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Alternative cancer diets

People with cancer sometimes try complementary or alternative therapies to help with diet problems or to treat cancer.

There is no scientific evidence that alternative diets can cure cancer.

Complementary and alternative therapies

There is an important difference between a complementary therapy and an alternative therapy.

A complementary therapy means you can use it alongside your conventional medical treatment. It may help you to feel better and cope better with your cancer and treatment.

An alternative therapy is generally used instead of conventional medical treatment.

Two of the main conventional cancer treatments are chemotherapy and radiotherapy. They have to go through rigorous testing to prove that they work.

Most alternative therapies have not been through such testing. So there is no scientific evidence that they work. Some types of alternative therapy may not be completely safe. They could cause harmful side effects.

People often use complementary and alternative therapies to feel more in control. For some people, they provide hope and psychological support.

But talk to your cancer doctor, GP, or specialist nurse if you're considering complementary or alternative therapies. Some treatments may interact. Also, let your complementary or alternative therapist know about your conventional cancer treatment.

Keep eating a well balanced diet

Keep eating a well balanced diet if you try any alternative diet. Even when taking a nutritional supplement, try to eat a balanced diet. 

It can be harmful to deprive yourself of protein, carbohydrates (including sugars) and fats. Your body needs them to repair itself and keep going.

Always ask to see a dietitian at your hospital about any diet or supplement. Talk it through with them. There are also organisations that give information and support.

For information and support, you can call the Cancer Research UK nurses free on 0808 800 4040, from 9am to 5pm, Monday to Friday.

Special cancer diets

There are many types of diets. Some claim to cure cancer or have certain benefits. There is no strong scientific evidence for some of these claims. Below are a few common diets. 

The Gerson regime has 3 main parts:

  • a strict organic vegetarian diet made up of fruit and vegetables high in potassium and low in sodium
  • vitamin and mineral supplements, and specific enzymes
  • coffee or castor oil enemas

Followers believe that changes to diet and nutrient intake can help to treat cancer. They also think that cancer is a symptom of disease of the whole body.

It aims to rid the body of toxins and strengthen the body’s immune system. This way, supporters say it can bring the body back to its normal metabolic state, and the body can heal itself.

Scientific research does not support any of these claims.

Gerson therapy may not be the best diet for you to follow when you are ill and already undernourished.

The alkaline diet tries to change the pH of the body through eating mostly alkaline foods. The pH is a number that shows how acidic or alkaline a substance is. A pH of less than 7 is acidic, and greater than 7 is alkaline. The pH of blood is about 7.4.

By trying to change the pH of blood to be more alkaline, followers of this diet believe that they can cure disease, including cancer.

They argue that cancer prefers an acidic environment. And that certain foods cause that environment. So by creating a more alkaline environment, the cancer cells can't survive.

Researchers found that there was a lack of evidence to say that an alkaline diet can prevent or cure cancer. They did a systematic review Open a glossary item of studies on an alkaline diet in 2016. The researchers also said that an alkaline diet could change the pH of urine to be more alkaline, but not that of the whole body. The body regulates the pH of blood through several internal processes. Food does not affect it.

Despite the alkaline diet being rich in certain vegetables and fruits, you can become malnourished. The diet limits you to certain foods. You may lack:

  • iron
  • calcium
  • zinc
  • vitamin B12
  • vitamin D

The ketogenic diet is a high fat, low carbohydrate, and low or unlimited protein diet. When the body uses fat and protein as energy, ketones become the energy to cells in the body. This is instead of glucose (from carbohydrates).

Early (preclinical) studies show that some cancer cells can't use ketones as energy. So, by changing the diet to be high in fat and low in carbohydrate, glucose levels are low, and cancer cells are starved. Normal body cells adapt and can use ketones to survive.

But these are early studies. We need more and better quality research on humans. Only then can we decide to use the ketone diet to prevent or cure certain types of cancers.

The ketogenic diet lacks fibre, fruit and vegetables. It can also lead to low levels of calcium, vitamin D and other salts (electrolytes). This diet can cause kidney stones in people with a family history of the condition.

A macrobiotic diet makes use of the Eastern idea of yin and yang. Yin and yang mean two opposite parts that complement each other and which make up all aspects of life. For example, darkness and light.

The macrobiotic diet aims to avoid foods containing toxins. Many people follow a completely vegan diet with no dairy products or meat. But some people eat small amounts of organic fish and meat.

Generally, the diet is made up of:

  • organic whole grains such as brown rice, barley, oats and buckwheat (half your food intake)
  • locally grown, organic fruits and vegetables (up to a quarter of your food intake)
  • soups made with vegetables, seaweed, beans, chick peas, lentils and fermented soy (miso) (up to a quarter of your food intake)

You should also prepare and cook your food in a certain way.

There are no scientific studies to say that a macrobiotic diet can prevent or cure cancer. But researchers are doing a trial called the DIANA-5 trial. It is for women with breast cancer. The trial looks at the effect of a:

  • macrobiotic diet
  • Mediterranean diet
  • exercise

A macrobiotic diet may lack:

  • vitamin B12
  • vitamin D
  • calcium

Diets based on not eating for some time, or eating very little, followed by a period of eating normally have become popular. This is also called intermittent fasting. Followers believe that it can help to:

  • improve health
  • lose weight
  • reduce cancer risk

Laboratory and animal studies have been looking at the effects of fasting on chemotherapy. These early studies showed that fasting might protect healthy body cells from chemotherapy. And that it might help chemotherapy to work better on cancer cells.

One study on women with breast or ovarian cancer showed that short term fasting during chemotherapy (24 hours before and 36 hours afterwards) improved quality of life and fatigue.

But these are early studies, and most of the studies on humans are small and based only on selected people with certain cancers. We need more research.

Health professionals don’t recommend that you fast before or during chemotherapy at the moment.

People eat organic foods for health and wellbeing or because they believe it is better for the environment and animal welfare. Many believe that organic food is healthier or has more nutrients. Organic means a way of farming and food production that uses:

  • fewer chemicals to kill pests and weeds (pesticides, herbicides and fungicides) and only natural substances if necessary
  • no man made products to nourish the soil (fertiliser)
  • high animal welfare standards

Researchers did a systematic review Open a glossary item of studies in 2019. They found that some of the observational studies in the review showed a lower incidence of non-Hodgkin lymphoma in people eating an organic diet. Non-Hodgkin lymphoma is a type of cancer that affects the lymphatic system, a network of vessels and glands found throughout your body.

But the researchers said that there was not enough evidence to say that an organic diet is beneficial in the long term. And that we need more research.

There is also no evidence that small amounts of pesticides found in foods increase the risk of cancer. Pesticides can be harmful when used improperly and not within the safe levels as stated by the law. In the UK, a pesticide can only be used once its safety has been tested.

Fruit and vegetables might sometimes contain low levels of chemicals, but this is far outweighed by the known health and cancer protective effects of these foods.

You should wash fruit and vegetables before eating to lower your exposure to these chemicals, but also to protect yourself from germs.

In the past, many people believed that dairy products contained hormones that could cause some types of breast cancer. Hormones can stimulate some cancer cells to grow. But farmers in the EU, by law, are not allowed to treat cows, goats and sheep with hormones that make them grow.

The World Cancer Research Fund (WCRF) says that there is limited scientific evidence that a diet high in calcium and dairy products can increase the risk of developing prostate cancer. So men should try not to have more than 700mg of calcium per day.

There is also limited scientific evidence that:

  • low fat dairy can protect against breast cancer in women who have not been through the menopause (premenopausal)
  • diets high in calcium can protect against breast cancer in women who have had the menopause (postmenopausal)

There is strong scientific evidence that dairy products reduce the risk of bowel (colorectal) cancer.

Healthcare professionals don’t recommend a dairy free diet to prevent cancer. Try to eat 3 portions of low fat dairy a day. It contains calcium, protein and some vitamins.

Other cancer remedies and supplements

Bromelain

Bromelain is a natural enzyme found in pineapples.

Laboratory and animal studies showed that bromelain might reduce inflammation. Researchers also used it in studies of patients with:

  • burn and skin conditions
  • pain and swelling

Animal studies showed that bromelain might prevent or treat certain cancers. And that it might stop them from growing. Bromelain might also be used alongside other cancer treatments.

But we need more research and better quality studies before doctors can use bromelain to prevent or cure cancer.

Essiac

Essiac is a herbal remedy from Canada. It is a mixture of roots, bark and leaves that you boil to make a drinkable liquid.

A Canadian nurse called Rene Caisse created Essiac. She named the remedy after herself. Essiac is her surname spelled backwards.

A commercial company now owns Essiac. Essiac is a registered trademark. Essiac Canada International is the only manufacturer that has rights to Rene Caisse's original formula of herbs.

People use Essiac because they believe it can:

  • cure or control their cancer
  • boost their immune system
  • help them to feel better

Several studies and reviews found that Essiac had no anti cancer effects. Essiac may cause nausea and vomiting. Other side effects were also reported.

Laetrile

Laetrile is a partly man made (synthetic) form of the natural substance amygdalin. Amygdalin is a plant substance found in raw nuts, bitter almonds, as well as apricot and cherry seeds.

Some people call laetrile vitamin B17, although it isn’t a vitamin.

People who use laetrile believe it might:

  • improve their health, energy levels and wellbeing
  • detoxify and cleanse the body
  • help them to live longer

Some studies have shown that laetrile can kill cancer cells in certain cancer types. But there is not enough reliable scientific evidence to show that laetrile or amygdalin can treat cancer. Despite this, it still gets promoted as an alternative cancer treatment.

Laetrile contains cyanide and can cause serious side effects and liver damage.

Turmeric

Turmeric is a spice grown in many Asian countries. It belongs to the ginger family and is the main ingredient of curry powder.

The main active ingredient in turmeric is curcumin or diferuloyl methane. Laboratory studies have shown curcumin has anti cancer effects on cancer cells. It seems to be able to kill cancer cells and prevent more from growing. It has the best effects on breast cancer, bowel cancer, stomach cancer and skin cancer cells.

At the moment, there is no clear evidence in humans to show that turmeric or curcumin can prevent or treat cancer.

People have reported stomach pain when eating too much turmeric.

Soy and oestrogen based supplements

Isoflavones are chemicals in soy products that are known for their health benefits. It is very similar to the hormone oestrogen. Oestrogen can stimulate some cancers, such as breast cancer, to grow. People often worry that foods or soy supplements containing isoflavones might have the same effect as oestrogen and cause cancer to grow.

But current research says that foods containing natural isoflavones are safe. Early studies also show that isoflavones may have some benefits in certain cancers. It may:

  • protect against cancer
  • reduce inflammation
  • reduce damage to cells
  • help DNA to repair

In breast and prostate cancer isoflavones may reduce the risk of cancer coming back. This is because isoflavones are similar to the hormone oestrogen and bind to the oestrogen receptors on cells. By doing so, it blocks oestrogen from being absorbed by cancer cells. However, these studies are based on Asian diets that contain large amounts of soy.

Soy can be a meat free source of protein and fibre in your diet. Health care professionals don’t recommend the use of soy supplements to protect against cancer.

Selenium, vitamin C and D

Many people with cancer use complementary and alternative medicines (CAMs). People believe that they can:

  • increase survival
  • reduce the risk of cancer coming back
  • help make cancer treatment work better
  • reduce side effects
  • boost their immune system
  • control their cancer

One type of CAM is antioxidants. Laboratory, animal and human studies have shown that antioxidants could slow down the growth of cancer cells.

But some vitamins and minerals could interfere with how well cancer drugs work. High dose antioxidants such as coenzyme Q10, selenium, vitamins A, C, E may help to prevent cell damage, but it may also stop cancer treatments from working well.

Selenium

One trial showed that selenium might protect against the overall risk of prostate cancer in men with a history of non melanoma skin cancer. But a systematic review in 2018 found that selenium supplements had no benefit in protecting against cancer.

Some randomised controlled trials showed a higher incidence of high grade prostate cancer and type 2 diabetes in people taking selenium supplements.

Vitamin C

People often take vitamin C in much higher doses than the recommended nutrient intake (RNI) of 40mg per day. Some people take it as a drip into the bloodstream (IV). High doses of vitamin C can cause side effects such as an upset stomach or kidney stones.

But there is no good quality research to say that that vitamin C helps chemotherapy to work better or help to reduce its side effects.

Vitamin D

There is not enough research on the best dose of vitamin D that has an effect on the bone health and survival of people with cancer.

Vitamin supplements 

If you can’t take in enough nutrients through a balanced diet or have a low level of a particular nutrient, your doctor or dietitian might suggest a dietary supplement. Ideally, a balanced diet with a variety of food rather than a supplement is preferred.

Supplements at a high dose could be toxic or harmful to your health. So a standard multivitamin and mineral supplement that contains about 100% of your daily requirements is enough.

Vitamin supplements in doses higher than the daily recommended nutrient intake could interact with cancer treatments. Check with a pharmacist or your healthcare team before taking any supplements.

Last reviewed: 
22 Apr 2020
Next review due: 
21 Apr 2023
  • Systematic review of the association between dietary acid load, alkaline water and cancer

    T Fenton and T Huang

    BMJ Open. 2016; 6(6): e010438

  • Pros and Cons of Dietary Strategies Popular Among Cancer Patients

    S Zick and others

    Oncology Journal, Integrative Oncology  November 15, 2018, Volume: 32, Issue: 11

  • Ketogenic diet in cancer therapy

    D Weber and others

    Aging (Albany NY). 2018 February; 10(2): 164–165

  • Weight Management and Physical Activity for Breast Cancer Prevention and Control

    J Ligibel and others

    American Society of Clinical Oncology Educational Book 2019 :39, e22-e33

  • The information on this page is based on literature searches and specialist checking. We used many references and there are too many to list here. If you need additional references for this information please contact patientinformation@cancer.org.uk with details of the particular issue you are interested in.