Diet and food supplements

Some people think about making changes to their diet, or about taking dietary supplements, such as anti-oxidants, after a cancer diagnosis.

Cancer and your diet

Many people make changes to their diet after a cancer diagnosis as a way of staying as healthy as possible. The most important changes people can make for their health are:

  • giving up smoking
  • increasing physical activity
  • eating a balanced diet
  • maintaining a healthy weight.

People often ask their doctor about ‘superfoods’ or foods that boost the immune system. But there isn’t any medical evidence that suggests these work.

There still is not enough clear information to make exact recommendations about what someone with cancer should eat. In general, cancer experts recommend following a healthy, balanced diet. Eating a wide range of foods that have the vitamins and minerals your body needs will have the most benefit.

If you are underweight or find it difficult to eat enough to maintain your weight, ask your doctor to refer you to a dietitian for specific advice.


Antioxidants, such as vitamins A, C and E, coenzyme Q10 and selenium are some of the most commonly taken dietary supplements.

Always tell your cancer doctor if you are thinking of taking antioxidants. Antioxidants can help to prevent cell damage. Because of this, some doctors have concerns that taking antioxidant supplements during cancer treatment may make cancer treatment less effective. Your cancer doctor may recommend that you don’t take antioxidant supplements during your treatment, unless it is as part of a clinical trial.

If you would like to discuss dietary supplements and get more information, you can contact us.

Dietary supplements

For our bodies to work properly, we need nutrients, such as vitamins, minerals, protein, fat, carbohydrate and fibre.

The best way to get these is by eating a healthy, balanced diet. However, some people with cancer are not able to get all the nutrients they need from their diet. If you are not able to eat a healthy balanced diet, your doctor may prescribe a daily multi-vitamin and multi-mineral supplement.

If you are concerned about your diet or nutrition, ask your doctor or nurse to refer you to a dietitian. They can give you advice on what to eat and may prescribe nutritional supplements for you.

Some people think that if something is good for you in small amounts, taking larger amounts is even better. But this isn’t always the case. Nutrients are essential for our health in small amounts. But they be can be harmful and cause unpleasant side effects when taken in large amounts. And some may interact with cancer treatments or lessen the effectiveness of them.

Despite a lot of research into cancer and dietary supplements, there isn’t enough evidence to suggest that taking them can help treat cancer or stop it from coming back. But research has found that taking certain supplements could increase the risk of some cancers developing.

It is important to talk to your cancer doctor or nurse if you are thinking of taking supplements.

Dietitians and nutritional therapists

Dietitians use current medical evidence to give specific advice to people with eating or weight problems. They also give advice on healthy eating in general. Some dietitians have specific training in helping people affected by cancer. Dietitians are regulated by the law and must meet a national standard of practice.

Nutritional therapists are different. Some nutritional therapists may be qualified to provide information on healthy eating, but they are not regulated in the same way as dietitians. Some nutritional therapists may try to improve your health using methods such as ‘detoxing’ or suggesting you take high-dose vitamins. These types of diets are not recommended for people with cancer.