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Treatment side effects and nutrition

Eating well can be a challenge when you have cancer. Sometimes it’s the cancer itself that prevents you from eating, digesting or absorbing food well. Usually it’s because of the side effects of cancer treatments.

These side effects will vary from person to person, and depend on the type of cancer, treatment and medicines you have. Most side effects that affect eating are temporary and gradually get better after treatment ends.

Worrying about the diagnosis and treatment can also affect your appetite. If this is the case for you, talk to a family member or friend, the social worker at the hospital, your doctor or a psychologist. You can also call our cancer nurses on 13 11 20.

How cancer treatments can affect nutrition

Cancer treatment may cause the following side effects affecting nutrition:

  • Surgery – difficulty chewing and swallowing, reflux, diarrhoea, constipation, difficulty absorbing nutrients, weight loss, pain and fatigue.
  • Chemotherapy – appetite loss, nausea, vomiting, constipation, diarrhoea, mouth sores, taste changes, lowered immunity, fatigue and weight loss.
  • Radiation therapy – appetite loss, fatigue, taste changes, nausea, vomiting, diarrhoea, dry mouth, difficulty chewing or swallowing, bowel obstruction, mouth sores, reflux, weight loss, pain and fatigue.
  • Hormone therapy – weight gain, appetite changes, nausea, increased cholesterol levels, constipation and mood changes.
  • Stem cell transplant – lowered immunity, sore mouth and throat, nausea, vomiting, diarrhoea, fatigue, loss of appetite and weight loss.
  • Steroid therapy – increased appetite, weight gain, increased risk of infection, stomach irritation and unstable blood sugar levels.
  • Targeted therapy – diarrhoea, nausea, vomiting, constipation, taste changes, mouth sores, fever, increased risk of infection and weight loss.
  • Immunotherapy – diarrhoea, bloody bowel movements, abdominal pain, bloating and weight loss or weight gain.



I went through all the symptoms you could think of – I had vomiting, diarrhoea, metallic taste in the mouth, and I lost a lot of weight. The nausea was really bad. It made my appetite go. I tried to eat, and all I could handle was dry biscuits. Chemotherapy took a toll on my body.  – Marie

Managing side effects

Lowered immunity

Cancer and some treatments (such as chemotherapy and stem cell transplants) can reduce your white blood cell level, making it harder for your body to fight infections. If this happens, you will need to take care preparing and storing food because you are more likely to get food-borne illnesses.

Wash your hands and knives, cutting boards and food preparation areas thoroughly with hot soapy water before and after cooking. Where possible, ask for meals to be made fresh when eating out and avoid pre-prepared foods that have been sitting for unknown periods of time.

Loss of appetite

Not feeling like eating is known as loss of appetite. This may happen because of the side effects of cancer itself or the treatment, such as feeling sick, not enjoying the smell of food, or worrying about the diagnosis and treatment.

Loss of appetite can contribute to weight loss and malnutrition. It is important to keep trying to eat so you can maintain your weight and meet your nutrition needs. 

How to manage loss of appetite

  • Eat small meals every 2–3 hours during the day, and keep to a regular eating pattern rather than waiting until you’re hungry.
  • Follow your appetite. It’s okay to eat what you feel like, when you feel like it. Putting on or maintaining your weight is the main focus at the moment.
  • Exercise before a meal. Gentle physical activity can make you feel hungry.
  • Use a smaller plate. A big plate of food may put you off eating.
  • Add extra energy to your food with butter, cream, cheese and sour cream.
  • Choose fluids that are high in kilojoules and protein, such as milk, milkshakes, smoothies or creamy soup. These may be easier to manage than a meal.
  • Make mealtimes more enjoyable by setting the table, playing music or eating with someone.
  • Manage side effects that may be affecting your appetite, such as dry mouth and nausea.



A common side effect of treatment is feeling extreme and constant tiredness (fatigue). Fatigue can be caused by treatment side effects that reduce the number of red blood cells (anaemia) or that affect your appetite.

Learn more

How to manage fatigue and nutrition

  • Eat a wide variety of foods. See a dietitian for advice tailored to you.
  • Plan ahead for when you feel too tired to cook. Buy frozen meals from the supermarket or prepare food in advance and store it in the freezer.
  • Cook in the morning when you are less likely to be tired.
  • Buy groceries online instead of going to the shops.
  • Ask for and accept offers of help with shopping and cooking from others. Use apps such as CanDo.
  • Keep snacks such as wholefood muesli bars, dried fruit, nuts and wholegrain crackers in handy locations, including your bag or car. This will allow you to keep your energy levels up if you have unexpected delays.
  • Use home delivery meal companies or services that bring pre-prepared food to you, or try companies that deliver ingredients with recipes that you can cook at home yourself.
  • Do regular exercise to help improve fatigue and appetite.
  • Eat with others to make meals as enjoyable as possible, particularly if you are feeling too tired to eat.

Changes in taste or smell

Some treatments can affect the taste and smell of foods. It may take several months for your sense of taste to return to normal. In some cases, changes may be permanent.

Some people find that even the taste of water is a problem. This can make it challenging to get through the recommended amount of water each day and to swallow medicines with water. Adding lemon, lime, fruit juice, cordial or fresh mint to water may make it easier to drink.

Talk to your doctor, speech pathologist, dentist or dietitian for support. 


During treatment, I developed an active sense of smell. I hated certain smells and did all I could to avoid them. My mouth felt very dry, which made food taste unappetising. Adding extra sauce helped. – Helen

Chewing and swallowing problems

Chewing and swallowing involve your lips, teeth, tongue and the muscles in your mouth, jaw and throat working together. 

Radiation therapy and surgery to the jaw, mouth or throat areas can make chewing and swallowing hard. These changes are usually temporary, but can sometimes be permanent. You may need to adjust the texture of foods to help manage side effects.

Problems chewing 

People with dentures who lose weight may find their teeth become loose. Treatment for head and neck cancer sometimes involves removing teeth. Both of these things can make it hard to chew.

Difficulty swallowing

If you’re having difficulty swallowing (dysphagia), you may need to change the consistency of food by chopping, mincing, pureeing or thickening it.

Signs that the texture of food is causing problems include:

  • taking longer to chew and swallow
  • coughing or choking while eating or drinking
  • feeling like food or drink is going down the wrong way
  • food sticking in your mouth or throat like a ball
  • throat clearing after meals.

A speech pathologist can assess how your swallowing is working and a dietitian can suggest ways to make sure you are getting enough nutritious food.

Feeding tubes

Severe swallowing problems can make it hard to eat and drink. You may need a feeding tube until swallowing gets easier. This will help you meet your nutrition needs.

A feeding tube is rare for most people with cancer, but is more of a possibility with cancers affecting the head and neck, stomach, oesophagus or lung. If a feeding tube is required, your treatment team will discuss this with you. 



Some cancers, treatments and medicines can cause stomach contents to come back up into the oesophagus (food pipe). This is known as reflux, and it can irritate the lining of the oesophagus.

Reflux can lead to a burning feeling in the upper chest, oesophagus and/or throat. This sensation is called indigestion or heartburn. Eating certain foods or lying down after eating can make heartburn worse. Heartburn may make you feel too uncomfortable to eat much, which could lead to weight loss.

Keeping a diary of the foods you eat and your symptoms can help you identify which foods trigger the heartburn. Talk to your doctor if you cannot find relief. They may be able to prescribe medicines to help.

How to manage reflux

  • Avoid large meals – try to eat three small meals and three snacks throughout the day.
  • Eat slowly and enjoy your meal. Avoid wearing tight clothing (especially belts) while eating.
  • Sip fluids between meals, rather than drinking large amounts at mealtimes.
  • Limit or avoid foods that may make heartburn worse – very spicy foods, high-fat foods (e.g. fried food, pastries, cream), acidic foods including tomato and tomato products, citrus fruits, vinegar, chocolate, coffee (including decaf), strong tea, soft drinks and alcohol.
  • After eating, sit upright for at least 30 minutes and avoid lying down or activities that involve bending over (including gardening).
  • Sleep with the head of the bed lifted by 15–20 cm. Put blocks under the front bed legs or use a wedge under the mattress.


Mouth health

Dry mouth

Radiation therapy to the head or neck area and surgery that affects the salivary glands can reduce the amount of saliva in your mouth, make your mouth dry or make your saliva thick and sticky (xerostomia).

Without enough saliva, bacteria can grow too quickly and may cause oral thrush, which will make eating and swallowing more difficult. A dry mouth can also make it harder to keep your teeth and mouth clean, which can increase the risk of tooth decay.

Mouth sores

Chemotherapy and radiation therapy can damage the cells lining the mouth and digestive tract, leading to ulcers and infections (oral mucositis). A sore can form on any soft tissue in your mouth, and make it painful to eat and swallow.

Your doctor can give you medicines to reduce pain and discomfort when you eat or drink. Try to eat softer foods. You may need to avoid hot, cold, salty, spicy or acidic foods and drinks. Mucositis usually gets better a few weeks or months after treatment ends.

Learn more

Nausea and vomiting

Nausea is feeling sick and vomiting is throwing up. It’s common to have them together. Cancer and its treatments can cause nausea and vomiting. 

If you have chemotherapy, you will be given anti-nausea medicine with your treatment and to take at home afterwards. In many cases, this will prevent severe nausea and vomiting, but some people do still feel sick and may vomit. It’s important to take anti-nausea medicine as directed – don’t wait until you feel sick.

Nausea and vomiting can also be triggered by stress, food smells, gas in the stomach or bowel, motion sickness or even the thought of having treatment.

After a person has had a few treatment sessions, they may link certain sights, sounds or smells with treatment and feel nauseated when they experience them. This is known as anticipatory nausea or vomiting, and it is more common in people having chemotherapy.

How to cope with nausea

  • Have a light snack before chemotherapy, and don’t eat for a few hours after.
  • Eat small meals every 2–3 hours. Going without food for long periods can make nausea worse.
  • Choose dry or bland snacks, including crackers, toast, dry cereals, bread sticks or pretzels.
  • Have cold foods or foods at room temperature as they have less aroma.
  • Drink fluids all day to avoid becoming dehydrated.
  • Try drinks and foods with ginger, including ginger tea, non-alcoholic ginger beer, ginger biscuits.
  • Avoid foods that are too sweet, fatty, fried or spicy, or that have strong smells.
  • Brush teeth regularly to help reduce tastes that may make you feel nauseated.
  • Don’t eat your favourite food when feeling nauseated as you may develop a permanent dislike. 

How to cope with vomiting

  • Take sips of fluids as often as possible. Try flat dry ginger ale, cold flat lemonade, weak cordial, or cold apple juice. Oral rehydration solutions, such as Hydralyte or Gastrolyte, can help keep you hydrated.
  • See your doctor if vomiting lasts for more than a day or if you can’t keep fluids down, as you may become dehydrated.
  • Slowly introduce more nourishing fluids once you stop vomiting, including milk or fruit drinks with added water so they are not too strong, clear broth and weak tea.
  • Have small amounts of solid foods once vomiting is under control, including plain dry biscuits, toast or bread, stewed fruits and yoghurt.
  • Increase how much you eat until you’re eating what is normal for you.
  • Listen to The Thing About Cancer podcast episode on appetite loss and nausea for support.



Diarrhoea is when you have loose, watery bowel movements several times a day. You may also get cramping and pain, and have an urgent need to go to the toilet.

Chemotherapy, radiation therapy to the abdomen or pelvis, some types of surgery, medicines, infections, reactions to certain foods, and anxiety can all cause diarrhoea.

For support, ask your doctor about anti-diarrhoea medicines, call the National Continence Helpline on 1800 33 00 66 and rest until you feel better.

How to manage diarrhoea

  • Drink plenty of water and other fluids such as diluted cordials and oral rehydration solutions (e.g. Gastrolyte) to prevent dehydration. Avoid high-sugar drinks, alcohol, strong caffeine or very hot fluids.
  • Watch for signs of dehydration such as dark yellow urine (pee) or urinating less than usual.
  • Choose foods that are low in insoluble fibre (e.g. bananas, mashed potato, white rice, white pasta, white bread, steamed chicken without skin, white fish). It may also help to eat foods that are high in soluble fibre (e.g. oats, barley, rye, legumes, peeled fruits and vegetables, avocado, soy products).
  • Avoid foods that are high in insoluble fibre (e.g. wholegrain breads, bran cereals, nuts and seeds, raw fruit, vegetable skins) and foods that increase bowel activity (e.g. spicy, fatty or oily foods, caffeine, alcohol or artificial sweeteners).
  • Switch to soy milk or lactose-free milk for a period of time. Having diarrhoea may affect your ability to digest the natural sugar in milk (lactose).



Constipation is when your bowel movements (faeces, stools or poo) are hard and difficult to pass. It can be caused by different factors including:

  • some chemotherapy and anti-nausea drugs
  • strong pain medicines (opioids)
  • eating less fibre
  • not moving around as much
  • not drinking enough (dehydration)
  • not eating enough.

If you have severe constipation with symptoms such as abdominal pain and swelling, nausea and vomiting, this may be sign of a blockage in the bowel (bowel obstruction). This needs urgent medical attention.

How to manage constipation

  • Drink 8–10 glasses of fluid a day to soften faeces.
  • Eat foods high in insoluble fibre (e.g. wholegrain breads, cereals or pasta; raw and unpeeled fruits and vegetables; nuts and seeds; legumes and pulses).
  • If you add foods with more insoluble fibre to your diet, drink more fluids to avoid the extra fibre making constipation worse.
  • Ask your doctor about using a laxative, stool softener and/or fibre supplement.
  • Plan to do some physical activity every day. Ask your doctor, exercise physiologist or physiotherapist about the amount and type of exercise that is right for you.
  • Visit your doctor if you see blood in your faeces. They’ll check for haemorrhoids or any other issues.
  • If you have had surgery for bowel cancer and have a stoma, ask your health care team for specific dietary advice. They may suggest eating more low-fibre foods to avoid constipation.


Dumping syndrome

This is a group of symptoms that develops when food moves too quickly from the stomach into the small bowel. You may have cramps, nausea, racing heart, sweating, bloating, diarrhoea or dizziness.

Dumping syndrome can develop after surgery to remove part or all of the stomach.

The symptoms can vary depending on what you eat. Foods and drinks high in sugar such as soft drinks, juices and cordial can make dumping syndrome worse. Symptoms often improve over time.

Your treatment team can suggest changes to what you eat and medicines to help manage dumping syndrome.

Learn more

Other types of bowel irritation

Some chemotherapy drugs, stem cell transplants and radiation therapy to the pelvic area can make the bowel swollen and sore. This is called colitis when it affects the colon (the large bowel), and proctitis when it affects only the rectum (the last part of the bowel before the anus).

You may feel the need to empty your bowels often, perhaps without much result. Straining can cause discomfort, and there may be blood or mucus in your bowel movements.

The small bowel may become irritated after chemotherapy or radiation therapy to the abdomen or pelvic area. This is known as enteritis and it can cause discomfort in the abdomen (like cramps or wind pain), pale and runny bowel movements, and more wind than usual.

How to manage bowel irritation

  • Eat and drink slowly, take small mouthfuls and chew your food well to avoid swallowing air.
  • Have foods low in insoluble fibre to reduce bowel irritation in the short term. Include foods high in soluble fibre to 'soak up' additional liquid in your bowel.
  • Avoid fatty, spicy or fried foods, and rich gravies and sauces.
  • Reduce foods such as corn, beans, cabbage, onions, pickles and fizzy drinks, which can produce wind.
  • Drink plenty of water, and eat soft or cooked peeled fruit, fine wholemeal bread and bran to provide soft bulk. You may be encouraged to take an oral rehydration solution, such as Hydralyte or Gastrolyte, to keep hydrated.
  • Do some gentle exercise, such as walking, to encourage more regular bowel movements.
  • Tell your doctor if symptoms don’t improve. Bowel irritation is usually temporary, with colitis and proctitis lasting up to 8 weeks and enteritis lasting 1–2 weeks after treatment ends.


Weight changes

Weight loss

It’s common for people diagnosed with cancer to lose weight. This is because the process of cancer cells dividing uses up a lot of energy, and treatment side effects can change your desire to eat or make eating difficult or painful.

Weight loss may depend on the type of cancer you have. Advanced cancer may mean the way the body absorbs food changes (cachexia). With the support of your cancer care team you can prevent or slow down weight loss.

Maintaining your weight, particularly your muscle stores, will help you stay strong and recover faster. Talk to your dietitian about nutritional supplement drinks or having a feeding tube.

During treatment when you don’t feel well enough to eat, just eating something is more important than making healthy food choices. Keep in mind that these changes are often temporary – you can return to the usual guidelines for healthy eating once you have recovered from treatment.

How to manage weight loss

  • Treat food like medicine – something your body needs regularly to feel better.
  • Set times for meals and snacks rather than waiting until you’re hungry.
  • Have your biggest meal when you’re hungriest and not too tired.
  • Eat your favourite foods at any time of day.
  • Carry snacks so you can eat any time you feel like it. Try hard-boiled eggs, muesli bars, dried fruit and nuts, crackers and fruit buns.
  • Choose drinks and snacks that are higher in protein and energy, e.g. drink full-cream milk rather than water and choose cheese and biscuits over lollies.
  • Add high-protein foods, e.g. poultry, fish, meat, eggs, tofu, dairy, nuts, seeds and legumes, to every meal or snack.
  • Add fats and oils to what you are already eating, e.g. use extra butter, avocado, nut butters, cheese, extra virgin olive oil and cream. Avoid food and drinks labelled low-fat or no fat.
  • Have dessert after meals.
  • Do some gentle exercise, e.g. a walk before meals to increase your appetite.
  • Make enriched milk to use in tea and coffee, cereal, soups, sauces, scrambled eggs, milkshakes and smoothies. Add 4 or more heaped tablespoons of milk protein to 1 litre of full-cream milk and mix thoroughly. Use straightaway, or keep refrigerated and use within 24 hours (stir before use).
  • Stock up on ready-to-use nutritional supplement drinks when you are travelling or on other occasions when it is difficult to prepare a meal. 

Nutritional supplements

If you cannot eat a balanced diet or are losing weight without trying, your doctor or dietitian may suggest nutritional supplements such as Sustagen, Ensure, Fortisip or Resource.

These are high in energy and protein, and provide nutrients that can help maintain your strength. Nutritional supplements are available as: 

  • powders to mix with milk or water, or sprinkle on food
  • ready-made drinks, puddings, custards and jellies.

They can be used as snacks between meals, or some can be added to drinks or meals. A dietitian can recommend the right nutritional supplement for you.

If you are having difficulty swallowing, talk to a speech pathologist for directions on thickening the supplements. Many pharmacies and supermarkets sell nutritional supplements. While you don’t need a prescription for many supplements, a prescription may make them cheaper to buy.

Weight gain

Although it is more common to lose weight during treatment, some people put on weight. This is more likely to happen with certain types of cancer such as breast cancer.

Weight gain can happen as a side effect of treatment and/or medicines:

  • some chemotherapy drugs can cause your body to retain extra fluid in cells and tissues. This is called oedema, and it can cause weight gain and make you feel and look puffy. If chemotherapy makes you feel nauseated, you may find snacking helps but means you eat more.
  • hormone therapy lowers the amount of hormones in the body, which slows your metabolism.
  • steroid therapy (corticosteroids) can cause a larger abdomen, fluid retention (oedema), and a rounded, puffy face. Steroids can also increase your appetite, which may mean you eat more and put on weight.

Feeling stressed or depressed can also make some people eat differently, and being tired because of the treatment may make it harder to exercise.

If you put on weight during treatment and are concerned, speak to your doctor or dietitian. It is important that your body gets enough nutrition, so do not try a weight loss diet without guidance from a health professional.

Nutrition for People Living with Cancer

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Expert content reviewers:

Jacqueline Baker, Senior Oncology Dietitian, Chris O’Brien Lifehouse, NSW; Lauren Atkins, Advanced Accredited Practising Dietitian, OnCore Nutrition, VIC; Dr Tsien Fua, Head and Neck Radiation Oncology Specialist, Peter MacCallum Cancer Centre, VIC; Rosemerry Hodgkin, 13 11 20 Consultant, Cancer Council WA; Clare Hughes, Manager, Nutrition Unit, Cancer Council NSW; John Spurr, Consumer; Emma Vale, Senior Dietitian, GenesisCare, SA; David Wood, Consumer.

Page last updated:

The information on this webpage was adapted from Nutrition for People Living with Cancer - A guide for people with cancer, their families and friends (2022 edition). This webpage was last updated in July 2022.

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