Milk thistle and cancer
Milk thistle is a plant that comes from the same group of flowers as the daisy. It is not a treatment for cancer.
Summary
- The medicinal compound in milk thistle is silymarin, an extract of milk thistle seeds.
- Milk thistle might help to treat some liver diseases such as hepatitis and cirrhosis.
- More research is needed before we will know if milk thistle can help prevent or treat cancer.
What is milk thistle?
People have been using the fruit and seeds of the milk thistle plant for hundreds of years. They use them as a herbal remedy for some liver problems.
The scientific name for milk thistle is Silybum marianum. It has many other names. This includes lady’s thistle, St Mary’s thistle, holy thistle and variegated artichoke.
The medicinal compound in milk thistle is silymarin, an extract of milk thistle seeds. It is an antioxidant that protects against cell damage.
Silymarin contains at least 4 major compounds, including silybin (the most active), isosilybin, silychristin, and silydianin. Most research has studied silymarin or its major compound silybin.
How you have it
Milk thistle supplements are available as capsules, tablets, powder and liquid extract.
Powdered milk thistle can be made into a tea.
Side effects
Milk thistle is generally considered safe. But check with you doctor first before taking it.
Women who are pregnant or breast feeding should not take this herb. If you are diabetic you should consult your doctor first.
Rarely, milk thistle can cause diarrhoea, feeling sick and heartburn.
If you have liver problems you should consult your doctor first. High doses of the herb can cause elevated levels of bilirubin and liver enzymes.
We need more research looking at how milk thistle might affect cancer treatments.
Generally antioxidant supplements are not recommended during chemotherapy or radiotherapy treatment. This is because they may block some of the cancer killing effects of these treatments.
Research into milk thistle and cancer
Research in the laboratory has shown that milk thistle might help to treat some liver diseases, such as hepatitis and cirrhosis.
A few trials have looked at milk thistle for people with cancer.
Trials have looked at silymarin (milk thistle) and chemotherapy. They wanted to see if milk thistle has a protective effect on the liver and kidneys.
One small trial gave silymarin before cisplatin chemotherapy. They gave some people silymarin for 7 days before cisplatin started. The other group of people had cisplatin without silymarin. They found that the people having silymarin had lower levels of 
nitrogen and creatinine.
Another trial gave a higher dose of silymarin for 2 days before cisplatin. They compared the people having silymarin to the people having cisplatin on its own. There was no difference between the two groups.
The authors say we need larger studies. So we can see what effect silymarin might have when given with chemotherapy.
One study in people with breast cancer looked at applying silymarin gel to the skin. They applied gel to the chest wall. This was following a mastectomy and during radiotherapy treatment.
The aim was to see if the silymarin gel could help prevent radiodermatitis. Radiodermatitis is sore, inflamed skin caused by radiotherapy.
People either had the silymarin gel or a placebo gel. They had the gel on the first day of radiotherapy treatment and continued for the full 5 weeks of treatment. The silymarin gel reduced the onset and severity of the radiodermatitis.
A few studies have looked at children with acute lymphoblastic leukaemia (ALL). They wanted to see if milk thistle could help with toxicity from chemotherapy.
One study gave silymarin to children having methotrexate for ALL. They wanted to see if the silymarin could protect the liver and kidneys. 80 children took part and either received silymarin or a . They found that silymarin improved some of the liver and kidney function results.
Another small study of 80 children with ALL looked at milk thistle and doxorubicin chemotherapy. Doxorubicin can cause heart problems. They wanted to see if milk thistle could reduce doxorubicin induced cardiotoxicity. They found that compared to placebo, milk thistle did reduce cardiotoxicity. More studies with larger numbers of people are now needed.
A number of companies on the internet claim that milk thistle can help to detoxify and protect your liver. They also claim that it can help to protect other organs of the body such as the gallbladder and spleen.
Some claim that it slows the growth of some types of cancer, including breast and prostate cancer.
It is possible that milk thistle may play a part in treating liver disease and some types of cancer. But we need a lot more research with larger numbers of people first. Reliable clinical trials can find out how useful milk thistle might be in preventing or treating cancer.
A word of caution
Make sure you check with your cancer specialist before you start taking milk thistle. They know about your individual situation, so can give you advice.
