Rest and Digest: Ways to Increase Parasympathetic Tone

Sympathetic vs. Parasympathetic Response

The sympathetic and parasympathetic nervous systems are divisions of the autonomic nervous system, which controls unconscious body functions (breathing and digestion) and every organ in our bodies.

The sympathetic nervous system prepares your body to flee from danger or fight back. It’s also triggered in response to mental or physical stress. During this fight-or-flight response, these physiological phenomena occur:

• Blood pressure increases

• Blood flow increases to muscles, lungs, and other areas essential for moving away from perceived danger

• Blood flow decreases to the digestive and reproductive systems

• Certain stress hormones, such as cortisol, and neurotransmitters, like epinephrine, increase to make us stronger and faster

• Glucose is released into the blood stream to be burned for quick energy

The parasympathetic nervous system is activated after a meal or in response to pleasure, and its physical effects tend to oppose those of a sympathetic response:

• Heart rate and respiration slow

• Blood pressure drops

• Intestinal activity increases

• Blood flow increases to the digestive tract

• Neurotransmitters like acetylcholine, which regulates muscle contractions, are released

• Stress hormones decrease

The sympathetic nervous system interacts with the hypothalamus–pituitary–adrenal (HPA) axis to control the body’s stress response. Stress signals the adrenal glands to secrete stress hormones and neurotransmitters (cortisol, epinephrine, and norepinephrine) in order to increase blood pressure and blood sugar. After the stressful event, the parasympathetic nervous system kicks in to decrease stress hormone production and lower blood pressure through the release of the neurotransmitters, such as acetylcholine. This balance maintains the body’s preferred state of homeostasis.

Why Balance Matters

If you’re suffering from chronic stress, your body spends too much time in “fight or flight” mode and not enough time in “rest and digest” mode, upsetting the balance between the parasympathetic and sympathetic nervous systems.

Chronic stressors tend to be unrelenting in today’s world. You might constantly worry about money, bad relationships, your job, or regularly get less than six hours of sleep each night, all of which continually trigger the sympathetic nervous system’s fight-or-flight response. Common symptoms of chronic stress include: 

• Fatigue

• Headaches

• Decreased immunity

• Sleep problems

• Mood swings

• Sugar and caffeine cravings

• Irritability or lightheadedness between meals

• Eating to relieve fatigue

• Dizziness when moving from sitting or lying to standing

• Digestive discomfort

Our bodies aren’t meant to withstand sustained stress. An overactive sympathetic response disrupts the HPA axis, induces chronic inflammation, and has been linked to a number of chronic health conditions, including cardiovascular disease, insulin resistance, obesity, a weakened immune system, high blood pressure, kidney disease, depression, poor sleep, and irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD).

Heart Rate Variability

We always advocate the use of your intuition when it comes to health. But a good, objective measure of autonomic nervous system balance is heart rate variability (HRV). HRV is a measure of the variation of time between each of your heartbeats. Variations between your heartbeats are normal and are controlled by your autonomic nervous system. HRV is a non-invasive and easy way to check for autonomic nervous system imbalances. If you are under a constant fight-or-flight mode due to chronic stress, your HRV will be low. In a healthier and more relaxed state, your HRV will be high. The healthier your autonomic nervous system is, the faster it will be able to switch gears and relax after experiencing acute stress.

For more information on how to check your HRV, check out this post.

Ways to Increase Parasympathetic Tone

If you aren’t managing your stress, your health will suffer (regardless of healthy eating and exercising on the regular). Try some of these techniques to encourage your rest and digest response on a regular basis:

Focus on deep breathing. Breathing exercises can increase vagal tone and facilitate digestive motility. Here are some breathing techniques to get you started.

Try meditation. Meditation has been shown to increase parasympathetic activity, decrease sympathetic activity, and improve heart rate variability.

Exercise. The sympathetic nervous system is activated during exercise, but regular exercise correlates with an increase in resting vagal tone and overall health. If you find you’re exhausted after exercise, or have poor muscle recovery, you’re probably overtraining, which can have the opposite effect. It’s important to find your “sweet spot” for the right amount of exercise for you.

Start a daily yoga practice. Yoga increases vagal activity through the combination of exercise, meditation, and deep breathing.

Get outdoors. Regular interaction with nature improves autonomic tone and heart rate variability.

Try cold-water immersion. No need for a polar plunge, even just splashing your face with cold water can jumpstart the parasympathetic nervous system, especially after strenuous exercise.

Yawn. The exaggerated inhale and exhale of a yawn elicits the parasympathetic response, most likely in a similar way as breathing exercises.

Chew gum. Chewing stimulates the parasympathetic nervous system.

Book a massage. Massage therapy has been shown to improve parasympathetic activity as measured by heart rate variability.

Try acupuncture. Acupuncture can increase vagal tone and reduce heart rate and inflammation.