For most of us, one nostril is more open than the other at any given time and this nostril ‘dominance’ switches periodically during the day under the influence of your autonomic nervous system (Eccles, 2000). The practice of alternate nostril breathing, or #nadishodan, in Yoga is designed to work with this to be “…calming for the nervous system and balancing for the mind.” There’s some science to back this up. More on my blog link in bio.
Known as the nasal cycle, sympathetic nerves constrict blood vessels in the nose to open and decongest one nostril (or both in times of stress), and, conversely, parasympathetic activity will dilate and increase secretion/congestion narrowing the other nostril (Kahana-Zweig et al., 2016).
The periodicity and variance of nostril ‘openness’, or patency, is highly individualised and can vary with posture, age, sleep, and handedness (Rohrmeier, Schittek, Ettl, Herzog, & Kuehnel, 2014; Searleman, Hornung, Stein, & Brzuszkiewicz, 2005). For example, it has been demonstrated in humans and animals that lying on one side can increase airflow in the top nostril. This isn’t a passive effect of venous pressure, it has been demonstrated as a product of change in vasomotor activity (Eccles, 2000).
There are a number of theories proposed for the purpose of the nasal cycle: optimisation of your sense of smell; brain hemisphere laterality and function; and/or supporting physiology for 'fight/flight' or 'rest/digest' behaviours (Kahana-Zweig et al., 2016). Nostril dominance has also been associated with disease, including migraine, respiratory, eye, and sleep disorders. However, there is scope for wider epidemiological study. One case study of adult schizophrenia, observed significant left nostril dominance during hallucination episodes over a period of several years (Shannahoff-Khalsa & Golshan, 2015).
There is also recent research of the therapeutic potential in unilateral or alternate nostril breathing practices. One 2017 study of the practice in 13 experienced healthy participants demonstrated that brain frequencies associated with sleep, deep meditation, and memory formation, theta, and that associated with waking activity, beta, were significantly reduced with this practice compared to quiet sitting (Telles, Gupta, Yadav, Pathak, & Balkrishna, 2017). This was interpreted as achieving a state of ‘waking calm’ rather than deep, sedative meditation. In contrast, alpha frequency was significantly lower and beta was significantly higher in the quiet sitting control group, potentially indicating greater rumination and arousal without the practice.
Furthermore, like meditation, experience appears to matter. Immediate effects of alternate nostril breathing were not shown in novices in two separate studies measuring heart rate variability (HRV) (Ghiya & Lee, 2012; Subramanian, P, & P, 2016). However, in a study where 25 participants received six weeks training, a parasympathetic response measured by HRV was observed following the practice (Sinha, Deepak, & Gusain, 2013).
In a 2014 study, 16 yoga practitioners displayed greater metabolic variability and stress recovery than 15 non-yoga practitioners and 15 metabolic syndrome patients after breathing including alternate nostril breathing (Tyagi, Cohen, Reece, & Telles, 2014). In a 2008 study, alternate nostril and left unilateral nostril breathing also demonstrated reductions in blood pressure compared to right unilateral nostril breathing in 21 participants with 3-months of training (Raghuraj & Telles, 2008).
It’s also important to remember that most of these studies were run in mostly young, male participants by Indian research centres. Therefore, they may have a selection, publication, or meta-bias in favour of yoga. While I find this practice beneficial for students and myself personally, more research is needed.
Eccles, R. (2000). Nasal Airflow in Health and Disease. Acta Oto-Laryngologica, 120(5), 580-595. doi:10.1080/000164800750000388
Ghiya, S., & Lee, C. M. (2012). Influence of alternate nostril breathing on heart rate variability in non-practitioners of yogic breathing. Int J Yoga, 5(1), 66-69. doi:10.4103/0973-6131.91717
Iyengar, B. K. S. Light on pranayama.
Kahana-Zweig, R., Geva-Sagiv, M., Weissbrod, A., Secundo, L., Soroker, N., & Sobel, N. (2016). Measuring and Characterizing the Human Nasal Cycle. PLoS One, 11(10), e0162918. doi:10.1371/journal.pone.0162918
Raghuraj, P., & Telles, S. (2008). Immediate effect of specific nostril manipulating yoga breathing practices on autonomic and respiratory variables. Appl Psychophysiol Biofeedback, 33(2), 65-75. doi:10.1007/s10484-008-9055-0
Rohrmeier, C., Schittek, S., Ettl, T., Herzog, M., & Kuehnel, T. S. (2014). The nasal cycle during wakefulness and sleep and its relation to body position. Laryngoscope, 124(6), 1492-1497. doi:10.1002/lary.24546
Searleman, A., Hornung, D. E., Stein, E., & Brzuszkiewicz, L. (2005). Nostril dominance: differences in nasal airflow and preferred handedness. Laterality, 10(2), 111-120. doi:10.1080/13576500342000329
Shannahoff-Khalsa, D., & Golshan, S. (2015). Nasal cycle dominance and hallucinations in an adult schizophrenic female. Psychiatry Research, 226(1), 289-294. doi:http://dx.doi.org/10.1016/j.psychres.2014.12.065
Sinha, A. N., Deepak, D., & Gusain, V. S. (2013). Assessment of the effects of pranayama/alternate nostril breathing on the parasympathetic nervous system in young adults. J Clin Diagn Res, 7(5), 821-823. doi:10.7860/JCDR/2013/4750.2948
Subramanian, R. K., P, R. D., & P, S. (2016). Alternate Nostril Breathing at Different Rates and its Influence on Heart Rate Variability in Non Practitioners of Yoga. J Clin Diagn Res, 10(1), CM01-02. doi:10.7860/JCDR/2016/15287.7094
Telles, S., Gupta, R. K., Yadav, A., Pathak, S., & Balkrishna, A. (2017). Hemisphere specific EEG related to alternate nostril yoga breathing. BMC research notes, 10(1). doi:10.1186/s13104-017-2625-6
Tyagi, A., Cohen, M., Reece, J., & Telles, S. (2014). An explorative study of metabolic responses to mental stress and yoga practices in yoga practitioners, non-yoga practitioners and individuals with metabolic syndrome. BMC Complement Altern Med, 14, 445. doi:10.1186/1472-6882-14-445