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The Vagus Nerve and Health: What’s the Connection?

by Valerie Polley | Dec 30, 2024 | 0 comments

The vagus nerve is a powerful piece of the body's communication network, linking the brain to various essential systems like the heart, lungs, and gut. It plays an important role in the autonomic nervous system, helping regulate involuntary functions such as heart rate, digestion, and immunity.

The impact of the vagus nerve on health has become a popular topic in both scientific research and popular wellness culture. So, what exactly is the vagus nerve, and how does it influence your health?

What is the Vagus Nerve?

The vagus nerve, which is the tenth cranial nerve, is the longest and most complex cranial nerve in the body. It extends from the brainstem down into the abdomen and branches out to various organs. The word "vagus" means "wandering" in Latin, which accurately describes its extensive reach in the body.

The vagus nerve is a key player in the parasympathetic nervous system, which counteracts the fight or flight response and promotes a "rest-and-digest" state. Its influence spans numerous functions, from controlling your heartbeat to enabling efficient digestion.

The Vagus Nerve and Gut Health

One of the most studied roles of the vagus nerve is its connection to gut health. It serves as the main communication highway between the gut and the brain—a relationship known as the gut-brain axis. This bidirectional communication is essential for regulating digestion, immunity, and even mood.

How the Vagus Nerve Affects Digestion

The vagus nerve stimulates the release of digestive enzymes and bile, which helps break down the food you eat. It also helps coordinate intestinal motility (the process of moving food through the digestive tract). Impaired vagal function can lead to GI disorders like irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD).

Gut Microbiota and the Vagus Nerve

The gut microbiome—the community of microorganisms living in the digestive tract—also interacts with the vagus nerve. Research suggests that beneficial gut bacteria produce metabolites that stimulate the vagus nerve.

Conversely, dysbiosis (an imbalance in gut bacteria) may disrupt vagal signaling and contribute to conditions like obesity and diabetes.

The Vagus Nerve and Mental Health

The vagus nerve's influence extends beyond physical health to mental well-being. It plays a key role in regulating the stress response and fostering emotional resilience.

Stress and Anxiety

Activation of the vagus nerve promotes relaxation by slowing the heart rate and reducing the production of stress hormones like cortisol. This vagal activity may help reduce anxiety and promote a sense of calm.

Mood and Depression

Emerging research suggests a link between low vagal tone (reduced vagus nerve activity) and depression. Vagal tone can be measured through heart rate variability (HRV), with higher variability indicating better vagal function.

Interventions like vagus nerve stimulation have shown promise in relieving symptoms of treatment-resistant depression, highlighting the nerve's significance in mood regulation.

The Vagus Nerve and Immune Function

The vagus nerve also plays a critical role in regulating immune function through its connections to the body's inflammatory response system. One of its most significant contributions is through the cholinergic anti-inflammatory pathway. It communicates with immune cells to release acetylcholine, which suppresses pro-inflammatory cytokine production. This prevents the excessive inflammation seen in conditions like rheumatoid arthritis and IBD.

The Vagus Nerve and Heart Health

The vagus nerve plays a key role in heart health by regulating heart rate and blood pressure. It slows the heart rate and helps it maintain a healthy rhythm. This function, known as vagal tone, is linked to better HRV, an indicator of heart health.

The vagus nerve also helps control blood pressure via the baroreflex, a mechanism that stabilizes blood pressure by slowing the heart rate when needed. The nerve's calming effects counteract stress-induced strain on the heart, which may reduce the risk of high blood pressure (hypertension) and other heart-related conditions. Some research suggests that vagus nerve stimulation can benefit people with heart failure by improving heart function.

How to Support the Vagus Nerve

Maintaining or improving vagal tone can have positive effects on your overall health. Here are some strategies to support your vagus nerve.

Deep Breathing and Meditation

Slow, deep breaths activate the parasympathetic nervous system, which directly stimulates the vagus nerve. Diaphragmatic breathing exercises or mindfulness meditation can enhance vagal tone over time.

Cold Exposure

Short bursts of cold exposure, such as splashing cold water on your face or taking a cold shower, can activate the vagus nerve and improve vagal tone.

Probiotics and Diet

Eating a diet rich in prebiotics (fiber that acts as fuel for your good gut bacteria) and probiotics can nurture the gut microbiota and by extension, promote a healthy vagus nerve. Foods like yogurt, kimchi, kefir, and fiber-rich fruits and vegetables are excellent choices.

Singing, Humming, and Gargling

These actions stimulate the vagus nerve through vibration in the throat. Singing or humming daily may be an easy and enjoyable way to support your vagus nerve.

Physical Activity

Exercise is another effective way to boost vagal tone. Activities like yoga and tai chi are particularly beneficial, as they combine movement with mindful breathing.

Potential Risks and Complications

While the vagus nerve is essential for health, its dysfunction can have significant implications. For instance, vagus nerve overactivity may contribute to conditions such as fainting or a dangerously slow heart rate. For this reason, interventions like vagus nerve stimulation should be undertaken under medical supervision.

It's also worth noting that while lifestyle changes can support vagal tone, they're not a cure-all. Chronic health issues involving the vagus nerve may need comprehensive medical treatment. 

Final Thoughts

The vagus nerve is a cornerstone of physical and emotional well-being, and it influences everything from digestion to mood to inflammation. Its integral role in the gut-brain axis underscores just how interconnected the different systems of the body are. By supporting vagal tone through simple, evidence-based strategies, you can enhance your overall health and resilience.

If you want to improve your health by increasing vagal tone, working with a registered dietitian can help. Click here to get in touch with Blue Tree Nutrition and book a session with a registered dietitian. 

Our gut microbiome (the community of trillions of microbes that live in our gut) plays a key role in maintaining metabolic and immune health. Gut dysbiosis occurs when the composition and diversity of our gut microbiome shift. This could include overgrowth of harmful bacteria or a decrease in beneficial bacteria. Gut dysbiosis has been linked to a wide range of negative health outcomes, including increased levels of inflammation and changes in metabolism.

Many people switch to non-nutritive sweeteners like sucralose, aspartame, and stevia for health reasons, and for decades, we've believed that they pass through our bodies without affecting us. But emerging research shows that these compounds interact directly with our gut microbiome and may have potential negative effects on our health. 

This article will review what we currently know about the relationship between non-nutritive sweeteners (including artificial sweeteners and calorie-free natural sweeteners) and the gut microbiome, plus practical advice for navigating sweeteners.

Sucralose

Sucralose (Splenda) is an artificial sweetener commonly used in baked goods, gums, and sugar-free beverages and is approximately 600 times sweeter than sucrose (table sugar). However, recent research has linked it to adverse health effects such as systemic inflammation, metabolic disease, and gut dysbiosis. For example, a 2022 study found that sucralose consumption increased harmful bacteria and reduced beneficial bacteria, which was associated with changes in insulin and glucose levels.

Additionally, a 2025 randomized controlled trial examining the effects of replacing added sugars with sucralose found that people with type 2 diabetes who consumed sucralose experienced reductions in both alpha diversity (the number and types of species present in a single person) and beta diversity (differences in microbial composition between people). Interestingly, the people with overweight and obesity without type 2 diabetes did not experience the same changes.

Overall, animal studies and limited human studies suggest that sucralose may trigger intestinal inflammation, likely through its effects on the gut microbiome. However, since most of the evidence we have comes from test tube or animal studies, these results should be interpreted cautiously.

Aspartame

Aspartame is another commonly used artificial sweetener that is about 200 times as sweet as sucrose. While it does contain some calories, because you don't need much of it to reach the same sweetness levels as sucrose, these calories are negligible.

Like sucralose, most of the research into the gut effects of aspartame has been done in animals. However, we do have some very small human studies. A 2022 randomized controlled trial (RCT) involving 20 healthy adults found that participants taking aspartame showed changes in both probiotic (beneficial) and pathogenic (harmful) bacteria, but the changes were specific to each individual. 

Why the differences? It's likely due to the "responder vs. non-responder" phenomenon. We all have differences in our "baseline" microbiome. While certain bacterial species are common in healthy populations, our microbiome is as unique as a fingerprint. Whether an artificial sweetener has positive or negative effects on our microbiome may depend on which species are already present in our gut, as well as on our habitual diet. This difference in responses makes it very challenging to draw firm conclusions about whether artificial sweeteners are harmful.

Stevia

Many people choose stevia because it's a "natural" zero-calorie sweetener. Studies have shown mixed results regarding the effects of stevia on the gut microbiome. For example, while some in vitro (test tube) and in vivo (animal) studies have reported potentially harmful effects of stevia on the gut microbiome, others have found no impact, and some even reported beneficial effects through inhibition of inflammatory pathways.

Additionally, a 2024 human study found that stevia had no significant effect on the gut microbiome. This highlights the importance of not forming conclusions based solely on test tube and animal studies. Overall, it appears that stevia is a potentially less-harmful alternative to artificial sweeteners like sucralose and aspartame.

Practical Advice for Navigating Sweeteners

Since the research on artificial sweeteners is still evolving, the decision to include or avoid them comes down to personal preference. Here are some tips for including them in your diet in moderation:

  • Try gradually reducing the amount you use: If you typically use two packets of sweetener in your coffee or tea, try gradually reducing to one packet. Our taste buds are highly adaptable, and you may find that one packet is sweet enough once you get used to it.
  • Check your labels: Low- or no-calorie sweeteners (such as sucralose, aspartame, and sugar alcohols like erythritol) are often hidden in low-sugar foods like protein bars, yogurt, and diet sodas. Awareness is the first step to reducing your intake.
  • Rotate your sources: If you do use artificial sweeteners, try switching up the types you use. Since different sweeteners may affect your gut microbiome in different ways, this may reduce the concentrated impact on your gut.
  • Switch to stevia: While animal and test-tube studies show mixed findings, human research indicates that stevia has a limited effect on the gut microbiome, making it a better choice for people seeking to support their gut health.

Another way to support your gut if you regularly use artificial sweeteners is to rebuild gut diversity with fiber and fermented foods, while focusing on whole-food sweeteners.

  • High fiber prebiotic foods (like legumes, whole grains, garlic, onions, asparagus, and under-ripe bananas) act as "fuel" for your healthy gut microbes. Aim to include a variety of these foods in your diet to support the microbes already in your gut.
  • Add fermented foods, like unpasteurized sauerkraut and kimchi, kefir, or kombucha, to your diet. Some fermented foods contain live, beneficial bacterial cultures, while others are rich in "postbiotics" (beneficial compounds like short-chain fatty acids, which are produced when bacteria break down prebiotics).
  • Try using whole-food sweeteners instead of artificial ones. For example, sweeten plain yogurt with vanilla extract and berries or add dates to smoothies or homemade energy bites.

Final Thoughts

Emerging research suggests that certain low- or no-calorie sweeteners, including sucralose and aspartame, may affect the gut microbiome, whereas stevia appears to have a less negative effect. While individual responses can vary with a person's unique baseline microbiome, certain artificial sweeteners may increase inflammation or reduce gut microbiome diversity.

If you need personalized support navigating sweeteners or supporting your gut health, Blue Tree Nutrition can help. Click here to get in touch!

 

 

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Hello, I am

Valerie

My name is Valerie Polley. I am a Indianapolis-based registered dietitian and owner of Blue Tree Nutrition. I consult with clients both local and far away.
I have a bachelor’s degree in nutrition from Purdue University and I have been practicing for 20 years.
I thoroughly enjoy helping clients through their gut health journey. I see a range of GI issues including, but not limited to celiac disease, IBS and SIBO. I also specialize in the FODMAP elimination diet.

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