Turmeric is a spice that is often used as a food flavouring and has been used for many years in herbal remedies. There is currently no research evidence to show that turmeric can prevent or treat cancer but early trials have shown some promising results.
Can turmeric prevent cancer?
Turmeric is also known as Indian saffron, jiang huang, haridra and haldi. It is a spice grown in many Asian countries. It belongs to the ginger family and is a major ingredient of curry powder.
The main active ingredient in turmeric is curcumin or diferuloyl methane, which laboratory studies have shown does have anticancer effects on cancer cells.
A phase I clinical trial looked at giving curcumin to 25 patients with precancerous changes in different organs. This study seemed to show that curcumin could stop the precancerous changes becoming cancer.
Research has also shown that there are low rates of certain types of cancer in countries where people eat curcumin at levels of about 100mg to 200mg a day over long periods of time.
But currently there is no conclusive research evidence to show that turmeric or curcumin can prevent or treat cancer.
Cancer treatment and turmeric
A number of laboratory studies on cancer cells have shown that curcumin does have anticancer effects. It seems to be able to kill cancer cells and prevent more from growing. It has the best effects on breast cancer, bowel cancer, stomach cancer and skin cancer cells.
A 2013 international laboratory study looked at the effects of a combined treatment with curcumin and chemotherapy on bowel cancer cells. The researchers concluded that the combined treatment might be better than chemotherapy alone.
A 2007 American study in mice seemed to show that curcumin helped to stop the spread of breast cancer cells to other parts of the body.
Doctors think that curcumin stays in the digestive system and is absorbed by the cells in the bowel. To find out more, a small study in the UK looked at how curcumin is absorbed from the human gut into liver cells. This study looked at how much of the curcumin is absorbed into both cancer cells and normal cells. This was a very small study of people with bowel cancer that had spread to the liver. They were given curcumin for 7 days before surgery.
During the surgery doctors removed liver tissue and they then then measured the levels of curcumin in the tissue. The results showed that the level of curcumin absorbed into the liver was not high enough to have any anticancer effect. The researchers suggested that future clinical trials of curcumin should focus on preventing bowel tumours. Several studies have shown that curcumin taken as capsules does get absorbed by the gut and is present in the blood. But the amount in the blood is small.
An American phase 2 study reported in 2008. 25 patients had curcumin treatment and 21 had tumours that could be measured. In 2 patients their tumours shrank or remained stable. In some patients their levels of particular immune system chemicals that destroy cancer cells went up. But the researchers found that blood levels of curcumin were very low because it is not well absorbed from the gut. Scientists have since developed injectable, fat soluble forms of curcumin which may improve the results.
These studies look promising but we need to do more clinical trials in humans before we will know if curcumin has any potential to treat cancer in people.
A trial is currently under way in Puerto Rico to find out whether curcumin can shrink precancerous growths in patients with a genetic disorder that greatly increases their risk of bowel cancer.
Side effects of turmeric
It is important to remember that turmeric used in cooking is very safe. But we don't know how safe curcumin is when used for medical reasons. So far, research studies seem to show that it causes few or no side effects. But we don't know much about the side effects of taking it in large amounts to treat or prevent cancer.
There have been some reports of stomach pain if too much turmeric is swallowed and skin problems if it is taken for a long time. For these reasons we recommend that if you use curcumin for reasons other than in cooking, you should talk to your doctor first.
Risks of turmeric supplements
The Medicines and Healthcare products Regulatory Agency (MHRA) has issued a warning about the turmeric-based food supplement Fortodol (also sold as Miradin).
Fortodol has been found to contain the strong anti-inflammatory drug nimesulide.
Nimesulide can cause serious damage to the liver and is not licensed as a medicine in the UK. The Food Standards Agency in the USA states that taking products that contain unknown amounts of nimesulide could be very harmful.
Fortodol and Miradin are sold in the UK and on the internet as food supplements. The FSA advises anyone taking these products to stop doing so immediately, and contact their doctor if they have any signs of liver disease.
The signs include yellowing skin (jaundice), dark urine, feeling or being sick, unusual tiredness, stomach or abdominal pain, and loss of appetite.