How cancer can affect eating

People with cancer may have different dietary needs. Some people feel well and able to eat normally. For others, weight loss or a poor appetite were symptoms that led to their diagnosis. If you had eating problems before you were diagnosed, you may need support to improve your diet. Speak to your doctor or dietitian before you start treatment.

Some eating problems may be related to the cancer itself. Depending on where the cancer is in your body, it can cause:

  • sickness (nausea or vomiting)
  • pain
  • poor digestion

The cancer may also change the way your body uses the food you eat. This means that you do not get all the nutrients you need.

Booklets and resources

Being referred to a dietitian

Qualified dietitians are experts in assessing people’s food needs. They can look at your diet and any specialist dietary requirements you have. They can advise you on which foods are best for you, and if any food supplements would be helpful.

If you have problems with your diet, you can ask your doctor at the hospital to refer you to a dietitian. In some hospitals, you can refer yourself. Contact the hospital’s dietetic department for more information. If you are not in hospital, your GP or district nurse can refer you to a community dietitian. 

How treatment can affect eating

Some cancer treatments can cause eating problems. Some problems are temporary and improve when you finish treatment. Others may last longer. Your doctor, specialist nurse or dietitian will advise you on what might help.


Some types of surgery can slow down your digestion. If you have surgery to your mouth, throat, oesophagus (gullet), stomach or bowel, you may need to adjust to changes in your eating pattern.

After some types of surgery, you may only be able to eat soft foods.


Radiotherapy to your head, neck or chest area can cause:

  • changes to taste
  • swallowing difficulties
  • a dry mouth
  • a sore mouth and throat
  • blisters in your mouth
  • thick saliva.

Radiotherapy to the abdomen (tummy) or pelvic area (the area between the hips) can make you feel sick or be sick. It can also cause diarrhoea.


Common side effects of some chemotherapy treatments include:

  • loss of appetite
  • feeling sick or being sick
  • constipation
  • diarrhoea
  • a sore mouth
  • changes to taste.

Targeted therapy

Targeted therapies can affect your appetite or your ability to eat. Problems might include changes to taste, a dry or sore mouth or feeling sick. 


Immunotherapy can cause side effects such as diarrhoea, nausea or a reduced appetite. These can affect your appetite and eating.

Following a special diet

Some people with cancer may have specific eating problems, for example people who have:

  • diabetes
  • a colostomy or ileostomy
  • had all or part of their stomach or bowel removed
  • had radiotherapy to their mouth or jaw.

If you have any of the above, you may need to follow a special diet. Your doctor, specialist nurse or dietitian can give you advice.

Cancer or treatments for cancer may temporarily increase your risk of infection. If your immunity is very low, you might need to avoid certain foods. We have more information about foods to avoid if you are at risk of infection.

Tube feeding

Sometimes cancer or cancer treatment causes eating problems that mean you cannot eat or drink enough to maintain your weight. Your cancer doctors or dietitian may suggest artificial nutritional support. This is when you are given nutrients through a tube. This tube may go either into the stomach or bowel (enteral nutrition), or into a vein (parenteral nutrition).

Coping with eating problems

There are things you can do if you are struggling with eating problems. We have more information on how to cope with eating problems due to:

  • tiredness (fatigue)
  • constipation
  • diarrhoea
  • wind
  • feeling sick (nausea)
  • changes in appetite
  • heartburn or indigestion.

We also have information about coping with mouth problems, including:

  • a sore or dry mouth
  • taste changes
  • difficulty chewing and swallowing.

Your feelings about eating problems

You may feel self-conscious about eating at home or out with family or friends. You may worry that changes in your eating will affect your relationships with your partner, family or friends. Or you may be anxious about what people think of your eating problems.

Many people find that it helps to talk to someone close to them. If you find it difficult to talk about your feelings with your family, you could speak to your doctor, specialist nurse or GP. There are ways they can support you.

If you are a carer

If you are the main carer for someone with cancer, it can be upsetting and difficult to know how to deal with eating problems, such as lack of appetite or weight loss. People who are ill often do not feel like eating.

The amount someone can eat may change each day, and their likes and dislikes may also change. Try not to put pressure on someone to eat. This can sometimes cause arguments. If you know when their appetite is at its best, you can make the most of it. For example, you could treat them to their favourite foods.

If the person you are caring for continues to struggle with food and is losing weight, speak to their doctor or nurse. They can refer them to a dietitian. The dietitian can advise on using nutritional supplement drinks if this is appropriate.

We have more tips about preparing and serving food.

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About our information

  • References

    Below is a sample of the sources used in our eating problems information. If you would like more information about the sources we use, please contact us at

    European Oral Care in Cancer Group – Oral Care Guidance and Support. 1st Edition. Available at: [Accessed 10.02.2020] 

    National Cancer Institute. Nutrition in Cancer Care. (PDQ) Updated 2019. [accessed March 2020] 

    The Royal College of Surgeons of England/The British Society for Disability and Oral Health. The oral management of oncology patients requiring radiotherapy, chemotherapy and/or bone marrow transplantation. Clinical Guidelines. 2018. 

    UK Oral Management in Cancer Care Group (UKOMiC), Oral Care guidance and support in cancer and palliative care (3rd edition), 2019. 

  • Reviewers

    This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer. It has been approved by Chief Medical Editor, Professor Tim Iveson, Consultant Medical Oncologist.

    Our cancer information has been awarded the PIF TICK. Created by the Patient Information Forum, this quality mark shows we meet PIF’s 10 criteria for trustworthy health information.

Date reviewed

Reviewed: 01 August 2020
Next review: 01 August 2023

This content is currently being reviewed. New information will be coming soon.

Trusted Information Creator - Patient Information Forum
Trusted Information Creator - Patient Information Forum

Our cancer information meets the PIF TICK quality mark.

This means it is easy to use, up-to-date and based on the latest evidence. Learn more about how we produce our information.