06/12/2013 12:22 pm ET | Updated Aug 12, 2013

How Diet Can Bug Your Gut

Microbes have traditionally been considered a threat, but a new frontier in science is yielding a lot of exciting information about their power inside us. The National Institutes of Health has an entire initiative dedicated to understanding how the collection of microbes, the Microbiome, that exist in various regions of the human body impacts our health and well-being.

The best way to see how this microbiota affects our health is by changing it. For example, serious intestinal conditions may be caused by bacteria called Clostridium difficile. One of the ways this is being treated is through fecal transplantation after intensive antibiotic treatment. This procedure involves the transfer of a healthy person's gut microbiome to a person who is suffering from sickness. In the most dramatic cases, this method has proven to be the only way to wipe out C difficile.

But this is not the only way to influence the gut microbiome. Microbes rely greatly on undigested dietary elements, making diet a crucial driver of change. In an international study that we conducted with colleagues at the University of Pittsburgh, the University of KwaZulu-Natal (South Africa), Imperial College (UK) and Wageningen University (Netherlands), and presented during Digestive Disease Week (DDW), we found that changing your diet can have a dramatic effect on your microbiota -- in as little as two weeks.

The purpose of the study was to evaluate the potential relation between diet, microbiome and colorectal cancer risk. While colorectal cancer is the second leading cause of cancer-related deaths for men and women, we focused our research on the group most at risk: African Americans. They have the highest colorectal cancer incidence and mortality rates of all racial groups in the U.S. This is particularly puzzling given that colorectal cancer incidence in native Africans is close to non-existent.

To explore this disparity, we switched the diet in healthy subjects from a traditional high fat, high meat, low fiber Western diet to a high fiber Zulu African diet and vice versa. For two weeks, we fed 20 healthy Zulu Africans 600 grams of meat per day and fed 20 healthy African Americans in Pittsburgh a traditional Zulu diet of corn-based porridge called phutu.

Stool samples were taken weekly for two weeks before and after the diet exchange. Even in such a limited timeframe, changes in the microbiome composition and function were significant. Specifically, we observed consistent alterations in the balance of beneficial (butyric and acetic acid producers) and detrimental (sulfide and ammonia producers) function of the microbiome. These diet-induced alterations in gut microbiota may contribute to differing levels of colorectal cancer risk and our findings point to new preventative and curative strategies.

While the clinical relevance of these findings needs further investigation, our results show unequivocally that the human gut microbiome is shaped by diet in a very dynamic manner. When we shared our findings at DDW, we were pleased with the conversations that ensued. Our findings offer insight into the disparity of colorectal cancer risk and help pave the way for new research as we further our collective understanding of the power the microbiome, especially how we can use certain factors, such as diet, to better control the microscopic life forms upon which our health, or disease, depend.

For more by Dr. Franck Carbonero, click here.

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