Reclaiming your Health: Modulation of the Gut Microbiota Through Diet

By Riley Forbes

The word “health” is subjective and personal. If you ask a group of people to define what being healthy means to them, the answers will likely involve freedom from illness and disease, eating consciously, sleeping 7 – 8 hours, and participating in daily exercise/activity. While all these are acceptable responses, one factor of health that is often neglected is the microbiome.

The gut microbiota is the collection of microbes in our gastrointestinal tract that have evolved in symbiosis with humans. In our intestinal tract there are over 100 trillion microorganisms. This outnumbers all of our cells in a ratio of 10:1! (Valdes Ana, et al., 2018) This recognition of the magnificent proportion of microbes that are present in the body is not only impacting how we define ourselves as a species – “super-organisms” – but also has, and will continue to have, a massive role of the health and survival of our species.

The gut microbiome has many implications for health—with research suggesting that it plays a role in the development of obesity, cancer (most noticeably colon cancer), gluconeogenesis (the generation of glucose—a preferred energy source in the body), Crohn’s disease, type 1 and 2 diabetes, cardiovascular disease, atherosclerosis and many more. Hopefully, I have gotten your attention. Now let’s dive into the function of the microbiome and how one’s diet can modulate the gut flora.

Figure 1: The relationship between lifestyle behaviors and biomarkers associated with health as compared to those that cause disease (From Valdes Ana, et al., 2018).

There are as many as 1,000 species of microbes that make up our gut microbiota and each have their own functions, however I will focus on the major functions of the gut microbiota and not individual/specific microbial species. The gut microbiota “provides essential capacities for the fermentation of non-digestible substrates like dietary fibres” which “supports the growth of specialized microbes that produce short chain fatty acids (SCFA)” (Fig. 1; Valdes Ana, et al., 2018). The most common types of SCFAs are butyrate, propionate, and acetate. Butyrate is essential for maintaining the gut barrier and preventing microbial imbalance, and providing fuel for cells that attack colon cancer cells. Propionate and acetate help to regulate gluconeogenesis and the metabolism of lipids and cholesterol which aid in controlling appetite.

Research from randomised controlled trials have linked high levels of SCFAs with decreased insulin resistance and lower rates of obesity. This finding can be linked to the importance of consuming dietary fiber which, as mentioned above, increases the production of SCFAs. According to the American Dietetic Association, it is recommended that women consume at least 25 grams of fiber a day, while men should aim to consume 38 grams a day. Based on these recommendations, Americans, and their microbes, are chronically deficient in fiber consuming a mere 14 grams per day on average, which less than half the daily recommended intake (Slavin, 2018)

Colon cancer, which is the second leading cause of cancer death in the West, has been associated with low intake of fiber. A study published in 2015 attempted to identify the mechanism behind high rates of colon cancer, by comparing the diets of African Americans to rural Africans. The diets of African Americans are similar to westerners and are high-fat and low fiber while rural Africans consume a diet low-fat and high fiber. After two weeks of switching their diets, the researchers noticed significant improvements in the African American participants’ mucosal inflammation which they associated with the increased butyrogenesis (O’Keefe, et al., 2018).

The recent fascination with the gut microbiota has led to the release of many studies, however scientists have just begun to uncover the complexities of the microbiome and its role in influencing our health. I encourage everyone who is triggered by a food craving or about to sit down to a meal, to stop and consider treating the organisms in your gut to a feast by adding some fibrous fruit or veggies to your plate while also feeding your soul.

References:

Valdes Ana M, Walter Jens, Segal Eran, Spector Tim D. Role of the gut microbiota in nutrition and health BMJ 2018; 361 :k2179

Slavin, J. L. (2008). Position of the American Dietetic Association: health implications of dietary fiber. Journal of the American Dietetic Association, 108(10), 1716–1731.

O’Keefe, S. J. D., Li, J. V., Lahti, L., Ou, J., Carbonero, F., Mohammed, K., … Zoetendal, E. G. (2015). Fat, fibre and cancer risk in African Americans and rural Africans. Nature Communications, 6, 6342. https://doi.org/10.1038/ncomms7342