Turmeric supplements and curcumin: what the evidence shows, why black pepper is added and the liver risks

Turmeric vs curcumin: what’s the difference?

Turmeric is a plant in the ginger family. Its rhizome (underground stem) is dried and ground into the yellow spice. Curcumin is turmeric’s main active compound and gives it its colour. Together with related compounds, it’s known as a curcuminoid.

A tub labelled “turmeric supplement” or “turmeric tablets” can contain:

• ground root – the same spice, just in a capsule;
• turmeric extract – a concentrate with far more curcuminoids than the spice;
• extract with piperine – a black pepper compound added to improve absorption;
• “enhanced” forms – curcumin in liposomes, micelles, oils or other carriers.

NCCIH points out that products are hard to compare: their real curcumin content varies, and they often contain other plant ingredients. So check the label for curcuminoids in milligrams rather than the weight of the powder.

Curcumin benefits: what the research shows

Turmeric has traditionally been used for indigestion, colds, arthritis and liver problems. Today it’s sold for inflammation, joints, skin, cholesterol and mood. The evidence so far:

NCCIH’s summary: there isn’t enough evidence to conclude that turmeric or curcumin helps with any health condition. Knee osteoarthritis is the best-studied use, and the effect there is small.

Curcumin for joint pain

Several meta-analyses found less knee pain and stiffness with curcumin. Memorial Sloan Kettering’s review notes trials where turmeric extract worked as well as paracetamol or an anti-inflammatory painkiller. But in a randomised trial with MRI scans, it didn’t change joint swelling or cartilage.

If you want to try it, treat curcumin as an add-on. Exercise and weight management are the core of osteoarthritis care, as our guide to glucosamine and other joint supplements explains.

Turmeric and black pepper: why piperine is added

Curcumin is poorly absorbed because the liver and gut wall break it down quickly. Piperine from black pepper slows this down, so more curcumin reaches the blood. Manufacturers do the same with liposomes, micelles and other carriers.

The catch is that better absorption cuts both ways. NCCIH states plainly that highly bioavailable curcumin may harm the liver, and many of the reported liver injury cases involved these products.

• Standard extract: NCCIH considers it likely safe in recommended amounts for up to 2–3 months.
• Piperine or “enhanced” forms: higher blood levels and more reports of hepatitis.
• Turmeric with pepper in food is ordinary cooking, not a therapeutic dose.

Turmeric and liver injury: Italy, the US and LiverTox

Turmeric has been a spice for centuries and is considered safe in food. Supplements are a different matter.

• Italy, 2019. In the first six months, the national herbal safety system received 28 reports of acute hepatitis, mostly with bile flow problems, after turmeric supplements. In all but one case, the link was rated at least possible, and the authorities took regulatory action.
• US DILIN network. 10 cases of turmeric-related liver injury, all since 2011. Five people were admitted to hospital and one died of acute liver failure. Injury appeared after 1–4 months, and 3 of the 7 products tested contained piperine.
• Genes. 7 of the 10 DILIN patients carried the HLA-B*35:01 gene variant. Risk may depend on inheritance, which you can’t check before buying.
• LiverTox, the US NIH reference on drug-induced liver injury, links turmeric products to several dozen cases of acute liver injury. It calls the injury well documented but probably very rare: roughly 1 in 10,000 to 1 in 100,000 people who take it.

Stop curcumin and see your GP straight away if you notice tiredness, nausea, poor appetite, dark urine, or yellowing of the skin or eyes.

Turmeric tablets: how to take them

There’s no single “right” dose of curcumin, because trials used different extracts and forms. So take the dose from the label of a standard extract that states curcuminoids in milligrams. The length of the course and how you feel matter more than the exact dose. And watch for turmeric in golden milk powders and joint blends: it adds up with your capsules.

For comparison, here’s an EFSA figure. For curcumin as the food colour E100, EFSA set an acceptable daily intake (ADI) of 3 mg per kg of body weight in 2010. For a 70 kg adult, that’s 210 mg a day. It’s a limit for a food colour, not a supplement dose, but many capsules contain more than that in a single serving.

Who should avoid curcumin: side effects and interactions

• Gallstones, blocked bile ducts, cholangitis or liver disease. The EMA advises against turmeric because it stimulates bile flow.
• Pregnancy and breastfeeding. NCCIH says turmeric supplements may be unsafe in pregnancy, and the EMA doesn’t recommend them.
• Under-18s – the EMA says safety hasn’t been established.
• Blood thinners such as warfarin, and antiplatelet medicines. Memorial Sloan Kettering says turmeric may raise the risk of bleeding, based on lab studies and one case report. The EMA monograph lists no known interactions, so the risk is uncertain, but ask first.
• Tacrolimus after an organ transplant: curcumin may increase its side effects.
• Chemotherapy. In lab studies turmeric interfered with some cancer drugs, so check with your oncology team.
• A family history of kidney stones. Memorial Sloan Kettering warns of a possible higher risk.

Common side effects are nausea, acid reflux, an upset stomach, diarrhoea or constipation. If you take several supplements or medicines, check our vitamin compatibility chart. For another herb sold “for the liver”, read our guide to milk thistle and silymarin.

How to choose a turmeric supplement on iHerb

1. Decide what it’s for. With no clear goal, turmeric in food is enough; not sure what you need at all? Try our vitamin check.
2. Check the warnings: gallbladder, liver, pregnancy, blood thinners.
3. Find the curcuminoids in mg on the label, rather than the weight of “turmeric root”.
4. Decide whether you want piperine: it’s better absorbed, but more hepatitis reports involve such forms.
5. Note an end date 8–12 weeks ahead, then judge whether it’s working.

Our supplement label guide shows how to work out the dose per serving and spot unnecessary extras. For more in this section, see skin, hair and joints.