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.

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

All cancer treatments have to go through rigorous testing to prove that they work.

Most alternative therapies have not been through this testing. So there is no scientific evidence that they work. 

Talk to your healthcare team if you're considering complementary or alternative therapies. Some types of alternative therapy may not be completely safe. They might interact with your medical treatment or cause harmful side effects.

Also, let your complementary or alternative therapist know about your conventional cancer treatment.

Try to eat a well balanced diet

It can be harmful to deprive yourself of:

• protein
• carbohydrates (including sugars)
• fats

Your body needs them to repair itself and keep going.

Try to eat a balanced diet, even if you are thinking about taking a nutritional supplement or trying an alternative diet. Ask to talk to a dietitian at your hospital about these diets or supplements. Also, let the dietitian know if you have problems with eating. For example if you have lost weight or have problems swallowing. 

Individual 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 that people ask us about. 

Gerson therapy

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

People who use Gerson therapy believe that changes to diet and nutrient intake can help to treat cancer and other conditions. They also think that cancer is a symptom of disease of the whole body.

Gerson therapy aims to rid the body of toxins and strengthen the immune system. Those following it say this brings the body back to its normal metabolic state, so it 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. This regime can have some harmful side effects.

Alkaline diet

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.

People following this diet believe that they can prevent and cure diseases, including cancer, by making the body's pH more alkaline. They argue that cancer prefers an acidic environment. And that certain foods cause that environment. By creating a more alkaline environment, the cancer cells can't survive.

Researchers carried out a systematic review of studies on an alkaline diet in 2016. They found that there was a lack of evidence to say that an alkaline diet can prevent or cure cancer. They 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, it also limits you to certain foods. It is low in protein and dairy, so you have a higher risk of becoming malnourished. You may lack:

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

Ketogenic diet

The ketogenic diet is a high fat, low carbohydrate, and low or unlimited protein diet. Usually, your body uses glucose (from carbohydrates) for energy. If you don’t have enough carbohydrates, your body breaks down fat and protein to release chemicals called ketones. Ketones become the energy to cells in the body. 

Early (preclinical) studies showed that some cancer cells can’t use ketones as energy. So, changing the diet to be high in fat and low in carbohydrate will lower glucose levels and starve cancer cells. Normal body cells adapt and can use ketones to survive.

But these are early studies which are mostly in animals. We need more and better quality research on humans. Only then can we know if the ketogenic diet can 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. People following this diet often stop due to suffering with: 

• tiredness (fatigue)
• diarrhoea
• constipation
• vomiting
• tummy pain 

Macrobiotic diet

The macrobiotic diet aims to avoid foods containing toxins. People following it believe that by eating a simple, healthy diet, we can live in harmony with nature. They also believe that the macrobiotic diet can prevent and cure cancer and other serious illnesses.

Many people follow a completely vegan diet with no dairy products or meat. But some people eat small amounts of organic fish and meat. The macrobiotic diet excludes any processed foods.

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 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. Many people following the diet will lose weight. Researchers believe it might not have enough calories or fluids for people having cancer treatment. 

A macrobiotic diet may lack:

• vitamin B12
• vitamin D
• calcium

Fasting

A fasting diet is based on not eating for some time, or eating very little, followed by a period of eating normally. This is also called intermittent fasting. People following it 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.

Some studies showed that short term fasting during chemotherapy improved quality of life and fatigue. Fasting reduced the number of chemotherapy side effects. But these are early studies. 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. Fasting may be harmful if you have other health problems like:

• diabetes
• heart disease
• weight loss or low weight

Organic diet

Many people 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 of studies in 2019. Some of the 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 .

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 not used properly 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 
• protect yourself from germs

Dairy

Research studies have looked into the role of dairy products in the development and recurrence of different cancers. Some have suggested that there might be a link between high fat dairy products and cancer survival. But we need more research.

Healthcare professionals don’t recommend a dairy free diet to prevent or treat cancer. Try to eat 3 portions of low fat dairy or dairy alternative a day as part of a balanced healthy diet. Dairy foods are a source of calcium, protein and some vitamins.

If you want to use a dairy alternative, make sure it is calcium fortified. This includes soya milk, yogurt or cheese.