During an episode of QI last week Stephen Fry brought up alternate nostril breathing. Supposedly, breathing in through one nostril sends oxygen to one brain hemisphere and through the other to the other brain hemisphere. This is "demonstrable" by checking for improved cognitive function related to each of the two hemispheres.
I just spent five minutes trying to kill off my left hemisphere, through oxygen deprivation, by blocking a nostril - no luck. Don't both nostrils send air to the lungs in equal amount?
The yoga literature seems awash with breathing exercises for alternate nostril breathing. For example http://bit.ly/81L2XC describes right nostril breathing as "to increase the Pranic energy , the physical energy, to revitalize the body. It increases the efficiency of digestive system, also boosts the nervous system." This is a slightly different claim from the idea that alternate nostril breathing can enhance brain function in one the two hemispheres.
Am I missing something or is this totally rubbish? I did find two studies on this subject done by the Yoga institute, neither of which appear to have controlled for the placebo effect.
Any test that compared cognitive function during left and right nostril breathing would have to:
- Ensure that subjects weren't influenced by the "expected" better spatial reasoning associated with one hemisphere or the better verbal function of the other
- Ensure that the mental gymnastics required to breathe only though a single nostril was not affecting cognitive ability (ie. holding it closed with a left or right hand or closing one nostril without the use of the hands).
- Postulate a possible, plausible causative effect such as oxygen absorption directly into the brain from the back of nose.
Is there any reliable evidence to support, what appears to be an absurd claim, that breathing though a single nostril has any benefit over breathing through both at the same time?
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