A new study shows the devastating impact of western diets on the risk of colon cancer.
American and African volunteers who swapped diets for just two weeks showed significant changes in colon cancer risk, researchers reported yesterday.
The experiment was carried out by Professor Jeremy Nicholson and his team at Imperial College London, UK. They explain that colon cancer is the fourth most common cause of death from cancer, causing 600,000 per year globally. Rates are much higher in the western world than in Africa or the Far East.
The team examined the potential role of diet and its effect on gut bacteria by recruiting 20 African American volunteers and 20 participants from rural South Africa. For two weeks, the groups swapped diets under "tightly controlled conditions".
Results appeared yesterday (28 April) in the journal Nature Communications. They suggest that the higher fibre African diet substantially reduced colon cancer risk. At before the experiment almost half the American volunteers had polyps, abnormal growths in the bowel lining that sometimes develop into cancer, whereas none of the Africans had polyps.
But after two weeks on the African diet, the American group had "significantly less inflammation in the colon and reduced biomarkers of cancer risk". In contrast, the African group showed "dramatically increased markers of cancer risk" after two weeks on the western diet. The experts believe that gut bacteria play an important role in this effect.
Professor Nicholson said: "We can’t definitively tell from these measurements that the change in their diet would have led to more cancer in the African group or less in the American group, but there is good evidence from other studies that the changes we observed are signs of cancer risk.
"The findings suggest that people can substantially lower their risk of colon cancer by eating more fibre. What is really surprising is how quickly and dramatically the risk markers can switch following diet change."
O’Keefe, S. J. D. et al. Fat, fibre and cancer risk in African Americans and rural Africans. Nature Communications 28 April 2015 doi: 10.1038/ncomms7342
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