In a recent study, researchers found that inhaling menthol boosted the cognitive ability of mice with Alzheimer’s. This unexpected discovery points to a potential new treatment option for this devastating disease.

A recent study using animal models found that short, repeated exposure to menthol can affect the immune system and prevent the cognitive deterioration that happens in people with Alzheimer’s disease.

Researchers discovered that mice’s levels of interleukin-1-beta, a protein involved in inflammatory response, dropped when they smelled menthol. They specifically observed a decrease in the protein interleukin-1-beta (IL-1β), which aids in controlling the body’s inflammatory response, which can provide natural defense but can also cause damage if improperly managed.

Additionally, researchers were able to improve cognitive function in the mice exhibiting Alzheimer-like symptoms by inhibiting this protein using a drug used to treat autoimmune diseases.

The findings demonstrate how immune modulators and scents may help treat this neurodegenerative illness.

Frontiers in Immunology published the research [1].

The Link between Menthol and Alzheimer’s

In the recent study, the researchers aimed to investigate the relationships among the immunological, central nervous, and olfactory systems. Their previous research reported that frequent exposure to menthol improved the immunological response in mice [2]. Here, the team concentrated on determining if it may also enhance their cognitive capacities.

During this investigation, researchers genetically modified mice to develop Alzheimer’s and repeatedly exposed them to menthol for six months. They examined their cognitive and immunological responses and contrasted them with mice in good health. Interestingly, after brief exposures to the substance, mice with Alzheimer’s displayed a notable improvement.

In particular, menthol enhanced memory and learning capacities, prevented cognitive decline, and regulated the immunological system.

Researchers discovered that it reduced interleukin-1 beta levels, a protein connected to Alzheimer’s disease memory issues. This protein, also known as a “cytokine,” damages cognitive function by causing inflammation in the brain. One way to lessen this inflammation and stop more cognitive deterioration is to lower interleukin-1 beta.

Menthol was also discovered to imitate the effects of artificially lowering T-regulatory cells, which assist in controlling inflammation and maintaining immune system balance. This discovery raises the possibility of using specific odors as medicines and offers a potential avenue for the treatment of diseases like Alzheimer’s.

The Link Between the Brain, Smell, & Immune System

The intricate relationships among various nerve cell types, immune cells, and neural stem cells are necessary to preserve the functional balance of the brain.

Numerous studies have examined the scents’ neurological and immunomodulatory effects in this complex network of connections. Earlier research has also shown a link between the loss of smell and the first signs of Alzheimer’s disease [3].

We already know that scents can affect our cognitive function, and prior studies have linked scents to our immune and nervous systems [4, 5]. 

Furthermore, we now know that a loss of smell can occasionally accompany certain central nervous system illnesses, such as schizophrenia, Parkinson’s, and Alzheimer’s.

Even while the intricacies of these linkages are still unknown, this new study offers some encouraging information that will advance our understanding of them.

How Can Inhaling Methanol Help?

Menthol lowers inflammation in the memory-related area of the brain. It seems to have immunomodulatory effects in the prefrontal cortex, a memory-related area that gets disrupted in Alzheimer’s patients.

Researchers also discovered that reducing the activity of T regulatory cells, an immune cell type with immunosuppressive function, enhanced the cognitive function of Alzheimer’s disease-affected mice and even produced a noticeable improvement in the cognitive function of young, healthy mice.

Both menthol exposure and T-regulatory cell blocking led to a decrease in IL-1, a protein that may be the cause of mice’s declining cognitive function. Furthermore, inhibiting this protein using a drug for treating certain inflammatory conditions improved the cognitive abilities of both healthy and Alzheimer’s mice.

More precisely, in mice with Alzheimer’s disease, menthol inhalation decreased the amount of cytokines (inflammatory chemicals) in this area compared to the control group. There was reduced inflammation in the brain as a result. At least one of the ways that the menthol-exposed mice showed improved cognitive function may be the cause of this outcome.

The research shows that inflammation is the primary factor behind Alzheimer’s and that developing drugs to address this pathological component may delay Alzheimer’s progression.

Can the Results be Applied to Humans?

Since these findings depict preliminary observations of lab mice, they cannot be extrapolated to Alzheimer’s in humans. Besides our brains being wired differently than mice’s, it is unclear how our olfactory systems and scent perception differ.

Nonetheless, this is an essential first step to better understand how to manage the condition until further research investigates the effects of menthol using a human sample.

The relationship between Alzheimer’s and smell requires more research, which may result in some intriguing methods. 

A Significant Advancement

The study’s team claimed that according to the findings, some scents may serve as Alzheimer’s treatments. We can employ odors to enhance health if we can identify which ones trigger different reactions in the brain and immune system.

Alzheimer’s Research Association is a non-profit organization dedicated to helping caregivers of Alzheimer’s disease and dementia. We provide the latest information and news about the illness and helpful tips to help caregivers cope with their daily caregiving challenges. We realize the most important thing that a caregiver needs is financial assistance. Therefore, we provide grants to caregivers to ease their financial burden. Caregivers can apply for grants here: Alzheimer’s Grant Application. 

You can also help caregivers in their endeavor by donating as much as possible: Donation To Alzheimer’s Research Associations.

References

• Casares, N., Alfaro, M., Cuadrado-Tejedor, M., Lasarte-Cia, A., Navarro, F., Vivas, I., Espelosin, M., Cartas-Cejudo, P., Fernández-Irigoyen, J., Santamaría, E. and García-Osta, A., 2023. Improvement of cognitive function in wild-type and Alzheimer’s disease mouse models by the immunomodulatory properties of menthol inhalation or by depletion of T regulatory cells. Frontiers in immunology, 14, p.1130044.

• Lasarte-Cia, A., Lozano, T., Pérez-González, M., Gorraiz, M., Iribarren, K., Hervás-Stubbs, S., Sarobe, P., Rabal, O., Cuadrado-Tejedor, M., García-Osta, A. and Casares, N., 2018. Immunomodulatory properties of carvone inhalation and its effects on contextual fear memory in mice. Frontiers in Immunology, 9, p.68.

• Tian, Q., Bilgel, M., Moghekar, A.R., Ferrucci, L. and Resnick, S.M., 2022. Olfaction, cognitive impairment, and PET biomarkers in community-dwelling older adults. Journal of Alzheimer’s Disease, 86(3), pp.1275-1285.

• Tizard, I. and Skow, L., 2021. The olfactory system: the remote-sensing arm of the immune system. Animal Health Research Reviews, 22(1), pp.14-25.

• Vance, D.E., Del Bene, V.A., Kamath, V., Frank, J.S., Billings, R., Cho, D.Y., Byun, J.Y., Jacob, A., Anderson, J.N., Visscher, K. and Triebel, K., 2024. Does olfactory training improve brain function and cognition? A systematic review. Neuropsychology review, 34(1), pp.155-191.

• Could inhaling menthol help improve memory in Alzheimer’s disease? Medical News Today. https://www.medicalnewstoday.com/articles/could-inhaling-menthol-help-improve-memory-in-alzheimers-disease. Published Online: 19th May, 2023. Accessed: 29th November, 2024.

• When mice with Alzheimer’s inhaled menthol, their cognitive abilities improved. The Conversation. https://theconversation.com/when-mice-with-alzheimers-inhaled-menthol-their-cognitive-abilities-improved-230330. Published Online: 11th June, 2024. Accessed: 29th November, 2024.

• Unexpected Link Between Menthol And Alzheimer’s Discovered in Mice. Science Alert. https://www.sciencealert.com/unexpected-link-between-menthol-and-alzheimers-discovered-in-mice. Published Online: 23rd October, 2024. Accessed: 29th November, 2024.