Can 25 Minutes of Silent Meditation “Flush” the Brain’s Waste?

By The Mindful Leader Team

Neurofluid Circulation Changes During Focused-Attention Meditation
PNAS · December 2025 · Vanderbilt University (Keating, Vago et al.) 

People often treat meditation formats as interchangeable. Apps, guided sessions, silent sits, breathwork, as though all paths deliver the same benefits. But neuroimaging research is beginning to show that specific physiological systems may only respond under particular conditions. A new study examined whether sustained, silent awareness of breath meditation could alter cerebrospinal fluid flow through the brain.

The Finding

Twenty-five minutes of awareness of breath meditation reduced regurgitant cerebrospinal fluid (CSF) flow through the cerebral aqueduct and increased low-frequency CSF oscillations near the skull base. These patterns resemble fluid dynamics observed during sleep and have been associated with waste clearance in animal models. The effect was observed among experienced meditators practicing silent, self-guided breath awareness, not among controls who voluntarily slowed their breathing to the same rate.

The breath controls, people with minimal meditation experience, matched the meditators' slower respiration rate but showed no change in CSF flow. This suggests that the physiological effect depends on something beyond breathing slowly. The attentional quality of the practice, not just the respiratory slowdown, appears to be what drives the change. The study did not measure whether these fluid changes actually remove waste or improve brain health over time.

What This Might Mean for Practice

A meditation teacher designing an eight-week program now has evidence that 25 minutes of silent, self-guided awareness of breath meditation produces a measurable physiological effect that other formats tested in this study did not. This does not prove that the practice prevents cognitive decline or that shorter formats provide no benefit, but it does suggest that silence and self-guidance affect the brain in ways that passive relaxation or controlled breathing may not.

It's also worth noting that the meditators in this study were not casual practitioners. They had deep, sustained practices, the kind of experience built over years of committed daily sitting and retreat practice. 

The Study

Researchers at Vanderbilt University recruited 23 experienced meditators and 27 controls with minimal meditation experience. All participants underwent two 25-minute MRI sessions.

Meditators practiced mind-wandering during the first session and silent, self-guided awareness of breath meditation in the second. Controls either repeated mind wandering twice (n=13) or practiced mind wandering followed by voluntary breath slowing (n=14).

The study used phase-contrast MRI to measure cerebrospinal fluid flow through the cerebral aqueduct, a narrow channel connecting brain ventricles, and BOLD MRI to assess CSF oscillations near the cervicomedullary junction and hemodynamic activity across gray matter.

Key Findings

• CSF flow became less turbulent. During meditation, the total volume of cerebrospinal fluid moving through the aqueduct decreased (from 4.60 to 4.17 mL/min). This was driven by reduced backward flow during the heart's relaxation phase, a pattern opposite to what occurs in aging and neurodegeneration, where backward flow increases. Forward flow remained unchanged.
• The effect was specific to meditation. Controls who simply slowed their breathing showed no change in CSF flow, suggesting the effect depends on sustained attentional focus or meditation expertise, not respiration rate alone.
• Low-frequency CSF oscillations increased. CSF signal power near the skull base rose in a specific frequency band (3.7–5.3 cycles per minute). Prior sleep research has observed similar oscillations and linked them to waste clearance in animal models.
• CSF and brain activity became coordinated. During meditation, CSF movement near the skull base synchronized inversely with hemodynamic activity across gray matter, a coupling pattern previously reported during sleep but absent during ordinary mind wandering.

What the Study Did Not Measure

The phrase "flush the brain" is metaphorical. The study cannot establish whether the observed fluid changes actually clear waste or support brain health over time; it simply measured fluid dynamics. Although the patterns resemble those observed during sleep, a state in which glymphatic clearance has been demonstrated in animal models, this study did not measure metabolite clearance, amyloid removal, or any clinical outcome. Claims that meditation "cleanses the brain" or "prevents cognitive decline" go beyond what was measured.

Implications for Learning, Practice, and Program Design

The study observed a distinct pattern of cerebrospinal fluid movement during 25 minutes of silent, self-guided breath awareness. This pattern did not emerge when participants with limited meditation experience simply slowed their breathing, suggesting that respiration rate alone does not account for the effect. Sustained attentional focus or accumulated meditation experience may play a role.

A facilitator might frame the finding this way: "Recent research suggests that 25 minute, silent, awareness of breath meditation may influence cerebrospinal fluid movement in patterns similar to those seen during sleep. We don't yet know whether this leads to long-term health benefits, but it points to a measurable physiological effect under specific conditions." Avoid claims such as, "This study proves meditation flushes toxins."

What to Watch Next

The researchers call for future investigations, including:

• Whether different meditation styles, including Open Monitoring, produce similar neurofluid changes, or whether the effect is unique to awareness of breath practice.
• Longitudinal studies to determine how duration and consistency of practice influence neurofluid dynamics over time, and whether novice practitioners can develop this response.
• Whether these CSF changes have clinical relevance for populations with neurodegenerative diseases or sleep disorders, where impaired neurofluid circulation is already implicated.

This article is part of our Research & Trends Series where we share the latest research and studies shaping our field.