Turmeric / curcumin

What it is

Turmeric is the yellow-orange root spice used in curries. Its main active group of compounds are the curcuminoids, of which curcumin is the best known. Turmeric powder as a spice contains only a few percent curcuminoids by weight, so supplements use concentrated extracts.

People take it mainly for joint aches and general inflammation. It has a long history in traditional Indian medicine, which is a big part of its popularity, but history is not the same as strong modern evidence.

How it works

Curcumin influences several inflammation-related signalling pathways in lab studies and acts as an antioxidant. The catch is that very little reaches the bloodstream from a plain extract, so how much of the lab activity applies to people is unclear.

What the evidence says

• Moderate Knee osteoarthritis pain
  Several small to mid-sized trials suggest a modest reduction in pain, roughly in the range of simple painkillers for some people, but trial quality varies.
• Limited General inflammation markers
  Some studies show small drops in blood markers, but this does not reliably translate into people feeling better.
• Limited Digestive complaints such as indigestion
  Small studies exist, results are mixed.
• Weak Exercise recovery and muscle soreness
  Small studies with inconsistent results.
• Weak Mood and cognition
  Early research only; not enough to draw firm conclusions.

Evidence ratings are our plain-English summary of how much good human research exists, not a promise of results. How we rate evidence.

Dosage and timing

• Most trials use 500-2,000 mg of curcuminoids a day, often split into two doses. Check how much curcuminoid is in each capsule, not just how much turmeric.
• Taking it with food and some fat helps absorption.
• Cooking with turmeric is fine and gives far lower amounts than supplements.
• There is no official UK upper limit for supplement doses; check current guidance and keep to the label.

Forms and what to look for

• Plain turmeric powder: poorly absorbed, low curcumin content.
• Curcumin with piperine (black pepper extract): increases absorption substantially, but piperine also affects how the liver and gut handle some medicines.
• Phospholipid, nanoparticle or other enhanced-absorption formulas: better absorbed, but not all have the same safety data. Higher absorption means higher exposure.
• Look for the standardised curcuminoid percentage (often 95%) on the label.

What to expect, and when

• Do not expect anything within days.
• Trials for joint pain usually run 4-12 weeks.
• If you notice nothing after about 8-12 weeks, it is probably not doing much for you.

Side effects

• Upset stomach, nausea, diarrhoea or reflux, mainly at higher doses.
• Yellow-tinted stools.
• Headache or dizziness in some people.
• Rarely, allergic skin reactions.

Interactions

• Blood thinners such as warfarin: curcumin may increase bleeding risk.
• Piperine can raise blood levels of some medicines by slowing how they are cleared; ask a pharmacist if you take regular prescriptions.
• Diabetes medicines: may add to blood-sugar lowering.
• Other supplements with liver effects, such as green tea extract at high doses, may add to the load on the liver.

Who should avoid it

• People with liver or gallbladder problems, or bile duct obstruction.
• Anyone on anticoagulants or due for surgery in the next couple of weeks.
• Pregnancy and breastfeeding, at supplement doses, as safety data is limited.
• Anyone with a history of kidney stones, as turmeric contains oxalate.

Risks and safety

• Regulators in several countries, including the UK and Italy, have reviewed reports of liver injury linked to turmeric and curcumin supplements, particularly high-dose or enhanced-absorption products. These are rare but can be serious. Stop and seek medical advice if you develop yellowing of the skin or eyes, dark urine or severe tiredness.
• Some products have been found to contain added synthetic dyes or very little actual curcumin.
• Higher-absorption formulas mean higher exposure, not necessarily more benefit.

Buying well: quality and testing

• Choose products stating the curcuminoid content, ideally standardised to around 95%.
• Third-party testing from USP, NSF or Informed Sport adds some confidence about contents.
• Be wary of products promising huge doses or miracle absorption.
• Check for added piperine if you take medicines.

Bottom line

Turmeric is a reasonable food and an overhyped supplement. If you have knee osteoarthritis and want to try it, a standardised curcumin product for a couple of months is a defensible experiment, as long as you have no liver issues and take no interacting medicines. Stay at label doses, watch for signs of liver trouble, and tell your doctor you are taking it.