Are you aware of how you are breathing? A study by the Federal University Sergipe in Brazil showed a higher occurrence of learning disabilities among mouth breathers, concluding that mouth breathers are more likely to have learning difficulties than nasal (鼻的) breathers.
While smell is a very important sense, the nose has other important responsibilities. When someone breathes through the mouth, they are ignoring several important functions of the nose. To name a few, the nose warms and wets the air you breathe to make it more suitable for your lungs. Nasal breathing also increases levels of nitric oxide (一氧化氮), a key molecule (分子) used throughout the body. Another very important function of the nose is that it controls airflow and helps prevent over-breathing. So how can you over breathe? Breathing in and out more air than necessary results in a state of reduced carbon dioxide (二氧化碳) in the blood. Brain function will be damaged when you breathe too much. The loss of carbon dioxide from improper breathing isn't serious enough to be easily noticeable. But over time the habit can take its toll on the brain and body.
Patrick McKeown, author of the Oxygen Advantage explains that if we breathe a relatively small amount of air by breathing slowly through the nose, we increase the amount of carbon dioxide inside us and can deliver more oxygen to our muscles and organs, including the heart and the brain. Scott Jurek, one of the famous marathon runners in the world, says that for runners，one of the most important things to learn is to practice nasal breathing. Anthropologist (古人类学家) Wade Davis has studied and lived with fifteen different groups of native people. Davis was most impressed by the fact that these hunters never opened their mouths to breathe during the hunt.
In the animal world, mouth breathing is rarely seen unless it is falling ill. In humans, chronic (长期的) mouth breathing can lead to cavities (龋洞), gum disease, lowered immune function, digestive disturbances, poor sleep quality, and can result in crooked teeth and even poorly developed facial structure.
