Cancer and Diet: What to eat and what to avoid

Whatever stage of cancer you are at, your diet and eating well is especially important. There are lots of myths about foods that can cause or cure cancer. So, what types of food should you be eating?

Why is diet important during cancer treatment?

It’s important to eat a balanced diet when you’re having cancer treatment. The right food helps your body stay strong and fight off infections. It can also help with energy levels and wellbeing.

It might not be easy to think about changing your diet when you have been diagnosed with cancer. Your treatment might affect your appetite. Nurses and dieticians will have tips to help make sure you’re getting everything you need and can eat in a way that works for you.
There are some great recipe books out there for while you’re having treatment. We like the Royal Marsden Cancer Cookbook. You might also find these online resources helpful:

Does having a healthy diet reduce my risk of cancer?

Eating a healthy and balanced diet can reduce your risk of cancer. But beware of so-called ‘cancer diets’ and superfoods which claim to cure cancer.

What does a healthy diet consist of?

A healthy diet can be different for every person. Just a few small changes could make a difference to how your body copes with treatment and your recovery. Eating the right types and portions of food can make your body stronger and make you feel healthier. A healthy diet means getting the right balance of things like fruit and vegetables, protein, dairy and carbohydrates. You can find out more below.

Fruit and vegetables

Fruit and vegetables should make up about a third of the food we eat every day. They are a good source of vitamins, minerals and fibre as well as usually being low in fat and calories. You should try to eat a wide variety of fruit and vegetables. Remember potatoes do not count as part of your five-a-day.
If you are struggling to include enough fruit and vegetables in your diet, why not try them hidden in dishes like soups, stews and pasta?


Fibre is important to help your body digest food properly. Studies have shown the risk of bowel cancer may be reduced by eating foods that are high in fibre.
Wholegrains are high in fibre. They can be found in foods like brown rice, wholewheat pasta, oats, beans, lentils and wholegrain bread.

Plant-based proteins

Your body needs protein and there are plenty of plant-based foods which can provide this.
Pulses – like lentils, peas and beans – and soy-based products – like soya milk, nuts and seeds – are rich in protein.
Protein should make up a quarter of your plate for a healthy balanced meal. Protein-rich foods can be a good source of vitamins and minerals and help repair any damage to your body.

Healthy fats

Eating some fat in your diet is important but eating too much of the wrong type of fats could lead to weight gain and other health problems.
Try to choose foods that contain unsaturated fats instead of saturated fats. These include oily fish such as salmon, sardines and mackerel.
Avoid high-fat snacks like biscuits and crisps. Instead try nuts, avocado and seeds.
Swap red meat for skinless fish and chicken. Try to bake, steam or grill instead of frying.

Healthy carbs

Carbohydrates are a good source of energy and contain a range of nutrients.
They are found in a lot of starchy foods like potatoes, bread, rice, pasta, and cereals. These starchy foods should be making up around a third of what you eat each day.
Choosing wholegrain or wholemeal starchy foods will also make you feel fuller as they contain more fibre.
Potato skins contain fibre and vitamins so leave them on where possible.

Vitamins and Minerals

Cancer can stop you absorbing some nutrients which can make you feel unwell. You may be offered dietary supplements if you have low levels of certain nutrients. The best way to get a good supply of vitamins and minerals is through a balanced and varied diet.

Example of a healthy diet

A healthy, balanced diet is especially important if you have been diagnosed with cancer. Ensuring you eat well can help increase your energy levels and keep up your strength.
A balanced diet should include:

  • A least 5 portions of fruit and vegetables a day
  • Dairy (or dairy alternatives)
  • Protein
  • Healthy carbohydrates.

You should also be drinking plenty of fluids, at least 6 to 8 glasses a day. An example of a balanced plate of food would include:

  • ¼ potatoes, pasta, rice or noodles
  • ¼ fresh chicken, fish, eggs or beans
  • ½ salad or vegetables.

Charlotte talks about how her attitude to food changed after her diagnosis and what she has learned from trying different diets.

Cancer fighting foods

Eating a healthy, balanced diet can help reduce the risk of cancer but there is no evidence that a single food can prevent cancer. You may have heard the term ‘superfood’ which people use for things like blueberries and broccoli. Some believe these ‘superfoods’ can prevent diseases like cancer but there is no scientific evidence to back this up.


If you have low levels of certain nutrients your doctor may prescribe dietary supplements. These can come in forms like tablets and powders and can include vitamins, minerals and proteins. Supplement drinks can be useful if you find it hard to swallow. It is important to talk to your doctor or nurse if you are thinking about taking supplements.

Foods to avoid during cancer treatment

Certain foods can affect how your cancer medication is broken down in your body. This includes grapefruit and Seville oranges, their juice, and products made from them like marmalade. If too much or too little of the cancer drug is broken down it might not work as well and could cause side effects.

Does eating processed and red meat cause cancer?

Evidence shows processed meat is a cause of cancer while red meat is a ‘probable’ cause of cancer. Processed meat includes bacon, ham, sausages and salami which have been changed or preserved. They should be avoided as much as possible. Red meat – beef, lamb, pork and goat – is a good source of protein, vitamins and minerals but it is recommended you limit the amount to 500g or less (cooked weight) per week.

What are carcinogenic foods?

If something is described as carcinogenic, this means it could cause cancer. Eating processed meat can cause cancer and red meat can increase the risk of cancer. There are many myths about foods causing cancer. There is no good evidence that eating things like tinned food, sugar, burnt food or eggs cause cancer.

Does a high fibre diet reduce my risk of cancer?

Eating a diet high in fibre can help to reduce the risk of cancer. Fibres from wholegrains, like brown rice, whole wheat pasta, oats and wholegrain bread, are the best. Try some simple swaps like changing your bread, pasta or rice to the wholegrain or brown alternatives.

Does a Ketogenic diet help fight cancer?

A ketogenic diet is very low in carbohydrates and is very hard to follow. There have been some clinical trials but the evidence does not show any benefits for cancer patients.

Can I drink alcohol if I have cancer?

Following a healthy, balanced diet does recommend avoiding alcohol as much as possible, although having the occasional drink is usually safe. Drinking alcohol can interfere with your treatment and can make some side effects worse so you should always speak to your doctor. Read more about alcohol and cancer treatment here.

Diet at different stages of treatment

Thinking about your diet might be the last thing on your mind when you are diagnosed with cancer – but making sure you eat and drink the right things could make a big difference before, during and after your treatment.

Before treatment

Being diagnosed with cancer and dealing with the uncertainty may affect your appetite. Being underweight can affect how well you cope with and recover from your treatment. If you can, try to continue to eat a varied, balanced diet.

Try to keep each meal balanced with plenty of fruit and vegetables, starchy carbohydrates, dairy products and some oils and spreads high in unsaturated fat. Protein is really important to help build muscle and in preparation for surgery. You should eat the same number of grams of protein as half your body weight in kilograms. So, if you weigh 60kg, you should have at least 30g of protein per meal, three times per day.

Drink plenty of fluids, like water, low fat milk or sugar free drinks and avoid alcohol as much as possible.

During treatment

Eating a varied diet during treatment can help you cope with some side effects. Being healthier and stronger could mean you can handle the best dose of cancer treatments. Sticking to a balanced diet can make you feel less tired and give you more energy. This could also help you fight off infections. Sticking to a healthy diet can also improve your mental health and wellbeing while you are going through treatment.

After treatment

When you are recovering from treatment, making sure you still eat a varied and balanced diet can help you heal faster.
It can also help you to feel physically and emotionally well and boost your immune system. It can reduce the risk of new cancers and other diseases.

Weight changes on cancer treatment

Coping with weight changes can be difficult. If you’re struggling with this have a chat with someone and try to focus on getting the nutrition you need to help your body.

Ben talks about his struggle with treatment and how he built himself back up afterwards by getting his diet back on track.