Therapies based on diet

It’s common for people with cancer to have questions about what to eat during and after treatment. People often consider changing their diet to help their body cope with the effects of cancer and its treatments, and to give themselves the best chance of recovery. Some complementary therapies incorporate general dietary advice, while others have their own specific approaches to diet.

What are the benefits?

Good nutrition before, during and after treatment can help you cope better with side effects, increase energy and maintain wellbeing. Vegetables and fruit contain vitamins, minerals and phytochemicals – natural substances such as antioxidants that may destroy cancer-causing agents (carcinogens).

While it’s best to get vitamins and minerals from eating whole foods, they are sometimes taken as supplements. If you were taking supplements before treatment, ask your oncologist if you can continue.

What are the side effects?

Some people claim that a particular diet can cure or control cancer on its own. However, there are no special foods, diets or vitamin and mineral supplements that have been scientifically proven to do this.

Unproven diets, particularly those that suggest cutting out whole food groups, are likely to be low in energy (kilojoules/calories), protein, fat, iron, calcium, zinc and vitamins. Following one of these diets can cause unwanted weight loss and tiredness, and lower your immune function. Cutting out whole food groups and losing weight may also contribute to malnutrition. This may make it harder for you to cope with treatment and may slow down your recovery.

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Taking care with special diets during treatment

During treatment some people follow a restricted diet, which may stop them getting enough nutrients for their body to work properly.

Gerson therapy

This involves drinking fresh juice several times a day, taking supplements, and having coffee enemas. There is no scientific evidence that Gerson therapy is an effective treatment for cancer, and evidence shows that coffee enemas can be dangerous if used excessively.

High doses of vitamins

Some people believe that taking high doses of certain vitamins will strengthen the body’s immune system during cancer treatment. However, there is little evidence to support this claim. In fact, many vitamins and minerals can be toxic at high levels, and may affect how chemotherapy, radiation therapy and other medicines work.

Alkaline diet

This diet claims eating high alkaline foods such as green vegetables, fruits, oily fish and nuts lowers the acidity levels in the body. A low acid level is said to stop cancer growth, but there’s no evidence to support this claim.

Macrobiotic diet

Generally, this diet consists of wholegrains, fruits and vegetables, and soups made with legumes and fermented soy (miso). This diet may cause you to lose weight. There is no evidence this diet cures cancer.

Keep your complementary therapists and other health professionals informed about any special diets you try before, during or after cancer treatment. Being informed about your diet will help them give you the best possible care.


This information was last reviewed in May 2018
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