To understand why CO2 in our blood is actually necessary, for our biochemistry to work right, please read https://www.kobo.com/us/en/ebook/breath-28
THIS is why the slow-deep breaths of yoga are actually optimal.
One's breathing has more effect on one's blood-CO2 than does the air's CO2-levels, obviously.
The deterioration of our breathing-habits goes along with the deterioration of our fitness, our posture, our absence-of-chewing ( thanks to processed-foods ), etc.
That is an important book.
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