Cases from the Drug-Induced Liver Injury Network [DILIN]. 2023. PMID 36252717, DOI 10.1016/j.amjmed.2022.09.026. Read the source
2. National Institute of Diabetes and Digestive and Kidney Diseases (NCBI Bookshelf). Turmeric - LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. 2025. Read the source
3. Environmental Research. Food safety policy enforcement and associated actions reduce lead chromate adulteration in turmeric across Bangladesh. 2023. PMID 37286126, DOI 10.1016/j.envres.2023.116328. Read the source
4. BMC Complementary Medicine and Therapies. Efficacy and safety of curcuminoids alone in alleviating pain and dysfunction for knee osteoarthritis: a systematic review and meta-analysis of randomized controlled trials. 2022. PMID 36261810, DOI 10.1186/s12906-022-03740-9. Read the source
5. Food Science & Nutrition. Curcumin/Turmeric Supplementation on Glycemic Control in Adults With Prediabetes and Type 2 Diabetes: A Systematic Review and Dose-Response Meta-Analysis. 2026. PMID 42005325, DOI 10.1002/fsn3.71748. Read the source
6. Gastroenterology. Efficacy and Safety of Curcumin in Treatment of Intestinal Adenomas in Patients With Familial Adenomatous Polyposis. 2018. PMID 29802852, DOI 10.1053/j.gastro.2018.05.031. Read the source
7. Journal of Medicinal Chemistry. The Essential Medicinal Chemistry of Curcumin. 2017. PMID 28074653, DOI 10.1021/acs.jmedchem.6b00975. Read the source
8. Frontiers in Pharmacology. A critical review of systematic reviews and meta-analyses of curcumin for knee osteoarthritis. 2025. PMID 41560742, DOI 10.3389/fphar.2025.1664319. Read the source
9. Annals of General Psychiatry. Efficacy of curcumin in depression: A grade-assessed systematic review and meta-analysis of randomized controlled trials. 2026. PMID 42472817, DOI 10.1186/s12991-026-00676-z. Read the source
10. Frontiers in Pharmacology. Curcumin and multiple health outcomes: critical umbrella review of intervention meta-analyses. 2025. DOI 10.3389/fphar.2025.1601204. Read the source
11. Planta Medica. Influence of piperine on the pharmacokinetics of curcumin in animals and human volunteers. 1998. PMID 9619120, DOI 10.1055/s-2006-957450. Read the source