Your Brain Is Running Low on Something Important (Vol. 03)
- May 12
- 7 min read
Updated: May 13
What NAD⁺ decline means for the aging brain, what the science shows, and why lifestyle may be the missing piece researchers are looking for.
TA Medical Research Team · Vol. 03 · 5 min read · Brain Health & Longevity Science
There is a conversation happening right now in neuroscience laboratories across the United States, Japan, Europe, and Australia. It involves a molecule your body depends on more than almost any other — and a question that has stubbornly resisted a clean answer. The molecule is NAD⁺. The question is whether restoring it can protect the aging brain. And the reason it is more complicated than it might seem has everything to do with what stands between your bloodstream and the neurons inside your skull.
01 The Most Energy-Hungry
Organ You Own
Your brain is roughly two percent of your body weight and consumes about twenty percent of the energy you produce. Every thought, every memory retrieved, every moment of sustained focus draws on a continuous supply of cellular fuel generated by mitochondria inside neurons. NAD⁺ sits at the centre of that system — powering mitochondrial energy production, activating the sirtuin proteins that govern how neurons respond to stress and damage, and enabling the repair systems that fix breaks in neuronal DNA before they accumulate into something more serious.
By the time most people reach their fifties, they have roughly half the NAD⁺ they had in their twenties. That is not a marginal change. It is a significant reduction in the resource that keeps the brain’s maintenance systems running — and researchers studying Alzheimer’s disease and age-related cognitive decline increasingly point to this decline as one of the upstream conditions that makes the aging brain more vulnerable.
02 What Animal Research Has Shown
In mouse models of Alzheimer’s disease, NMN has been shown to improve memory and learning, reduce neuroinflammation, preserve mitochondrial function inside aging neurons, and slow the protein accumulation most closely associated with cognitive decline. Studies on hippocampal neurons — the cells most critical to memory and most vulnerable to aging — have shown meaningful preservation compared to unsupplemented controls. The consistency of these findings across multiple independent research groups is one reason brain aging has become one of the most active frontiers in NAD⁺ research globally.
Brain Outcome | Animal Evidence | Current Human Status |
Memory & learning | Strong in multiple models | Human trials show variable results |
Neuroinflammation | Consistently reduced | Mechanisms still being mapped |
Mitochondrial function | Preserved in aging models | BBB delivery still unclear |
Hippocampal neurons | Preserved in aging studies | Human neuroimaging underway |
Blood NAD⁺ elevation | Blood NAD⁺ elevation observed | Yes — human studies confirmed increased blood NAD⁺ |
“The Brain’s Protective Checkpoint”
— What Is the Blood-Brain Barrier?
The brain is the most protected organ in the body. Blood circulates throughout the entire body, delivering nutrients and oxygen to every cell, but when it comes to what is allowed to enter the brain, there is an especially strict screening system in place. A very fine layer of cells lining the brain’s blood vessels — this is the mechanism known as the “blood-brain barrier.”
This barrier exists to prevent harmful substances and pathogens from entering the brain. At the same time, however, it can also block things we actually want to deliver there, such as drugs and nutrients. Whether a substance can pass through depends greatly on the size and shape of the molecule, as well as its lipid solubility — in other words, how easily it dissolves in fat or oil.
The basic structure of this barrier is fundamentally the same in both mice and humans. So then, why do the results seen in mouse experiments not necessarily apply directly to humans? The reason lies not in the barrier itself, but in the differences in the environment beyond it.
The mice used in research are, in many cases, young and healthy, living under tightly controlled conditions in which diet, sleep, and stress are carefully regulated. Even when adjusted for body weight, the doses used in mouse studies are often several times higher than those typically taken by humans. In addition, because mice have much faster metabolic rates, the cycle of NAD⁺ production and utilization is also much faster.
Furthermore, in animal experiments, researchers can directly extract and measure brain tissue after administration. In humans, however, the only practical option is usually to measure NAD⁺ levels in the blood, making it difficult to directly confirm what is actually happening inside the brain itself.
In other words, the issue is not simply “whether it can cross the barrier,” but whether the brain on the other side is in a condition capable of properly utilizing the NAD⁺ that arrives there.
03 Where the Picture Gets
More Complicated
The data from animal studies is impressive. However, as mentioned earlier, experimental conditions and metabolic rates differ greatly between mice and humans, and the methods available for directly measuring what is happening inside the brain are still limited. Human studies have consistently confirmed that NMN increases NAD⁺ levels in the bloodstream. However, the blood and the brain are not the same compartment — and to what extent that increase is directly reaching neurons has still not yet been fully clarified.
WHERE THE SCIENCE CURRENTLY STANDS In human studies, it has been consistently confirmed that taking NMN increases NAD⁺ levels in the bloodstream. However, how effectively that NAD⁺ is utilized within the brain may vary greatly depending on the condition of the brain at that particular time — including levels of inflammation, the health of the mitochondria, and the cellular environment shaped by everyday lifestyle habits. In other words, NMN helps supply fuel to the brain. But whether that fuel can be utilized to its fullest potential depends on the brain’s own “state of readiness” to receive and use it. This is not a reason to stop taking NMN. Rather, the question researchers are now actively trying to answer is: under what conditions can NMN work more effectively for the brain? |
Researchers are now working to better understand how rising NAD⁺ levels influence different tissues throughout the body, including the brain. Current evidence also suggests that sleep, exercise, inflammation, and overall metabolic health may influence how effectively cells are able to use NAD⁺ for repair, energy production, and maintenance.
04 The Conditions That Matter
Research points consistently to four conditions that determine whether elevated NAD⁺ translates into meaningful biological benefit — particularly for the brain.
 | Movement. Exercise activates AMPK — a cellular energy sensor that directly stimulates NAD⁺ production and use. For the brain, it increases cerebral blood flow, reduces neuroinflammation, and drives BDNF production, which supports neuronal survival and new connection formation. A body generating no demand for cellular repair is a body that will make limited use of restored NAD⁺. |
 | Reducing inflammation. CD38 — an enzyme activated by inflammatory signals — is one of the primary consumers of NAD⁺ in the body. Chronic low-grade inflammation keeps it active, continuously depleting the supply regardless of supplementation. A diet based on whole foods, reduced refined sugar, and plant diversity works directly against this drain — and reduces neuroinflammation in the process. |
 | Sleep. Deep sleep is when the brain conducts most of its cellular maintenance — clearing metabolic waste through the glymphatic system, running DNA repair, and processing NAD⁺-dependent recovery. Consistently poor sleep leaves these systems perpetually behind. Supplementation alone cannot compensate for what disrupted sleep takes away. |
 | Minimising depletion. Excess alcohol, chronic stress, and high caloric intake without physical demand all actively deplete NAD⁺. NMN works most effectively when the conditions driving that excess depletion are also being addressed. |
05 Thinking About This as a System
What the research describes is a system rather than a single lever. Movement creates demand for restored NAD⁺. Diet and sleep protect the supply and reduce the forces depleting it. NMN replenishes what aging and modern life take away. Each element makes the others more effective — and the gap between animal results and human trials may reflect, at least in part, the inconsistency of lifestyle conditions across real-world populations rather than a fundamental failure of the biology.
THE FRAMEWORK NMN restores the NAD⁺ that aging depletes. Movement creates the demand that makes it biologically meaningful. Diet and sleep protect the supply and reduce the forces working against it.
More NAD⁺ alone is not enough. Brain cells must also remain healthy enough to repair damage, maintain mitochondria, and properly use that energy over time. |
06 Where the Research Goes From Here
New neuroimaging technologies are now being developed that may allow researchers to measure NAD⁺ directly inside the living human brain. Using advanced forms of magnetic resonance imaging (MRI), scientists are beginning to track NAD-related signals inside brain tissue without the need for surgical sampling — helping close the gap between blood measurements and what is actually happening inside neurons. Several research groups are now designing studies that examine not only NMN supplementation itself, but also how sleep, exercise, inflammation, and metabolic health may influence the brain’s response to NAD⁺. The direction of the science is not away from NAD⁺ as a target for brain health. It is toward a deeper understanding of the conditions under which it may produce its most meaningful effects.
The science is still unfolding. Brain aging may be more changeable than we once believed.
KEY RESEARCH REFERENCES
Gao L. et al. (2024). NMN preserves mitochondrial function in Alzheimer’s models. Cell Death & Disease, Nature Publishing Group.
Science Advances (2025). NAD⁺ reverses Alzheimer’s neurological deficits via RNA splicing and tau pathology pathways.
Mills K.F. et al. (2022). Oral NMN increases brain NAD⁺ in animal models. Nutrients / MDPI.
Yi L. et al. (2023). Efficacy and safety of β-NMN in healthy middle-aged adults. GeroScience, 45(1), 29–43.
Verdin E. (2015). NAD⁺ in aging, metabolism, and neurodegeneration. Science, 350(6265), 1208–1213.
Rajman L., Chwalek K. & Sinclair D.A. (2018). Therapeutic potential of NAD-boosting molecules. Cell Metabolism, 27(3), 529–547.
This article is for educational and informational purposes only. It reflects published peer-reviewed research and is not intended as medical advice. Please consult a healthcare professional for personal health decisions.
TA Medical · NMN Research Frontline · Research Information Media · Vol. 03
