Should I take dietary supplements during cancer treatment?

There are no benefits from taking dietary supplements during cancer treatment.

If you eat a healthy and varied diet, it’s likely you will be getting enough vitamins and minerals. There can be risks if you take dietary supplements during treatment, as certain vitamin and mineral supplements can reduce the effect of radiation and chemotherapy. You should only take supplements if your doctor has advised you to.

What are dietary supplements?

Dietary supplements are intended as a supplement to your daily diet and can contain one nutrient, such as vitamin C, or a combination, such as a multivitamin supplement. Dietary supplements come in the form of pills, powders, drops, capsules or drinks.

We recommend that you only take supplements if you are deficient in a certain nutrient. If you think you may be low in a particular vitamin or mineral, it’s best to speak to your doctor. If a supplement is advised, it is best to choose one that contains up to 100% of the RNI (reference nutrient intake – the RNI tells you how much of a vitamin or mineral you need in a day).

If you’re planning on using certain dietary supplements during radiation or chemotherapy, you should discuss this with your doctor and dietitian first.

What does the research show?

Some supplements can have a bad effect such as increasing the growth or number of tumours. Supplements can also react with cancer treatment. A number of scientific studies have shown that taking supplements reduced how well a treatment worked.

Other studies showed that patients taking supplements had a lower survival rate than patients who did not take supplements. As such, we don’t advise taking supplements unless they have been recommended by your doctor or dietitian.

What about natural remedies. Can they help?

There’s also no evidence that natural remedies can stop or reduce the chance of cancer recurring or improve survival from cancer. However, any supplements recommended or advised by your doctor may help you to feel better.

If you’re considering taking homeopathic, natural, or herbal remedies that haven’t been prescribed for you, you need to discuss this with your doctor before you start taking them to check they are safe for you.

Our advice

If you have a poor appetite or are unable to eat a healthy diet due to cancer or the side effects of your treatment, then you might be deficient in some vitamins and minerals.

If you’re worried, then it’s important to talk about your diet with a doctor or dietitian. A dietitian will be able to tell you if you should be taking certain supplements. If your diet changes – or you’re placed on a special diet – you should speak to your doctor or dietitian about using supplements.

> Tips for dealing with loss of appetite during cancer

> Find out more about living with cancer


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