Turmeric has a long history of use as a traditional medicine and as a food ingredient. The turmeric you buy is the spice made by drying and grinding up the root of the Curcuma longa plant. Curcumin is one of the natural chemical constituents in turmeric, and is thought to be one of the ingredients that has medicinal benefits and effects. Sales of turmeric have been growing over the past several years and it is now among the top selling natural products in the USA. It has also been receiving increased scrutiny by researchers and regulators, as serious reports of liver injury associated with consumption are becoming more frequent.
Clinical trials with turmeric have not been impressive from an efficacy perspective. There is some suggestion of benefit for conditions like knee osteoarthritis, mucositis, high triglycerides, or allergic rhinitis, but no persuasive evidence for routine medical use has been established. The main challenge with using curcumin as a medicine seems to be that the chemical is poorly absorbed. Manufacturers have come up with several different formulations (e.g., nanoparticles, liposomes) which complicates the interpretation of any trial. Doses vary widely from 100mg to several grams per day, and formulations include tablets, liquids, and root extracts. The poor absorption may also be responsible for its safety profile, which is generally considered safe orally even at daily doses measured in grams when consumed for several weeks. However, some turmeric supplements are now marketed as being combined with black pepper which substantially improve its absorption. (If you haven’t already seen the Marc Maron bit on turmeric and black pepper, it’s pretty funny.) Piperine, a component of black pepper, appears to inhibit glucuronidation (a metabolic process) in both the intestines and liver. Through inhibition, the amount of curcumin available to the body is greater. Consequently, the potential risk of unwanted or harmful effects is also increased. Other means to increase the absorption, such as nanoparticles, have also been developed.
Through better absorption, higher (effective) doses seem to be resulting in more cases of liver damage. Cases have occurred in weeks to months after routine ingestion begins – it is reported to start with fatigue, nausea, and poor appetite, followed by dark urine and jaundice. Recovery is usually rapid when the turmeric consumption is discontinued.
A recent paper published in the American Journal of Medicine describes ten cases of liver injury associated with turmeric. The Drug-Induced Liver Injury Network (DILIN) was established in 2003 as a cooperative agreement across academic centres and studies liver-related injuries associated with medications bout also herbal products and other dietary supplements. In this paper, all cases between 2004 and 2022 in which turmeric was implicated as a cause were reviewed. Causality was assessed, and available product was analyzed for the presence of turmeric. Ten cases of turmeric injury were reported, all since 2011, with six since 2017. Five of the ten were hospitalized, and 1 patient died of acute liver failure. Chemical analysis confirmed turmeric in all seven of the available products tested. Three products also contained piperine.
Genetics may also play a factor in putting some individuals at higher risk of liver damage from turmeric. Seven cases were found to carry the HLA-B*35:01 allele that has already been implicated as a potential biomarker that predicts liver damage from other products like green tea and Polygonum multiflorum, a Chinese herbal medicine. It is also associated with the risk of injury from regular medications as well. This allele is carried by 5-15% of the US population.
Based on concerns about health claims associated with turmeric and the potential but rare risk of serious harms, Italy recently prohibited health claims linked to turmeric and put a warning on products derived from Curcuma longa root. This followed reports of about 20 cases of liver damage in the country attributed to use:
IMPORTANT WARNING In case of liver, biliary or calculosis abnormalities in the biliary tract, the use of the product is not recommended. Do not use during pregnancy and lactation. Do not use for prolonged periods without consulting your doctor. If you are taking medications, it is it is advisable to hear the opinion of the doctor.
Conclusion: Turmeric has rare but serious risks
Turmeric supplements have medicinal promise but their role is not well established. Combining turmeric with black pepper demonstrably increases the absorption of the drug. Liver damage is a rare but seemingly-real risk of consumption. If consumption as a supplement is considered, use with or without piperine should be held consistent. Research into genetic risk factors for liver damage from supplements like turmeric are still preliminary but have the potential to identify those at greater risk of harm. Until then, whether it’s turmeric or any other dietary supplement, carefully monitoring for signs and symptoms of liver damage or other harms is important.