London - Eating just one steak a week increases the risk of bowel cancer by more than two-fifths, a major study reveals.
Scientists warn that four portions of red meat – less than a single 10oz steak – could make you 42 percent more likely to develop the disease.
And even having just two portions a week increases bowel cancer risk by almost a fifth, the Oxford research found.
The study, involving 500 000 middle-aged men and women, is one of the largest so far to look at the link between bowel cancer and our diets. Its findings come only days after the World Health Organisation warned processed meat was as big a cancer threat as cigarettes.
A typical portion size for red or processed meat is about 70g, official guidelines say – equivalent to two rashers of bacon, two slices of ham or one sausage.
But a quarter pounder burger is 200g – nearly three times this level – while a 10oz steak from a restaurant is equivalent to 284g, or more than four portions.
Bowel cancer is already the second- biggest cancer killer in the UK, leading to 16 000 deaths a year. Only lung cancer kills more patients.
Alarmingly, the research also found that adults who ate large amounts of fibre – found in fruit, vegetables or wholegrain foods – did not have a significantly lower risk of developing bowel cancer than those who consumed very little.
For years, NHS guidelines have urged Britons to eat five portions of fruit and veg a day, and opt for wholemeal bread and pasta to avoid cancer and other illnesses.
Mark Flannagan, chief executive of Beating Bowel Cancer, said: “We must not underestimate the importance of diet in reducing your risk of bowel cancer.
“The evidence suggests there is a strong link between red and processed meat and bowel cancer, so we recommend eating both in moderation.”
Experts think the chemical haem in red meat damages the DNA of cells in the digestive system, triggering tumour growth.
But processed meat – including ham, sausages, bacon and burgers – is thought to be even more harmful as it contains cancer-causing additives as well as being high in fat and salt.
Professor Tim Key and Dr Kathryn Bradbury, of Oxford University, looked at the records of 500 008 British men and women aged 40 to 69. They had completed detailed questionnaires about how often they ate meat in a typical week, and were tracked over a four-year period between 2006 and 2010.
Over that time, 1 503 of the participants developed bowel cancer. The analysis showed that adults who had red or processed meat four times a week were 42 percent more at risk than those who had it once or not at all.
And those who ate it at least twice a week were 18 percent more at risk compared with vegetarians.
Professor Key, who will present the findings tomorrow at the National Cancer Research Institute conference in Liverpool, said: “People need to be aware of the risks and make modest changes if necessary.
“Eating things other than meat seems to be the sensible approach. So eating plant-based proteins such as beans, chicken or fish.”
The questionnaires only asked adults how often they ate red meat each day – not how much.
But the researchers said their consumption could be estimated from average portion sizes. They now plan to carry out further analysis involving a more detailed survey of 200 000 men and women, asking exactly how much meat they consume.
Current British government guidelines recommend adults should eat no more than 70g of red or processed meat a day, or 500g over the course of a week.
But these guidelines are likely to be changed following the World Health Organisation’s report, which warned that red and processed meat were more dangerous than initially thought.
Officials classified processed meat on the same cancer-causing level as cigarettes, asbestos and arsenic.
Red meat was placed one grade lower as “probably cancerous”, although experts are less clear about the risks.
NHS guidelines also state adults should aim for 25g of fibre a day – five pieces of fruit or veg – to protect against bowel cancer, heart disease and obesity.
But the Oxford research found no significant link between high fibre consumption and decreased bowel cancer risk.
Sarah Williams, Cancer Research UK’s health information manager, said: “This study adds to the evidence that regularly eating these meats can increase the risk of bowel cancer.”
But she added: “This study suggested that how often people eat meat affects risk, but it only followed participants up [over] an average of less than four years.
“So we would need more detailed studies over a longer time to prove this conclusively.”
The latest study was not able to determine whether eating processed meat is more harmful than red meat.
The researchers also stressed that, despite the evidence, red and processed meat cause far fewer cases of cancer than smoking.
Statistically, about 61 out of 1 000 Britons develop bowel cancer.
These latest findings would mean that out of 1 000 Britons who ate red or processed meat four times a week, 78 would get the illness.
Daily Mail