The heart and brain are often treated as separate entities in medicine—cardiologists focus on one, neurologists on the other. Yet, they’re deeply intertwined. Your brain’s health hinges on its blood supply, which relies entirely on your cardiovascular system [1]. Poor circulation starves the brain, leading to immediate issues like brain fog, poor focus, memory lapses, anxiety, or fatigue. Over time, chronic poor circulation can contribute to serious conditions like Alzheimer’s or Parkinson’s [2].

Circulation: The Lifeblood of Your Body

Your body houses roughly 30 trillion cells, and over 80% of them are red blood cells. These cells deliver oxygen and nutrients, remove carbon dioxide and waste, and transport hormones, heat, and immune cells throughout the body [3].

“More than 80% of all cells in the human body are red blood cells.”
— Sender et al., PLoS Biology, 2016 [4]

Your circulatory system is a marvel. If laid end-to-end, its blood vessels—arteries, veins, and capillaries—would stretch over 100,000 kilometers, enough to wrap Earth two and a half times. This vast network ensures every cell gets the oxygen and nutrients it needs. The brain, despite being just 2% of your body weight, demands 20% of your oxygen and glucose. Without steady blood flow, brain cells can die within minutes [5]. The heart and circulatory system are the brain’s lifeline.

CO₂: The Brain’s Blood Flow Maestro

While oxygen is critical, carbon dioxide (CO₂) is the key regulator of cerebral blood flow. Your brain’s blood vessels respond acutely to CO₂ levels. Higher CO₂ dilates vessels, boosting blood flow and oxygen delivery. Lower CO₂, often from overbreathing or inactivity, constricts vessels, reducing oxygen to the brain even if oxygen levels are normal [6].

“CO₂ is the most potent physiological regulator of cerebral blood flow.”
— Willie CK et al., Journal of Physiology, 2014 [6]

“For every 1 mmHg drop in arterial CO₂, cerebral blood flow decreases by 2–4%.”
— Ainslie PN & Duffin J, Journal of Physiology, 2009 [7]

The Bohr Effect: CO₂ and Oxygen Delivery

Overbreathing to “get more oxygen” can backfire. Low CO₂ levels cause hemoglobin to cling to oxygen, reducing its release to tissues, especially the brain. This is the Bohr effect, a principle established over a century ago and still central to physiology [8].

“Low CO₂ makes hemoglobin hold onto oxygen more tightly, impairing delivery to tissues—especially the brain.”
— Bohr et al., 1904; confirmed in modern physiology [8]

Why Circulation Matters for Mental Clarity

When CO₂ levels drop, blood flow to the brain decreases, leading to brain fog, dizziness, anxiety, and poor cognitive performance. Chronic low CO₂ from subtle overbreathing may contribute to:

• POTS and orthostatic intolerance
• Migraines and tension headaches
• Alzheimer’s and Parkinson’s
• Depression, anxiety, and panic disorders
• ADHD, mental sluggishness, and fatigue

Support Your Brain with Every Breath

To optimize brain health, focus on circulation-friendly habits. Breathe slowly and gently through your nose to maintain healthy CO₂ levels. Incorporate low-intensity activities like walking to boost circulation and promote calm. A healthy heart ensures a sharp mind—nurture both with every breath and step.

Footnotes:

[1] Nat Rev Neurosci. 2011 Nov 3;12(12):723-38. doi: 10.1038/nrn3114. PMID: 22048062; PMCID: PMC4036520.

[2] Neurol Res. 2004 Jul;26(5):517-24. doi: 10.1179/016164104225016254. PMID: 15265269.

[3] Crit Care. 2005;9 Suppl 4(Suppl 4):S3-8. doi: 10.1186/cc3751. Epub 2005 Aug 25. PMID: 16168072; PMCID: PMC3226163.

[4] PLoS Biol. 2016 Aug 19;14(8):e1002533. doi: 10.1371/journal.pbio.1002533. PMID: 27541692; PMCID: PMC4991899.

[5] Geroscience. 2017 Aug;39(4):465-473. doi: 10.1007/s11357-017-9980-z. Epub 2017 Jun 3. PMID: 28578467; PMCID: PMC5636768.

[6] J Physiol. 2014 Mar 1;592(5):841-59. doi: 10.1113/jphysiol.2013.268953. Epub 2014 Jan 6. PMID: 24396059; PMCID: PMC3948549.

[7] Am J Physiol Regul Integr Comp Physiol. 2009 May;296(5):R1473-95. doi: 10.1152/ajpregu.91008.2008. Epub 2009 Feb 11. PMID: 19211719.

[8] Skandinavisches Archiv Für Physiologie 16.2 (1904): 402-412.

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