FAQS: DIET AND CANCER RISKDISPELLING SOME COMMON DIET-RELATED MYTHS ON FOODS AND RISK OF CANCER

DOES SUGAR INCREASE THE RISK OF CANCER?

The cells in our body use sugar (glucose) for energy.Cancer cells grow faster than usual, which requiresa lot of energy, leading to the suggestion that sugar‘feeds’ cancer cells. But there is no strong evidencethat cutting sugar out of your diet will preventcancer or stop cancer cell growth or that eatingmore sugar will cause cancer cells to speed theirgrowth. However, sugary foods and drinks whenconsumed frequently or in large quantities can leadto weight gain, and being overweight and obese islinked to an increased risk of a number of differenttypes of cancer including breast, pancreatic, liver,ovarian and colorectal cancers.

CAN DAIRY FOODS INCREASE THE RISK OF CANCER?

SUGAR

In a review of the research available, the World CancerResearch Fund concluded that evidence suggests dairyproducts like milk and yogurt decrease the risk of colorectalcancer. There is no strong evidence linking dairy products toany other types of cancer although there is some limited(inconsistent) evidence that diets high in dairy products orcalcium may decrease the risk of breast cancer, but mayincrease the risk of prostate cancer. It is sometimes wronglyreported by the UK press and populist media that animalsare routinely given hormones to increase their milk yield,and that milk and dairy foods contain added hormones thatcan increase cancer risk. However, in the UK and EU addinghormones to the diet of animals to enhance milk productionor to dairy products is banned.

MILK &

DAIRY

PRODUCTS

'Cutting out sugar doesn’t help treat cancer, and sugar doesn’tdirectly cause cancer’ Cancer Research UK

'....cancer experts do not recommend following a dairy-free diet totry to reduce the risk of cancer.’ Macmillan Cancer Support

AND ON ALTERNATIVE DIETS FOR PEOPLE HAVING CANCER TREATMENT

CAN ALKALINE DIETS PREVENT CANCER?

Despite a lack of evidence, the idea that ‘acidic’ dietscan increase your risk of cancer is still promoted inthe popular media. Some laboratory based studiessuggest cancer cells thrive in an acidic environment,so an alkaline diet is promoted to correct this. Infact, the pH (level of acidity) in our bodies is tightlyregulated by the kidneys within a very narrowrange.  Any extra acid or alkali is removed throughurine so food choices may affect the pH of your urinebut will not change your body acidity. The alkalinediet promotes fruit and vegetables, and it is possiblethat a diet high in these may have cancer protectiveeffects due to their nutrient and bioactivecompounds rather than their acid/alkalinepromoting qualities. However, the alkaline diet alsopromotes exclusion of many foods, several of whichcontribute beneficial nutrients to most people's diet.

ALKALINE

DIETS

'Altering the cell environment of the human body to create a less-acidic,less-cancer-friendly environment is virtually impossible’ American Institute

of Cancer Research

DO LOW CALORIE SWEETENERS CAUSE CANCER?

‘Earlier cancer scares linked with certain sweeteners have beendiscredited’ World Cancer Research Fund

LOW CALORIE

SWEETENERS

Low calorie sweeteners have been thesubject of safety scares after the findingsof animal studies with significantscientific shortcoming suggested thatthey could cause cancer. However, largeand more recent human studies havesince provided strong evidence that theydo not increase the risk of cancer. In theEU, all low calorie sweeteners undergo arigorous safety assessment by theEuropean Food Safety Authority (EFSA)before they can be used in foods anddrinks.

CAN VEGAN DIETS PREVENT CANCER?

Some research has suggested an association betweenvegan diets and a lower risk of cancer but findings aresomewhat inconsistent. It does not appear that vegandiets are any more protective than plant-based diets thatinclude moderate to small amounts of animal foods. TheWorld Cancer Research Fund recommendations for cancerprevention include eating more plant-based foods such aswholegrains, fruit, vegetables, pulses, nuts and seeds, andeating less red and processed meat. These diets tend toprovide higher amounts of dietary fibre, as well as lowerintakes of fatty/processed meat, refined grains, sugars-sweetened foods and drinks and saturated fat than otherdietary patterns. A healthy vegan diet will typically sharethese characteristics and this may underlie many of thehealth benefits observed. Importantly, we should bear inmind that exclusion of animal products per se does notnecessarily equate to a healthy diet. Poor choices can bemade within any dietary pattern.

VEGAN

DIETS

‘There is no direct evidence that following a vegan diet reduces the riskof developing cancer' World Cancer Research Fund

WILL EATING A 'SUPERFOOD' PREVENT CANCER?

'SUPER-

FOODS'

The term ‘superfood’ is often used to describe foods withsupposed health ‘superpowers’, ranging fromblueberries to broccoli to green tea. However, this termshould be treated with caution as there is no evidencefor any one particular food making a major difference tocancer on its own. That said, some compounds found infoods that have been labelled with this term, such asantioxidants in fruits and vegetables or curcumin inturmeric, have been shown to affect cancer cells in labstudies. However, the compounds tested in a lab areoften in a different form or dose to how we eat them inthe diet, so we need considerably more research toinvestigate any potential links. Including a variety offoods in a healthy, balanced diet is key to good health.

'The term ‘superfood’ is really just a marketing tool, with littlescientific basis’ Cancer Research UK

Diet and Cancer TreatmentThere is a lot of confusion around what we eat in relation to cancer, and some alternative

diets or nutritional therapies have been claimed by the media to treat cancer such asGerson’s Therapy, the ketogenic diet or high-dose vitamin C (see below for details on these).

These types of diets are typically restrictive and hard to follow, and there is no scientific

evidence that they can cure cancer. Reputable scientific cancer organisations do not supportalternative therapies like Gerson’s for cancer treatment.

In fact, what we do know from the science is that weight loss is linked to poorer outcomes,so it's important to eat as well as you can when you have cancer. You may be given specificdietary advice, but this should be given by a health professional like a registered dietitian

who is qualified to advise you.

If you wish to follow any alternative diet you should only do so under the supervision andguidance of your doctor or dietitian. Stopping your conventional cancer treatments and

methods of symptom control can be harmful.

Ketogenic dietGerson's therapy

A therapy based on aregimen of a large

quantity of organic fruitand vegetable juices in

addition to coffeeenemas and nutrition

supplementation. There is no scientific

evidence that Gerson'sTherapy can treat

cancer, and in somecases it could be

harmful to your health.

High-dose vitamin CSupporters of this high fat,very low carbohydrate dietbelieve that cancer cells are

dependent on sugars andstrictly reducing the intake ofcarbohydrates can starve the

tumour. While studies onketogenic diets in mice withbrain tumours have shown

some positive results, there isa lack of large-scale clinical

trials in humans.There is currently no scientific

evidence supporting theeffectiveness of the ketogenicdiet in treating brain or other

tumours.

High intravenous doses ofvitamin C are being

researched in a numberof clinical trials, mainly inthe US, but research is in

the early stages. There is currently no

reliable evidence fromclinical trials in humansthat intravenous high-

dose vitamin C is aneffective way to treatcancer. It may also

interfere with cancertreatment.

For references used to develop this resourceemail postbox@nutrition.org.uk

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Last reviewed October 2019