The Importance of Good Vagal Tone, Supported by Calming Essential Oils

The vagus nerve is the master regulator of the “rest and digest” part of your autonomic nervous system (ANS), the parasympathetic nervous system (PNS). It puts your body and mind in a state of restoration and repair, so its subconscious functions effortlessly occur. As a result, this tenth cranial nerve profoundly influences the heart, gut, brain, and lungs.

In contrast, a heightened sympathetic nervous system (SNS), the “fight and flee” part of the ANS, keeps us in heightened arousal. In this condition, survival vs. thriving is paramount. This is why optimizing the calming response of  the vagus nerve is paramount for healing any illness, disease state, or psychological disorder.

The polyvagal theory is an innovative approach to dealing with PTSD (post-traumatic stress disorder) based on the vagus nerve’s functions. It specifies concepts and techniques that optimize vagal tone (vagus nerve function) to put one into a state of safety and ease. In this condition the mind-body is balanced and social relationships thrive.

Essential oils are vagal nerve modulators that support the vagus nerve’s influence on our physiology, psychology, and biochemistry. Through various mechanisms, oils can enhance our brain health, mood, and calm our reactive nervous system down. The feeling of safety that emerges from aromatherapy allows for more rational response patterns to life and in relationships. It complements the polyvagal theory in that they also modulate one’s ability to heal, grow, and release trauma.

In this article, we will explore some of my favorite essential oils to support vagal tone. I will review the three that I use based on clinical experience and that also have some evidence of impacting the PNS. I will also discuss some of the cited studies’ caveats on these oils’ impact on the vagus nerve. Finally, I highlight two honorable mentions.

Essential Oils and Heart Rate Variability (HRV)

Before we discuss essential oils for their impact on the vagus nerve, it’s important to know how vagal tone can be measured. One way it can be determined is indirectly by heart rate variability (HRV). HRV is the amount of time between heartbeats which is caused by the flux of SNS and PNS stimulation and dominance. This provides more insight into the functioning of the ANS. Furthermore, an optimal HRV measurement is also believed to reflect self-regulatory capacity, adaptability, resilience, and cognitive performance.

The specific essential oils that I have selected have evidence in clinical studies to favorably modulate HRV or to alter physiological parameters that demonstrate PNS dominance (e.g., lowered blood pressure, heart rate, anxiety, or stress levels.) Although this post only highlights three essential oils, due to their multi-factorial biochemical, neurological, physiological, and emotional effects on the PNS, I believe most “calming oils” can likely help to tonify the vagus nerve.

Three Essential Oils to Calm the Nervous System and Support the Vagus Nerve

1. Lavender Essential Oil

Lavender is perhaps the most well-known essential oil for relaxation. It has been shown to support sleep, lower anxiety, ward off infections, relieve muscle strain, and enhance immunity.

In a comprehensive review of the effects of lavender oil on the nervous system, the authors provided an analysis of animal and human clinical trials using it via different application methods. The in vivo results indicated that lavender oil could protect the brain by modulating inflammatory pathways and altering the neurotransmitters (brain signals) dopamine, GABA (gamma-aminobutyric acid), and serotonin.

In pre-clinical and clinical research, the calming effects of lavender oil were supported by studies showing its impact on sleep, pain, and mood. Furthermore, human studies demonstrated changes in the brain when inhaling this oil. Through neuroimaging using functional magnetic resonance imaging (fMRI) and electroencephalography (EEG), lavender oil was found to induce relaxation in association with changing brain wave patterns (increased alpha waves).

Overall, the soothing effects of lavender on the nervous system are well-known, yet surprisingly, the studies on HRV are not as straightforward.

Lavender Oil and HRV

In a randomized between-subject double-blinded study with 97 subjects, orally administered lavender capsules (dosages of 100 and 200 mcl) were tested against placebo for its effect on physiological and psychological anxiety responses to film clips. In the experiment, participants first viewed a neutral film clip. This was followed by watching another one that provoked anxiety. Finally, subjects were exposed to a light-hearted recovery clip. Researchers evaluated subjective anxiety and mood and measurements from the State Trait Anxiety Inventory (STAI) and Positive and Negative Affect Scale (PANAS) pre- and post-experiment. They also assessed heart rate (HR), galvanic skin response (GSR), and heart rate variation (HRV) at baseline and during the trial.

Overall, the authors found that there was a trend towards reduced STAI, GSR, HR, and an increase in HRV (a positive result) for neutral film clips for both sexes and for anxiety-producing clips in females with the lavender oil. They reported, “HRV significantly increased at 200 microl during all three film clips in females, suggesting decreased anxiety.”

Their conclusion states: “These findings suggest that lavender has anxiolytic effects in humans under conditions of low anxiety, but these effects may not extend to conditions of high anxiety.”

There are some caveats to the study I found including:

• Dosage: The higher dosage used of 200 microliters of lavender would equate to about 4 drops. This would be on the lower dosage range for Silexin, an encapsulated, standardized lavender oil used in Europe used to treat anxiety. (Silexin is dosed at 80-160mg, about 3-6 drops.) A higher dose of 5-6 drops may have been more effective.
• Standardization: Standardization to chemical constituents was not clearly indicated, though a high-quality brand was used. This could impact biochemical effects.
• Comparison between groups: Baseline scores for anxiety weren’t as high in males. This can make it harder to determine a difference in effect post-intervention and may account for why the lavender oil was more effective in females.
• Duration: The peak of lavender in the blood stream was found to be highest at 10-15 minutes, the time of viewing of the anxiety clip. More exposure to the oil may have been indicated in the recovery state. This would support restoration and inspire a feeling of safety to ensue.

In another study the effects of 12 weeks of lavender aromatherapy on sixty-seven women aged 45-55 years with insomnia was assessed. The researchers measured self-reported sleep and heart rate variability (HRV). Overall, the authors concluded:

The study demonstrated that lavender inhalation may have a persistent short-term effect on HRV with an increase in parasympathetic modulation. Women receiving aromatherapy experienced a significant improvement in sleep quality after intervention. However, lavender aromatherapy does not appear to confer benefit on HRV in the long-term followup.

Dosage is the big caveat I have with this study as well. The research design was set to only dose lavender oil two times a week. We know that peak concentration of this oil is within minutes, so an exposure that is so intermittent shouldn’t be expected to modulate long-term changes in HRV. There were other problems with the study including the quality of the oil used and additional procedural issues. Yet, as noted in agreement with the previous study, the authors found there were postive effects on HRV in the time the lavender was being used. This study in women supports that HRV and vagal tone are impacted by lavender oil; however, we would likely see a greater long-term effect if continual use of lavender was administered.

In conclusion, based on the literature from pre-clinical and clinical trials, lavender does appear to have a positive effect on the PNS and HRV, but the results aren’t overly impressive from these few trials for HRV. I believe this is due to trial flaws. Based on clinical experience, lavender’s traditional use in aromatherapy, and other studies on its calming PNS effects, I believe lavender oil is beneficial for increasing vagal tone.

Three Essential Oils to Calm the Nervous System and Support the Vagus Nerve

1. Lavender Essential Oil

Lavender is perhaps the most well-known essential oil for relaxation. It has been shown to support sleep, lower anxiety, ward off infections, relieve muscle strain, and enhance immunity.

In a comprehensive review of the effects of lavender oil on the nervous system, the authors provided an analysis of animal and human clinical trials using it via different application methods. The in vivo results indicated that lavender oil could protect the brain by modulating inflammatory pathways and altering the neurotransmitters (brain signals) dopamine, GABA (gamma-aminobutyric acid), and serotonin.

In pre-clinical and clinical research, the calming effects of lavender oil were supported by studies showing its impact on sleep, pain, and mood. Furthermore, human studies demonstrated changes in the brain when inhaling this oil. Through neuroimaging using functional magnetic resonance imaging (fMRI) and electroencephalography (EEG), lavender oil was found to induce relaxation in association with changing brain wave patterns (increased alpha waves).

Overall, the soothing effects of lavender on the nervous system are well-known, yet surprisingly, the studies on HRV are not as straightforward.

Lavender Oil and HRV

In a randomized between-subject double-blinded study with 97 subjects, orally administered lavender capsules (dosages of 100 and 200 mcl) were tested against placebo for its effect on physiological and psychological anxiety responses to film clips. In the experiment, participants first viewed a neutral film clip. This was followed by watching another one that provoked anxiety. Finally, subjects were exposed to a light-hearted recovery clip. Researchers evaluated subjective anxiety and mood and measurements from the State Trait Anxiety Inventory (STAI) and Positive and Negative Affect Scale (PANAS) pre- and post-experiment. They also assessed heart rate (HR), galvanic skin response (GSR), and heart rate variation (HRV) at baseline and during the trial.

Overall, the authors found that there was a trend towards reduced STAI, GSR, HR, and an increase in HRV (a positive result) for neutral film clips for both sexes and for anxiety-producing clips in females with the lavender oil. They reported, “HRV significantly increased at 200 microl during all three film clips in females, suggesting decreased anxiety.”

Their conclusion states: “These findings suggest that lavender has anxiolytic effects in humans under conditions of low anxiety, but these effects may not extend to conditions of high anxiety.”

There are some caveats to the study I found including:

• Dosage: The higher dosage used of 200 microliters of lavender would equate to about 4 drops. This would be on the lower dosage range for Silexin, an encapsulated, standardized lavender oil used in Europe used to treat anxiety. (Silexin is dosed at 80-160mg, about 3-6 drops.) A higher dose of 5-6 drops may have been more effective.
• Standardization: Standardization to chemical constituents was not clearly indicated, though a high-quality brand was used. This could impact biochemical effects.
• Comparison between groups: Baseline scores for anxiety weren’t as high in males. This can make it harder to determine a difference in effect post-intervention and may account for why the lavender oil was more effective in females.
• Duration: The peak of lavender in the blood stream was found to be highest at 10-15 minutes, the time of viewing of the anxiety clip. More exposure to the oil may have been indicated in the recovery state. This would support restoration and inspire a feeling of safety to ensue.

In another study the effects of 12 weeks of lavender aromatherapy on sixty-seven women aged 45-55 years with insomnia was assessed. The researchers measured self-reported sleep and heart rate variability (HRV). Overall, the authors concluded:

The study demonstrated that lavender inhalation may have a persistent short-term effect on HRV with an increase in parasympathetic modulation. Women receiving aromatherapy experienced a significant improvement in sleep quality after intervention. However, lavender aromatherapy does not appear to confer benefit on HRV in the long-term followup.

Dosage is the big caveat I have with this study as well. The research design was set to only dose lavender oil two times a week. We know that peak concentration of this oil is within minutes, so an exposure that is so intermittent shouldn’t be expected to modulate long-term changes in HRV. There were other problems with the study including the quality of the oil used and additional procedural issues. Yet, as noted in agreement with the previous study, the authors found there were postive effects on HRV in the time the lavender was being used.

This study in women supports that HRV and vagal tone are impacted by lavender oil; however, we would likely see a greater long-term effect if continual use of lavender was administered.

In conclusion, based on the literature from pre-clinical and clinical trials, lavender does appear to have a positive effect on the PNS and HRV, but  the results aren’t overly impressive from these few trials for HRV. I believe this is due to trial flaws.

Overall, based on clinical experience, lavender’s traditional use in aromatherapy, and other studies on its calming PNS effects, I believe lavender oil is beneficial for increasing vagal tone.

2. Bergamot Oil

Bergamot essential oil (BEO) has evidence from human trials for calming psychological stress and anxiety. This is an indication that it modulates the PNS.

In one random crossover study with 41 healthy, young females, researchers sought to test BEO’s psychological and physiological effects. They also wished to determine some relevant pharmacological mechanisms. For the study, all subjects participated in 3 experimental setups for 15 minutes each:

• rest (R)
• rest + water vapor (RW)
• rest + water vapor + bergamot essential oil (RWB)

After resting 10 minutes, the participants completed the Profile of Mood States, State-Trait Anxiety Inventory, and Fatigue Self-Check List. During the rest period and 15-minute exposures, high-frequency (HF) heart rate values were calculated from HRV values and salivary cortisol (CS) levels were also analyzed. This study was well designed, though small. The authors made an effort to determine BEO standardization and quality.

The results indicated that cortisol was lowest and HRV, fatigue scores, and negative emotions improved most with the BEO (RWB) condition. As was noted in the lavender trial above, HRV did not increase as expected across all conditions. Since it takes around 10-15 minutes for peak dosage and the need for restoration, this again signifies dose may not have been optimal.

Combining my clinical experience, this small study, and the compilation of other human studies on its soothing impacts, I feel bergamot is another good essential oil to support the vagus nerve.

3. Ylang Ylang Oil

Ylang Ylang has several human studies demonstrating that it is calming to the heart, indicating it influences the vagus nerve. For example, in one small study with 29 men, inhalation of ylang ylang oil in a fragranced room for 20 minutes decreased heart rate (as measured by electrocardiogram, EKG) and lowered blood pressure. The researchers used a standardized oil; however, one of the major caveats was that they heated the essential oil. This can damage the delicate constituents! Furthermore, their standardized ylang ylang oil was a little different in that other ylang ylang chemotypes. Yet, even with these study flaws, the results were still favorable.

In a similar study which explored how the inhalation of ylang ylang effected physiology, it was also found this oil has relaxing properties. The scientists reported the effect to be “harmonization and subjective,” yet, the physiological parameter of blood pressure was still favorably affected across participants. What this means is that the authors found that the subject’s evaluation of the pleasantness of the odor impacted the robustness of their response:

Scientific evaluations of the effects of fragrances on humans are rather scarce. The aim of this investigation was to study the effects of ylang-ylang oil (Cananga odorata, Annonaceae) on human physiological parameters and self-evaluation. Twenty-four healthy volunteers participated in the experiments. Fragrances were administered by inhalation. Physiological parameters recorded were skin temperature, pulse rate, breathing rate and blood pressure. Self-evaluation was assessed in terms of alertness, attentiveness, calmness, mood, relaxation and vigor. Additionally, fragrances were rated in terms of pleasantness, intensity and effect.

The present investigation showed that ylang-ylang oil may be characterized by the concept of “harmonization” rather than relaxation/sedation. Compared to an odorless placebo, ylang-ylang oil caused significant decreases in blood pressure and pulse rate as well as significant increases of subjective attentiveness and alertness. Correlational analyses revealed that the observed effects are mainly due to a subjective odor experience. (Bolding my emphasis)

Other studies with Ylang Ylang that Demonstrate PNS Balancing

• One small study with ten volunteers compared inhalation of three different essential oils (a form of tea tree, patchouli, and ylang ylang) on physiological parameters. It was found that ylang ylang decreased pulse rate, lowered blood pressure, had a relaxing effect, reduced the stress index, and relaxed the brain (as evidence via EKG via increased alpha brain activity.)
• In another study with 40 subjects, transdermal application (on the skin) of ylang ylang oil resulted in lower blood pressure and increased skin temperature (indicating vasodilation) as compared to almond oil. Subjects also reported improvements in feelings of relaxation and calmness.

Honorable Mentions

Petitgrain Oil

Though not an oil I often use in my practice, I did run across a well-done study on a less familiar oil. In this trial, the researchers aimed to determine the efficacy of aromatherapy for improving work performance and lowering stress. The subjects were 42 administrative university workers who were exposed to petitgrain essential oil diffusion for 20-25 minutes. The results indicated an improvement in HRV and in the Stait-Trait Anxiety Inventory [STAI] and the Profile of Mood States [POMS].

Fir Oils

The phytoncides found in fir oils have been shown in several studies to support body defenses and relieve stress (via lowering cortisol). I have used these oils to evoke feelings of safety and provide grounding for my clients.

Summary: Essential Oils for the Vagus Nerve

Essential oils that have a reputation for being calming. They have been shown to positively influence brain health, mood, and soothe our reactive nervous system.

Through their impact on the PNS, they can act as vagus nerve modulators that support our physiology, psychology, and biochemistry. They complement the polyvagal theory in that they also arouse a feeling of safety that allows one to heal, grow, connect, and release trauma.

Three of my favorite essential oils to support vagal tone include lavender, bergamot, and ylang ylang oil. This is based on my clinical experience, their traditional use in aromatherapy, and current research. Fir oils and petitgrain oil also have some support for soothing the mind-body and balancing the PNS.

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References

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