For years they've berated meat-lovers, desperately trying to convert people to veganism. 

But going plant-based really could harm your health, if new research is to be believed. 

For adding meat and milk proteins to your diet could help ward off tumours linked to bowel cancer, scientists have said.  

Tests on mice, by researchers in Japan, now show that a diet that includes these molecules could reduce the risk of tumours growing in the small intestine. 

The scientists, who today labelled the findings 'important', also warned people against deliberately restricting themselves of such foods to combat bloating or weight control, if they don't suffer with allergies. 

In the study, scientists used mice with a genetic mutation that makes them prone to developing tumours in the intestines — similar to the condition familial adenomatous polyposis, found in humans, which rasies risk of colon cancer. 

Split into two groups, one was given a diet free of meat and milk proteins, while the other was fed a normal diet over six weeks. 

Those consuming a normal diet developed fewer tumours in their small intestine. But both had the same number in their large intestine. 

After introducing albumin — a protein found in meat — to the protein- free programme, researchers saw the same tumour-suppressing effects on the small intestine. 

They also found that the diets influenced the number of T cells — a type of immune 'fighter' cell. Mice consuming plant-based diets recorded fewer T cells in the small intestine. 

Writing in the journal, Frontiers in Immunology, scientists suggested this highlights the importance of food proteins in maintaining a healthy immune system. 

Diets free of milk and meat are sometimes adopted by people without severe gastrointestinal conditions or allergies as a healthy way to lose weight or reduce bloating and inflammation, they said. 

'The new findings suggest that this could be risky and emphasizes that these kinds of diets should not be used without a doctor’s recommendation.'

Interest in a plant-based diet has soared in recent years, with vegans citing ethical, environmental or health reasons. 

The exact numbers of vegans now in the UK is almost impossible to establish.

But one recent survey suggested around 600,000 people are believed to be on a plant-based diet, while another in 2021 claimed that almost a third of Brits used alternative milks.

Latest Government figures suggest around 2.4million adults are living with a food allergy in the UK, with hospital admissions for severe reactions more than tripling within the last 20 years. 

Children with allergies are considered to be especially at risk from severe reactions as, due to their smaller body size, small amounts of allergens provoke bigger reactions.

The findings come just months after experts continued to express their ongoing concern over an 'epidemic' of bowel cancers among young people.

Small bowel cancer, cancer that develops in the small intestine, accounts for around 1,800 cases in the UK each year, according to Cancer Research UK.  

Data shows the disease has risen by 50 per cent in 20, 30 and 40-somethings, which are defined as 'early onset' cancer cases, over the past 30 years.

Oncologist Dr Shivan Sivakumar, from the University of Birmingham, previously described the situation as an 'epidemic'.

He said: 'There is an epidemic currently of young people (under 50) getting cancer. 

'It is unknown the cause of this, but we are seeing more patients getting abdominal cancers.' 

Experts have been stumped on what is driving the phenomenon with theories including our increasing taste for junk food — and a co-current rise in obesity, affecting the health of our digestive system.

However, cancer specialists have told MailOnline this doesn't explain the rise in the disease in young people, a significant portion of which are otherwise perfectly fit and healthy.

One of the recognised victims of the trend is Deborah James — known as 'bowel babe' — who was diagnosed at just 35 and raised millions for charity in her final days in 2022. 

James spoke of her rigorous exercise routine, and being in the best shape of her life when she developed the illness. 

Male celebrities have also been struck by the disease. Black Panther actor Chadwick Boseman was killed by colon cancer at just 43.  

Analysis suggests deaths from bowel cancer overall in the UK are set to rise by 2,500 a year between now and 2040.

Meanwhile, the number of people in the UK diagnosed with the disease will rise by around a tenth in the same period.

Bowel cancer currently kills just shy of 17,000 Brits each year with only half of those diagnosed expected to survive 10 years after learning they have the disease.