Be good to your gut.

I recently found myself in a conversation with several close friends who either just became or are about to become MDs. In this conversation, we discussed some of the health myths that are proliferated by the media which ultimately have no impact on our health but make large dents in our wallets across our lives. Among the topics discussed was whether supplementing your diet with probiotics improves your health. Probiotics are live bacteria that exist naturally in your digestive system as well as in some foods, such as yogurt, that are associated with improved digestive and immune functioning. So, in the spirit of ScienceForWomen, I went straight to the literature to get some answers.

I found more than several studies; some with animal models, some in humans, some among healthy individuals, and some among specific clinical populations. So far, it appears that, among humans, the jury is still out on whether there are clear benefits of probiotics, while some specific strains of probiotics can be very influential for specific syndromes or intended benefits. Unfortunately, several studies have found that probiotics are effective in reducing symptoms of problems like IBS and chronic pain, but no more effective than the placebo-effect. What stood out among these mixed findings was a recent study examining functional connectivity in the brain before and after regular ingestion of probiotic supplements.

Functional connectivity is a fancy term among neuroscientists to describe how regions of the brain are connected and communicate with one another. Overall, you want different systems in the brain to be well-connected with one another, but also to work efficiently, thus only requiring communication between different regions as necessary to get the same behavioral results. Put more simply, if one person can remember their grocery list with 10,000 neurons while another can remember the same grocery list with only 5,000, the former is using more brain power to do the same task (and may even have depleted resources to do a later task) and therefore is less efficient.

Dr. Kirsten Tillisch of UCLA and her colleagues conducted a study to test the effects of daily ingestion of probiotics on brain functioning. To do this they recruited 36 healthy adult women to participate in their study. Participants completed an fMRI which looked at their brain functioning while doing an emotional attention task. Participants completed 20 trials of matching sad or angry faces, and 20 trials of matching geometric shapes. This task was designed to measure “activity of brain regions that control central processing of emotion and sensation” that are often dysregulated among individuals with anxiety disorders, and chronic illness such as fibromyalgia and IBS. A third of these women were then randomly assigned to receive daily doses of a fermented milk-product with probiotic (FMPP) for 4 weeks, a third were randomized to receive a non-fermented milk-product with no probiotic (control) for 4 weeks, and the remaining third were randomized to not change their diet. The research team used an automated phone system to remind participants to take their dose each day, while also collecting daily records of participant compliance with taking the product. After the 4 weeks, participants returned to the laboratory to complete the same fMRI task, examining whether there were differences in brain functioning and connectivity when completing the same attention task.

After the 4 week intervention, there were no differences in GI symptoms or mood across the three groups. So, that’s probably bad news for people that buy probiotics for those reasons. They also found that participants who were randomized to the probiotic condition had reduced activity in three regions of the brain: the insula, periaqeuductal gray, and the somatosensory cortex compared with before the intervention and with their peers during the attention task. In comparison, the no intervention group actually had increased activity in these regions of the brain, while the control group had no changes in any regions of the brain during the task. In addition they found a decrease in resting connectivity in emotional reactivity centers of the brain, such as the prefrontal cortex and the amygdala. What’s cool is that this was the first study to show that probiotics can modulate brain activity, although so far we don’t know why exactly. One hypothesis is that daily ingestion of probiotics alter basic metabolic processes which influence multiple systems in the body, including efficiency of the brain. The results of this study suggest that use of probiotics can actually influence the resting state of connectivity in the brain which serves as the template or default from which the brain responds to stress in the environment. In other words, your brain may be more optimally calibrated for the life you lead.

Unfortunately, this study was conducted with a small sample size due to the costly nature of neuroimaging research so time will tell whether a larger study would clarify these results, especially with the “placebo effect” observed. However, the design of the study including pre- and post- intervention brain scans allows for careful comparisons within and between participants throughout the study. Another caveat of this study, is that the effect of the intervention didn’t result in better behavioral performance in the task. This may be due to the simplicity of the task, but is still important to keep in mind. This study is not suggesting that probiotics make you smarter, but rather that using probiotics daily over at least a month can influence basic brain functioning and connectivity.

So what’s the point? Lots of people take probiotics. Some because they think it helps with weight loss, some because they were recently on antibiotics, some because they have IBS or another chronic syndrome. In the case of probiotics, they don’t appear to be harmful, but also may not be delivering the symptom relief you are looking for. As with any other medical decision, talk to your doctor about the use of nutrition supplements before making them a regular part of your life. What I think can be taken away from this research is yet another study showing the interdependence between the mind and the body. As a psychologist, I spend a lot of time talking about how to use psychological resources to improve overall health, because most people focus on how physical health influences psychological well-being, but the relationship is truly bidirectional. Eat well, think carefully, sleep enough, show gratitude, and stay active.

Tillisch, K., Labus, J., Kilpatrick, L., Jiang, Z., Stains, J., Ebrat, B., ... & Mayer, E. A. (2013). Consumption of fermented milk product with probiotic modulates brain activity. Gastroenterology.