Diet during breast cancer treatment

Breast cancer treatments, such as chemotherapy and hormone therapy, can sometimes affect what you want to eat and drink.

Your usual routine may be disrupted, which can affect your eating pattern.

Feeling worried or stressed can also affect your appetite, causing you to eat more or less than usual.

Most people feel ready to eat the same day as their surgery or in the days following. You will likely be asked to eat something at the hospital before you go home. Eating well will help your body recover and heal.

It’s hard to tell how your body will react to chemotherapy. You may be able to eat normally throughout your treatment or the side effects may change your eating habits.

Find out more about chemotherapy side effects.

Risk of infection

Chemotherapy can cause a drop in white blood cells, which can increase your risk of getting an infection. You’ll have regular blood tests throughout your treatment to check your blood count.

If you’re at an increased risk of infection, you may be given some specific dietary advice to follow. Your treatment team will explain more about this if necessary.

Although there aren’t any particular foods that will boost your white blood cell count, it’s important to follow a healthy diet.

Follow good food hygiene when storing, preparing and cooking food. This is particularly important if you’re at increased risk of infection.

You can find useful information on food safety when your immunity is low on the Macmillan Cancer Support website.

Healthy eating during chemotherapy if your appetite is small

Your appetite might change during treatment.

If your appetite is small, or taste changes are affecting your diet, eating little and often can be better than having large meals. It may help to:

• Eat 5 or 6 small meals or snacks each day instead of 3 bigger meals
• Drink milkshakes, smoothies, juice or soup if you don’t feel like eating solid food
• Do something active, if you feel able to, as exercise can increase your appetite – you might have more of an appetite if you take a short walk before eating
• Avoid drinking lots of liquid before or during meals

Foods to eat during chemotherapy if your appetite is increased

Some drugs given alongside chemotherapy, such as steroids, can increase your appetite. If you’re worried about gaining weight:

• Choose low-fat foods and drinks
• Eat plenty of fresh fruit and vegetables
• Watch out for the sugar content of food including some “diet” foods
• Avoid sugary drinks

Feeling sick (nausea) and being sick (vomiting)

You may feel sick or be sick during and after your chemotherapy. Anti-sickness drugs may help – your chemotherapy team can help find 1 that works for you.

Drink plenty of fluids, such as water or herbal teas. Taking frequent sips is better than trying to drink large amounts in 1 go. Herbal teas such as mint or ginger can help if you’re feeling sick.

Eating little and often can also help if you’re feeling sick.

Some people find eating cold food makes them feel less sick because hot food can smell stronger and trigger their nausea.

Sore mouth

Chemotherapy can make your mouth sore or dry, making it uncomfortable to eat.

You might find it helpful to:

• Clean your teeth or dentures with a soft brush after eating and floss gently
• Use an alcohol-free mouthwash (your chemotherapy team may recommend one)
• Choose soft or liquid foods such as soups, stews, smoothies and desserts
• Soothe your mouth and gums with ice cubes and ice lollies
• Drink sugar-free fizzy drinks or fizzy water to freshen your mouth
• Use a straw to drink
• Avoid crunchy, salty, very spicy, acidic or hot foods
• Avoid citrus drinks like lemon, lime, orange and grapefruit juice

If you have dentures, clean them regularly and try not to wear them all the time.

Smoking and drinking alcohol can make a sore mouth worse.

Taste changes

Your taste may change during chemotherapy, making foods taste bland or different. You may prefer to eat strongly flavoured foods or use herbs and spices when cooking.

Try a variety of foods to find the ones you like best. As well as going off your usual foods, you may like foods you previously didn’t like.

Some types of chemotherapy can give you a metallic taste in your mouth. Using reusable plastic or wooden cutlery, instead of metal, can help reduce the metal taste. Using glass pots and pans when cooking can also help.

Constipation

Eating and drinking less than usual, being less active and taking certain medications can all lead to constipation.

Eating high-fibre foods can help. These include:

• High-fibre breakfast cereals, such as bran flakes or shredded wheat
• Beans and lentils
• Vegetables (fresh or frozen)
• Fruit (fresh, frozen, canned and dried)
• Brown rice
• Wholemeal bread
• Wholewheat pasta

Drink plenty of fluids (6 to 8 glasses of water a day) and do some regular exercise such as walking if you’re able to.

If you’re still having problems with constipation, ask your treatment team or GP for advice. They can prescribe medication to help if necessary.

Diarrhoea

Occasionally, some chemotherapy drugs can cause diarrhoea. Your treatment team or GP can prescribe medication for diarrhoea if necessary. Drink plenty of fluids to avoid dehydration.

Contact your chemotherapy team if you have 4 or more episodes of diarrhoea in 24 hours.

Short-term fasting around the time of chemotherapy

Some studies suggest short-term fasting around the time of chemotherapy may help reduce side effects. However, more research is needed before any recommendations can be made.

If you’re thinking about fasting, always talk to your treatment team or GP first.

Having radiotherapy normally doesn’t cause any dietary problems but it’s still good to eat a balanced diet and drink plenty of fluids.

If you’re having radiotherapy around your collarbone or breastbone, you may have a sore throat, dry mouth, difficulty swallowing or indigestion. If this happens, speak to your treatment team. Taking liquid pain relief, such as liquid paracetamol, before eating may help.

If you have to travel for your treatment, take a drink and snack with you and plan meals that are easy to prepare for when you get home.

Weight gain

If you’re having hormone therapy, you might find your weight increases. This may be because you’re less active due to fatigue or joint pain, or because of appetite changes. Weight gain is also a common menopausal symptom.  

High cholesterol

Hormone therapy drugs such as anastrozole and letrozole can increase the level of bad cholesterol (LDL) in your blood.

If you have too much bad cholesterol it can build up in your artery walls, leading to artery disease or other health conditions.

Following a healthy diet and maintaining a healthy body weight can help to reduce levels of bad cholesterol.

Your GP can tell you more about how cholesterol levels are measured and what dietary changes you may need to make.

Find out more about cholesterol on the British Heart Foundation website.

Simple tasks like shopping and cooking can feel exhausting during treatment and as you recover.

Try to accept any offers of help, even if you’re used to coping on your own. You can also take advantage of online shopping or ask local shops if they have a telephone ordering and delivery service.

It’s important to have fresh food in your diet, but if you can't shop regularly, frozen and tinned fruit and vegetables are full of nutrients and can be great alternatives. Choose tinned fruit in juice rather than syrup and tinned vegetables that have less salt.

Find out more about coping with fatigue during and after treatment. Macmillan Cancer Support has an information booklet called Coping with fatigue.

If you’re already following a specific diet because you have a medical condition – such as diabetes, Crohn’s disease or irritable bowel syndrome (IBS) – having breast cancer doesn’t mean your diet has to change.

If you’re concerned about how your breast cancer treatment may affect your diet or any existing condition, talk to your breast care nurse or treatment team. They can talk to a dietitian or other medical staff to ensure any existing condition remains under control during your treatment.