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.