Your gut microbiome inhabits your digestive tract and helps break down food. So, it's only logical it'll affect your digestive health.

But… how would one explain the link between poor gut health and increased stress reactivity, alongside risk for various mental health conditions such as anxiety disorders and depression then [1]?

Well, as unrelated as the two concepts — i.e. gut health and mental well-being — may appear at first glance, they're interconnected. Read on to find out how.

What’s the difference between good and poor gut health?

Good gut health (specific strains and their amounts in the microbiome) can look wildly different from individual to individual [2]. In general, though, researchers define good gut health as [3]:

• A balance between symbiotic and pathogenic microbiome: The gut microbiome consists of microbes — bacteria, fungi, parasites, and viruses — that are both helpful and potentially harmful. Most are symbiotic (good), while some, in smaller numbers, are pathogenic (disease-promoting or bad). In a healthy body, good and bad microbes coexist without problems. But this delicate balance can be disrupted.
• High gut microbiome diversity: Studies consistently link having a diverse population of gut microbes with better health, physically (e.g., lower risk of metabolic syndrome) and emotionally [4, 5].

So, in that sense, gut dysbiosis — a phenomenon where your gut microbiome becomes unbalanced or loses diversity — is a sign of poor gut health [6].

Gut health and mental well-being: what’s the relationship?

So, why and how does gut dysbiosis impact your mental well-being? Most of it comes down to gut-driven inflammation’s adverse effects on the gut-brain axis.

See: gut dysbiosis could contribute to increased intestinal barrier permeability [7].

This may allow substances, like undigested food particles, to sneak past the intestinal lining into the bloodstream where they don’t belong — causing widespread inflammation that [8]:

1. Affects the hypothalamic-pituitary-adrenal (HPA) axis: The HPA axis' primary function is to regulate the stress response [9]. Inflammation may contribute to HPA axis dysregulation, which, in turn, is associated with chronic stress and various psychiatric conditions like depression and anxiety disorders [10].
2. Decreases levels of gut bacteria beneficial to mental well-being: Gut inflammation further exacerbates dysbiosis by promoting the growth of bad gut bacteria [11]. These crowd out mental-health-beneficial strains of probiotic gut bacteria, like species of Lactobacillus (e.g., L. paracasei, L. acidophilus, L. plantarum, and L. fermentum) that have been shown to help improve stress resilience and alleviate anxiety symptoms [12, 13, 14, 15, 16].
3. Lowers production of mood-regulating neurotransmitters: Gut inflammation could decrease the amount of acetate, propionate, and butyrate — short-chain fatty acids (SCFAs) — produced in the colon [17]. So how is this related to your mental well-being? SCFAs are involved in synthesizing several mood-regulating neurotransmitters, including serotonin, gamma-aminobutyric acid (GABA), and dopamine [18]. Put simply, gut dysbiosis could cause neurotransmitter imbalance in the brain, increasing stress reactivity, plus risk for depression and anxiety disorders [19, 20, 21].

What next? Here’s how to improve your gut health

Of course, there are many other mechanisms (via the gut-brain axis) through which gut health could influence mental well-being.

But the important takeaway is this: gut health and mental well-being are closely related.

Take care of your gut health, and your mental well-being will likely improve. How? By taking prebiotics or probiotics. To understand which of the two to take, let’s look at how they differ [22]:

• Probiotics: Live, beneficial microorganisms
• Prebiotics: Substrates that are selectively utilized by the host microorganisms conferring health benefits

As mentioned earlier, even amongst people with good gut health, no two individuals' gut microbiota will look the same. Everyone differs in the variety and abundance of species in the gut microbiota.

So, to reap the most health benefits from probiotics, you'd have to source for the specific organism(s) — genus, species, and strain — already present in your microbiome: an impossible task without gut microbiome testing.

Thankfully, you won't run into this concern with prebiotics. You can rest assured that they will feed the good gut bacteria already thriving in your gut, helping them flourish [23].

Better still, if you've undergone microbiome testing and are supplementing with probiotics native to your unique gut microbiota. Prebiotics could further improve the survivability rate of the probiotics in your digestive tract, boosting the chances that they successfully coax your gut health into a more balanced, diverse state [24].

How much prebiotics should you take, though?

According to the International Scientific Association for Probiotics and Prebiotics (ISAPP), anywhere between 3 to 5 grams would suffice [25].

Takeaway

Your gut and brain communicate through the gut-brain axis. So, when your gut health suffers, your mental well-being does, too.

To foster good gut health (plus keep stress, anxiety, and depression at bay), focus on gut microbiome balance and diversity. Ensuring 3-5g of prebiotics intake daily helps nourish and maintain a well-balanced gut microbiota.

References

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