BACKGROUNDTurmeric is a spice widely used in Indian cooking and in the country's traditional medicine, called Ayurveda.
The powder is made from the dried rhizome (underground stem) of Curcuma longa, a member of the ginger family. The plant grows in tropical climates across southeast Asia and is used in making curries and mustards. The principal active ingredient is called curcumin, which has been used to treat numerous ailments, particularly stomach problems, sprains, arthritis and inflammatory diseases.
In recent years, attention has been directed towards using curcumin to prevent or treat cancer. Curcumin’s various uses might all arise from its effect on the immune system. Studies have shown that curcumin influences several components in the immune system’s complex network of biological processes.
The effects are not always beneficial. Curcumin is an antioxidant, but also has the opposite effect of promoting oxidation in certain environments. This broad range of effects, coupled with its inexpensiveness, has led to much interest in it as a food supplement. On the other hand, its potential usefulness is limited by its lack of solubility in water and its poor absorption after ingestion.
EVIDENCE FROM STUDIES
Several high-quality studies have found that curcumin has beneficial effects in various laboratory models used to inhibit cancer cells. These preliminary tests are important in identifying useful new compounds, and in pointing to potential side effects. With curcumin, models of lung cancer showed worrisome results, suggesting that large doses of curcumin might cause harmful effects to smokers and ex-smokers.
Two studies have given curcumin to patients with early stages of cancer. Both were small studies (one with only five patients), using widely varying doses and did not have controlled groups to compare patients. A small percentage of patients showed improvements, but it was impossible to know if this was due to curcumin or the natural course of the cancer. Two studies are currently under way in the US examining curcumin’s role in preventing colon cancer.
Patients with advanced pancreatic cancer are typically treated with gemcitabine. Laboratory studies showed that curcumin can enhance the effect of gemcitabine. A clinical trial tested this combination in 17 patients and found better results than when the drug is used on its own. However, many patients found the 8gms of curcumin caused severe abdominal pain and stopped taking it.
PROBLEMATIC ASPECTS
The average diet in India includes an estimated 2-2.5g of turmeric per day (60-100mg curcumin) with no apparent adverse effects. Two safety studies found that patients with advanced colon cancer could take up to 3.6g curcumin per day with no side effects. The severe abdominal pain reported in the pancreatic cancer trials has only occurred with the combination of curcumin and gemcitabine.
Last year, the Food Safety Authority of Ireland recalled two curcumin food supplements called Fortodol and Leppin Miradin. Severe liver damage was reported in Scandinavian patients who took these supplements. Swedish authorities found samples of the products were contaminated with nimesulide. This anti-inflammatory medicine has been taken off the market in Ireland and many other countries because it causes liver damage.
RECOMMENDATIONS
Curcumin is an ingredient of turmeric which has shown much promise in laboratory studies. However, research is only now moving into clinical trials. These should confirm whether curcumin will have a role in helping prevent or treat cancer. For the moment, turmeric can spice up your food and may bring some general health benefits as well.
Dónal O’Mathúna has a PhD in pharmacy, researching herbal remedies, and an MA in bioethics, and is a senior lecturer in the School of Nursing, Dublin City University
