he observed a consistent lifestyle habit among the Native American communities he encountered: a preference for nose breathing over mouth breathing. He also observed that they had perfectly straight teeth. He repeatedly heard that this was because they believed that mouth breathing made an individual weak and caused disease, while nasal breathing made the body strong and prevented disease. He also observed that mothers repeatedly closed the mouth of their infants while they were sleeping, to instill nasal breathing as a habit. Yoga Yogis such as B. K. S. Iyengar advocate both inhaling and exhaling through the nose in the practice of yoga, rather than inhaling through the nose and exhaling through the mouth. They tell their students that the "nose is for breathing, the mouth is for eating." See also Aerophagia Breath-holding spell Hiccup References Further reading External links Effects of Mouth Breathing (and role of nasal breathing) - WebMD (video clip) Nose Orthodontics Respiration Respiratory physiology Respiratory system