For years they have been criticizing meat lovers, desperately trying to convert people to veganism.
But adopting a plant-based diet could actually harm your health, according to new research.
Adding meat and dairy protein to the diet could help prevent tumours linked to bowel cancer, scientists say.
Tests on mice, conducted by researchers at JapanThey now show that a diet that includes these molecules could reduce the risk of tumors growing in the small intestine.
The scientists, who described the findings as “important” today, also warned people against deliberately restricting such foods to combat bloating or control weight, if they do not suffer from allergies.
Antigens found in foods such as milk, peanuts and eggs have long been known to cause allergic reactions. Even in people who are not allergic, the immune system often recognises these antigens as foreign substances.
In the study, scientists used mice with a genetic mutation that makes them prone to developing tumors in the intestines, similar to familial adenomatous polyposis, found in humans, which increases the risk of colon cancer.
Divided into two groups, one was given a protein-free diet of meat and milk, while the other was fed a normal diet for six weeks.
Those who ate a normal diet developed fewer tumors in the small intestine, but both had the same number in the large intestine.
After introducing albumin (a protein found in meat) into the protein-free program, the researchers observed the same tumor-suppressing effects in the small intestine.
They also found that diet influenced the number of T cells, a type of immune “fighter” cell. Mice on plant-based diets had fewer T cells in their small intestine.
Writing in the diary, Frontiers in immunologyThe scientists suggested that this highlights the importance of dietary protein in maintaining a healthy immune system.
Dairy- and meat-free diets are sometimes adopted by people without serious gastrointestinal conditions or allergies as a healthy way to lose weight or reduce bloating and inflammation, they said.
Bowel cancer can cause blood in the stool, a change in bowel habits and a lump in the bowel that can cause blockages. Some people also experience weight loss as a result of these symptoms.
‘The new findings suggest this could be risky and emphasize that such diets should not be used without a doctor’s recommendation.’
Interest in a plant-based diet has increased in recent years, with vegans citing ethical, environmental or health reasons.
It is almost impossible to establish the exact number of vegans currently in the UK.
But a recent survey suggested that around 600,000 people are thought to be following a plant-based diet, while another in 2021 claimed almost a third of Britons were using alternative milks.
The latest Government figures suggest that around 2.4 million adults are living with a food allergy in the UK, and that hospital admissions for severe reactions have more than tripled in the past 20 years.
Children with allergies are considered to be at particular risk of severe reactions because, due to their smaller body size, small amounts of allergens cause larger reactions.
The findings come just months after experts continued to raise concerns about an “epidemic” of bowel cancers among young people.
Analysis published by the Bowelbabe Fund, set up in memory of Deborah James (pictured), projected that if current trends continue, bowel cancer cases will rise from the current 42,800 to 47,700.
Actor Chadwick Boseman is a famous face who died from early-onset cancer, medically defined as a case of the disease that attacks someone under the age of 50; in the case of the Black Panther star it was colon cancer.
Small bowel cancer, a cancer that develops in the small intestine, accounts for around 1,800 cases in the UK each year, according to Cancer Research UK.
Data show the disease has increased by 50 percent among those in their 20s, 30s and 40s, who 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 currently an epidemic of cancer among young people (under 50 years old).
‘The cause of this is unknown, but we are seeing more patients with abdominal cancer.’
Experts don’t know what’s driving this phenomenon, and some theories include our growing taste for junk food and a concomitant rise in obesity, which affects the health of our digestive system.
However, cancer specialists told MailOnline that this does not explain the rise in the disease among young people, a significant proportion of whom are perfectly fit and healthy.
One of the acknowledged victims of this trend is Deborah James, known as “the gut girl”, who was diagnosed with the disease at just 35 and raised millions for charity in her final days in 2022.
James spoke of his rigorous exercise routine and being in the best shape of his life when he developed the disease.
The disease has also affected male celebrities. Black Panther actor Chadwick Boseman died of colon cancer at the age of 43.
The analysis suggests that overall bowel cancer deaths in the UK will rise by 2,500 a year between now and 2040.
Meanwhile, the number of people in the UK diagnosed with the disease is set to rise by around a tenth over the same period.
Bowel cancer currently kills almost 17,000 Britons every year and only half of those diagnosed are expected to survive 10 years after learning they have the disease.