The Less Well Known Treatment For Gut Issues: Photobiomodulation


Welcome to my blog entitled ‘The Less Well Known Treatment For Gut Issues: Photobiomodulation”.

Before we start, other blogs that you might be interested in, include:

What Is Photobiomodulation (PBM)?

Photobiomodulation is the newly adopted term to describe the therapeutic application of low levels of red and/or near-infrared (NIR) light to treat a multitude of different diseases and disorders.

What Is Photobiomics?

An even more recent term which is defined as: ‘the combined effects of light (photobiomodulation or otherwise) on metabolomic factors, the microbiome, and the interaction between the two.’

How Does Photobiomodulation Work?

The mechanisms of action of photobiomodulation have been widely investigated in recent years, and additional mechanistic information is still being discovered.

Nevertheless, it is generally accepted that the single most important chromophore in the red and NIR regions of the spectrum is cytochrome c oxidase (CCO).

A chromophore is the part of a molecule responsible for its color.

Cytochrome c oxidase (CCO), is unit IV of the mitochondrial respiratory chain – our mitochondria are a sub-component of all of our cells and the site of energy production. Mitochondria used to be bacteria (1.5 billion years ag0) and we now understand they sense, integrate, and orchestrate human health.

Watch this interview with Ray Griffiths to learn more about our mitochondria:

When CCO absorbs light, the enzyme activity is increased leading to:

  • Increased electron transport.
  • More oxygen consumption.
  • Higher mitochondrial membrane potential.
  • Increased ATP production.

How Does Photobiomodulation Effect The Gut?

We have different levels of evidence, most coming from animal research:

  • Circadian rhythm changes.
  • Vitamin D.
  • Immune modulation (anti-inflammatory)

The effect of the circadian rhythm on the microbiome has been demonstrated and the bacteria responsible for decreased gut integrity and increased lipopolysaccharide transport are upregulated in mice after disruption of the sleep/wake cycle.

In addition to circadian rhythm, light also has an indirect effect on the microbiome through vitamin D, produced by the action of sunlight on keratinocytes. Vitamin D is known to boost immune function by the induction of antimicrobial peptide genes and the regulation of tight junction proteins in the epithelial layer of the intestine and to maintain microbiome homeostasis and protect against colitis in mice, possibly by controlling inflammation.

The alteration of the microbiome, that was observed in mouse experiments, may be due to a secondary effect of PBM, affecting the mouse inflammatory response, and in turn affecting the gut microbiome (1).

This is entirely feasible, given the intimate relationship between the microbiome (healthy and dysbiosis) and the inflammatory response. It is hypothesised that this effect may be due to the well-known anti-inflammatory and redox signalling effect of PBM.

PBM can reduce pro-inflammatory cytokines, such as IL-6, TNF-α, IFN-γ, and change the activity of macrophages and neutrophils. (1)

The Gut Brain-Axis and Photobiomodulation

PBM treatment could remediate mitochondrial dysfunction in gut neurons, reinstating the complex bidirectional communication system between the enteric nervous system and the central nervous system (the gut/brain axis). (1)

This may have particular significance for neurodegenerative conditions, such as Alzheimer’s and Parkinson’s diseases, both of which involve early pathological abnormalities in the gut/brain axis.

Another theory the authors laid out was that the local effect of PBM on inflammatory pathways may have systemic consequences:

It is possible that circulating immune cells (mast cells, macrophages, etc.), stimulated by PBM, could transduce protective signals from distal tissues to sites of injury such as the brain, heart, or gut. (1)

The authors of this paper have shown in a previous study that PBM, delivered as low-level laser, to the abdomen of healthy mice can produce a significant change in the gut microbiome.

PBM significantly altered the microbial diversity of the microbiome, an effect most pronounced in mice treated three times per week with NIR light (808 nm). (1)

Recent preliminary work from the authors laboratory (unpublished research) has also indicated that changes in the human microbiome occur after treatment with PBM, including increases in Akkermansia muciniphila, Bifidobacterium sp., and Faecalibacterium sp., all recognised as correlated with a healthy microbiome, and decreases in the Firmicutes:Bacteroides ratio, proposed as an indicator of gut health.

Schematic illustration of the wide variety of human diseases and disorders that have been treated by PBM. (1)


PBM may serve as a way to beneficially change the microbiome for a number of different inflammatory and neurological diseases (such as cardiovascular and Parkinson’s diseases). The obvious approaches to try to improve the microbiome in humans such as diet, probiotics, and fecal transplants have had some success, but these treatments do not amount to a complete solution for the entire problem. Fecal transplants are currently being used for Clostridium difficile infection, irritable bowel disease, ulcerative colitis, and are also being considered for some nonintestinal metabolic diseases. Fecal transplants have been shown (in mice) to suppress neuroinflammation and TNF-α signaling, and to reduce the symptoms of Parkinson’s disease and dysbiosis. PBM has the potential to act as an adjunct treatment (along with modifications of diet and exercise) to rebalance the microbiome. A healthy microbiome would balance SCFA production, serotonin/kynurenine pathways, trimethylamine metabolism, and dopamine and neurotransmitter production, which, in turn may affect the outcome of some of the most difficult-to-treat diseases, including Parkinson’s disease, multiple sclerosis, amyotrophic lateral sclerosis, attention-deficit/hyperactivity disorder, and autism spectrum disorder


  1. “Photobiomics”: Can Light, Including Photobiomodulation, Alter the Microbiome? (click here)
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