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The Gut-Brain Connection

And the yogurt study

One spring afternoon two years ago, I lost site of my son at a playground. This probably did not last for more than 10 seconds, but that was before he started answering to his name. I have seen how relaxed parents of normally developing, i.e. neurotypical, kids are at playgrounds, since they know that when they call out their child’s name they will hear a response. It’s different with a child that will not respond. So I used to be vigilant to a high degree, never loosing site of him. For that 10 seconds the panic did set in. Of course in 10 seconds he hadn’t moved too far, and once I adjusted the search perimeter I found him right away. But that moment was enough for me to feel a deep sinking feeling in my stomach. Once my gaze spotted him, I felt the immediate movement of that feeling out of my stomach, and the throbbing pain of a resounding migraine. This was not just a headache, and anyone who has ever had a migraine will know that it is impossible to mistake the pain.

The reason why I am sharing this short story is, that for me this was one of the most acute connections between the gut and the brain that I have personally felt. We have all had gut related feelings and experiences, and the sayings abound: “Butterflies in the stomach”, “I can’t stomach that”, “Trust your gut”, “The way to a man’s heart is through his stomach”… Hmm, that last one always sounded a bit sexist to me, but I thought to keep it in my secret arsenal if it ever came to it. I didn’t really get to test it out, but what if the path to everybody’s “heart”, regardless of gender, is in their gut. This is just the start of an intriguing journey for me when it comes to neuroscience and the gut microbiome, so bare with me. I wanted to begin by sharing one fascinating study showing the link between the gut and the brain. After all, for the past several months I had been throwing my favorite new phrase around “You know, it all makes sense, it’s related to the gut-brain connection”. And, thus, it was time for me to start uncovering what is known of that connection out there in the vast space of the academic literature.

I liked this study because it seemed to be the first one to establish that consumption of probiotics in fermented milk can affect our brain. Since I have been working on setting up different dairy ferments for the last few months, and my next few blogs will be on how to make them, I thought this was a perfect start.

The study from 2012 [1] showed that after consuming a fermented milk product with probiotic (FMPP) as they refer to it, twice daily for four weeks, there were observable changes in the brain activity of participants. I think that’s pretty cool. I have to add though, that the study was supported by Danone (Dannon). This is listed as a conflict of interest, and the study was performed at UCLA, it is widely cited, and it is obviously of very rigorous nature, but where funding comes from is something I like to be mindful of. The specific FMPP used was chosen because of previous studies showing positive effects on the GI tract. It contained the following probiotic bacteria: Bifidobacterium animalis subsp Lactis, Streptococcus thermophiles, Lactobacillus bulgaricus, and Lactococcus lactis subsp Lactis.

Thirty-six healthy women participated in the study. They were separated into 3 groups: a group that consumed the FMPP twice daily for 4 weeks, a control one that consumed a non-fermented milk product of the exact consistency as the fermented one, and a no intervention group that did not consume anything at all. Functional MRI (fMRI) brain scans were performed at the beginning and at the end of the study of the participants’ resting brain activity and during an emotional attention task. Functional MRI measures changes in blood flow to specific brain regions to determine if they are in use or not by a method called blood oxygenation level-dependent contrast.

During the emotional attention task the women had to match photos of an angry or a sad face to one of two other photos. Doesn’t sound like a very nice pastime. To quote the paper: “The task engages widespread affective, attentional, sensory, and integrative brain regions that likely act as a rapid preconscious regulatory system engaged to prepare for potentially threatening situations”. I was a bit curious about the emotional attention task, and specifically the pictures. It seems like there is a set of pictures called the International Affective Picture System which is used in studies like these (I couldn’t verify if this was the set that was used for this specific study). The set of pictures is not publicly available, I am assuming so that the studies remain unbiased. (On an interesting for me side note it was developed at the University of Florida, and as a product of the Florida State University system, I always listen with a mixture of attentiveness and a bit of friendly annoyance when I hear of the good stuff that has come out of UF.) Intriguingly though, there is a set of similar pictures developed at Harvard called the OASIS image database, and available to the public, which can be found on the website of one of the authors [2]. Of course I had to download it to check the sad and angry faces. I scrolled quickly through the thumbnails of the set of images to get to those photos, as some of the other images were obviously very disturbing. After seeing the photos I can imagine that the task during the fMRI would not have been pleasant at all. This is important for me because at some point I want to find the full extent to which probiotic foods can help us with stress and anxiety among other things.

The very exciting conclusion of the study was that after 4 weeks there were noticeable differences in the fMRI scans of the FMPP group, showing a decrease in activity in a “widely distributed network of brain regions”. In the Control group there was no change, while there was an increase in activity in the No-Intervention group. The researchers also found that not only were the scans in the FMPP group different during the emotional task, but that they also differed during the resting state of the brain. This is interesting since it seems possible that the state of our brain at rest is related to how we respond to different tasks when our brain is activated. From what I am understanding since this was an experience related to negative stimuli the reduction in brain activity should point to a reduced state of anxiety, while performing an unpleasant task. This study just focused on establishing the link between the gut and the brain, and did not focus on the full scope of possible interventions or the exact mechanism that induced the change. The hypothesis was that the change in the gut microbiota would modulate brain activity, which the study proved was what happens.

The fact that consuming probiotics can affect how our brain functions raises a million questions I want to answer and that I will be looking into in detail. How exactly does our gut microbiota communicate with the brain, and what changes in it can alleviate neurodevelopmental delays among many other things? But before I dive into that, in the next posts I want to share all that I know about fermenting dairy, as a way to influence the gut microbiota and also just because it’s pretty delicious. I will get back to the research after that.


1. Consumption of Fermented Milk Product With Probiotic Modulates Brain Activity, K. Tillisch et al., Gastroenterology, June 2013 Volume 144, Issue 7, Pages 1394–1401.e4

2. OASIS image database,

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