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Treatment side effects and nutrition

Cancer treatments kill cancer cells, but in the process they damage normal healthy cells and cause side effects. These side effects vary from person to person, and depend on the type of treatment, the part of the body treated, and the length and dose of treatment. Most side effects are temporary and go away after treatment ends. There are ways to control and manage side effects.

Some treatment side effects can, in turn, affect what you can eat and how much. These include:

  • fatigue
  • poor appetite and weight loss
  • changes in taste and smell
  • chewing and swallowing problems
  • dry mouth
  • nausea and vomiting
  • constipation
  • diarrhoea
  • other types of bowel irritation
  • heartburn.

Feeling anxious about the diagnosis and treatment can also affect your appetite. Talk to a family member or friend, the social worker at the hospital, or your doctor if you are experiencing these feelings.

Call Cancer Council 13 11 20 for free booklets on surgery, chemotherapy, radiotherapy and specific types of cancer.

Treatment and common side effects affecting nutrition
  What it is Side effects*
surgery the partial or total removal of a tumour or body part difficulty swallowing (oesophagus, voice box), diarrhoea (bowel, stomach, pancreatic), incomplete absorption of nutrients
chemotherapy the use of drugs to kill or slow the growth of cancer cells loss of appetite, nausea, vomiting, constipation, diarrhoea, mouth sores, taste changes, difficulty swallowing, lowered immunity, fatigue
*depends on area receiving treatment
the use of radiation to kill cancer cells or injure them so they can’t grow and multiply loss of appetite, fatigue, taste changes, nausea, vomiting, diarrhoea, dry mouth, difficulty swallowing, bowel obstruction, mouth sores
steroid therapy drugs given orally or by injection increased appetite, weight gain, increased risk of infection, stomach irritation
stem cell transplant the process of replacing stem cells destroyed by high- dose chemotherapy lowered immunity, sore mouth and throat, nausea, vomiting, diarrhoea, fatigue, loss of appetite
hormone therapy drugs that block the hormones that help some cancers grow weight gain, increased cholesterol levels
targeted therapies drugs that attack cancer cells while minimising harm to healthy cells diarrhoea, nausea, vomiting, constipation, taste changes, mouth sores, fever, increased risk of infection


A common side effect of treatment is feeling extreme and constant tiredness (fatigue) that doesn’t improve with rest. Fatigue can be caused by treatment side effects that reduce the number of red blood cells (anaemia) or that affect your appetite.

How to manage fatigue
  • Plan ahead for when you feel too tired to cook. Prepare food in advance and store in the freezer.
  • Cook in the morning when you are less likely to be tired.
  • Shop online for groceries if you don’t have the energy to go to the supermarket.
  • Ask and accept offers of help with shopping and cooking from family and friends.
  • Do regular exercise to help improve fatigue and appetite.
  • Keep snacks such as muesli bars, dried fruit, nuts and crackers in handy locations, e.g. in your bag or car.
  • See a list of quick snacks you can prepare.
  • Use services such as Meals on Wheels or other home delivery meal companies that bring pre-prepared food to you.
  • Eat with others to encourage your appetite, particularly if you feel too tired to eat.
"I was not as active before cancer as I am now. I walk a week. It gives me more energy and helps clear my mind. If I don’t do any walking, I really notice the difference in my energy levels and mood." – Rima

Loss of appetite

You may lose your appetite because of the effects of cancer itself, the treatment, or other side effects, such as feeling sick, not enjoying the smell of food, or feeling upset. This is a common issue for people diagnosed with cancer.

How to manage loss of appetite
  • Eat small meals frequently, e.g. every 2–3 hours. Keeping to a regular eating pattern rather than waiting until you’re hungry will mean your body gets the nourishment it needs to maintain your weight.
  • Use a smaller plate – a big, full plate of food may put you off eating.
  • Eat what you feel like, when you feel like it, e.g. have cereal for dinner or a main meal at lunch.
  • Include a variety of foods in your diet as this may help improve your overall intake.
  • Sip fluids throughout the day, and replace water, tea and coffee with drinks or soups that add energy (kilojoules/calories), such as milk, milkshake, smoothie or soup. These are also good if you find drinks or soups easier to manage than a meal. See recipes.
  • Relax dietary restrictions. During treatment, maintaining your weight or regaining weight you have lost is more important than avoiding full-fat and other high-energy foods.
  • Gentle physical activity can stimulate appetite, e.g. take a short walk around the block.
  • Make meals as enjoyable as possible, e.g. play music, light candles or eat with friends.

Changes in taste or smell

Some treatments and their side effects can change the way some foods taste or smell. Chemotherapy can change the taste receptors in the mouth. Radiotherapy or surgery to the head, neck and mouth area may damage the salivary glands and tastebuds on the tongue. Food may taste bitter or metallic, or may not have as much flavour as before.

People often say that, “All food tastes the same”, “Food tastes like cardboard”, “Food tastes metallic”, “I no longer like the taste of my favourite food” or “I’ve gone off red meat, chocolate and alcohol”.

It’s common to have taste changes during treatment and for a short time afterward. Sometimes it can take several months for taste changes to return to normal.

If you have a sore mouth, sore throat or swallowing difficulties, talk to your doctor, speech pathologist, dentist or dietitian – some of the suggestions for managing taste changes (see table below) will not be suitable.

See Understanding Taste and Smell Changes for more information.

"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
How to manage changes in taste or smell
Taste changes
  • Add extra flavour to food if it tastes bland, e.g. fresh herbs, lemon, lime, ginger, garlic, soy sauce, honey, chilli, pepper, Worcestershire sauce or pickles. See the marinade recipes.
  • Experiment with different food, as your tastes may change. You may no longer like bitter drinks (e.g. tea, coffee, beer or wine) or sweet food (e.g. chocolate) even if you liked them before treatment. It is common to prefer savoury food over sweet.
  • If meat tastes bad during treatment, replace it with other protein sources, e.g. cheese, eggs, nuts, dairy foods, seafood, baked beans, lentils or chickpeas.
  • Add small amounts of sugar to food if it tastes bitter or salty.
  • Use a straw so the taste of drinks isn’t as strong.
Smell changes
  • Choose cold food or food at room temperature – hot food smells stronger.
  • Reheat pre-prepared meals in the microwave so the cooking smell doesn’t put you off eating.
  • Stay out of the kitchen, if possible, when food is being prepared. Ask family or friends to cook.
  • Turn on the exhaust fan, open a window or cook outside on the barbecue to help reduce cooking smells.

Chewing and swallowing problems

After surgery to the mouth or throat, chewing and swallowing may be difficult and painful. Radiotherapy and chemotherapy to this area can also cause temporary problems. If teeth are extracted, chewing may be more difficult. People with dentures who have lost weight may also find their teeth become loose, which can make eating difficult.

Signs that the texture of food is causing problems include taking longer to chew and swallow, coughing or choking while eating or drinking, or food sticking in your mouth or throat like a ball.

Changing food textures

If you’re having difficulty swallowing, you may need to change the consistency of your food by chopping, mincing or pureeing (see types of food textures, below). This can make it easier to get enough nutrition, and reduce the risk of losing weight and strength.

A speech pathologist can monitor your ability to swallow during and after treatment, and suggest modifications to the texture of your food once your ability to swallow and chew begins to improve. Ask your doctor for a referral.

Sometimes, people may need to remain on a texture-modified diet after their treatment. However, this is different for everyone and will depend on the type of cancer or treatment received. In rare cases, a person with severe difficulty swallowing will need a feeding tube to ensure adequate nutrition. If this is required, your dietitian, speech pathologist or doctor will discuss it with you.

Types of food textures

Food can be chewed but not necessarily bitten. It should be easily broken up with a fork and need little cutting. Sauce or gravy can be added to make it softer.

Minced and moist

Food should be soft and moist and easily form into a ball in the mouth. Small lumps can be broken up with the tongue rather than by biting or chewing. Food should be easily mashed with a fork and may be presented as a thick puree with obvious lumps in it. Lumps should be soft and rounded with no hard or sharp bits.

Smooth pureed

Food is smooth, moist and lump-free. It may have a grainy quality and is similar in consistency to commercial pudding. The texture of smooth pureed food means it can be moulded, layered or piped to make it look more appealing.

Texture-modified diet

If you have been told that you need to follow a texture-modified diet, you may find it difficult to know what to eat or drink. The sample menu below provides some meal, snack and drink suggestions for each of the different texture categories. You can also try some of the recipes.

Your dietitian can help to identify foods and fluids that will be easy to eat and drink, and can work out if the texture-modified diet is meeting your nutrition needs. A speech pathologist can also assess whether you need to change the consistency and thickness of fluids. Find a dietitian or speech pathologist.

Sample menu and snack ideas*
Minced and moist
Smooth pureed
Breakfast scrambled or poached eggs porridge or wheat biscuits with lots of milk and little texture strained or pureed porridge
Lunch egg and mayonnaise sandwich with crusts cut off soup with vegetable or meat pieces no bigger than 5 mm well-cooked pasta that has been pureed in a blender with added sauce
Dinner casserole with small pieces of tender meat and well-cooked vegetables moist macaroni cheese pureed chicken blended with extra gravy or sauce
Snacks mango mashed banana pureed pear pushed through a sieve
Dessert soft cake with lots of custard soft cheesecake without the crust ice-cream
Drinks fruit smoothie milkshake milk
Avoid nuts, dried fruit, dry or gristly meat, raw vegetables, muesli, hard cheeses nuts, hard vegetables, all bread and crackers, dried food, lollies (jubes, marshmallows) meat, eggs, cereals or vegetables that have not been pureed in a blender, peanut butter

* Some food may need modification for people requiring thickened fluid.

Dry mouth

Radiotherapy to the head or neck area, some chemotherapy drugs and some pain medicines can make your mouth dry, cause mouth ulcers, or change the amount of saliva in your mouth. A dry mouth can increase the risk of tooth decay and infections such as oral thrush, which will make eating harder.

How to relieve a dry mouth
  • Keep your mouth clean with regular mouthwashes to prevent infections.
  • Gargle with 1⁄2 tsp salt or 1 tsp bicarbonate of soda in a glass of water.
  • Choose an alcohol-free mouthwash to avoid irritating your mouth further.
  • Use a soft toothbrush when cleaning your teeth.
  • Ask your dentist or health care team about suitable mouth rinses or oral lubricants.
  • Limit alcohol and coffee as these are dehydrating fluids, and avoid smoking.
  • Avoid rough, crunchy or dry foods (e.g. chips, nuts, toast, dry biscuits); salty or spicy foods that sting your mouth; or very hot or cold food.
  • Soften food by dipping it into milk, soup, tea or coffee, or moisten with sauce, gravy, cream, custard, etc.
  • Cut, mince or puree food to avoid drying out food with too much chewing.
  • Sip fluids with meals and throughout the day.
  • Chew sugar-free gum to stimulate the flow of saliva.
  • Suck on ice cubes to keep your mouth moist.
  • Try making the soup recipes.

Nausea and vomiting

Feeling sick (nausea) and vomiting are often side effects of cancer, its treatment or some medicines. They often occur together, but not always. Vomiting sometimes follows nausea and may be caused by treatment, stress, food odours, gas in the stomach or bowel, motion sickness or even the thought of having treatment.

Some people experience nausea and vomiting a few hours after treatment, while for others it starts 24 hours later. After a person has had a few treatments, they may connect certain sights, sounds or smells with treatment and feel nauseated when they experience them. This is known as anticipatory nausea or vomiting and is more common in people receiving chemotherapy.

How to cope with nausea and vomiting
  • Have a light snack before treatment, and wait a few hours before eating again.
  • Eat small meals 5–6 times during the day. Going without food for long periods can make nausea worse.
  • Snack on dry or bland foods, e.g. crackers, toast, dry cereals, bread sticks or pretzels. See more snack ideas.
  • Choose cold foods or foods at room temperature instead of hot, fried, greasy or spicy foods.
  • Eat and drink slowly, and chew your food well.
  • Try foods with ginger, e.g. ginger biscuits or ginger beer.
  • Avoid foods that are overly sweet, fatty, fried, spicy or oily, or that have strong smells.
  • Brush teeth regularly to help reduce unpleasant tastes that may make you feel nauseated.
  • Don’t eat your favourite food when feeling nauseated to avoid developing a permanent dislike.
  • Take anti-nausea medicines as prescribed. Let the doctor know if the medicines don’t seem to be working.
  • Sip small amounts of fluids as often as possible. Try dry ginger ale, cold flat lemonade, soda water, Lucozade or chilled tomato juice. Sucking on a hard lolly, crushed ice cubes or an iceblock can be soothing.
  • See your doctor if you can’t keep fluids down, or if vomiting lasts for more than 24 hours, as you may become dehydrated.
  • Introduce drinks slowly once the vomiting has stopped, e.g. clear, cool drinks; diluted fruit drinks; Bonox/Bovril (beef extract rich in iron, minerals and vitamins); clear broth; and weak tea.
  • Start eating small amounts of plain foods once vomiting is under control, e.g. dry biscuits; pretzels; toast or bread; jelly; cooked cereals (such as lemon sago or boiled rice); and soft stewed fruits, such as apples, pears or peaches.
  • Introduce milk gradually and in small amounts, or have yoghurt, which is more easily digested.
  • Gradually increase your food intake until your eating returns to what is normal for you. Your doctor or dietitian may advise you to take a nutritional supplement on your good days to make up for the days when you can’t eat properly.

Constipation and diarrhoea

Cancer treatments may cause constipation and/or diarrhoea. These bowel changes occur for various reasons.


This is when your bowel motions are infrequent and difficult to pass. It can be caused by different factors including: regularly taking opioid medicines; having a diet low in fibre; not getting enough exercise; not having enough fluids to drink (dehydration); or having a low overall food intake.


This means your bowel motions are watery, urgent and frequent. You may also get abdominal cramping, wind and pain. Cancer treatment, medicines, infections, reactions to certain foods and anxiety can all cause diarrhoea.

The tips below may help you manage diarrhoea. You may also want to consider using oral rehydration drinks, e.g. Gastrolyte, to replace lost electrolytes. Ask your pharmacist for instructions on using these products. If these don’t work, ask your doctor to prescribe anti-diarrhoea medicines.

Rest as much as possible as having diarrhoea can be exhausting.

To find out more about managing diarrhoea, call the National Continence Helpline on 1800 33 00 66. Continence nurses offer confidential advice and have pamphlets on strengthening exercises that may help you ‘hold on’.

How to manage bowel changes
  • Soften stools by drinking 8–10 glasses of fluid a day, e.g. water, herbal tea, milk-based drinks, soup, prune juice.
  • Eat foods high in fibre, e.g. wholegrain breads, cereals or pasta; raw and unpeeled fruits and vegetables; nuts and seeds; legumes and pulses.
  • If you are increasing the amount of fibre in your diet, increase fluids to prevent the extra fibre making constipation worse.
  • Ask your doctor about using a laxative, stool softener and/or fibre supplement.
  • Exercise every day. Check with your doctor, exercise physiologist or physiotherapist about the amount and type of exercise that is right for you.
  • If you have had surgery for bowel cancer, see information about managing surgery side effects and speak to your health care team about specific dietary advice.
  • Drink plenty of fluids to avoid becoming dehydrated. Water and diluted cordials are better than high-sugar drinks, alcohol, strong caffeine or very hot/cold fluids. Signs of dehydration include passing urine less often and having dark urine.
  • Choose low-fibre foods, e.g. bananas, mashed potato, rice, pasta, white bread, oats, steamed chicken without the skin, white fish.
  • Avoid foods that increase bowel activity, e.g. spicy, fatty or oily foods; caffeine; alcohol or artificial sweeteners.
  • Try soy milk or lactose-free milk if you develop a temporary intolerance to the natural sugar in milk (lactose).
  • Don’t eat too many raw fruit and vegetable skins and wholegrain cereals as they may make diarrhoea worse.
Types of fibre

Fibre is found in cereals, fruits and vegetables. It is made up of the indigestible parts or compounds of plants, which pass mostly unchanged through the body. It helps to keep the digestive system healthy. There are different types of fibre.

Insoluble fibre

This is found in the skin of fruits and vegetables; wholegrains and cereals; fibrous vegetables such as carrots and celery; and nuts and seeds. Insoluble fibre helps to absorb water and make stools bulkier, which can help if you have constipation.

Soluble fibre

This is found in oats; barley; rye; legumes (lentils, kidney beans, chickpeas); peeled fruits and vegetables; avocado; and soy milk and soy products. Eating more soluble fibre can help if you have diarrhoea.

Other types of bowel irritation

Chemotherapy or radiotherapy to the abdomen or pelvic area can irritate your intestines, leading to abdominal discomfort or more wind (gas) than usual.

Irritation of the large bowel (colitis) and rectum (proctitis)

Colitis is the inflammation of the inner lining of the large bowel (colon and rectum). Proctitis is the inflammation of the rectum. These conditions may occur after external or internal radiotherapy to the pelvic area. The severity of either colitis or proctitis depends on the dose and frequency of radiotherapy, and the size of the tumour.

How to manage bowel irritation
  • Eat and drink slowly, take small mouthfuls and chew your food well to avoid swallowing air.
  • A diet low in insoluble fibre (see below) may reduce bowel movement and irritation in the short term.
  • Avoid fatty, spicy or fried foods, rich gravies and sauces.
  • Drink plenty of water.
  • Eat soft or cooked fruit, fine wholemeal bread (without coarse pieces of grain or seeds) and bran to provide soft bulk.
  • Reduce foods such as corn, beans, cabbage, onions, pickles and fizzy drinks, which can produce wind.
  • Try some gentle exercise, such as walking, to encourage healthy bowel movement.

These conditions may make some people feel the need to empty their bowels more often, perhaps without much result. Straining can cause discomfort, and there may be some blood or mucous in bowel motions. Diarrhoea, nausea and vomiting are also common. These symptoms are usually temporary and may last for up to eight weeks after radiotherapy finishes.

Irritation of the small bowel (enteritis)

This may occur after chemotherapy or radiotherapy to the abdomen or pelvic area. You may experience some abdominal discomfort (like cramps or wind pain), episodes of fluid and pale bowel motions, and more wind than usual. These changes usually improve 1–2 weeks after treatment ends. Speak to your doctor if your symptoms last longer.

Heartburn (indigestion)

Some cancers and treatments can cause heartburn, which is a burning sensation in the upper chest, oesophagus and/or throat. It’s caused by the contents of the stomach coming back up into the oesophagus (reflux).

Heartburn may make you feel too uncomfortable to eat much, which could lead to weight loss. If the tips below don’t relieve heartburn, let your doctor know as medication may help.

How to manage heartburn
  • Avoid large meals; try to eat 3 small meals and 3 small snacks throughout the day.
  • Eat slowly and take the time to enjoy your meal. Avoid wearing tight clothing while eating, especially belts.
  • Sip fluids between meals, rather than drinking large amounts at mealtimes.
  • Limit or avoid foods that may make heartburn worse, e.g. chocolate, highly seasoned spicy foods, high-fat foods (e.g. fried food, pastries, cream, butter and oils), tomato and tomato products, citrus fruits, coffee (including decaf), strong tea, soft drinks and alcohol.
  • Straight after eating, sit upright for at least 30 minutes and avoid lying down or activities that involve bending over (e.g. gardening).

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