Common questions about diet and cancer

Can diet reduce the risk of cancer coming back?

People often ask whether what they eat can reduce their risk of the cancer returning. There is some early evidence from breast and bowel cancer studies that diet may affect the chances of the cancer coming back. But there still is not enough clear information to make precise recommendations about what someone with a type of cancer should eat. In general, cancer experts recommend following a healthy, balanced diet for the whole body and not just the prevention of one type of cancer.

For most people, the factors that are likely to have the greatest impact on their health include diet, weight control and regular physical activity. The biggest difference will probably be from a combination of factors, rather than from making one change.

Your healthcare team (this includes your GP, dietitian, doctors and nurses) are the best people to advise you whether there are any lifestyle changes you can make that may help reduce your risk of cancer coming back.

What foods should I avoid when I have low immunity?

If your medical team has told you that your immunity may be low during treatment, ask them whether there is any special dietary advice you should follow.

For most people, low immunity will not last long, so there is no need to follow a special diet. If you are having more intensive chemotherapy or a bone marrow transplant, your specialist doctor and nurse will explain more about which foods you need to avoid when your immunity is low.

Here are a few general tips:

  • You should avoid pâté, raw eggs and any product containing raw egg (such as homemade mayonnaise), raw seafood, probiotic food products, unpasteurised milk and cheeses made from unpasteurised milk (such as parmesan, and mould-ripened and blue-veined cheeses).
  • Ensure your hands are clean while cooking and before eating.
  • Make sure your food is well-cooked, especially meat and fish.
  • If you eat raw foods, such as salads or fruit, make sure they are washed thoroughly.
  • Store food following the instructions on the packaging, and check the best before and use-by dates.
  • Be careful when eating out. Be aware of food choices and how food is prepared and cooked.

Should I take dietary supplements?

For most people, a healthy, balanced diet provides all the nutrients they need. Large doses of vitamins, minerals and other dietary supplements are not usually recommended. But people who find it difficult to eat a balanced diet may benefit from taking a multivitamin or mineral supplement containing up to 100% of the recommended daily allowance. A doctor, nurse or dietitian will be able to advise on this.

Supplements may help in some situations, such as for people who cannot absorb all the nutrients they need because of surgery for stomach cancer. And people at increased risk of bone thinning (osteoporosis) may also benefit from taking calcium and vitamin D supplements to help strengthen their bones.

Studies looking at whether taking supplements can reduce the risk of developing certain cancers have been disappointing. In general, the evidence shows that taking supplements does not reduce the risk of cancer. There is even evidence that taking high doses of some supplements can increase the risk of cancer developing in some people.

It is possible that some supplements may interfere with how cancer treatments work and make them less effective. If you are currently having cancer treatment, it is important to get advice from your cancer specialist before taking any supplements. They can advise you about any you should take, and which doses might be suitable for you. They can also tell you about any possible side effects and interactions with other medicines.

There are no specific vitamin pills I would recommend, unless these have been prescribed specially by your consultant. Eating a well-balanced and varied diet should give you all the vitamins you need.

Jenny, dietitian

What about ‘superfoods’?

There is no scientific evidence for any particular food being a ‘superfood’. The greatest benefit to your health is likely to come from eating a balanced diet that includes a wide and varied combination of foods.

Instead of concentrating on a particular ‘superfood’, it is better to aim for a varied and healthy diet, including lots of different types of fruit, vegetables and wholegrain foods. This will help you make sure you are getting the widest possible variety of nutrients. It will also make your diet more enjoyable and interesting, and will probably be cheaper too.

Should I follow a dairy-free diet?

Many research studies have looked for a link between diets that are high in dairy products and cancer (particularly breast and prostate cancer). But these studies have not found a clear link. Because of this, cancer experts do not recommend following a dairy-free diet to try to reduce the risk of cancer.

Dairy products are an important source of protein, calcium and some vitamins. But they can be high in fat. Choose low-fat products to avoid putting on weight. Calcium is needed for strong bones, and may help reduce the risk of bowel cancer.

If you decide to follow a dairy-free diet, you will need to make sure you get enough calcium from other foods, such as:

  • tinned sardines and salmon (with bones)
  • dark green, leafy vegetables, such as spinach
  • kidney beans
  • dried figs
  • foods fortified with calcium, such as some types of soya, rice, almond or oat milk.

There are no so-called “superfoods” that we would suggest you have. There is a lot of information out there that promotes these sorts of foods, but the general principles of a “healthy diet” remain.

Jenny, dietitian

Does sugar feed cancer?

Sugar does not directly increase the risk of cancer or encourage it to grow. But sugar contains no useful nutrients, apart from energy, and we can get all the energy we need from healthier sources. Too much sugar can lead to weight gain.

It is best to limit the amount of sugar in your diet, unless you have received specialist advice from a dietitian. Foods high in sugar include biscuits, chocolate, sweets, syrups, cake, fruit juice and fizzy drinks.

Watch our diet and cancer - ask an expert playlist

In these videos, Jane Clarke talks about a variety of food groups and answers your questions about diet and cancer.

Watch our diet and cancer - ask an expert playlist

In these videos, Jane Clarke talks about a variety of food groups and answers your questions about diet and cancer.

Should I only eat organic food?

Many people wonder whether they should follow an organic diet to prevent cancer coming back. Some studies claim that organic fruit and vegetables have better flavour and stay fresh for longer. But others find them expensive and do not see the value of them compared to non-organic products. So far, no research has been done to find out whether an organic diet is more effective than a non-organic diet at stopping cancer coming back.

Some people may worry that pesticides used in non-organic farming may cause cancer. In the UK, a pesticide can only be used once its safety has been tested. Laws ensure that all agricultural pesticides are used within a safe level.

Genetically modified (GM) crops have been proved to be safe in the time they have been grown. But some people might feel that the long-term effects are unknown, and so choose not to eat them.

It is your choice whether you buy organic or non-organic food. Current advice is to thoroughly wash all fruit and vegetables before use, whether they are non-organic or organic. This removes any form of pesticide and harmful bacteria.

Do anti-cancer diets work?

There has been a lot of publicity about alternative diets for treating cancer over the past few years. Many dramatic claims for cures have been made. It is understandable that people may want to know about diets that seem to offer the hope of a cure. However, there is no evidence that these diets can shrink a cancer, increase a person’s chance of survival, or cure the cancer.

Some people get satisfaction from following these types of diet, but others find them expensive, unpleasant to eat and time-consuming to prepare. Some diets may lack important nutrients or be unbalanced in other ways, and may even be harmful. Some of the diets can be difficult to follow and you might be left feeling guilty if you find it hard to follow the instructions.

It can be confusing to have conflicting advice about what to eat. Dietitians, doctors and specialist nurses recommend a well-balanced and enjoyable diet as the best way to keep healthy. If you do choose to follow a specific diet, it might be worth speaking with a dietitian to check whether you are missing any important nutrients.

A juice diet is not necessarily something health professionals would recommend during chemotherapy or at any time. I would be concerned that you might be missing essential nutrients found in other foods.

Jenny, dietitian