Supplements are a growing share of liver injury cases. A discussion paper prepared for the UK Committee on Toxicity's July 2026 meeting pulls together the registry data. In the US Drug-Induced Liver Injury Network, supplements went from 7% of cases in 2004–05 to 19% by 2010–12. The Spanish registry saw a rise from 2% to 13% over a similar stretch. The paper names Garcinia cambogia, green tea, turmeric, ashwagandha and multi-ingredient products as the ones implicated most often. It is a secretariat paper for discussion, which the document itself says does not represent the Committee's views. It also notes a gap: there is no UK-specific data, so nobody can say how common this is in Britain.
Green tea extract is the best-measured case. According to NIH LiverTox, drinking green tea has not been linked to liver injury. Concentrated extract is a different product. A randomized, placebo-controlled trial published in Cancer Prevention Research gave 1,021 women with normal liver tests either high-dose green tea extract or placebo for 12 months. ALT rose by an average of 5.4 U/L more in the extract group. 26 women (5.1%) on the extract developed moderate or worse liver test abnormalities, an odds ratio of 7.0 against placebo. ALT returned to normal when the extract stopped and rose again when it was restarted. That stop-and-restart pattern is the strongest evidence in this field that the extract caused the rise. LiverTox notes that no clinically apparent liver injury was seen in this trial. The rises were caught because the trial tested blood on a schedule.
Turmeric: the high-absorption versions. Plain curcumin is poorly absorbed, and for years turmeric was not linked to liver injury in any consistent way. According to the NIH LiverTox entry on turmeric, cases started appearing after manufacturers began boosting absorption with piperine (black pepper extract) or lipid nanoparticles. Onset has ranged from a few weeks to eight months, typically 1 to 4 months. Blood tests at onset showed marked ALT and AST rises, often above 1,000 U/L, with only mild rises in alkaline phosphatase (ALP). Recovery was quick once the product stopped. The UK Committee on Toxicity's 2024 statement, summarised in the 2026 discussion paper, found that turmeric at supplement levels may pose a liver risk even at low intakes, because the reaction is idiosyncratic.
Ashwagandha leaves a different pattern. The NIH LiverTox entry on ashwagandha describes injury appearing 2 to 12 weeks after starting, usually with a cholestatic or mixed pattern, where ALP rises further relative to its normal range than ALT does, plus jaundice and itching. The jaundice was often long-lasting but resolved completely in most reports. Rare deaths and emergency transplants have been reported, particularly in people with existing liver disease or cirrhosis. The COT paper adds that the UK Food Standards Agency logged a rising number of ashwagandha incidents between February 2021 and December 2024 and asked the Committee for a safety review, which is ongoing.
The shape of your liver panel carries information. Clinicians classify liver injury with the R ratio: ALT divided by its upper limit of normal, divided by ALP over its upper limit. The COT paper sets out the cut-offs: 5 or above is hepatocellular, 2 or below is cholestatic, and anything in between is mixed. In the LiverTox descriptions above, turmeric cases push ALT far higher than ALP, while ashwagandha tends to show a cholestatic or mixed picture. The green tea trial found its signal in ALT and AST. The ratio narrows the list of causes. It cannot prove a supplement did it, and diagnosis remains a process of ruling other causes out.
A normal dose is no guarantee, and doctors often never hear about it. The COT paper describes most herb-induced liver injury as idiosyncratic, with responses that are not dose dependent, so "I only take the label dose" offers no protection. At EASL Congress 2026, speakers cited a study in which a quarter of patients had not told their primary care doctor about herbal or supplement use. Scale matters too: LiverTox describes symptomatic injury from green tea extract as low compared with how widely it is used. For most people these products cause no liver problem at all.
What to do with your own results. If ALT, AST, ALP or bilirubin comes back raised, write down every supplement you take, including blends where green tea extract or turmeric is one ingredient among many, and when you started each one. Give that list to your doctor with the result. A repeat test after stopping, agreed with your doctor, is how the green tea trial separated cause from coincidence. Do not restart a product just to see whether the numbers move again. If you have jaundice, dark urine or itching, contact your doctor now rather than waiting for a routine retest.
For what ALT, AST, ALP and bilirubin each measure, see our liver function blood test guide. For other supplements that shift specific markers, see how supplements affect blood test results.