What the Heck is the Gut Microbiome?
Composition with jars of pickled vegetables. Marinated food

What the Heck is the Gut Microbiome?

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Digestive Health has always been an interest of mine. Since 2004, when I was recruited to be part of a Scientific Advisory Board for Danone, the mind-gut connection has been a fascinating topic for my clients and one of my most popular presentation requests. The interest in digestive health is not slowing down. In fact, it is predicted to continue to be a nutrition trend in 2015. For this Grow with Nutrition post, I’m sharing with you the details of the gut microbiome and its importance to our health.

Gut Microbiome
The gut microbiome is simply defined as a large and dynamic community of bacteria that live within the gastrointestinal tract (1). I like to call it our individual ecosystem which can be affected by food and lifestyle choices. Within the gastrointestinal tract, active bacteria perform specific functional roles that contribute to health including: fermentation of indigestible carbohydrates; enhancing the immune system, and affecting brain activity.

Digestive health

In my recent post Do you have Fermented Foods Fever? I discuss how fermented foods can be beneficial for digestive health. One of the main functional roles of the gut bacteria is to ferment (break down) indigestible carbohydrates. Certain gut bacteria ferment indigestible carbohydrates, such as dietary fibre, and produce short chain fatty acids (SCFA). The greater the diversity of SCFA production, which is depended on the gut microbiome, may result in a protective digestive health effect (2).

 Immune health

Another role of the gut bacteria is to enhance the immune system. Two gut main bacteria responsible for this are Bifidobacteria and Lactobacilli. Research has demonstrated when critically ill patients received either a probiotic supplement (containing several strains bacteria) or two placebos, the patients in the probiotic group had an increase in two beneficial immune health components (both IgA and IgG concentrations level went up) (3).

Brain health

Follow your gut instinct and you’ll realize the mind-gut connection is significant. “Cranky gut equals a cranky mind!” In a 2013 study, participants consumed a fermented milk product with probiotics Lactobacillus and Bifidobacterium for four weeks. The results showed the brain regions controlling emotions and sensation were positively affected when the individuals consuming the fermented milk were performing standardized emotional tests (4).


In the recent literature, it is said that there is a different gut microbial profile (or ecosystem) in overweight and obese individuals. The gut has two main groups of bacteria which are Firmicutes and Bacteriodetes. In a 2014 study, faecal samples were collected and analyzed from 11 lean, and 11 overweight and obese individuals (5). The researchers found a higher abundance of the gut bacteria Firmicutes and a higher Firmicutes to Bacteriodetes ratio in the overweight and obese participants, compared to the lean participants.

The gut mircobiome and our health is an emerging area of research and one of my favourite speaking topics. The study of the relationship between obesity and the ecology of gut microbiome may provide meaningful treatments and biomarkers for susceptibility to weight gain. Future human research is needed in all areas of the gut microbiome.


  1. Gosalbes, M., Durban, A., Pignatelli, M., Abellan, J., Jimenez-Hernandez, N., Perez-Cobas, A. Metatrascriptomic approach to analyze the functional human gut microbiota. PLoS ONE. 2011[cited 2014 Nov 1] 6(3): e17447
  2. Reimer, A., Pelletier, X., Carabin, I., Lyon, M., Gahler, R., Woods. Faecal short chain fatty acids in healthy subjects participating in a randomized controlled trial examining a soluble highly viscous polysaccharide versus control. Journal of Human Nutrition and Dietetics. 2012. 25: 373-377
  3. Alberda, C., Gramlich, L., Medding, J., Field, C., McCargar, L., Kutsogiannis, D., et al. Effects of probiotic therapy in critically ill patients: A randomized, double-blind, placebo-controlled trial. American Journal of Clinical Nutrition. 2007; 85:816-823.
  4. Tillisch, K., Labus, J., Kilpatrick, L., Jiang, Z., Stains, J., Ebrat, B., et al. Consumption of fermented milk product with probiotic modulates brain activity. Gastroenterology. 2013;144:1394-1401.
  5. Rahar-Rozenbloom, S., Fernandes, J., Gloor, G., Wolever, T. Evidence for greater production of colonic short-chain fatty acids in overweight than lean humans. International Journal of Obesity. 2014: 1-7.
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