Scientists make 'profound' discovery about food and cancer as they hunt for cause of colon tumor explosion in young people

Scientists investigating the explosion of colon cancers in young people say they've made 'profound' discoveries about the role differences in diet play. 

The researchers compared and contrasted 176 past scientific studies in an effort to drill-down into the specifics of just how six popular diets impact gut microbiomes in humans — and which diets lead to a rise in gut bacteria linked to tumor growth.

Building off these nearly two hundred studies, their sweeping review found that a Western diet high in sugar, saturated fat and processed foods had the biggest risks.

But the team found that a high fiber diet used to control diabetics' blood-sugar had a protective effect against changes linked to the cancer.

The study also raised a high degree of skepticism toward the health benefits of high-protein and ketogenic diets, often popular with health conscious athletes. 

One microbiologist who worked on the new review study called it 'a significant milestone' that provides 'tangible data' on how the microbiome is relevant health. 

The Western diet appeared to reduce the diversity of bacteria in the gut, leading to an explosion in Bacteroides species tied to obesity.

These foods also left behind a soup of additives and preservatives that these researchers found were linked to a 'surge of chronic inflammation' in the gut.

A Western diet — low in fiber, fruits and vegetables — also made it harder for the digestive system to breakdown any healthy fiber after it was eaten, the team found.  

Western diet-eaters also had fewer bacteria species that produce short-chain fatty acids, the researchers said, which can help to reduce inflammation in the gut. 

Chronic, or long-term, inflammation in the gut is concerning because it can lead to damaging mutations in cells, which increase the chance they become cancerous.

Ultra-processed foods — like donuts, pizza and chips — have previously been linked to a higher risk of inflammation and associated health risks.

On the other hand, those following a green Mediterranean diet — rich in fruits, vegetables and olive oil as well as green tea and protein-rich aquatic plants, like Mankai (duckweed) — had the best health outcomes overall.

The researchers said it triggered a surge in 'health-promoting bacteria' in the gut and reduced the abundance of those linked to cellular damage.

Many of the 176 studies reviewed for the new analysis, published this week in the journal Nature Reviews Microbiology, turned to a bacterial genetic identification technique called 'metagenomic sequencing' to survey the gut microbiome.

The method has also been used to study the hidden microbial world by ecologist in the wild and to assess the environmental health of polluted, post-industrial sites.

Just one of those studies alone, for example, tracked the changes in gut bacteria for 307 male participants alongside their dietary behaviors across half a year.

All told, the scientific reviewers broke this mountain of research down into studies of six different broad categories of diet: the Western diet and the Mediterranean diet, but also high-fiber, high-protein, plant-based and ketogenic diets. 

A high-fiber diet, or one involving plenty of whole grains, is popular among those with chronic constipation or aiming for weight loss.

And the review suggested it had a protective effect against colon cancer, type-2 diabetes and inflammation specifically because it changed the mix of bacteria within the gut microbiome.

The high-fiber plant matter consumed was found to lead to a 'substantial increase' in the populations of Lactobacillus and Bifidobacterium bacteria — which release beneficial compounds, like the short-chain fatty acids, that can reduce inflammation.

The plant-based, or vegetarian, diet was also found to lower the risk of colon cancer because polyphenols in the plants prompted the growth of other beneficial bacteria.

The plant-based diet in particular showed a rise of one particular group of bacteria, of the genus Akkermansia, which help fight bacterial diseases, the researcher wrote. 

Researchers called for more research into the ketogenic diet — or high fat diet — warning of a history of past studies that show it can cause sudden drops in populations of 19 different species of beneficial bacteria, called Bifidobacteriums.

Like Akkermansia, these Bifidobacteriums also play a crucial role 'regulating the immune system,' the researchers said, by curbing the growth of infectious bacteria. 

But the team also raised concerns over high-protein diets including lots of red meat.

In their review, they noted that the breakdown of meat in the gut can lead to the release of hydrogen sulfide — which can cause damaging mutations to nearby cells. 

'Our review highlights the profound impact of different diets on the gut microbiome,' the review's lead author Dr Catherine Stanton said in a statement.

'This understanding is crucial for developing dietary recommendations that promote health and prevent disease,' said Dr Stanton, who works for Teagasc, a public-private Irish state organization that studies food and agriculture.

'It's fascinating to see how dietary choices can influence the balance of micro-organisms in our gut,' she added, 'and their metabolic functions.'

The review comes amid a race among researchers to understand the explosion in colon cancer cases among under-50s.

About 17,000 people under 50 years old are now developing the disease every year, surging nearly 50 percent in just two decades — from 12,000 cases annually in 1999.

The colon cancer rate among those in their late 20s and early 30s has risen by an estimated 70 percent over the same period.

Other cancers are also surging among young people including those of the bile duct — in the intestines — breasts and appendix. 

Kate Middleton, 42, was among younger celebrities to bravely reveal they had cancer this year — while actress Olivia Munn, 43, revealed last year she was suffering from breast cancer.

Scientists are stumped as to the cause of the surge in cancers in young people — and have so far blamed everything from surging obesity rates to regularly eating processed food.

Meanwhile, a separate study has suggested an additive used in Red Bull and other energy drinks could fuel the growth of cancerous cells.

A team of Government-funded researchers launched a $25million probe to investigate the cause of the rise in March this year.

Colon cancer is particularly concerning because it often doesn't trigger symptoms until later stages when it is more advanced — and harder to treat.

Guidelines currently say all Americans over 45 years old should be screened for the cancer, but some physicians are calling for this age limit to be reduced further.