A study looking at the use of herbal medicines and dietary supplements by people with cancer

Cancer type:

All cancer types





This study looked at the type of supplements that people with cancer take, and the potential risks and benefits.

More about this trial

Some people use complementary and alternative medicines (CAMs) alongside cancer treatments prescribed by their doctors. 
People may use them to help with sickness, tiredness (fatigue) or pain, or to improve their feeling of wellbeing. But some types of CAM may interact with other treatments or have side effects.
In this study, the researchers looked at the use of herbal and dietary supplements. They hoped to learn more about the:
  • types of supplements people with cancer are using
  • potential benefits 
  • possible harm they can cause
  • interactions between supplements and treatments prescribed by doctors

Summary of results

The research team found that the dietary and herbal supplements people used in this study did not cause side effects.
This study was open for people to join between 2013 and 2014, and the researchers reported the results in 2016.
About this study
The research team sent questionnaires to nearly 1,500 people who were having treatment for cancer, and 375 people completed one and sent it back.
The questionnaires asked them:
  • which treatments their doctor had prescribed for them
  • if they had taken any herbal or dietary supplements as well
  • whether they felt they’d had a benefit from the supplements or not
The results showed that 127 out of 375 people (34%) had taken a dietary or herbal supplement at the same time as treatment prescribed by their doctor. 
The research team found that the people taking part had taken 101 different supplements. The most commonly used supplements were:
  • glucosamine 
  • cod liver oil
  • multivitamins
  • vitamin C
  • omega 3 fatty acids
  • vitamin D
  • green tea
They had also been prescribed 167 different standard medicines. In total there were more than 1,200 different combinations of supplements and treatments.
Possible interactions
The study team looked at other research and reports to find out about possible interactions between supplements and prescribed treatments. 
Out of the possible combinations of treatments and supplements in this study, they found that:
  • 1,225 had no record of any interaction
  • 22 may cause problems but doctors didn’t think the evidence was very reliable
  • 5 could potentially cause problems but there wasn’t much evidence
  • 1 was considered a significant risk, but the patient had already stopped taking the supplement
  • 1 was potentially life threatening and should be avoided, but again the patient had stopped taking the supplement
When this study was done, much of the published information about supplements was from laboratory research rather than research with people. It can be difficult to predict possible problems from laboratory research.
The research team found that the combinations in this study were not harmful and that no one had any serious side effects. 

Quality of life

The research team asked the people taking part if they thought they’d had any benefit from the supplements they’d taken. Of those who replied:
  • 82 said they thought they’d had a benefit from the supplements
  • 28 said they hadn’t had a benefit but hadn’t had any problems either
  • 2 said they’d had problems caused by the supplement
The research team concluded that most people who were taking supplements were not at risk of side effects, but the study wasn’t large enough to say for sure that supplements are safe. They recommend that health care professionals give advice about supplements on an individual basis.
Where this information comes from
We have based this summary on information from the research team. The information they sent us has been reviewed by independent specialists (peer reviewed Open a glossary item) and published in a medical journal. The figures we quote above were provided by the trial team who did the research. We have not analysed the data ourselves.

Recruitment start:

Recruitment end:

How to join a clinical trial

Please note: In order to join a trial you will need to discuss it with your doctor, unless otherwise specified.

Please note - unless we state otherwise in the summary, you need to talk to your doctor about joining a trial.

Chief Investigator

Saud Alsanad

Supported by

Duchess of Kent Hospice
Nettlebed Hospice
Oxford University Hospitals NHS Trust
Royal Embassy of Saudi Arabia 
Sobell House Hospice Charity Limited
University of Reading

If you have questions about the trial please contact our cancer information nurses

Freephone 0808 800 4040

Last review date

CRUK internal database number:


Please note - unless we state otherwise in the summary, you need to talk to your doctor about joining a trial.

Charlie took part in a trial to try new treatments

A picture of Charlie

“I think it’s really important that people keep signing up to these type of trials to push research forward.”

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