Carbon dioxide is usually treated as something the body needs to get rid of.
Your cells produce it as they use oxygen for energy. Your blood transports it to your lungs. Then you breathe it out.
But carbon dioxide isn’t merely a waste product.
Within a healthy range, the CO₂ naturally produced by your body helps regulate blood pH — in other words, its acid-alkaline balance — as well as oxygen delivery and blood flow through the brain.
And researchers now believe that carefully controlled changes in carbon dioxide may help the brain flush out two proteins strongly associated with Alzheimer’s disease.
In a small human study, rhythmic exposure to higher levels of CO₂ appeared to activate the brain’s natural waste-removal system. It increased signs of beta-amyloid leaving the brain and appeared to improve tau clearance among participants who already had elevated tau.
If the findings hold up in larger studies, they could represent an entirely new way to target one of the defining problems in Alzheimer’s.
A possible way to help the brain clean house
The brain has a waste-removal network known as the glymphatic system.
Cerebrospinal fluid moves through brain tissue, collecting proteins, metabolic waste and other unwanted substances. That waste is then transported out of the brain and toward the bloodstream, where the body can process and eliminate it.
The glymphatic system is especially active during deep sleep. This may be one reason consistently poor sleep has been associated with cognitive decline and a greater risk of dementia.
Researchers have been looking for ways to activate this cleaning process while people are awake. One possibility involves carbon dioxide.
As CO₂ levels rise, blood vessels in the brain expand. When CO₂ falls, the vessels narrow again. Researchers suspected that repeatedly raising and lowering CO₂ could create a pumping motion that helps move cerebrospinal fluid through the brain.
To test the theory, Dr. Sephira Ryman and colleagues from The University of New Mexico School of Medicine, the Mind Research Network (MRN) — a division of Lovelace Biomedical Research Institute — and the New Mexico Veterans Affairs Health Care System conducted a small 12-person study.
Eight had normal tau levels. Four had greater tau buildup, and three members of that group had mild cognitive impairment, which can sometimes precede dementia.
Participants wore masks while their brains were scanned. Every 35 seconds, the masks switched between ordinary air and air containing a higher concentration of carbon dioxide. The full session lasted 30 minutes.
This rhythmic CO₂ exposure caused blood vessels in the brain to repeatedly expand and contract, apparently stimulating the glymphatic system.
What researchers saw afterward could have important implications for Alzheimer’s.
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Evidence that damaging proteins were leaving the brain
After the session, all 12 participants had higher levels of beta-amyloid in their blood.
That might sound bad at first. But the researchers believe the increase occurred because the protein had moved out of the brain and entered the bloodstream.
Beta-amyloid is naturally produced in the brain. But when too much accumulates, it can stick together and form the plaques that are one of the hallmarks of Alzheimer’s disease.
The researchers also saw signs that tau clearance had improved among the four participants who began with elevated tau.
Tau normally helps maintain the internal structure of nerve cells. However, abnormal tau can form tangles that disrupt communication between brain cells and contribute to their eventual death.
Why this could be a big step
The researchers are exploring rhythmic CO₂ delivery as a potential treatment for neurodegenerative diseases. Work is also underway on a prototype device that could administer precisely controlled breathing treatments.
Larger and longer trials will be needed to determine whether repeated sessions produce lasting changes — and, most importantly, whether those changes preserve thinking and memory.
Research is also exploring whether controlled breathing could create smaller, natural fluctuations in carbon dioxide and cerebrospinal fluid flow.
Slow abdominal breathing, such as that practiced in yoga, tai chi, qigong and meditation, changes the rhythm and mechanics of respiration. Researchers say these practices may stimulate oscillations in cerebrospinal fluid that could potentially activate glymphatic movement while people are awake.
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Give your brain its best chance to clean house
The experimental treatment used in the study was precisely controlled under medical supervision, so deliberately inhaling CO₂ or restricting your breathing is not a safe way to reproduce the effect.
For now, deep, restorative sleep remains one of the most established ways to support the brain’s natural waste-clearance cycle — making it especially important to address conditions such as sleep apnea that repeatedly interrupt sleep. But it’s not the only way…
Regular physical activity can help. In a human study, 12 weeks of cycling enhanced the flow of fluid through the brain’s lymphatic drainage vessels. And a recent mouse study showed that simple abdominal contractions can help cerebrospinal fluid wash over the brain.
Breathing through your nose also has advantages…
When your nasal passages are clear, nasal breathing adds natural resistance that encourages slower, more controlled respiration and reduces the risk of over-breathing that can lower CO₂ too far.
The nose and paranasal sinuses also produce nitric oxide. As you inhale through your nose, small amounts of this gas travel toward the lungs, where nitric oxide helps widen blood vessels and may support blood flow and oxygen exchange.
That does not mean nasal breathing has been shown to clear amyloid or tau. But it may help maintain the steady breathing patterns and balanced gas exchange. Mouth breathers may not reap these full benefits.
This new research certainly changes the way we might think about every breath.
Oxygen may be the gas that keeps us alive. Carbon dioxide is the gas we exhale.
Yet between the inhale and the exhale, CO₂ helps regulate how blood and oxygen reach the brain — and may even provide the pulse needed to help wash damaging proteins away.
Sources
CO2 Treatments May Clear Alzheimer’s Proteins From the Brain — HuffPost UK
Researchers Study Whether Intentionally Manipulating Blood Carbon Dioxide Levels Might Enhance Brain Health — University of New Mexico Health Sciences Center
Long-term physical exercise facilitates putative glymphatic and meningeal lymphatic vessel flow in humans — Nature Communications
Nitric Oxide and the Paranasal Sinuses — The Anatomical Record
FAQ: CO2 Treatments and protein markers of Alzheimer’s
In a small study involving 12 people, controlled pulses of higher-CO₂ air appeared to activate the brain’s glymphatic waste-removal system. Researchers found signs that beta-amyloid moved from the brain into the blood and that tau clearance improved among participants with elevated tau. Larger trials are needed to determine whether the effect can produce lasting benefits.
The researchers believe the increase occurred because beta-amyloid had moved out of the brain and entered the bloodstream. Once brain waste reaches the circulation, other organs can help process and eliminate it. The finding does not mean that higher blood beta-amyloid is always beneficial; its significance depends on why and when it rises.
The glymphatic system is a waste-removal pathway that uses cerebrospinal fluid to carry proteins, metabolic byproducts and other debris away from brain tissue. It is thought to become especially active during deep sleep.
No. The study used precisely controlled concentrations of carbon dioxide while participants were monitored. Slow abdominal breathing may create smaller natural changes in CO₂ and cerebrospinal fluid movement, but it has not been shown to clear beta-amyloid or tau in the same way.
Nasal breathing has not been proven to prevent Alzheimer’s or remove its associated proteins. It may encourage slower respiration and carries nitric oxide produced in the nose and sinuses toward the lungs, which may support blood flow and oxygen exchange. It should be viewed as one part of healthy respiration, not an Alzheimer’s treatment.
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