You have a world living inside of you.

I’m not just being sappy. I mean it!

We’ve often viewed bacteria and microorganisms as something to kill and sanitize away, but an increasingly large pool of research and studies points to the integral role they may play in our physiologies and neurology. As a result of this, current food culture is saying “all hail” to probiotic foods, even though they’ve existed for centuries. As pro- and pre-biotics support the health of the microorganisms that live in the human intestines, this promotes their ability to function and flourish. Scientists are now viewing these residents of our gut as crucial as an organ, and work in tandem with the newest recognized division of our nervous system, the ENS.

The ENS, two thin layers of nerve cells lining your gastrointestinal tract from esophagus to rectum, is thought to modulate mood through our digestive processes. The tasks of breaking down and absorbing nutrients from food are delegated to the gut, which works independently of the brain’s command but is equipped with somewhere around 400 to 600 million neurons. These neurons produce about 95% of the serotonin and 50% of the dopamine found in your body, as well as some other major chemicals such as ghrelin and leptin.

So, the ENS and the community that lives within it seem to be a major bodily hotspot for influencing our behaviors and moods, controlling our sleep patterns and our stress responses, as there have been findings that bacteria too may be able to produce their own versions of neurotransmitters. Good bacteria aid in nutrient absorption; protect against pathogenic flora, viruses and parasites; prevent infection by acting as a physical barrier against toxins that could leak into the intestines; neutralize food toxins, perhaps as a second liver; control certain immune cells thereby preventing autoimmunity and unnecessary inflammation (Perlmutter 2015). In studies conducted on mice that were altered not to have any microorganisms in their guts, the mice were shown to have poor ability to cope with their stress, chronic inflammation, and lower levels of brain-derived neurotrophic factor (BDNF). This protein is produced by good gut bacteria and is really important for the growth and survival of neurons, thereby allowing for learning, memory, and higher thought processes. Alzheimer’s, epilepsy, anorexia nervosa, depression, schizophrenia, OCD, and many more neurological conditions are linked to low levels of BDNF.

Several studies have also shown that levels of pathogenic intestinal flora are elevated in the guts of children with autism as compared to children without the disorder. It has been found that children with autism had 10,000 times the normal level of aerobic gram negative bacteria such as E. coli (Rosseneu ). What does it mean to be a “gram-negative bacteria?” It means that these bacteria do not retain the purple dye used in some bacterial differentiation methods. The combination of fats and sugars, lipopolysaccharide, that is the major component of the outer membranes these bacteria are shown to be endotoxins that can induce the inflammatory response system and lead to many autoimmune diseases and depressive symptoms found in major depressive disorder.

What if obesity were less to do with will power and genetics, and more to do with the composition of microbiota existing in one’s gut? New research shows that the little bugs that dwell in our intestines play a crucial role in our metabolism.

While bacteria as a whole seem to aid in the digestion of food, the type of food they are most efficient in breaking down will vary. Firmicutes are equipped with more enzymes to digest complex carbohydrates and can extract more energy from fats; Bacteriodetes specialize in breaking down fibrous matter into shorter fatty acid molecules that the body can use for energy. If you’re a home for too many types of bacteria that can efficiently extract more calories from food, you’re prone to absorbing more than you need. The ratio of these two bacteria listed above are now looked upon as the “obesity biomarker,” as lean individuals will have less Firmicutes and more Bacteriodetes, whereas heavier individuals will have a higher ratio of Firmicutes to Bacteriodetes (Pearson 2006).

The quality of our diet, the quality and diversity of our gut bacteria, and our obesity risk are all interconnected. Eating foods that promote the proliferation of good bacteria (sauerkraut, yogurt, kimchi, legumes, and high-fiber vegetables) as well as diminishing foods that promote the presence of bad bacteria (refined sugar- and fat-based products) can lead to a more favorable composition. Stress, lack of sleep, and exposure to antimicrobial soaps, sanitizers, and environmental pollutants can do the opposite!

The Good

  • Exercise: Promotes the right bacterial balance and positively influences the gut’s balance of bacteria to favor colonies that prevent weight gain.
  •  Fermented foods are probiotic because bacteria have converted the sugar molecules in these foods into lactic acid. By creating an acidic (low pH) environment, pathogenic bacteria are unable to thrive. These include:
    • Live, cultured yogurt, an exceptionally probiotic, healthy-bacteria-promoting food. In studies conducted on mice with genetic predispositions to weight gain, those fed probiotic yogurt three times a week remained lean even while consuming just as much fast food as control mice.
    • Other fermented foods such as kefir, kombucha, tempeh, kimchi, sauerkraut, pickled fruits and vegetables, and cultured condiments (see another blog post about this here!)

The Bad

  • Antibiotics: As observed in the NYU Microbiome project, mice that received doses of antibiotics comparable to the amount that livestock receive (based on drug to bodyweight ratio) had their body fat increase 15% more than those not exposed to the drug. Fluoroquinolones and sulfur-based antibiotics trigger the overgrowth of C. Diff., a clostridia strain of bacteria that is correlated with autism and carbohydrate cravings. Processed carbohydrates feed these bugs and causes the colonies to grow.
  • Fructose is a feeder of pathogenic bacteria and disrupts a healthy microbial balance.
  • Artificial sweeteners like saccharin, sucralose, and aspartame are said to change the microbiome in ways that favor dysbiosis.


The study of the ENS and the microbiome that resides within all of us are new and exciting, uncharted territories. I hope you take comfort in the fact that you’re never truly alone with all three pounds worth of bugs in your intestines, because if you’re treating them right, they can help heal you!


Pearson, H. (2006, December 20). Fat people harbour ‘fat’ microbes. Retrieved May 29, 2016, from

Perlmutter, D., & Loberg, K. (n.d.). Brain maker: The power of gut microbes to heal and protect your brain–for life.

Rosseneu, S. (2003, October). Aerobic gut flora in children with autism specturm disorder and gastrointestinal symptoms. In Defeat Autism Now Conference. San Diego (CA).


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