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Senior man playing chess and displaying reduced neurodegenerative condition

NAC and Brain Aging

N-acetyl-L-cysteine (NAC) restores cellular glutathione, a key antioxidant that drops with age. Studies suggest NAC reduces brain aging and the risk for neurodegenerative conditions.

Scientifically reviewed by: Dr. Gary Gonzalez, MD, in August 2023. Written by: Judith Sauer.

NAC, or N-acetyl-L-cysteine, is an amino acid that has become popular because of its ability to reduce respiratory illness and improve immunity.1-4

Researchers have discovered that NAC is also beneficial for brain health.

NAC accomplishes this by helping the body produce glutathione, a potent antioxidant.

With age, declining glutathione levels may accelerate the progression of neurodegenerative disorders.5,6

Using advanced brain imaging technology, scientists found that even a single-dose infusion of NAC significantly increased levels of glutathione in healthy individuals and those with chronic conditions.7

NAC has been shown in other studies to help protect brain function into older age and potentially reduce risk for neurodegenerative conditions.8

Glutathione and Brain Aging

Glutathione levels drop with advancing age.5

This leaves tissues vulnerable to oxidative stress and the development of chronic disease conditions.

The process is a vicious cycle.

As glutathione levels drop, the brain’s defenses weaken. It becomes more susceptible to oxidative injury. Higher levels of oxidative stress contribute to the progression of cognitive dysfunction.9

Autopsy studies show that patients with mild cognitive impairment and Alzheimer’s disease have depleted glutathione levels in certain areas of the brain.10

Decreased glutathione has been observed in other conditions such as Parkinson’s disease, schizophrenia, bipolar disorder, and even major depression.11-15

Studies show that NAC is an effective way to boost glutathione levels in the body.8

NAC Boosts Glutathione

N-acetyl-L-cysteine (NAC) is a compound that can replenish cellular glutathione levels.

Animal and human studies show that NAC can increase levels of glutathione in the brain.7,8,14,16

One human study used magnetic resonance spectroscopy, an imaging technology that is able to determine the concentrations of specific compounds in the brain of a living human.7

It showed that a single infusion of NAC led to an increase in brain glutathione from baseline, averaging an approximately 43% increase among all participants. The increase was greatest (averaging 55%) in subjects with Parkinson’s disease.

Whole-body blood antioxidant status was also significantly improved.

Maintaining glutathione levels into older age may help reduce the risk of age-related conditions caused by oxidative damage.6

Modulating Neurotransmitter Systems

Abnormalities of certain neurotransmitters can lead to the development of several conditions of the brain, from addiction to schizophrenia. N-acetyl-L-cysteine (NAC) has been found to have a beneficial impact on some of these neurotransmitters and their activity.8

For example, glutamate is the most abundant excitatory neurotransmitter in the brain. It plays vital roles in cognition, learning, memory, and more. But problems with improper glutamate neurotransmission occur in several disorders of the nervous system.

One of the most important glutamate receptors, the NMDA receptor, has been shown in animals to have a binding site for glutathione.17-19 By increasing glutathione levels, and via other mechanisms, NAC may help normalize the function of this glutamate receptor and improve the balance of glutamate signaling.8

In animal models of schizophrenia, NAC helps balance glutamate systems in the brain, improving symptoms of the disease.20

Because of these actions, NAC is being actively studied and shows promise in helping treat various neurological and neuropsychiatric conditions in humans.8,21-24

Reducing Homocysteine Levels

Boosting glutathione isn’t the only way NAC can help maintain brain health. It can also lower potentially dangerous levels of the amino acid homocysteine.25,26

Elevated levels of homocysteine are a risk factor for the development of cardiovascular disease and stroke. Research has revealed that high homocysteine is also a risk factor for cognitive decline and dementia.27-29

In 2018, a group of experts put out an International Consensus Statement declaring that elevated homocysteine is a modifiable risk factor for cognitive decline, dementia, and Alzheimer’s disease in older adults.29

Modifiable risk means that its levels can be changed by intervention and that this action may lower risk for these conditions.

Elevated homocysteine levels are common in older age.27 The good news is that oral NAC intake has clearly been shown to help reduce homocysteine levels in several clinical trials.25,26,30,31

The dose of NAC used in these studies varied from 600 mg to 4,000 mg per day. All dosages led to a significant decline in homocysteine levels.25,26,30,31 Higher doses led to greater reductions, up to as much as a 50% reduction.30

What you need to know

Protect the Brain with NAC

  • N-acetyl-L-cysteine (NAC) is a nutrient that can be used by the body as a precursor in the synthesis of new glutathione.
  • Glutathione levels tend to drop with age.
  • Low levels of glutathione are seen in the brains of those suffering from cognitive decline and dementia, as well as various other chronic conditions of the nervous system.
  • Brain scanning technology in humans has shown that NAC use boosts the production of glutathione in the brain, shielding against oxidative damage.
  • Studies have found that NAC acts by various other mechanisms to protect the brain, including lowering levels of harmful homocysteine and modulating neurotransmitter systems.
  • Human trials of NAC for dementia and other neuropsychiatric conditions are currently in progress. In animal studies, NAC has shown benefits in models of accelerated aging, Alzheimer’s disease, stroke, and Parkinson’s disease.

Trials of NAC for Disorders of the Brain

The use of NAC has shown clear benefits in several animal models of brain disease. Some examples include:

  • Improved cognition in a mouse model of accelerated aging,16
  • Prevention of learning/memory impairment in mouse models of Alzheimer’s disease,32,33
  • Up to a 50% reduction in stroke infarct size along with a similar improvement in neurological function in rodent models of stroke,34-36
  • Significantly reducing motor dysfunction in a rat model of Parkinson’s disease.37

Studies in roundworms show that NAC can extend lifespan.38,39

Human trials of NAC for brain-related conditions from dementia to psychiatric disorders are currently underway.

But there are already some early signs that using NAC to increase brain levels of glutathione may translate into improvements in symptoms of brain disease.

For example, one study looked at the use of NAC in the early stages of probable Alzheimer’s disease.40 It found that there was a significant improvement in brain executive functioning, such as verbal fluency.

This is an especially promising finding since lower verbal fluency at diagnosis has been shown to be predictive of death in Alzheimer’s patients.41

Studies also suggest that NAC can be useful in the management of various psychiatric conditions, including schizophrenia, substance abuse disorders, autism, depression, and obsessive-compulsive disorder.22,23

The results of human trials of NAC are expected to be released in coming years, but preliminary studies show that it has the potential to help maintain brain health well into older age.


Glutathione levels drop with age.

Research shows that patients with mild cognitive impairment and Alzheimer’s disease have lower glutathione levels in certain areas of the brain.

N-acetyl-L-cysteine (NAC) has been shown in both animal and human studies to boost glutathione levels.

By increasing glutathione, reducing homocysteine, and modulating neurotransmitter systems, NAC holds promise in reducing brain aging, maintaining brain health into older age, and managing various brain-related conditions.

If you have any questions on the scientific content of this article, please call a Life Extension Wellness Specialist at 1-866-864-3027.


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