Diet swap shows how Western diet increases cancer risk

April, 2015. A new study reported by the BBC this week provides a dramatic demonstration of the effect of diet on the gut – and shows that deterioration of bowel health, which may bring increased cancer risk, is far more rapid than generally believed.

In a US-based experiment, 20 US volunteers swapped their diet – high in fats and sugars, and low in fibre – with a group of 20 volunteers from rural Africa, who were used to a low-fat, high-fibre diet.

The experiment ran for just two weeks, but even within this time the effects became evident. The US volunteers – whose diet contained a higher proportion of pulses and beans – had reduced instance of bowel inflammation, while the African group suffered deterioration in bowel health. Their new diet consisted of typically fatty, Western junk foods with a high red meat content, such as burgers and fries. In medical tests, it was found that there were not only significant changes to the cells lining the gut, but the bacteria that live in the bowel as well.

While the study is small, its findings support other research among Japanese migrants to Hawaii, which showed that it takes only one generation of Westernisation to change their low incidence of colon cancer to the higher rates seen amongst native Hawaiians. What this new study suggests, however, is that dietary changes can have an immediate impact on the gut.

Lead researcher Dr Stephen O'Keefe, from the University of Pittsburgh, is quoted as saying: "In just two weeks, a change in diet from a Westernised composition to a traditional African high-fibre, low-fat diet reduced these biomarkers of cancer risk, indicating that it is likely never too late to modify the risk of colon cancer."

Other research has already shown that a high intake of dietary fibre, particularly cereal and whole grains, reduces bowel cancer risk, while eating red and processed meat increases the risk. It is estimated that as many as a third of bowel cancer cases could be avoided by healthier eating.

Justin Davies, Consultant Colorectal Surgeon at Addenbrooke’s Hospital, Cambridge and Clinical Adviser at Check4Cancer, comments: “This confirms much that we already know about diet and its relationship to colorectal cancer. The European Prospective Investigation into Cancer (EPIC), running since 1992, has demonstrated that higher consumption of red meat increases cancer risk ­– eating 100 to 120 grams of red meat per day can increase risk by up to a third (30%) – whilst increased fibre intake reduces risk of bowel polyps and cancer, a finding confirmed by a meta-analysis conducted in 2011.

“While we can’t draw firm conclusions from so small a study as the diet swap, it does strongly suggest that changes to bowel health and cancer risk can be brought about much faster than is often thought. This may, at first, seem alarming news, but we can take it as a positive. Often with issues such as this people put off acting on health because the benefits – and potential damage – seem so distant. This study shows that if people act to improve their diet now, they may be starting to reap the benefits within days, rather than months or years.”