What it is
Curcumin is the main curcuminoid in turmeric rhizome, of which it makes up about 3% of the weight according to the 2017 review (1 to 6% of the dry weight of whole extracts according to LiverTox). People buy it in capsules for joint pain, inflammation, recovery and as a "natural anti-inflammatory".
What the label does not say
- What is absorbed is not what is swallowed. The 2017 review describes low absorption, rapid metabolism and rapid elimination; with piperine, bioavailability rises by 2,000%, and LiverTox also cites lipid nanoparticles. Two "500 mg" capsules, with and without these carriers, do not deliver the same dose to the blood.
- The liver: LiverTox gives turmeric a score of A, a well-documented cause of clinically apparent liver injury: typical onset 1 to 4 months, cases linked to high-bioavailability forms, HLA-B*35:01 allele in more than 70% of cases versus 10 to 15% of controls, usual resolution within 1 to 3 months after stopping, a few cases of liver failure with death or transplant. In 2025, Health Canada concluded that a link is possible and had the statement added to labels.
- The cases described by LiverTox involved ordinary doses: 500 mg per day, or 1,000 mg with 5 mg of black pepper. The problem is not primarily an overdose.
- Kitchen turmeric is not curcumin in a capsule: at about 3% curcumin, it would take tens of grams of powder to approach the 500 to 1,500 mg of curcuminoids used in the trials, whereas the monograph caps the rhizome at 9 g per day. The NCCIH also notes that the actual content of products varies.
The forms on the shelf
- Rhizome powder and low-concentration extracts: the Canadian monograph for oral turmeric covers 1 to 9 g of dried rhizome per day and extracts up to 35% curcuminoids, with herbal medicine claims.
- Concentrated extracts (75% curcuminoids and more) and isolated curcumin: a separate Health Canada monograph (September 26, 2025), up to 1,500 mg of curcuminoids per day (500 mg per dose) or 1,200 mg of curcumin (400 mg per dose).
- Enhanced-absorption formulations (piperine, phospholipids, cyclodextrin, nanoparticles): Health Canada excludes them from that monograph, writes that "dosage forms/formulations that enhance absorption are not supported" and requires a separate submission.
Published reference values
- Health Canada: up to 1,500 mg of curcuminoids per day (500 mg per dose) or 1,200 mg of curcumin (400 mg per dose) for concentrated extracts, with the claim "helps to relieve joint pain and inflammation"; 1 to 9 g of dried rhizome for the powder.
- Osteoarthritis trial doses: 500 mg of curcuminoids per day with piperine over 6 weeks (40 participants), 1,500 mg per day over 4 weeks against ibuprofen, 1,000 mg per day over 8 weeks (101 participants, a single trial). The NCCIH judges these initial data positive and is waiting for higher-quality trials.
- Adverse effects according to the NCCIH: nausea, vomiting, reflux, stomach pain, diarrhea or constipation.
When
The osteoarthritis trials last 4 to 12 weeks and liver injury typically occurs after 1 to 4 months: how long you take it counts as much as the dose. Fatigue, nausea, loss of appetite, dark urine or jaundice call for stopping immediately according to the NCCIH, and the Canadian label must carry these warning signs.
Keep apart from
- Anticoagulants and other medications: Health Canada requires the statement "consult a health care practitioner if you are taking medications, including anticoagulants"; a medical decision, not a matter of spacing doses by the hour.
To mention to a professional
- Liver or bile duct disorder (a statement required by Health Canada), use of medications including anticoagulants, pregnancy (the NCCIH judges turmeric supplements possibly unsafe) and breastfeeding: check with a health care professional.
From the plate first
Turmeric powder, at about 3% curcumin, flavours a dish without approaching the doses in capsules; the liver injury described by LiverTox and the NCCIH involves supplements, mostly high-bioavailability ones, not the spice.
Sources
- NCCIH, Turmeric
- LiverTox (NCBI Bookshelf), Turmeric
- Health Canada, natural health product monograph, Concentrated turmeric extracts and isolates (September 26, 2025)
- Health Canada, natural health product monograph, Turmeric, Oral
- Health Canada, product monograph, Joint Health Products, Multiple Ingredient
- Health Canada, Health Product InfoWatch, October 2025 (turmeric and curcuminoids, risk of hepatotoxicity)
- Hewlings and Kalman, Curcumin: A Review of Its Effects on Human Health, Foods (2017)
- Lopresti et al., An Investigation into the Effects of a Curcumin Extract on Osteoarthritis Pain of the Knee, Nutrients (2021, individual trial)
Educational information, drawn from the sources above. It does not replace the advice of a health professional, who remains the reference for your situation, your medications, pregnancy or breastfeeding.