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Diet Over Genes for Bowel Cancer Risk

The Western diet has a lot to answer for.

In an insightful study researchers from the University of Pittsburgh asked 20 African Americans to do a diet switch with 20 rural Africans (from KwaZulu-Natal) for two weeks.

The scientists invited the two groups to stay at local centres, where their diets were reversed for a fortnight. Instead of their traditional high-fibre, low fat meals, the rural Africans consumed a high-fat, high-protein diet of sausages, hash browns, burgers and fries. Meanwhile, the African Americans switched to a low-fat, high-fibre diet including corn fritters, mango slices, pulses, beans, bean soup and fish tacos.

While the answer is obvious in terms of what diet is better for us, what is frightening is the speed in which the body responded to the change in diet – especially regarding biomarkers for bowel cancer.

The results from this study suggested high-fibre diets could have a dramatic, positive effect on reducing colon cancer among populations most at risk.

To determine these biomarkers, researchers ran tests on the microbes living in the guts of the two groups.

They found that the American and African diets were associated with very different populations of gut microbes. The rural Africans had more carbohydrate-fermenting bugs that produced a chemical called butyrate, a chemical that has anti-cancer properties. Meanwhile, on the high-fat western diet, the gut microbes produced more bile acids, which may increase cancer risk.

Imaging (from colonoscopies) revealed polyps (which can become cancerous masses) in nine of the Americans, but none of the rural Africans. This indicates that their actual diet was already negatively  impacting on their bowel health.

The results of this study suggest that diet may affect cancer risk by changing the populations of microbes thriving in the gut and the chemicals they produce.

Rates of colon cancer are much higher in African Americans (65:100,000) than in rural Africans (<5:100,000). These higher rates of bowel cancer are associated with higher animal protein and fat, and lower fibre consumption, higher bile acids and higher mucosal proliferative biomarkers of cancer risk.

It appears than that it is differences in diet rather than genetics that influences this considerable discrepancy.

The lead researcher Dr Stephen O’Keefe noted  “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.”


Emeds Comment

The results of this research can of course be viewed in two ways.

While it is very encouraging that just two weeks of better dietary improvements can bring about changes in health markers that are implicated in bowel cancer, on the flip side two weeks of poor diet can also impact on biomarkers indicating a body undergoing a dis- ease process.

This study reinforces that any change in diet will bring about changes in the way your body metabolises foods.

An important point to note here is the massive impact diet can have over our health and how the argument “It’s my genes,  I have little influence over the likelihood of developing certain diseases” is quite incorrect.

It is diet, environment and microbial genes that are likely to be much more important than individual human genes in determining individual bowel cancer risks.

A person’s health fate is not just determined by the genetic dice at birth. It also shows that how you roll the dice in the game (diet, lifestyle and environmental factors) is far more important.


Further Reading 



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