DO TRENDY LOW-CARB DIETS RAISE THE RISK OF CANCER?

FIRST came the Atkins, Dukan and South Beach diets. Today, it’s the trendy ketogenic diet, or keto, a lowcarb, high- f at plan which even has its own internet hashtag #LCHF.

Advocates cl ai m t hat t hese approaches help people shed weight fast, control blood sugar, beat type 2 diabetes, and even fight off cancer by avoiding eating carbohydrates.

People swap pasta for strips of courgette, rice for finely shredded cauliflower, and bread for lettuce leaves.

Some of these diets are more restrictive t han others. They range from 130g of carbs a day – which would mean you could still eat a large baked potato, a portion of rice and still have some left over – to just 30g, which is the equivalent of just two slices of wholemeal bread.

That it helps shift weight is in no doubt. Abandoning c a r bs i nvolves stripping significant calories from your diet.

But while it is touted as one of the most effective ways to slim, there may well be a huge downside to following the lowest-carb plans in the longer term. A review of the data, published in the European Heart Journal in April, found a ‘significant and positive’ chance that these diets were assoc i a t e d wi t h an increased risk of dying from ‘ any form’ of cancer.

The study, carried out by experts from an international panel, involved looking at half a million participants over a period stretching up to 16 years.

Initially, they examined 24,825 people who had taken part in the US National Health and Nutrition Examination Survey during 1999 to 2010. They found those eating the least carbs were, overall, 32 per cent more likely to die of any cause, and 35 per cent more likely to die of cancer than those eating the most carbs. These findings were then confirmed by combining the results of a f urther seven studies involving nearly 450,000 people, which revealed very low-carb dieters were eight per cent more likely to die of cancer. Of course, these studies were based on surveys, so it’s hard to be sure if factors other than carb i nt a ke were also at play. But lead author Proessor Maciej Banach, from the Medical University of Lodz in Poland, said: ‘These diets should be avoided. ‘They might be useful in the short term to lose weight, lower blood pressure and improve blood glucose control, but our study suggests that in the long term they are linked with an increased risk of death from any cause.’

A crucial problem is that very low- carb diets often lack fibre – plant matter which comes from bread, oats, grains and many fruits and veg. Fibre has long been proven to have a protective effect against bowel cancer specifically, a condition which affects one in 15 men, and one in 18 women in the UK. More than 50 per cent of cases are preventable, and 28 per cent are linked to consuming too little fibre.

The official advice is that, by eating three portions of fibre-rich foods a day – from porridge, fruit and veg to a slice of bread or a handful of nuts – our risk could reduce by 20 per cent.

It we all did this, it could save thousands of lives.

Fibre is protective in two ways. First of all, it increases the bulkiness of our waste and reduces the amount of time it takes to move through our digestive system, which means toxins spend less time in the bowel.

It also provides fuel for the ‘good’ bacteria in our systems, which in turn produces a fatty acid called butyrate. This protects the cells in t he bowel a nd makes tumours less likely to develop.

As it stands, nine in ten adults fail to consume the recommended 30g of fibre a day as it is. So cutting out food groups that contain fibre may mean straying even further from the target.

Dr Ian Johnson, emeritus fellow at the Quadram Institute Bioscience, says: ‘ Based on t he evidence, eating a diet low in fibre over a long period of time could lead to an increased risk of colorectal cancer.

‘ A ketogenic diet over just a couple of years might not have an effect – but the truth is, we just don’t know.

‘The protective effect of fibre might be about two- fold if you compare those who eat least with those who eat the most.’

CUTTING OUT SUGAR WON’T CURE CANCER

THE email spread like wildfire. It looked like a paper from the respected US research institution, Johns Hopkins University in Baltimore, and contained the claim: ‘Sugar is a cancer-feeder. By cutting off sugar, it cuts off one important food supply to the cancer cells.’

There was only one problem – it was a hoax.

But it became so widespread when it was circulated in 2007 that staff at Johns Hopkins were forced to issue a public statement to deny any involvement.

The theory persists, however, and is regularly trumpeted on social media by health gurus to

Serve meat with a yogurt dip – ‘good’ bacteria neutralises any carcinogenic chemicals formed when grilling

justify cutting all sugar – but particularly refined white sugar – out of the diet completely.

Sugar is often described by its opponents as ‘cancer’s favourite food’ and the ‘white death’.

The myth suggests that cancer cells need lots of glucose – the fuel which powers all of the body’s cells – to develop, so cutting it out will literally starve the cancer and stop it from growing.

While it sounds convincing, it is simply not true.

Katie Patrick, a nutrition expert from Cancer Research UK, warns: ‘All our healthy cells need glucose too, and there’s no way of telling our bodies to let healthy cells have the glucose they need, but not give it to cancer cells.’

Following severely restricted diets with very l ow amounts of carbohydrate could damage health i n the l ong term by eliminating foods that are good sources of fibre and vitamins, they add.

This is particularly important for cancer patients, because some treatments can result in weight loss and put the body under a lot of stress.

While on the subject of sweet things, another well-worn health myth: the man-made sweetener aspartame – used in everything from fizzy drinks, including Diet Coke and Coke Zero, to chewing gum – causes cancer (as well as multiple sclerosis, bl i ndness, depression, memory loss and birth defects). The theory has been thoroughly debunked. Yet rumours, often in the form of fake health news posted online, continue to circulate. Since aspartame was launched in the 1980s, studies have suggested that it could be linked to increased rates of brain tumours and leukaemia in rats, leading to worrying headlines. But it was later revealed that s o me a ni mals were fed t he equivalent in sweetener to 20 cans of Diet Coke, every day, for months, until they died. Despite this fact, the whiff of suspicion remains: in 2015, Pepsi dropped aspartame from its US Diet Pepsi drink in response to consumer fears over safety, replacing it with sucralose, another type of sweetener.

Yet the overwhelming evidence from robust scientific trials is that aspartame is safe.

No human studies have found any link to cancer or other problems, and two major reviews – by the European Food Safety Authority and US National Cancer Institute – have concluded the sweeteners are safe.

Sophia Lowes, health information manager at Cancer Research UK, says: ‘The link to cancer was between sweeteners and animals but it was never translated into a link in humans.’

Some say an alkaline diet – free of acidic foods like citrus fruits – protects against cancer. But no study has ever proved the claim.