Eating red meat just once a day increases your risk of bowel cancer by a fifth, a study by Oxford University suggests.
The research based on almost half a million British men and women found that even moderate consumption of ham and bacon was linked to an increased chance of developing the disease.
Scientists recommended cutting intake of red and processed meat to no more than twice a week, in light of the findings.
Bowel cancer is the third most common type of cancer in the UK, with around 23,000 diagnoses annually.
It has long been linked to heavy consumption of red meat – especially processed types.
However, the new research suggests that even a modest intake of such foods had a significant impact.
The study, part-funded by Cancer Research UK, found that every 25 grams of processed meat eaten daily – equivalent to a rasher of bacon or a slice of ham – increased the risk of bowel cancer by 20 per cent. Every 50 grams of unprocessed red meat – a lamb chop or thick slice of roast beef – was linked to a similar increase in risk.
Overall, those sticking to Government guidelines on red and processed meat consumption carried risks around a fifth higher than those who limited their intake to very small amounts.
Department of Health guidelines say that while meat is a good source of protein, vitamins and minerals, people should cut their intake of red and processed meat to about 70 grams per day – the equivalent of around three rashers of bacon.
For the new study, published in the International Journal of Epidemiology, experts examined data from 475,581 people aged 40 to 69 at the start of the study and followed them for an average of 5.7 years.
During this time, 2,609 people developed bowel cancer.
The new study found that people consuming an average of 76g per day of red and processed meat had a 20 per cent higher risk of bowel cancer compared with those who ate 21g per day.
For processed meat only, the risk was 19 per cent higher for those who had an average of 29g per day – about one rasher of bacon or a slice of ham – compared with those who had an average of 5g per day.
And for unprocessed red meats, the risk was 15 per cent higher for people who ate 54g per day – about one thick slice of roast beef or one lamb chop – on average compared with those who had 8g per day.
The study also found that those with the highest intake of fibre from bread and breakfast cereals had a 14 per cent lower risk of bowel cancer.
Around one in every 15 men and one in every 18 women will develop bowel cancer during their lifetime.
Cancer Research UK's expert in diet and cancer, Professor Tim Key, who co-authored the study and is deputy director at the University of Oxford's cancer epidemiology unit, said: "Our results strongly suggest that people who eat red and processed meat four or more times a week have a higher risk of developing bowel cancer than those who eat red and processed meat less than twice a week.
"There's substantial evidence that red and processed meat are linked to bowel cancer, and the World Health Organisation classifies processed meat as carcinogenic and red meat as probably carcinogenic.
"Most previous research looked at people in the 1990s or earlier, and diets have changed significantly since then, so our study gives a more up-to-date insight that is relevant to meat consumption today."
Existing evidence points to an increased bowel cancer risk for every 50 grams of processed meat a person eats per day, but the new study found that risk increases at just 25 grams per day.
Dr Julie Sharp, Cancer Research UK's head of health information, said: "The Government guidelines on red and processed meat are general health advice and this study is a reminder that the more you can cut down beyond this, the more you can lower your chances of developing bowel cancer.
"This doesn't necessarily mean cutting out red and processed meat entirely, but you may want to think about simple ways to reduce how much you have and how often.
"Although breaking habits we've had for a long time can be hard, it's never too late to make healthy changes to our diet.
"You could try doing meat-free Mondays, looking for recipes using fresh chicken and fish, or swapping meat for pulses like beans and lentils in your usual meals."
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Do you consume more than 70 grams of red meat daily? Would you consider cutting down to reduce the risk of bowel cancer?