GPs and specialists may also have tried to explain the benefits of , say , vaccination , only to be told ‘ that ’ s just your opinion ’. Dr Google ’ s blog experts know better .

My field of nutrition is particularly plagued with experts . Celebrity chefs , sellers of supplements , sportspeople and some alternative medicine devotees claim to know more about human nutrition than those with degrees in biochemistry and physiology , and postgraduate degrees in human nutrition .

‘ Doctors don ’ t know ’ Enter ‘ cancer and diet ’ into a Google search and there are millions of entries , many based on spurious ideas . Some list foods that must be avoided because they “ cause cancer ”, or “ strengthen the cancer cells ” or “ distract the immune system from focusing on killing cancer cells ”.

In many cases , along with the virtues of raw foods and their living enzymes , the site encourages expensive supplements that “ doctors don ’ t know about ”.

For patients with cancer , these diets , pills , powders and juices may sound more appealing than the advice from a doctor , dietitian or organisations such as the Cancer Council , the National Cancer Institute or the World Cancer Research Fund ( WCRF ).

These reputable sources may be dismissed by some because they discuss reducing risk rather than cures .

Many people do not understand what we regard as ‘ evidence ’ — studies , preferably multiple randomised trials , published in quality , peer-reviewed journals .

Any evidence statement in the NHMRC ’ s dietary guidelines , for example , required at least five highquality studies with minimal bias .

Even then , the evidence statements were graded and checked by an external

methodologist to ensure all review activities were completed in a transparent , accurate , consistent and unbiased way .

This is to ensure that any work can easily be doublechecked by other researchers .

This systematic approach is a far cry from the ‘ evidence ’ of a miracle cure from Tom of Brisbane or Mrs Wilson from Tasmania .

For the public , however , Tom or Mrs Wilson ’ s testimonials may seem like the miracle they are hoping for . Sadly , opinion and hype override facts , producing ‘ alternative facts ’.

The media doesn ’ t always help . With few filters , and at times simply reproducing media releases from someone selling some product , dramatic stories sell . Straight facts may not .

For example , when yet another study finds significant benefits from higher consumption of vegetables , the media is not interested . No drama there , they claim , everyone already knows how valuable vegetables are .

That just 7 % of Australians achieve the recommended five servings of vegetables a day only confirms the lack of interest in something so ordinary by media standards .

Finding the right sources For patients with any kind of cancer , it ’ s unrealistic to think they won ’ t go straight to Google .

We should at least advise them which sites have valid information . The WCRF regularly updates advice on diet and particular types of cancer , and their advice is in plain English and suitable for the public .

The WCRF website ( www . wcrf . org ) includes lifestyle changes to reduce cancer risk , and has a valuable , continuous update project . It also includes issues currently in the media , such as cancers related to excess weight , the relevance of burnt toast , hot drinks , dietary supplements , and processed and preserved foods .

Their prevention guides for those who have survived cancer are useful too . Best of all , they ’ re not trying to sell anything .

EVIDENCED-BASED ADVICE ON NUTRITION AND CANCER

To reduce cancer risk , patients need to :

• Eat more vegetables and legumes

• Include two pieces of fruit to their daily diet

• Eat wholegrain products ( oats , wholegrain breads and grains )

• Avoid processed meats

• Keep intake of red meat low ( less than 450g / week )

• Minimise consumption of alcoholic drinks

Details for evidence for these foods and different types of cancer are discussed in the Australian Dietary Guidelines ( see : www . eatforhealth ).

MANY CLAIM THAT SINCE THE POPULATION HAS GROWN FATTER OVER THE PAST 30 YEARS , THE ADVICE AND GUIDELINES FROM GENUINE NUTRITIONISTS MUST BE FAULTY .

I advise patients to steer clear of any site that has products for sale ( supplements , books or devices ), and suggest that Cancer Research UK and some Cancer Councils here in Australia may know more than popular television hosts .

Even though there is no evidence that any food or diet can cure or prevent cancer , it ’ s important for patients to look after their bodies by having a healthy diet , and for their families to know there is good evidence that what we eat can reduce the risk of cancer ( see box ).

As with diet and cancer , the expertise of those with some knowledge of how weight loss occurs is less exciting than those promising some puff of magic will make excess fat ‘ fall off ’.

The purveyors of instant weight loss offer diets and supplements . Many claim that since the population has grown fatter over the past 30 years , the advice and guidelines from genuine nutritionists must be faulty . That almost no one has read or followed the guidelines seems to pass unnoticed .

It ’ s true that the way many food companies interpret dietary guidelines is faulty .

Australia ’ s guidelines have always recommended avoiding too much added sugar , but we have a range of junk foods with some of their fat replaced by sugar and refined starches .

The huge range of junk food and drinks is a major cause of obesity . These products now contribute 35 % of adults ’ and

more than 40 % of children ’ s kilojoules .

Our message to patients has to be that obesity is a multifactorial problem and can only be controlled by lifelong changes .

These include what and how much we eat and drink , as well as how much time we spend sitting or doing something more active . Changing these requires not just individual willpower , but also systemic changes .

There is no doubt that genetic factors play a role in obesity , although they can ’ t explain the rapid increase in obesity over the past few years .

Sleep patterns and the gut microbiome are also attracting research funding . But the fact remains that the food industry has been successful in selling us more food . We waste lots of food , but we also eat more .

The food industry spends millions of dollars advertising and promoting junk foods and drinks , as well as alcohol , because persuasion works to increase sales .

And the federal and state governments do nothing to hinder them .

HEALTHY HIPSTERS : TURMERIC AND GREEN JUICES

THERE is scant evidence that these products provide the benefits claimed by some popular books and blogs . However , as long as they don ’ t replace a healthy diet or proven medical care , there ’ s no harm in using them and there may be some psychological benefits . My advice is that as long as no one is ripping a patient off , then there ’ s no harm in adding fresh turmeric or green juices to a healthy diet .

Tax and town planning The Federal Government could help by controlling children ’ s increasing exposure to promotions for junk food through advertising and ‘ advergaming ’ ( product placements in videogames ).

They could also tax unhealthy foods and subsidise fruits and vegetables .

State governments could control the kinds of foods and drinks offered in schools , and both state and local governments could insist on town planning that encourages active transport and free recreation .

However , it ’ s also up to us as healthcare professionals , and the organisations that represent us , to show we care , and lobby for these changes . ●

Dr Stanton OAM is a leading nutritionist and visiting fellow at the school of medical sciences , University of NSW , Sydney .