In recent years, scientists have uncovered an increasingly complex relationship between the brain, the gut, and the body’s immune system. This interconnected network, often referred to as the brain-gut axis, plays a central role in regulating our health, mood, and response to disease. When inflammation strikes this system, it can lead to a range of problems—from digestive disorders to cognitive issues. A promising and non-invasive approach to addressing such inflammation is photobiomodulation (PBM), a technique that uses specific wavelengths of light to influence cellular and tissue processes. New research is beginning to reveal how PBM may benefit not just isolated organs, but the entire brain-gut axis. This article explores five key studies that illuminate how light, when applied thoughtfully, might help ease inflammation and restore balance between the brain and the gut.
Light Wavelengths and Gut Inflammation: Insights from an In Vitro Model
A 2025 study by Kang et al. investigated how different wavelengths of PBM could influence inflammation in the gut using a lab-based model of intestinal tissue. Their research found that specific light wavelengths had distinct effects on inflammatory markers. Notably, red (660 nm) and near-infrared (810 nm) light significantly reduced inflammation-related gene expression, including TNF-α and IL-6, in lipopolysaccharide (LPS)-induced inflamed intestinal cells (Kang et al., 2025).
Moreover, these wavelengths helped maintain the integrity of the intestinal barrier by preserving tight junction proteins like ZO-1 and occludin. These proteins are crucial for keeping harmful substances from leaking through the gut lining. The findings suggest that the therapeutic potential of PBM lies in its ability to reduce inflammation while supporting gut structure and function. By carefully selecting light wavelengths, it may be possible to target specific biological processes in the gut that contribute to chronic inflammation.
Brain-Gut Photobiomodulation in Chronic Stress
A striking study by Sancho-Balsells et al. in 2024 extended the potential of PBM from the gut to the brain. Using a model of chronically stressed mice, the researchers applied light therapy through the skull and observed both cognitive and gut-related improvements. This form of brain-gut PBM restored memory and learning deficits in the mice, while also regulating intestinal inflammation and microbiota imbalances (Sancho-Balsells et al., 2024).
The team discovered that these benefits were connected to the activation of Sirtuin 1 (Sirt1), a protein known for its role in cellular resilience and anti-inflammatory effects. PBM helped modulate this pathway and reduce neuroinflammation in areas of the brain linked to memory and emotion. At the same time, changes in gut microbiota composition—in particular, the increase of beneficial bacteria such as Lactobacillus—suggested that light therapy indirectly improved gut health by influencing the brain.
This research points to a new concept: light delivered to the brain might also have downstream effects on gut health, and vice versa. It highlights the two-way communication of the brain-gut axis and the ability of PBM to serve as a bridge across it.
Targeting Neuroinflammation through the Microbiome: Low-Level Laser Therapy on Gut Bacteria
In a 2025 study published in Lasers in Medical Science, da Silva and colleagues explored how low-level laser therapy (LLLT), a form of PBM, might affect the gut microbiota and, through it, brain inflammation. Their work centered on the idea that the gut microbiome—the billions of bacteria living in our digestive tract—can influence brain inflammation via immune signaling and metabolic pathways (da Silva et al., 2025).
The researchers demonstrated that applying PBM to the abdominal area of animal models led to positive shifts in gut bacterial composition, including increases in anti-inflammatory species. These microbiome changes were associated with a reduction in neuroinflammation, suggesting that PBM might help regulate the immune signals traveling from the gut to the brain.
This supports the concept of "bottom-up" PBM: applying light to the gut to achieve changes in brain health. It also shows that the effectiveness of PBM might not always require direct application to the brain; instead, targeting the gut could be an indirect but powerful way to manage brain-related inflammation and possibly related disorders.
The Role of the Gut and Oral Microbiota in Alzheimer’s-Related Neuroinflammation
A 2024 review by Popescu et al. broadened the conversation by discussing how disturbances in both gut and oral microbiota may contribute to neuroinflammation in Alzheimer’s disease. The researchers emphasized that changes in microbial communities, especially in older adults, can activate immune responses that affect the brain over time (Popescu et al., 2024).
Though this paper did not focus directly on PBM, it adds important context for understanding why interventions like PBM that stabilize or restore healthy microbiota could be valuable. By reducing microbial-driven inflammation, particularly in the aging brain, PBM might help delay or prevent some forms of neurodegeneration.
Additionally, this research supports the idea that oral and gut health are tightly linked to brain function, further strengthening the rationale for targeting the entire brain-gut-microbiome axis when designing light-based therapies.
“Photobiomics”: How Light Might Influence Microbial Communities
A foundational concept in this field was introduced by Liebert et al. in 2019, who coined the term "photobiomics" to describe the intersection of PBM and the microbiome. Their paper reviewed evidence that PBM can alter bacterial populations in both animal and human models, with potential benefits for immune regulation and overall health (Liebert et al., 2019).
Liebert and colleagues highlighted how light may not only impact human cells but also directly affect the bacteria living within us. Some wavelengths may encourage the growth of beneficial species or suppress harmful ones. They also proposed that PBM could influence microbial behavior indirectly, through its effects on host cells and immune pathways. This two-pronged effect suggests that PBM might serve as a tool to support microbial balance and reduce chronic inflammation.
While “photobiomics” is still an emerging concept, this paper laid the groundwork for future studies on how light and microbes interact—a key component in understanding the brain-gut connection.
Conclusions and Future Directions
Together, these five studies build a compelling case for the role of photobiomodulation in addressing inflammation across the brain-gut axis. From direct effects on gut cells to indirect modulation of brain function through microbial changes, PBM appears to offer multiple avenues for therapeutic intervention.
Kang et al. (2025) showed that wavelength-specific PBM can reduce gut inflammation and support intestinal barrier integrity.
- Sancho-Balsells et al. (2024) revealed that brain-directed PBM could restore memory and rebalance the gut microbiota in stressed mice.
- da Silva et al. (2025) demonstrated how targeting gut bacteria with PBM could lead to reduced neuroinflammation.
- Popescu et al. (2024) highlighted the gut and oral microbiota’s role in brain disease, reinforcing the need for comprehensive approaches.
- Liebert et al. (2019) provided a framework for understanding how PBM might shift microbial communities in ways that benefit overall health.
This growing body of research suggests that PBM might be more than a local therapy—it may be a systemic regulator. By tapping into the brain-gut-microbiome axis, PBM could help treat or prevent chronic inflammatory conditions that affect both the mind and body.
Yet challenges remain. Translating these findings from lab models to humans will require carefully controlled clinical trials. Questions also remain about optimal dosages, treatment durations, and how best to deliver light for brain-gut effects.
Still, the potential is clear. Light therapy, already well-known for healing wounds and relieving pain, may soon be recognized for something even more profound: restoring balance to one of the most important networks in the human body.
References:
Kang M, Jo J, Shin H, Kang HW. Therapeutic potential of wavelength-dependent photobiomodulation on gut inflammation in an in vitro intestinal model. J Photochem Photobiol B. 2025 Jun 18;269:113201. doi:10.1016/j.jphotobiol.2025.113201. PMID: 40543454.
Sancho-Balsells A, Borràs-Pernas S, Flotta F, et al. Brain-gut photobiomodulation restores cognitive alterations in chronically stressed mice through the regulation of Sirt1 and neuroinflammation. J Affect Disord. 2024 Jun 1;354:574-588. doi:10.1016/j.jad.2024.03.075. PMID: 38490587.
da Silva LE, Martins DF, de Oliveira MP, et al. Photobiomodulation of gut microbiota with low-level laser therapy: a light for treating neuroinflammation. Lasers Med Sci. 2025 Feb 4;40(1):64. doi:10.1007/s10103-025-04319-9. PMID: 39903307.
Popescu C, Munteanu C, Anghelescu A, et al. Novelties on Neuroinflammation in Alzheimer's Disease-Focus on Gut and Oral Microbiota Involvement. Int J Mol Sci. 2024 Oct 19;25(20):11272. doi:10.3390/ijms252011272. PMID: 39457054.
Liebert A, Bicknell B, Johnstone DM, et al. "Photobiomics": Can Light, Including Photobiomodulation, Alter the Microbiome? Photobiomodul Photomed Laser Surg. 2019 Nov;37(11):681-693. doi:10.1089/photob.2019.4628. PMID: 31596658.
