Why Breathing Out Is Even More Important Than Breathing In
When we think about breathing, we often focus on inhaling — taking in fresh air, filling our lungs with oxygen. But science reveals a surprising truth: breathing out, or exhalation, might actually be the more important half of the breath cycle for our health, stress management, and overall well-being.
Here’s why exhalation matters so much — and how doing it properly can transform both your mind and body.
Exhalation Removes Carbon Dioxide and Balances Blood Chemistry
The primary function of exhalation is to eliminate carbon dioxide (CO₂), a metabolic waste product. When CO₂ isn’t efficiently expelled, it accumulates in the blood, potentially leading to a condition known as respiratory acidosis — a dangerous shift in blood pH levels that can affect multiple organ systems (Guyton & Hall, 2016).
Maintaining a proper balance between oxygen and carbon dioxide is essential for keeping the blood pH stable, typically around 7.35–7.45. Surprisingly, at rest, our drive to breathe is more influenced by rising CO₂ levels than by a lack of oxygen. In other words, your body demands exhalation to clear CO₂ more urgently than it needs to inhale fresh oxygen (West, 2015).
Longer Exhalations Promote Relaxation and Stress Relief
Extending the duration of your exhalation has powerful physiological effects. Longer, slower exhalations stimulate the vagus nerve, which activates the parasympathetic nervous system — the body’s built-in relaxation mode. This activation leads to a reduction in heart rate, decreased anxiety, and improved emotional regulation (Porges, 2011).
Dr. Andrew Huberman, a neuroscientist at Stanford University, emphasizes the effectiveness of longer exhalations as a tool for immediate stress relief. His research indicates that when the exhale phase is longer than the inhale, the body naturally shifts into a calm, balanced state (Huberman Lab Podcast, 2022).
In mindfulness-based practices such as meditation and Sophrology, breathwork often centers on controlled, extended exhalations. These methods have been shown to not only manage stress but also enhance mental clarity and emotional resilience.
Nasal Exhalation Offers Additional Health Benefits
The manner in which we exhale is equally important. Breathing out through the nose, rather than the mouth, provides several additional benefits:
- Preservation of nitric oxide (NO): The nasal passages produce nitric oxide, which helps dilate blood vessels and improve oxygen uptake in the lungs (Lundberg, Weitzberg, & Gladwin, 2008).
- Improved autonomic regulation: Nasal breathing slows the respiratory rate, enhancing baroreflex sensitivity, which supports cardiovascular health (Spicuzza et al., 2000).
- Promotion of calmness: While mouth breathing is often linked to the sympathetic “fight-or-flight” response, nasal breathing encourages parasympathetic activity, anchoring the body in a state of relaxation (Porges, 2011).
Therefore, especially during rest, sleep, or relaxation techniques, nasal exhalation is highly recommended.
4. When Mouth Exhalation Is Useful
Although nasal breathing is optimal in most circumstances, there are instances where mouth exhalation can be beneficial. One such situation is during high-intensity physical activity, where rapid expulsion of CO₂ is necessary to meet the body’s increased metabolic demands.
Additionally, Dr. Huberman recommends a technique called the “physiological sigh” for rapid emotional reset: take two inhales through the nose (one deep breath followed by a short, sharp second inhale), then exhale slowly and fully through the mouth. This method has been scientifically shown to reduce stress and restore calm in under a minute.
Breathing is a natural, automatic process, but that doesn’t mean we should ignore it. Scientific research makes it clear that exhalation deserves as much, if not more, attention than inhalation.
By focusing on longer, slower, and nasal-based exhalations, you can:
- Maintain healthy blood chemistry,
- Soothe your nervous system,
- Support heart health,
- And manage stress more effectively.
As Dr. Huberman notes, “If you want immediate control over your mental and physiological state, controlling your exhale is one of the most powerful levers you have.”
So the next time life feels overwhelming, pause. Let go of your breath slowly, fully, and mindfully — and notice how everything begins to shift.
References
Guyton, A.C., & Hall, J.E. (2016). Textbook of Medical Physiology (13th ed.). Elsevier.
West, J.B. (2015). Respiratory Physiology: The Essentials (10th ed.). Lippincott Williams & Wilkins.
Porges, S.W. (2011). The Polyvagal Theory: Neurophysiological Foundations of Emotions, Attachment, Communication, and Self-Regulation. W.W. Norton & Company.
Lundberg, J.O., Weitzberg, E., & Gladwin, M.T. (2008). The role of nitric oxide in human physiology. American Journal of Respiratory and Critical Care Medicine, 178(6), 587-593.
Spicuzza, L., Gabutti, A., Porta, C., Montano, N. (2000). Slow Breathing Reduces Chemoreflex Response to Hypoxia and Hypercapnia, and Increases Baroreflex Sensitivity. Journal of Hypertension, 18(9), 1445-1449.
Huberman, A. (2022). The Science of Stress, Calm, and Mental Resilience. Huberman Lab Podcast.
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