Anuloma Viloma Timer
The ‘left nostril, right brain’ claim rests mostly on a 1987 study of five people.
If you have spent any time around alternate nostril breathing online, you have met the claim in some form. Breathe through the left nostril and you light up the right side of your brain. Breathe through the right and the left side wakes up. Alternate the two and you “balance your hemispheres”. It is a tidy story, it fits the symmetry of the practice, and it shows up in captions, course pages and app descriptions alike.
It is worth knowing where it comes from, because the answer is smaller than the confidence it is usually stated with.
The study behind the story
In 1987, David Werntz, Reginald Bickford and David Shannahoff-Khalsa published a paper in the journal Human Neurobiology called “Selective hemispheric stimulation by unilateral forced nostril breathing”. They had people breathe forcefully through one nostril while recording their brain activity with EEG. They reported that the EEG amplitude was larger over the hemisphere opposite the nostril being used, and that the pattern held in all five of their untrained subjects.
Five out of five is a clean result. It is also five people. The work grew out of an earlier line of research by the same group on the nasal cycle, the natural shift in airflow from one nostril to the other every few hours, and on whether that cycle tracks shifts in brain activity. It was interesting, careful for its time, and exploratory.
What came after
Later studies, many of them from the same research group, reported results that supported the opposite-side idea, including some performance tasks that shifted slightly depending on which nostril was in use. Other work has not lined up so neatly. A more recent high-density EEG study of paced nostril breathing found changes in brain connectivity on the same side as the breathing nostril, not the opposite one.
That does not mean the original finding was wrong. It means the question is still open, the samples are small, the methods differ, and the direction of the effect is not agreed. “Your left nostril feeds your right brain” is a hypothesis with a few small studies behind it, not an established fact. Neither is “it balances your hemispheres”, a phrase that sounds like a finding but does not describe any measurement in particular.
What holds up better
If you want the part of alternate nostril breathing that has more weight behind it, look at something less glamorous: blood pressure.
In 2024, Nam and colleagues published a systematic review and meta-analysis of randomised controlled trials of alternate nostril breathing and blood pressure in Complementary Medicine Research. Six trials with 525 participants went into the pooled analysis. On average, systolic blood pressure came out about 7 mmHg lower with alternate nostril breathing than with the control conditions.
The honest caveat has to come with it. The trials varied a great deal (the statistical measure of that, I-squared, was 93 percent), so the average hides a wide spread of results. The fair summary is “lower on average, and the studies varied a lot”. A wider 2025 review of pranayama for mental health came to a similar shape of conclusion: promising, with an evidence base that is still small and methodologically limited.
That is a less exciting headline than brain balancing. It is also a more useful one, because it points at what the practice actually does well: it slows your breathing down, gives the exhale time, and asks for steady attention for a few minutes. Those are things you can feel tonight, and things trials can measure over weeks.
Why it is still worth doing
The yogic texts that describe nadi shodhana never talked about left and right hemispheres. They talked about channels, a moon side and a sun side, and about steadiness of the breath and mind. Modern science has its own vocabulary, and it should be held to its own standard: when a claim rests on five people, say so.
None of that makes the practice weaker. Sit upright. Close the right nostril and breathe in slowly through the left. Switch, and breathe out through the right, a little longer than you breathed in. Keep it smooth and quiet, and stop if you feel lightheaded. Five minutes is a good start.
You do not need to believe your brain is being rebalanced to notice that you feel calmer at the end. That part, at least, is easy to test for yourself.
Anuloma Viloma Timer is free on the App Store. No subscription necessary.