The fecal microbiome is a diverse ecology, like the amazon jungle or the Great Barrier Reef. We are just beginning to learn what this means for our overall health and wellbeing. When we think of the fecal microbiome, we think of a world with a multitude of different organisms with different functions. Just like we would not expect a dolphin to be living in the Alps, we don’t expect certain organisms in the fecal microbiome to live outside of their area in the gastrointestinal tract. Those organisms that live in our mouth are different from those that survive in our stomach, which are different still from those that live within our small intestine and, as you guessed it, different from those that live in our colon. What’s also fascinating about our fecal microbiome is that it is not static. Instead, it is always changing, just like the world around us.
We hear a lot about the effects of global warming and how it has changed many ecosystems in the world. These changes are most obvious in areas of lush diversity like the amazon or the Great Barrier Reef. These once highly diversified areas have now lost some of their complexity due to environmental changes. We are seeing the same loss of range in the fecal microbiome within our bowels: In a fascinating paper called Starving Our Microbial Self, Dr. Erica Sonnenburg describes the sometimes deleterious effects of our changing diet on the fecal microbiome. Although most people think that it is mainly during the present modern era that major changes in our diet have occurred with the availability of a wider range of processed foods, actually, massive changes in diet go back to greater than 10,000 years ago so that the diversification in how and what we eat has likely shaped our microbiota for centuries. 10,000 years ago we were predominantly hunters and gatherers and our microbiota was impacted by those early food sources. We know that our ancestors ate 50 – 200 grams of fiber a day. That is up to ten times more than most people eat today. The impact of becoming an agricultural society likely decreased our fecal microbiota substantially making it less diverse. Then the industrial revolution occurred and crop diversity and food diversity decreased further. And finally, between 100 years ago and the present, we have continued to follow this decrease in diversity in our microbiota with efficiency in farming, decreased food types, sanitization of foods and the addition of food additives. And once again, the types of bacteria in our microbiome have shifted. Researchers believe that many bacteria may have gone extinct because of this ever changing availability of whole foods and dependence on processed foods. Sonnenburg describes our Western lifestyle, which includes a diet low in microbiota accessible carbohydrate (MAC) as one which selects for specific microbiota and alters the overall membership and functionality of the fecal microbiome. When compared with indigenous people who continue to consume a traditional diet, a strong link between diet and microbiota diversity is seen. In fact looking at the microbiota of traditional cultures provide a glimpse of what the human microbiota may have looked like during the Neolithic Revolution in agriculture as humans embraced cultivated foods. There is debate on whether having a microbiota which is more diverse and similar to those that were found in our ancestors is essential for a person’s complete wellbeing. We must remember that their diets were not always complete and malnutrition was not uncommon. With that being said, common diseases seen in our Western society such as heart disease, asthma, and the many immune dysregulations such as IBD were rare in traditional cultures. The plasticity of our microbiota to adjust to the profound changes brought on by our modern lifestyle is amazing. But the consequences of this change with very low in microbiota accessible carbohydrates (MAC) has likely lead to low diversity microbiota with lower small chain fatty acid production which may be a major reason the rate of Western diseases has increased so dramatically in the last 100 years.
So what does this tell us? Should we go out and start eating like cavemen… not necessarily. There is a balance between improving our microbial health and eating a diet that is healthy for our microbial diversity. Although cavemen did not likely develop type II diabetes, inflammatory bowel disease, cardiovascular disease, their diet had major gaps as well. We can get the same beneficial effect on the microbiome by eating a variety of healthy foods especially foods rich in fruits and vegetables, plants that have complex fibers and a lot of roughage.