Why eating red meat can cause bowel cancer
Scientists believe they may have discovered why eating red meat is linked to higher chances of bowel cancer. The pigment that gives a steak or mince its distinctive red colour is to blame, they suggest. Haem – the part of the blood’s haemoglobin that binds in oxygen to allow it to be transported around the body – is found in much higher quantities in red meat than in white meat.
It contains iron, which produces the red colour. While red meat – which includes beef, lamb, pork, veal, venison and goat – has been linked to cancer for several decades, the new understanding of the mechanism by which it causes cancerous cells to form is likely to help in prevention.
The breakthrough may also create a new way to detect who is at greater risk of bowel cancer by looking for a chemical marker produced by bacteria in the gut.
Researchers from the University of Utrecht in the Netherlands discovered the link between haem and bowel cancer by feeding the red pigment to mice.
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They found the mice suffered damage to their gut lining.
On closer inspection, they discovered that the bacteria in the gut were turning the haem into hydrogen sulphide.
This is the chemical which produces a smell like rotten eggs and damages the cells lining the gut.
To repair the damage, the cells rapidly regrow, but this rapid regrowth creates a greater chance of a cancerous tumour forming. The breakthrough may create a new way to detect who is at greater risk of bowel cancer by looking for a chemical marker produced by bacteria in the gut.
The research, published in the journal Proceedings of the National Academy of Sciences, also found that the adverse effects of eating meat were stopped by antibiotics, which kill the bacteria.
The scientists suggest that hydrogen trisulphide, a chemical produced by the gut bacteria, could be a useful chemical marker indicating who is most at risk of bowel cancer.
Bowel cancer is one of the biggest killers in the UK. Around 40,000 people are diagnosed with it every year – one every 15 minutes. Red meat is a good source of protein minerals and vitamins, but research increasingly suggests too much is bad for long-term health.
The NHS recommends that we eat no more than 70g (2.5oz) a day.
This is the equivalent of three thin slices of roast beef, lamb or pork, each about the size of half a piece of sliced bread. Around one in three in the UK eat more than the recommended amount.
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While cutting down can raise the risk of iron deficiency, other good sources of iron include lentils, beans, eggs, fish, chicken, turkey, nuts and breakfast cereals. Last year research suggested that risk of bowel cancer is increased by a key sugar called Neu5GC found in red meat which can cause inflammation of cells. Red meat has been linked to other health problems.
A Swedish study found men who ate large amounts of processed red meat had a higher risk of death from heart failure. Research by the Harvard School of Public Health found that eating three rashers of bacon eaten per day raised the risk of breast cancer in women by more than 20 per cent. Other studies have linked higher consumption of red meat to increased risks of type 2 diabetes and prostate cancer.
Meat, fish, and colorectal cancer risk: the European Prospective Investigation into cancer and nutrition
Clinical Report from 2007 (47 biologists)
Colorectal cancer risk was positively associated with intake of red and processed meat and inversely associated with intake of fish. The study included 366, 521 women and 153, 457 men, most aged 35–70 years at enrollment between 1992 and 1998, who were recruited in 23 centers in 10 European countries
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