Food and cancer FAQs

Some studies have shown that acidic environments help cancer cells grow so it has been suggested that creating an alkaline environment will stop the growth of cancer. These studies have looked at cells in a petri dish so don’t represent what actually happens in your body.

Your body regulates the acid/base balance in your blood within very tight limits. The pH of your body is slightly alkaline, and any shifts from the normal pH range are quickly dealt with by your body’s systems. Some foods can change the pH of your urine, for example meat can make it more acidic and fruit and vegetables can make it more alkaline. Changing the pH of your urine is just one of the ways your body keeps your overall blood pH within the narrow range it needs to be at. There are no foods or special products (e.g. alkaline water or alkalising greens) that can change the pH of your blood.

For example, vitamin C is sensitive to heat, so raw fruit and vegetables have the highest amount of vitamin C. Some nutrients (like vitamin C and B vitamins) are water soluble so move out of the food and into the cooking water if boiled. Steaming or microwaving fruit and vegetables uses less water so results in less loss of these nutrients. Some compounds (like lycopene in tomatoes) become more available to our bodies when cooked.

Some people claim that certain diets can cure cancer. This is not true. No special foods or diets have been scientifically proven to prevent or cure cancer. Here are some red flags to help spot a diet that may be dangerous to your health.
Does the diet

Exclude a whole food group?
Include a large amount of a specific food?
Cost a lot of money?
Take a lot of time to prepare?
Result in unwanted weight loss during treatment?
Prevent you from enjoying social occasions?
Include special supplements?

If you said yes to one or more of these red flags, it might be time to reassess if this is right for you. Discuss the diet with your treating team or Cancer Council nurse.

There is no evidence to suggest that frozen foods cause cancer. Frozen fruits and vegetables are just as nutritious as fresh, as modern freezing techniques lock in the nutrients at the time of harvesting. Frozen fruit and vegetables are a cheap and convenient way of getting the recommended two serves of fruit and five serves of vegetables each day.

See our Iron in food information sheet to inform you of: Good iron food sources, how to increase iron adsorption from food, recommended daily intake of iron and iron supplements.

A ketogenic diet is one that contains no carbohydrates (your body’s preferred source of fuel). When there is no carbohydrate, your body can turn fat into ketones which are then used as fuel. There is interest in this diet for cancer because some animal studies have found an effect on the growth of glioma (a kind of brain cancer) cells.

There is not currently good evidence that a ketogenic diet is helpful for humans with cancer. There is also a high risk of malnutrition when following such a strict diet. Getting enough fibre, vitamins and minerals can be difficult, and following a strict ketogenic diet can be stressful and expensive. Many healthy foods like wholegrains, some vegetables, fruit and dairy are all excluded. People report headaches, constipation, diarrhoea and nausea when trying this diet. Medical supervision is recommended on this kind of diet to ensure balance and minimise side effects. Speak to your doctor or an accredited practising dietitian if you’re interested in trying it.

This is a chemical that the body converts into cyanide. It has been researched since the 1950’s and there is no good quality evidence that it can treat any cancer. The sale of raw apricot kernels (high in laetrile) has been banned in Australia and New Zealand because it can be very dangerous to health.

For most people it is more beneficial to eat whole fruit and vegetables and drink water than to drink a lot of juice. Juices and smoothies can, however, play a role in a healthy diet and can be useful if people are struggling to eat enough healthy foods. Sometimes it is easier to drink a smoothie than eat a meal. Here are a few things to keep in mind if someone is thinking about using smoothies or juices.

Most juices contain hardly any fibre. This is one of the most beneficial parts of fruit and vegetables. Blitzing (rather than juicing) is better for this reason.
Blitzing food in a high-powered blender can decrease the fibre content. This means that some of the effects on digestion will be different to if you’re eating the whole food
It can be very easy to drink a lot of juice, and therefore a lot of excess sugar and kilojoules
Replacing meals with juices or smoothies may lead to unwanted weight loss

A small amount of research has suggested that regular use of probiotics may have a small benefit in preventing the development of some cancers. we don’t yet know how reliable this link is, for example people who take probiotics may also eat healthier foods and do more exercise, and it may be these other factors that lead to the reduced rates of cancer people taking probiotics. At this stage we would not recommend taking probiotics for cancer prevention.

There is some evidence that probiotics can prevent or treat chemotherapy or radiotherapy related diarrhoea. The studies were not of high enough quality to make a general recommendation for their use for this purpose, and further research is needed. As some studies did show an effect and there wasn’t any evidence of negative outcomes, it may be worth talking to your doctor about trialling probiotics if you are having problems with diarrhoea while you are going through chemotherapy or radiotherapy or after treatment.

CAUTION: Some studies have shown taht using probiotics while receiving immunotherapy can result in a lower response to treatment. Anyone undergoing immunotherapy, or whose immunity is lower than normal (immunocompromised), should NOT take probiotic supplements.

Anyone undergoing treatment for cancer should talk to their doctor before taking any supplements, including probiotics.

Eating red meat, and particularly processed meat (cured with preservatives and additives) is associated with an increased risk of bowel cancer. Lean red meat is however a good source of iron, zinc, vitamin B12 and protein. To balance the risk and benefits of eating red and processed meats Cancer Council recommends

Avoiding processed meats like bacon, ham, salami and prosciutto
Only eating moderate amounts (less than 500g per week) of red meat
Try lentils, beans, tofu, fish, eggs and chicken instead of red meat

Further reading: Red meat, processed meat and cancer (Cancer Council NSW)

Soy products contain plant compounds called isoflavones that can act like weak oestrogen in the body. As oestrogen is linked to breast cancer, there have been concerns that eating soy foods may affect your risk of developing or recovering from breast cancer.

A number of studies have investigated the link between soy consumption and breast cancer. Most studies have not found a link between soy and the risk of developing breast cancer, while some studies have found that people who eat more soy are less likely to develop breast cancer.

Research also suggests that women diagnosed with breast cancer who consume soy products have a reduced risk of mortality and breast cancer recurrence, with this decreased risk seen in both ER+ and ER– breast cancers. However more studies are needed in this area to fully clarify the link.

Taking into consideration the current evidence, it is recommended that people diagnosed with breast cancer who already consume soy foods as part of their normal diet should continue to do so. The evidence is not currently strong enough to suggest that people who don’t normally consume soy foods should start. Avoid taking soy or isoflavone supplements as it is not clear if these products are safe for women with breast cancer.

Alkaline food - can an alkaline diet cure cancer?

Further reading:

Cooking - does cooking affect the nutritional value of fruit and vegetables?

Dodgy diets - how do I spot a dodgy diet?

Freezing food - can freezing food give you cancer?

How much iron do I need each day?

Ketogenic diet

Laetrile/ amygdalin/ B17

‘Nutribullet’ or blitzer - is it a good idea for me to use a ‘Nutribullet’ or blitzer to make juices and smoothies? Will it have an effect on the nutritional value of my food?

Probiotics and cancer

Red meat - does eating red meat give you cancer?

Soy foods - do soy foods increase your risk of developing or recovering from breast cancer?

Further reading:

Sugar and cancer

Further reading

Superfoods that cure cancer

Supplements - can supplements cure cancer?

Vegan diet

Further reading:

Vegetables - what tips do you have for eating more veggies?

Vitamin C - high dose

Further reading