Diet problems caused by treatment

The treatments most likely to cause problems with eating and drinking are chemotherapy, radiotherapy, surgery to the digestive system, biological therapy and bone marrow and stem cell transplants.

Some treatment side effects are difficult to control but there are things that can help. You may have to take medicines to stop you feeling sick. Or have extra nutrients in high calorie and protein drinks. In extreme situations you may need to have tube or drip feeds.

Chemotherapy can affect healthy cells as well as cancer cells. This is what causes most of its side effects. Different chemotherapy drugs cause different problems. The side effects that are most likely to cause problems with your eating and digestion include

• Loss of appetite (anorexia)
• Feeling and being sick
• Diarrhoea and constipation
• Infections
• Mouth problems (e.g. changes in taste, ulcers, sore, dry mouth, painful swallowing)

We have more detailed information about the side effects of cancer drugs.

Radiotherapy damages healthy cells as well as the cancer cells. The side effects of radiotherapy that can cause temporary nutritional problems will depend very much on the part of the body is being treated. For example, radiotherapy to the head and neck can cause

• Loss of appetite (anorexia)
• Taste changes
• Mouth ulcers
• Difficulty swallowing
• Dry mouth
• Sore and inflamed gums

If the area being treated with radiotherapy is your stomach or abdomen then some of the side effects most likely to affect your eating and digestion are

• Diarrhoea
• Feeling and being sick
• Pain
• Inflammation in the bowel
• Blockages in the bowel making it difficult to absorb nutrients (long term side effect)

Radiotherapy can also cause tiredness. This may affect your appetite and put you off your food. Many people who are having treatment feel so tired they don't feel like cooking or eating, leading to weight loss. We have more detailed information about the side effects of radiotherapy to specific areas of your body in our radiotherapy section.

After any surgery, you may not feel like eating much for a while. But it is important to eat foods high in calories and protein to help with healing and fighting infection. If you are malnourished before surgery then you are more at risk of getting an infection and it will take more time to recover from your operation. People who are very malnourished before surgery may need tube or drip feeding to build them up beforehand or help them recover afterwards.

Surgery to your digestive system is most likely to cause longer lasting problems with diet. The problems you have will depend on what you had surgery for. You could have swallowing problems after surgery to the gullet (oesophagus) or voice box (larynx). Diarrhoea can be a problem after bowel, stomach or pancreatic surgery. We have information on

• Diet after cancer of the voice box (larynx)
• Diet after oesophageal surgery
• Diet after stomach surgery
• Diet and pancreatic surgery
• Diet after bowel surgery

There are different types of biological therapies - these are treatments that use natural body substances or drugs that block natural body processes. Biological therapies can cause side effects. The side effects that are most likely to cause problems with nutrition are

• Feeling and being sick
• Loss of appetite (anorexia)
• Diarrhoea
• Fever
• Tiredness

We have more information about biological therapies in our cancer treatment section. 

Bone marrow or stem cell transplants are used to treat a variety of different types of cancer. They are sometimes called bone marrow rescue or stem cell rescue. This is because bone marrow cells or stem cells (or cells collected from umbilical cords) are used to replace the cells in your bone marrow that have been killed off by high dose chemotherapy or total body radiotherapy. There is more about bone marrow and stem cell transplants in CancerHelp UK.

The side effects for bone marrow and stem cell transplants are really the same as for chemotherapy. You are having the same drugs, just higher doses. But because you are having higher doses, the side effects can be more severe and can last longer, especially if you also have total body irradiation (TBI). The main side effects that can cause problems with diet are

• Sickness
• Diarrhoea
• Sore mouth and sore throat
• Difficulty eating and drinking (including loss of appetite)
• Feeling tired and run down

If you have a transplant from a relative or an unrelated donor, there is a risk of a condition called graft versus host disease (GVHD). This can cause severe diarrhoea and weight loss. You can find out more about it in our GVHD section.

Some people having bone marrow transplants benefit from having food through a tube into their stomach (enteral nutrition) or intravenous (drip) feeds called ‘parenteral nutrition (PN)’. We have more information about drip and tube feeding in our managing diet problems section.

There is more about other aspects of diet and cancer treatments in the main sections on chemotherapy, radiotherapy and other cancer treatments.