Common cancer diets: the myths and the facts

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Dairy

Myth:

• Hormones used in the production of milk promote hormone related cancerous tumour growth.

Facts:

• There is no link between dairy containing diets and risk of cancer or promoting cancer growth as a result of hormones.
• There is evidence suggesting a protective role of dairy in the development of breast cancer through increased intake of calcium, vitamin D, butyrate, conjugated linoleic acid and lactoferrin.

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Soya

Myth:

• Isoflavones, found in soy products have a similar chemical structure to the hormone oestrogen. Oestrogen can stimulate some cancers, therefore it was thought foods containing isoflavones might have the same effect.

Facts:

• Current evidence suggests that a diet containing naturally occurring Isoflavones is safe.
• Soya foods can be used as part of a healthy balanced diet as a non-meat source of protein and provide fibre.

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Sugar

Myth:

• Sugar feeds cancer cells.

Facts:

• Cutting out sugar in diet does not restrict glucose (sugar) to cancer cells.
• Sugars are found in a number of healthy foods including complex carbohydrates, fruits and vegetables. These are high in fibre, vitamins and minerals and have been linked with a lower risk of cancer.
• It is recommended to reduce excessive sugar in the diet, particularly in the form of ‘free sugars’ or ‘simple’ sugars (for example those found in sugary drinks) as these are linked with being overweight.

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Alkaline

Myth:

• An acidic environment promotes ill health whereas an alkaline environment is beneficial and promotes good health. It is claimed that the food you eat can affect the body’s pH and that as our blood is naturally alkaline (~pH 7.4) eating acid foods upsets the balance.

Facts:

• No consensus on grouping foods as acid or alkaline with many misclassified.
• Blood pH (7.4) is tightly regulated by the kidneys and respiratory system. Any excess acid is excreted in the urine. Blood pH is not altered by dietary intake.
• The alkaline diet suggests that eating an alkaline diet can create a hostile alkaline environment and therefore kill cancer. However neither cancer cells nor healthy cells can survive in an alkaline environment.
• There is no scientific literature establishing the benefit of an alkaline diet for curing cancer.
• The only situation in which blood pH is altered is during metabolic acidosis, when an individual is critically ill.

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Ketogenic

Myth:

• The ketogenic diet decreases tumour size and spread.

Facts:

• The ketogenic diet is a low-carbohydrate diet. There are variations, with specific proportions of macronutrients depending on the type of ketogenic diet followed.
• The existing research is on animals and in brain tumours.
• Human data is based on single cases and demonstrated weight loss, which may be a concern.
• A high protein intake may counteract the ketogenic diet by providing glucogenic amino acids for production of glucose when the level of protein consumed exceeds the normal non starvation protein turnover.
• A ketogenic diet can cause symptoms of constipation, diarrhoea and fatigue.
• Adherence may be low due to palatability, and prolonged dietary restrictions.

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Fasting

Myth:

• Fasting can improve effect and symptoms of chemotherapy.

Facts:

• There is some evidence that short term fasting (STF) might increase the effectiveness and tolerability of chemotherapy, most of the studies are in early stages or in animals.
• These preliminary studies are based on small groups and mostly in breast and ovarian cancer.
• The fasting regimes caused side-effects including: headaches, hunger, weakness, nausea, light-headedness and weight loss.
• Due to the lack of strong evidence and the risk in certain people it is not advised if you have certain conditions, such as heart disease, diabetes or previous or existing eating disorders. A low body mass index (BMI≤19kg/m2) or history of recent weight loss.

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Supplements

Myth:

• Complementary alternative medicines can increase survival and reduce recurrence, optimise treatment, alleviate side effects and boost immune system.

Facts:

• Some vitamins and minerals could interfere with how well cancer drugs work. High dose antioxidants (coenzyme Q10, selenium, vitamins A, C, E) may help prevent cell damage but may stop chemotherapy from working as efficiently.
• Check with your oncology team before taking any supplements

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(Source : British dietetic Association)

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