Ways we can impact our microbiome

I’ve written before about probiotics and the microbiome, but some recent discoveries have inspired me to talk more about the impact our microbiome has on our mental health and the huge impact our everyday choices have on our microbiome.

It should come as no surprise that what we eat — and the microbes that help us along — affect our mental health. Since our digestive system responsible for digestion: breaking down our food into fuel our bodies can use. But also, since there is immune tissue in the GI tract, our digestive system contributes to our immune system. Not only that, it ALSO makes hormones! Though we often think of each system (digestive, immune, endocrine) as operating “in its own lane,” these systems are all integrated and have a tremendous amount of connection and overlap. In fact, though dividing the body into systems is helpful for learning about them, the truth is that the body (and mind and spirit) is an integrated, whole unit. All the systems that keep us thriving can’t really be isolated since they are all, by definition, interconnected.

Knowing this, it may not come as a surprise to you that the vast majority of our serotonin — about 95% of it — is made in the gut! [1] Yes! One of the main hormones targeted by anti-depressants (SSRI stands for “Selective Serotonin Reuptake Inhibitor”) is produced in our digestive system! So it also makes sense that several disorders, such as anxiety, depression, and autism spectrum disorders now have well-established links to functional GI issues. And GI disease (eg, irritable bowel syndrome, irritable bowel disease) often involve psychological symptoms that are associated with changes of the gut microbiome. [1]

Recently, a study out of Harvard Medical School found that gut microbes in pregnant women produced allopregnanolone — the exact hormone researchers have found to be an effective treatment for postpartum depression! Not only that, but the flatulence (gas) produced by one microbe caused another microbe to make said allopregnanolone. [2] All of this highlights not only the fact that even something as everyday (and sometimes problematic) as gas can be an important part of our overall health. But also, it is a reminder of the huge role our microbiome plays in our mental health — including postpartum depression! Clearly, our microbiome is so much more powerful and important than we thought even just a few years ago.

I get excited about this because impacting our microbiome is a huge opportunity to change our health for the better with everyday decisions. Namely, what we choose to eat and how we choose to support our microbiome.

The initial determinants of our microbiome are how we were born (vaginally or via a C-section), whether or not we were breastfed, and how often we received antibiotics in the first few years of life. We don’t have much agency around that, and, often, neither do our parents, who don’t always get to choose their “dream” version of childbirth or parenthood.

Later, though, is when it gets even more exciting. Since we can, by choosing foods and practices that support a healthy microbiome, start taking real action around ensuring that our microbiome has the healthy diversity that will lead us to even more vibrant health.

One of the easiest and most delicious ways we can do this is to incorporate both PRObiotics and PREbiotics into our lives. PRObiotics are the actual microbes (e.g., bacteria), while PREbiotics are are non-digestible plant fibers those microbes use as fuel. We need both for a robust and healthy microbiome. PREbiotics may sound fancy, but they are found in everyday foods like bananas and asparagus.

What about probiotics in food? Many people recommend fermented foods as a source of probiotics. In the interest of being comprehensive, though, it’s worth mentioning that some take issue with this. As the official definition of probiotics is “living microorganisms, that when administered in adequate amounts, confer a health benefit on the host” some say that fermented foods are not probiotics, since some fermented foods are not tested for how much and what strains of microbes they contain at the time of consumption OR the health benefits associated with those strains in that amount.

This may sounds like splitting hairs — and it is, to a certain extent. But it does highlight the importance of finding fermented foods that document what strains and how much of those strains are present at the time of consumption (meaning when you eat it). That doesn’t mean that the kimchi you make at home doesn’t contain beneficial microbes. It just means it can’t technically be called a probiotic unless you can prove which strains of beneficial microbes it contains and in what amount.

Now that we’ve gotten clear on that, fermented foods like kimchi, sauerkraut, yogurt, and kefir typically do contain beneficial microbes, and they can be a wonderful addition to your diet. In fact, many cultures include fermented foods in their traditional cuisine (e.g., yogurt in India, kimchi in Korea, sauerkraut and kefir in Central Europe) — likely because at some point they noticed that it helped their digestion and overall health.

And there are other things that you can do to support your microbiome. Eating a whole apple — core and all (as long as it’s organic!) — exposes us to far more beneficial microbes than eating the apple without its core. [3] I specify organic because that same study found significantly more bacteria that are harmful (like Enterobacteriales) in conventionally grown apples. But — excitingly — the cores of organic apples have been found to contain Lactobacillus [3, 4] and even Bifidobacteria species [4]. Which are two of the most common beneficial strains in probiotic supplements and foods. Clearly, not all bacteria are created equal.

In fact, even the exact same bacterium (singular form of bacteria — not trying to show off here, just trying to be accurate) can be helpful or harmful, depending on where you encounter it. E.coli in the intestines helps with digestion, vitamin production, and protecting against harmful bacteria. But if you eat something contaminated with E.coli — especially certain dangerous strains — it can cause severe illness and even death. This is why it is so important to wash our hands thoroughly after using the bathroom and making sure our food is washed and handled properly

But eating foods that contain healthy microbes and prebiotics, as well as a variety of whole foods, especially plants, are just a few of the ways to support your microbiome.

Others are:

• Be thoughtful about antibiotic use: Antibiotics are necessary and lifesaving! But overusing them or misusing them (like when we take antibiotics for a viral illness or to treat fluid in the ear that is not an infection) can kill off your good bacteria along with the bad, which can disrupt the balance in your gut microbiome.  Taking a probiotic supplement while and for at least 2 weeks after antibiotic use may help support the maintenance of a healthy microbiome even with antibiotic use. Though there is some conflicting research, one study showed that adding of probiotics to antibiotic interventions seemed to preserve the diversity of the gut microbiome when using antibiotic interventions. [5]. Taking probiotics while taking antibiotics has also been shown to reduce the side effect of diarrhea that many experience when they take antibiotics. [6]. While we’re on this topic, make sure to ALWAYS take antibiotics as directed (i.e., finish them!) Probiotics can play a role here as well, as one study showed that probiotics may reduce the risk for certain infectious diseases and, thereby, reduce the need for antibiotics. In this way and also through other mechanisms (like reducing side effects so people are more likely/able to take their whole course of antibiotics), probiotics may reduce the spread of antibiotic resistance. [6]. If you do need antibiotics, please take them! But finish the whole course and take probiotics as well.

• Avoid artificial sweeteners: Artificial sweeteners have been correlated in some (but not all) studies with dysbiosis (changes in the gut microbiome that can lead to disease or dysfuntion), some of which have been linked to insulin resistance and other health issues. [7]  One study found that artificial sweeteners are associated with increased caloric consumption and weight gain, as they appear to change the host microbiome, which not only leads people to not feel full but also alters the body's ability to keep blood sugar levels within a stable range [8].

• Manage stress levels: Not only does stress and inflammation impact the microbiome in negative ways [9, 10] , changes in the microbiome have profound consequences on the stress response! [10] So supporting your parasympathetic nervous system in times of stress can improve your microbiome — which can, in turn, improve your stress levels!

• Eating an anti-inflammatory (AI) diet: The AI diet is not only plant forward but also addresses the inflammation that can cause dysbiosis. My favorite versions of the AI diet philosophy are Dr. Andrew Weil’s AI food pyramid and Dr. Hilary McClafferty’s AI food table

• Exercise regularly: Many studies have shown that exercise has a beneficial effect on the microbiome [11, 12] — yet another reason to get moving!

• Sleep well: There is quite a bit of evidence showing that the gut microbiome not only affects digestive, metabolic and immune function but also regulates sleep and mental states through the microbiota-gut-brain axis. [13] AND multiple studies (though not all) have shown that getting good sleep supports a healthy gut microbiome. [13, 14]

As time goes on, we are learning more and more about how powerfully our microbiome impacts our health. And, as you can see, there are so many ways we can influence our microbiome to ensure we live the most vibrant lives possible.

REFERENCES:

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2. McCurry MD, D'Agostino GD, Walsh JT, Bisanz JE, Zalosnik I, Dong X, Morris DJ, Korzenik JR, Edlow AG, Balskus EP, Turnbaugh PJ, Huh JR, Devlin AS. Gut bacteria convert glucocorticoids into progestins in the presence of hydrogen gas. Cell. 2024 Jun 6;187(12):2952-2968.e13. doi: 10.1016/j.cell.2024.05.005. Epub 2024 May 24. PMID: 38795705; PMCID: PMC11179439.

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8. Pearlman M, Obert J, Casey L. The Association Between Artificial Sweeteners and Obesity. Curr Gastroenterol Rep. 2017 Nov 21;19(12):64. doi: 10.1007/s11894-017-0602-9. PMID: 29159583.

9. Zeng MY, Inohara N, Nunez G. Mechanisms of inflammation-driven bacterial dysbiosis in the gut. Mucosal Immunol. 2017;10(1):18–26. doi: 10.1038/mi.2016.75.

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11. Mailing LJ, Allen JM, Buford TW, Fields CJ, Woods JA. Exercise and the Gut Microbiome: A Review of the Evidence, Potential Mechanisms, and Implications for Human Health. Exerc Sport Sci Rev. 2019 Apr;47(2):75-85. doi: 10.1249/JES.0000000000000183. PMID: 30883471.

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