You Are What You Eat?

You Are What You Eat?

Editor Note: New research reveals even tighter bonds between gut health and overall health - body AND mind.

Ever heard the expression, you are what you eat? More and more we are finding that what we consume affects our brains, not just our bodies.  Many physicians have started educating their patients on the dangers of the Standard American Diet (SAD) and heavily processed foods.  In this endless merry-go-round of what is considered healthy, fat has been demonized and lately carbs and sugar.  But is the picture much more complex? Could it be that it’s not completely what we eat, but what the billions of bacteria in our gut “let” us eat?



Gut microbiomes have become a hot topic lately.  From actual scientific research to health adjacent businesses marketing probiotics, from everything to anxiety to erectile dysfunction.  But the actual science is exciting and something to explore in healing our brains!


For a long time many of us psychiatric physicians have seen a mind-brain-gut connection.  When we get excited or nervous we have “butterflies in our stomach.” Many gag when disgusted or have a bathroom run when anxious.  The most common side effects when starting SSRIs (Selective Serotonin Reuptake Inhibitors, a class of antidepressants) are gastrointestinal (nausea, vomiting, diarrhea).  It is true that the gastrointestinal tract has more neurons and serotonin receptors than our actual brain. This is why the gastrointestinal tract is often called the second brain.  How are the second brain and the brain connected? The hypothesis is through the vagus nerve, but the story is still unfolding. 


The whole picture may be even more intricate and beautiful, a symphony of interplaying neurotransmitters and our resident gut bacteria and what we eat.  A study in Belgium found that people with Major Depressive Disorder were consistently missing two strains of gut bacteria, Coprococcus and Dialister.  Of course it is unknown if the missing gut bacteria caused the plummet in mood or if they are the effect of depression, but the finding was interesting and consistent in the study (the findings of the missing gut bacteria were replicated in Belgians and again in a Dutch population).  Coprococcus was found to have a pathway linked to dopamine production, a key neurotransmitter linked to mood.  In Switzerland, there is a trial underway to use FMT (fecal microbiota transplants) to see if depression can be reversed.  


Commercially, there are several companies that will perform FMT for a fee for anything from autism, to Parkinson’s to SIBO (small intestine bacterial overgrowth).  Even though the science to prove the efficacy is in its infancy, you can easily get a stranger’s microbiome with a few clicks on the internet.  


What about what we eat?  Well since we have different bacteria, we can “tolerate” different foods.  Being a plant-based physician myself, I do believe that eating a variety of plants (even if you do eat meat, fish, eggs and dairy) is a great way to increase the biodiversity of your gut bacteria.  Plants are great prebiotics and feed the bacteria we have, and fermented plant products are great probiotics. The exception is if one has bacterial overgrowth in the small bowel where there are not supposed to be much bacteria (SIBO), in which case the gut moves too slowly and the overgrowth occurs.  Adding probiotic foods would make the problem worse until it is known what is causing the decreased gut motility and SIBO. Subclinical hypothyroidism and other hormonal issues are often the culprit and it is good to have a team of doctors on the case. Diet wise, a simple diet is introduced with easy to digest pureed fruit and cooked vegetables.  Each week or so one may advance the diet and see how the gut responds. 


Besides eating plants, one can adhere to a whole food and unprocessed diet as much as possible for good results in mood.  A study last year in Molecular Psychiatry found an observational link in those who avoided a pro-inflammatory diet and their mood. Another recent study looked at an “antidepressant food score” and spinach scored the highest, with plant antidepressant foods scoring much higher on their scale than animal antidepressant foods.  The score was calculated by looking at 12 nutrients which met the level of “evidence criteria” and were considered “antidepressant nutrients.” These were folate, iron, long chain omega-3 fatty acids (EPA, DHA), magnesium, potassium, selenium, thiamine, vitamin A, vitamin B6, vitamin B12, vitamin C, and zinc.


As the picture evolves, we will see more clearly how mood and food and our host gut microbiome are intertwined.  Until then, it is probably best to eat the rainbow, listen to your body and stay tuned. 




Valles-Colomer, M., Falony, G., Darzi, Y. et al. The neuroactive potential of the human gut microbiota in quality of life and depression. Nat Microbiol 4, 623–632 (2019).


Mol Psychiatry. 2019; 24(7): 965–986.  Published online 2018 Sep 26. doi: 10.1038/s41380-018-0237-8  PMCID: PMC6755986  PMID: 30254236


World J Psychiatry. 2018 Sep 20; 8(3): 97–104.  Published online 2018 Sep 20. doi: 10.5498/wjp.v8.i3.97  PMCID: PMC6147775  PMID: 30254980

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