After a diagnosis, it’s common to have many questions about food and cancer. The following answers address some of the most common concerns.
Learn more about:
- Can food cause cancer?
- Should I avoid processed meats and red meat?
- Is organic food better?
- Should people with cancer follow a special diet?
- Does sugar feed cancer?
- Is fasting a good idea?
- Why should I see a dentist before starting treatment?
- How important is exercise?
The link between food and cancer is complex. There are many different types of cancer and many different causes of cancer, only some of which are understood.
Cancer starts when cells begin to grow out of control. The reason for this change is not always known, but lifestyle and diet sometimes play a part. Poor eating habits combined with other lifestyle factors (such as smoking, too little exercise, drinking too much, being overweight and too much sunlight exposure) may, over a long period of time, increase the risk of developing some cancers.
The World Health Organization classifies processed meats such as bacon, ham and salami as Group 1 carcinogens. This means there is a definite link with cancer, and it puts processed meats in the same category as other causes of cancer such as tobacco, alcohol and ultraviolet radiation. Red meat is classified as a Group 2A carcinogen, which means it probably causes cancer, but the evidence isn’t as strong. These classifications do not indicate the risk of getting cancer; they describe the strength of the evidence that these foods are linked to cancer.
To reduce cancer risk, Cancer Council recommends that you eat little, if any, processed meats such as bacon, ham and salami. Cancer Council also recommends eating no more than 455 g of cooked lean red meat (e.g. beef, lamb, pork, kangaroo, goat) per week – for example, you might have a 100 g serve 3−4 times per week. Add extra vegetables to your plate, or try fish, chicken, eggs or legumes (such as chickpeas or lentils) instead of red meat. If you are losing weight or struggling to eat enough during cancer treatment, check with your dietitian what foods are right for you.
Organic farmers and food producers grow and produce food without using synthetic pesticides or fertilisers. They also don’t use seeds, plants or animals that have had their genetic make-up altered in a laboratory, or expose food to radiation to extend shelf life.
Some people believe it’s better to eat organic food because they’re not eating extra chemicals in their food. However, there is no strong evidence that organic food is better for you, or that it will help you recover faster or reduce the risk of cancer coming back.
Organic fruits and vegetables contain the same vitamins and minerals as those grown in the usual way and can be more expensive to buy. Focus on eating a variety of fruits and vegetables, rather than whether or not they’re organic.
|Before changing what you eat, following a specific diet, or taking a lot of vitamins or mineral supplements, it is important to talk to your doctor or dietitian. They can discuss the advantages and disadvantages of different diets.|
If you’ve been diagnosed with cancer, you may be thinking about changing your diet to help your body cope with the effects of cancer and its treatment, and to give yourself the best chance of recovery. After a cancer diagnosis, some people find that they give more attention to having a well-balanced diet, which can have many benefits. Others need to adjust their diet to make sure they are getting the nutrition they need.
Some people claim that a particular diet can cure or control cancer on its own. Often these diets are promoted on websites or in the media. However, there are no special foods, diets or vitamin and mineral supplements that have been scientifically proven to do this.
Many unproven diets encourage people to:
- eliminate one or more basic food groups (e.g. all dairy or all carbohydrates)
- include large amounts of specific fruits and vegetables or their juices; and
- take special supplements.
These unproven diets are often expensive and can be harmful. Following one of these diets can cause unwanted weight loss and fatigue, and weaken your immune system. This may make it harder for you to cope with treatment and lead to malnutrition. Diets that cut out whole food groups are likely to be low in energy, protein, fat, iron, calcium, zinc and vitamins, all of which are essential for your organs to work properly. Unusual diets can also make it hard to eat at restaurants or other people’s homes, which may prevent you from enjoying social occasions.
For more on this, see Complementary therapies.
While everyone should try to limit added sugar in their diet, sugar occurs naturally in many foods, and carbohydrates (such as potatoes, pasta and grains) break down into sugar in the body.
You may hear that because cancer cells use sugar to grow, cutting out all sugar and carbohydrates from your diet will stop the cancer growing. This is a myth and can be harmful. The healthy cells in your body also use sugar to grow, so changing your diet in this way would mean missing out on the sugar that helps your vital organs work. If you are losing weight or struggling to eat enough, eating foods with sugar in them may help to keep your energy levels up. You can talk to a dietitian about what foods are right for you after a cancer diagnosis.
Some people think that eating very little (fasting) helps treat cancer, but there is not enough evidence to support this and it can be harmful. Not eating enough can leave you feeling tired, weaken your immune system and affect your ability to cope with treatment. This may lead to treatment delays or reduce the amount of treatment you receive. It is important to try to eat a wide variety of food, and to eat enough to meet your body’s needs so you maintain strength during treatment.
Cancer treatment often causes side effects that affect your mouth and teeth, such as mouth ulcers, dry mouth, tooth decay and mouth infections. These problems can make it hard to eat, and poor oral health can make them worse. This is why it is important to have a check-up with your dentist before treatment starts, especially if your treatment includes radiation therapy to the head or neck, some types of chemotherapy, or the drugs known as bisphosphonates (used to treat bone disease).
Your dentist can check the health of your teeth and identify any problems early. You can also ask your dentist or your cancer treatment team for advice about caring for your teeth and mouth before, during and after treatment.
For more on this, see Mouth health and cancer treatment.
Along with eating well, physical activity is important for general health and wellbeing. Any activity that gets your body moving and speeds up your breathing and heartbeat can help you achieve or maintain a healthy body weight, improve your mood, and prevent some conditions, such as heart disease, type 2 diabetes and even some cancers.
Australia’s Physical Activity and Sedentary Behaviour Guidelines for Adults encourage everyone to move more and sit less.
Adults should aim to be active on most, preferably all, days of the week. Any physical activity is better than none, so if you are not physically active at all, try to gradually build up to the recommended amount. The aim is to be as physically active as your abilities and condition allow. Find out more about the general guidelines.
Exercise is now recommended for most people during and after cancer treatment. Research shows that regular physical activity can:
- help manage fatigue and other common side effects of cancer treatment
- increase appetite
- speed up recovery
- strengthen muscles and bones
- improve circulation and energy levels
- reduce stress and improve your mood
- reduce the risk of the cancer coming back (for some cancer types) and of developing other health problems
- reduce isolation (if exercising with others)
- improve quality of life.
Check with your oncologist or GP before starting an exercise program, and see a physiotherapist or exercise physiologist to develop an exercise plan that suits your situation. A physiotherapist or exercise physiologist may be part of the team at your hospital or treatment centre, or your GP can refer you to one in private practice.
For more on this, see Exercise after cancer diagnosis.
Jenelle Loeliger, Head of Nutrition and Speech Pathology Department, Peter MacCallum Cancer Centre, VIC; Rebecca Blower, Public Health Advisor, Cancer Prevention, Cancer Council Queensland, QLD; Julia Davenport, Consumer; Irene Deftereos, Senior Dietitian, Western Health, VIC; Lynda Menzies, A/Senior Dietitian – Cancer Care (APD), Sunshine Coast University Hospital, QLD; Caitriona Nienaber, 13 11 20 Consultant, Cancer Council WA; Janice Savage, Consumer.
View the Cancer Council NSW editorial policy.
Click below to download a PDF booklet on this topic.
Exercise and cancer
Exercise has many benefits both during and after cancer treatment, helping with side effects, speeding up recovery, and improving quality of life
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