Walk into any yoga study and you’ll hear a constant stream of chatter about the benefits of yoga. Yoga improves strength, flexibility, joint stability, and the list goes on. One I hear often is folks who do yoga regularly claim to get sick less frequently. And, when they do get sick, they say they heal faster. As an immunologist I am intrigued by these kinds of statements. I turned to the scientific literature to see if I could find corroborating evidence and a possible explanation for these claims.
Stress & The Immune System
First, consider the idea of stress. There are numerous studies which demonstrate the body’s response to stress, both chronic and acute (J Neuroimmune Pharm (2006) 1: 421–427). In an acute setting, we know it as the “fight or flight” response. The sympathetic nervous system floods the body with epinephrine, increases heart rate, blood pressure, and respiration rate. Oxygen is delivered quickly to the necessary organs and muscle tissue. This is a fantastic response if you’re being chased by a sabretooth tiger. RUN! NOW! FAST! The additional oxygen delivery makes it easier for your muscles to respond and for you to get away. Many people also experience this if they have an uncontrolled fear, such as a fear of heights or public speaking. Dry mouth, sweaty palms anyone? It’s not as useful in those settings, but evolutionarily speaking, the response is the same.
On the other hand, chronic stress can stimulate this response over an extended period of time. Eventually, this can lead to a prolonged increase in heart rate and blood pressure and what has come to be known as ‘adrenal fatigue’ or the body’s inability to properly regulate epinephrine and other hormones.
From an immune system perspective, this kind of chronic stress response leads to an increase in inflammatory mediators, compounds typically used by the body to respond to bacterial or viral infections or assist in wound healing by modulating the cells of the immune system. If immune cells receive stimuli continuously, they eventually stop responding, a state known as anergy. This is how stress can decrease an individual’s ability to respond to infections or heal tissue damage. In people with chronic disease states, such as rheumatoid arthritis, Crohn’s disease or Hashimoto’s thyroiditis, this prolonged inflammation can lead to flare-ups that cause organ, joint and tissue damage.
Controlling the Stress Response
Knowing this, then, how can yoga possibly help? As we’ve already noted, the stress response, chronic or acute, is controlled via the sympathetic nervous system. To counter that, we have to find a way to initiate the parasympathetic response. We may not negate the stress response entirely, but we can certainly mitigate it a bit. So, how do we do it?
According to a paper published in the journal Nature in 2000, stimulation of the vagus nerve (the longest cranial nerve that runs from the brainstem all the way down through the thoracic cavity to the abdomen and regulates heart rate, respiration and digestion) attenuates systemic inflammation in response to bacterial toxins (Nature 405, 458-462. 25 May 2000). More recent studies in the Journal of Trauma and Acute Care Surgery demonstrate that vagus nerve stimulation decreases gut injury and lung damage following trauma or severe blood loss (J Trauma Acute Care Surg. 2012 August; 73(2): 338–342). Numerous other studies point to vagus nerve enervation as the crux between the nervous, endocrine and immune systems.
This suggests to us that, if we can find a way to stimulate the vagus nerve, we can potentially decrease the level of inflammation in our bodies, improve overall health and boost our ability to respond appropriately to injury or illness when they do occur.
The Impact of Yoga & Breathing
Enter deep yogic breathing. Fancy advanced pranayama not required. It is enough to use slow, controlled breathing. A review published this year in Advances in Mind-Body Medicine (Adv Mind Body Med. 2015 Winter; 29(1):18-25) points to controlled, rhythmic breathing and details the numerous studies that show this simple practice to be highly effective to alleviate stress and improve healthcare outcomes.
The best news of all, is that absolutely anyone can use the tool because the benefit is traced to the breath. No asana is required. A simple meditation that focuses on breath control is all you need. This kind of breathing is certainly built into the yoga practice, but applied to any form of exercise or meditation the technique can be equally effective!
Happy breathing, yogis, and cheers to your improved health!