Summary of Essentials: Breathing for Mental & Physical Health & Performance | Dr. Jack Feldman

Overview of Essentials: Breathing for Mental & Physical Health & Performance | Dr. Jack Feldman

This Huberman Lab Essentials episode revisits Andrew Huberman’s conversation with Dr. Jack Feldman — a leading respiratory neurobiologist — on how breathing is generated, how respiratory rhythms interact with brain state and behavior, and practical breathing tools for mental and physical health. The discussion covers respiratory mechanics and evolution, the brain circuits that create breathing rhythms, physiological sighs and gasps, links between breathing and emotion/cognition (including recent rodent work), and practical breathing practices and supplements (notably magnesium L‑threonate).

Key takeaways

• Breathing is generated by a small brainstem oscillator (the pre‑Bötzinger complex) that initiates inspiration via motor output to the diaphragm and intercostal muscles; expiration at rest is largely passive.
• Mammalian diaphragmatic breathing is mechanically efficient and likely enabled higher continuous oxygen supply that supported larger, energy‑hungry brains.
• Physiological sighs (one deep breath roughly every ~5 minutes) serve to reopen small alveoli and maintain lung surface area; periodic large breaths are important for lung health and were incorporated into mechanical ventilator strategies.
• Multiple pathways link breathing to brain state: respiratory rhythm signals via the olfactory system, vagal afferents (lung mechanoreceptors), chemoreception (CO2/pH), and volitional motor commands from cortex.
• Controlled breathing (slow, paced practices) can alter emotional and cognitive circuits. Rodent experiments that imposed slow‑breathing protocols showed reduced fear responses, supporting a causal mechanism beyond placebo.
• Magnesium L‑threonate (MgT) shows promising preclinical and some clinical signals for enhancing synaptic plasticity and cognition; dosing/tolerability and more research are needed.

Breathing mechanics, evolution, and brain centers

• Mechanical basics:
  • Inhale = diaphragm contracts (moves down) + ribcage expands → lung expansion → airflow in.
  • Exhale at rest = passive recoil of lung and thorax after inspiratory burst ends.
• Pre‑Bötzinger complex:
  • A small bilateral cluster in the brainstem that produces inspiratory rhythm; output drives diaphragm and inspiratory muscles.
• Active expiration and other oscillators:
  • A second oscillator (near facial nucleus / retrotrapezoid region) controls active expiration (e.g., forced exhale, exercise, “shh”).
• Evolutionary perspective:
  • Mammals have a diaphragm; earlier vertebrates (amphibians/reptiles) breathe differently (active expiration, passive inspiration) and have fewer alveoli.
  • Mammalian lungs pack enormous alveolar surface area (hundreds of millions of alveoli) into a small chest; diaphragm is mechanically efficient to ventilate that surface.

Physiological sighs, gasps, and clinical implications

• Sighs:
  • Occur roughly every ~5 minutes; function to reopen partially collapsed alveoli and preserve lung surface area and gas exchange.
  • Mechanical ventilation protocols improved survival once periodic large breaths (sighs) were added to mimic natural physiology.
• Gasps and overdose:
  • In dying mammals, breathing can slow and then large gasps (dying gasp) may auto‑resuscitate; suppression of these reflexes by drugs (e.g., barbiturates + alcohol) could contribute to fatal respiratory failure.
• Clinical relevance:
  • Vagus nerve signals and respiratory mechanics can influence mood and autonomic state; electrical vagus stimulation can reduce treatment‑resistant depression, implying physiological respiratory inputs can also matter.

How breathing affects brain state and emotion

• Multiple pathways mediate breathing’s influence on brain function:
  • Olfaction: nasal airflow modulates olfactory bulb rhythms, which project widely through the brain.
  • Vagal afferents: lung stretch and visceral signals reach the brain via the vagus and can modulate mood/anxiety circuits.
  • Chemosensation (CO2/pH): CO2 changes alter brain pH and strongly drive ventilatory control; chronic CO2 changes can provoke panic or anxiety.
  • Volitional motor signals: conscious control of breathing sends cortical signals that can have collateral effects on other brain circuits.
• Mechanistic rodent data:
  • Researchers trained mice to slow breathing (by ~10x relative rate) 30 minutes/day for 4 weeks. Those mice showed reduced fear responses in standard conditioning tests — effects comparable in magnitude to major amygdala manipulations.
  • Rodent studies avoid human placebo effects and allow mechanistic interrogation (circuit mapping, causality).
• Hypothesized mechanisms:
  • Respiratory rhythms may “disrupt” maladaptive neural circuits (e.g., depressive or fear circuits), enabling gradual weakening of those circuits with repeated practice — analogized to filling in or breaking a rut.

Practical breathing recommendations (what Feldman and Huberman use)

• Keep it simple and try short practices first:
  • Start with 5–10 minutes of paced breathing; see whether you feel better over a few days.
  • Common, simple protocol used by Feldman: box breathing — 5s inhale, 5s hold, 5s exhale, 5s hold (sometimes doubled to 10s each).
  • Other practices (Wim Hof, etc.) are useful to engage people but may be more intense for beginners.
• Timing:
  • Short practices can be used to restore alertness (e.g., after lunch slump) or reduce arousal/anxiety.
  • For therapeutic aims, longer or repeated practice may be needed (rodent protocol used 30 min/day for 4 weeks).
• Physiological sigh awareness:
  • Allow normal sighing; occasional deep breaths help maintain alveolar recruitment.
• Cautions:
  • Hyperventilation (excessive breathing) can lower CO2 and provoke anxiety or panic in susceptible individuals; paced slower breathing can restore CO2 and reduce anxiety in some patients.
  • Individuals on CNS‑depressant drugs must be cautious — suppression of protective respiratory reflexes can be dangerous.

Magnesium L‑threonate (MgT) — summary and evidence

• Mechanistic rationale:
  • Elevated intracellular/brain magnesium can enhance synaptic plasticity (LTP) and memory formation in cellular and animal models.
  • MgT is more bioavailable to brain tissues than many other magnesium salts and crosses barriers more effectively in preclinical work.
• Human data (small trial summary):
  • Double‑blind placebo‑controlled trial in people with mild cognitive decline: placebo arm improved ~2 years (placebo effect); MgT arm improved ~8 years on a general cognitive score (Spearman G‑factor) after three months. Results described as impressive but require replication and more detailed diagnostics.
• Practical notes:
  • MgT products are commercially available; dosing in trials is product‑specific and may be higher than what some people tolerate (GI side effects possible).
  • Feldman reports taking half a dose to reach high‑normal serum magnesium and avoid GI issues; individual tolerability varies.
• Caveats:
  • More large, independent clinical trials and mechanism work in humans are needed to confirm cognitive benefits and optimal dosing.

Limitations, open questions, and caveats

• Many human breathing studies face placebo and expectancy effects; rodent work helps establish causality but translation requires care.
• Specifics such as optimal breathing rates, session duration, and long‑term dosing/schedule for different conditions are still being determined.
• Some mechanistic pathways (e.g., exactly which projections mediate fear reduction with slow breathing) require more mapping and causal tests.
• Supplements like MgT show promise but need larger, replicable, well‑controlled clinical trials and attention to dosing/tolerability.

Practical action items (quick start)

• Try a brief daily breathing practice: 5–10 minutes of box breathing (5s inhale, 5s hold, 5s exhale, 5s hold). Use after lunch or during stress.
• Allow natural sighs; if you’ve been breathing shallowly for long periods, occasionally take a deeper breath to help alveolar recruitment.
• If you experience chronic anxiety with hyperventilation, consult a clinician; slowing breath and restoring CO2 can be therapeutic in many cases.
• Consider MgT only after researching product quality, dosing, and tolerability; consult your clinician if you are on medications or have renal issues.

Notable quotes

• “Every breath begins with neurons in the pre‑Bötzinger complex beginning to be active.” — Jack Feldman
• “We sigh about every five minutes…in order to maintain the health of our lung.” — Jack Feldman
• “My mice don’t believe in the placebo effect.” — Jack Feldman (on the value of mechanistic rodent studies)

This summary captures the main scientific points and actionable recommendations from the conversation. For practitioners and listeners: short, regular breathing practice is low‑cost, low‑risk, and often subjectively helpful; mechanistic research is rapidly advancing and supports real neural and behavioral effects beyond placebo.