Red Light Therapy for Gut Health

The Human Gut

The human gut, also known as the gastrointestinal tract (GI tract), consists of the esophagus, stomach, small intestine, and large intestine. In simple terms, it is a tube or passageway for food that passes from the mouth to the anus. Each part of the gut has its own job to do, which is usually described as the digestion and absorption of food, and the excretion of digestive waste products. 

In recent years, however, a critical new role has emerged for the human gut, specifically the large intestine. As the last part of the GI tract, the large intestine receives food after most of the nutrients are absorbed and functions to reabsorb water and some remaining minerals. While this final step in the processing of food is essential, equally (if not more) important is the role of the large intestine as host to the gut microbiome, which is being described as a “major determinant of health.” 

The Gut Microbiome

The human body contains over 150 times more genes from resident microorganisms (such as bacteria, viruses, and fungi) than from its own human cells. With a total weight of just over 2kg, microbial cells outnumber human cells by around 10 to 1. Most of these organisms went unrecognized until the last two decades. However, we now know that the body is literally teeming with invisible inhabitants, which comprise what is referred to as the human microbiome. The combined human and microbiome genome is referred to as the “holobiome”. 

The term “resident” is an apt descriptor when it comes to the microbiome. These organisms live inside the body, from birth to death. They also reside on the surface of the skin. And while the germ theory of disease has conditioned us to believe that most microorganisms are pathological, in fact the human microbiome is one of the most important biological predictors of health. The opposite is also true: alteration in the microbiome is an important predictor of disease. The microbiome communicates with the body, and the body communicates with the microbiome. This crosstalk is essential for human health. 

The human microbiome can be broken down into several divisions, based on location. The microbiome that lines the mouth is the oral microbiome; the microbiome that lines the skin is the cutaneous microbiome; the microbiome that lines the vagina is the vaginal microbiome; and the microbiome that lines the digestive tract is the gut microbiome. The gut microbiome is the most well researched biome.

The role of the gut microbiome is complex and spans a wide range of diverse functions. Gut microbes are involved in the metabolism of carbohydrates, lipids, and proteins, and help to extract nutrients from food. In the gut, they produce useful molecules such as short chain fatty acids and vitamin K. Gut microbes also manufacture neurotransmitters such as serotonin, and through the gut brain axis, regulate many aspects of cognitive function. The microbiome is also involved in the metabolism of ingested drugs and toxins. 

The gut microbiome starts its development in utero and continues throughout the fetal period, with further colonization during delivery. Most gut microbes are acquired post partem, with breast milk as an important source in early life. A diet containing predominantly plants and whole foods is considered optimal to support the gut microbiome, with fiber being of utmost importance. Processed food, food that is high in sugar, and low fiber diets are bad for gut health. It has been recommended that dietary guidelines be revised to support a healthy gut microbiome.

In addition to diet, there are several other factors that influence the health of the gut microbiome. According to the Canadian Digestive Health Association, non-dietary ways to strengthen the microbiome including: avoiding antibiotics, regularly sleeping for at least 8 hours per night, getting regular exercise, and engaging in stress reducing activities. Evidence is also accumulating that gut microbiome health can be supported by therapy with red and near infrared light

Light Therapy

Light therapy (also known as photobiomodulation) is the application of light with specific wavelengths to the body for the purposes of influencing biology. The most common form of light therapy uses red light (RL), which is visible as the color red, and/or near infrared light (NIRL), which is not visible but can be felt as heat. The RL used in light therapy usually ranges from 600 to 700 nanometres (nm), with the unit nm referring to distance the light wave travels in one cycle. The NIRL used in light therapy usually ranges from 800 to 900nm.

RL and NIRL are naturally produced by the sun, which gives off solar radiation. The term radiation describes energy that is transmitted in the form of waves or particles. The spectrum of light in our environment consists of both light we can see (visible light) and light that our eyes can’t perceive (invisible light). This is called the electromagnetic spectrum. The visible light spectrum is quite narrow, consisting of wavelengths that range from 400 to 700nm and span from violet to red in color. RL is part of this visible light spectrum, while NIRL is not.

Red and near infrared light therapy is the application of artificially generated light in the red and near infrared spectral bands. The term “red light therapy” usually describes the use of both RL and NIRL, although only the red light produced by the device is visible to the naked eye. IRL can still be perceived by the body as heat when it contacts skin.

How Does Red Light Therapy Affect Gut Health?

Red light can affect gut health both through effects on the microbes in the microbiome, as well as on the gut cells of the human host. It’s hard to tease out precisely what is happening in this complex microenvironment, but one thing is clear: light therapy administered to the gut has a positive biological effect.

Research has indeed shown that light can modify the microbiome. For example, when RL or NIRL was applied to the abdomen of mice, the composition of the microbiome shifted to include more of a bacterial strain that is associated with better health. Bacteria have also been found to respond to the direct application of RL.

Light therapy also impacts human cells. Light is absorbed in cells by molecules called chromophores, many of which are found inside the mitochondria. Mitochondria are the powerhouses of the cell, which make the energy currency of the cell known as ATP. Mitochondria are also involved in regulating the production of molecules called reactive oxygen species (ROS), which play a role in normal cellular function but can be harmful in high amounts. This is known as oxidative stress. Through its effects on mitochondria, light therapy can increase cellular energy production and modulate oxidative stress. Intestinal oxidative stress is associated with disease.

Through effects on cellular metabolism and ROS production, as well as through reduction of other molecules such as reactive nitrogen species and prostaglandins, light therapy can decrease inflammation. Both RL and NIRL have anti-inflammatory effects, and unlike anti-inflammatory medications (such as NSAID’s), do not cause side effects. Inflammation is a hallmark of many gut disorders, such as Crohn’s Disease and Ulcerative Colitis. 

By improving the health of the gut (both the microbiome and human gut cells), a wide range of positive effects are observed, including:

Gut Dysbiosis

When the gut microbiome is dysregulated, there is an adverse effect on its human host. This is called gut dysbiosis. Poor dietary choices, sedentary lifestyle, increased stress, and use of antibiotics (and other pharmaceuticals) can cause the gut microbiome to become unhealthy. This causes a loss of integrity of the gut lining, also known as leaky gut. In turn, the gut becomes permeable to things like microbes and food fragments, which activate the immune system and trigger an inflammatory response. Chronic inflammation ensues, and a vicious cycle is established in which the gut becomes increasingly compromised, which worsens the inflammation. Dysbiosis also impairs metabolism. 

Gut dysbiosis has been associated with an enormous range of human disease, including metabolic syndrome, neurological disorders, immune system disorders, autism, psychiatric disorders, obesity, systemic inflammation/autoimmunity, type 2 diabetes, chronic pain, multiple sclerosis, inflammatory bowel disease, and eye diseases. A 2021 article in The Guardian described that “The great opportunity – but also the great difficulty – of gut microbiome science is that poor gut health is associated with such a vast range of conditions.” This means that there is enormous potential to reduce human disease by improving the health of the gut microbiome, although it is important to acknowledge that our understanding of these relationships is still limited. 

Clinical Applications of Light Therapy to the Gut

The use of light to improve health dates back thousands of years. Sunlight has been used in medicine since at least the time of the Ancient Greeks, to treat conditions such as tuberculosis, skin disorders, and bacterial and fungal infections. However, the practice fell out of favor during the 20th century as modern societies embraced the medical pharmaceutical model of therapeutics. Over the last decade, there has been an increasing interest in harnessing the power of light as a therapeutic, and a wide range of applications are being explored.

Several studies have investigated what happens when RL and/or NIRL light is applied to the abdomen. Interestingly, the bulk of this research has been done using abdominally applied light to treat brain disorders, rather than for GI tract diseases. This is because of the important relationship between the gut microbiome and the brain, through a pathway known as the gut-brain axis (GBA), which involves bidirectional communication between the gut (including the microbiome) and the brain. The GBA plays an important role in brain, gut, and immune health. Alterations in the gut microbiome may be associated with disease through the GBA.

RL and NIRL applied to the abdomen (as well as the neck, head and nose) of Parkinson’s disease (PD) patients has been shown to modulate the composition of the gut microbiome, with a shift towards more “healthy” bacteria. Light applied to the abdomen and neck for 12 weeks also decreased symptoms such as impaired mobility in PD patients, with improvements lasting for up to a year. PD is a degenerative brain disease that causes motor symptoms (such as balance and gait problems) and non-motor symptoms (such as depression, sleep disorders, and cognitive impairment). It affects around one million people in the US, and over 10 million people globally. 

Application of RL and NIRL to the abdomen (as well as the head) has also been used in the treatment of Alzheimer’s Disease (AD). In a 2022 clinical trial of patients with mild to moderate AD, those receiving light therapy showed improved cognitive function relative to the control group. Alzheimer’s Disease (AD), a form of dementia, is a neurodegenerative disease that comprises 70% of dementia cases. AD affects 1 in 10 US adults over the age of 65, or 5.7 million Americans. 

It has been suggested that light therapy applied to the abdomen may be useful in reducing depression. The composition of the gut microbiome has been linked to depression, with depressive patients showing higher levels of certain bacteria that are involved in the synthesis of neurotransmitters such as serotonin and GABA. These neurotransmitters are involved in the regulation of mood. Gut microbiome composition has been strongly associated with mental well-being.  

Given the associations between brain diseases and the GBA, it has been suggested that targeting the microbiome holds great potential in the treatment of neurodevelopmental and neurodevelopmental diseases. In addition to AD and PD, these include diseases such as multiple sclerosis, autism spectrum disorder, attention-deficit hyperactivity disorder, migraine, post-operative cognitive dysfunction, and long COVID. According to researchers from Australia, many studies are currently underway “with the aim of restoring the microbiome and potentially altering the course of these brain conditions.” 

Light therapy may also be helpful in modifying the microbiome in diseases that primarily affect other body systems. For example, in a case report of a patient with breast cancer, application of NIRL to the abdomen was associated with increased diversity of gut microbes, which is considered to be a healthy change. The authors suggest that light therapy may be a way to improve gut health in patients with chronic disease. Most patients with chronic disease use medications which may adversely affect gut health (especially the microbiome).

There is also great potential to use light therapy to treat gut disorders. For example, animal research has found that application of RL to the abdomen of rats with experimentally induced colitis (a form of inflammatory bowel disease) improved many markers of gut health, including reducing inflammation. There is interest in studying the use of light therapy to improve gut health in human subjects as well. Notably, a study using NIRL applied to the abdomen (as well as the front of both thighs) is currently underway to assess whether treatment reduces pain, fatigue, and depression in patients with inflammatory bowel disease. Effects on the gut microbiome will also be measured. 

Using Light Therapy for Gut Health

There are many light therapy devices on the market today that could be used at home to target gut health. With so many options available, how can you know which device is best for you? Here are five issues to consider.

  1. Style Preference: To treat the gut with light therapy, light should be applied to the abdominal area. Two types of devices are most appropriate for abdominal applications: (i) a light panel, or (ii) a light wrap. Your personal level of comfort with a device is important. Imagine yourself using it – Do you want to stand in front of the device, or would you prefer the flexibility of being able to lie down while wearing it? Do you want a device that is wireless, or can you commit to being close to an electrical outlet so that you can plug it in? Think about your personal preferences and choose accordingly.
  1. Laser vs LED: Light therapy is administered using either laser or LED lights. While early light therapy research was done using lasers, LED lights have become much more popular over the last decade. The research described in this article includes both types of light sources. In 2018, Dr. Michael Hamblin – the world’s leading light therapy expert – concluded that LED lights using comparable parameters to lasers performed “equally well”, which is very important because LED powered light therapy devices can be made at a fraction of the cost of laser devices. For at home use, look for a device that uses LED lights as safe and affordable option.
  1. Light Color/Wavelength – As described in this article, both RL and NIRL have been used in studies of light therapy to treat gut disorders. Positive results have been observed when these wavelengths were used either together or individually. So, look for products that use RL and NIRL either alone or in combination.
  1. Light Intensity – Light intensity refers to the amount of light being delivered by a device. It is also referred to as irradiance. The required intensity when using light therapy to impact gut disorders is unclear. There is variability in light intensity between studies, and no studies have directly compared different intensities. Since light is being delivered to the skin of the abdomen, it may be prudent to follow the advice given for light therapy to the skin, and mimic the intensity of the sun, which is around 24 mW/cm2. This is described as the “sweet spot” between higher intensities, which can have harmful effects, and lower intensities, which will have no effect at all. Placing a high intensity device directly on the skin could be harmful. Choose a sun-mimicking product and don’t overdo it when it comes to treatment frequency and duration.
  1. Education – While light therapy education will not change the specific functionality of a device, it does have the potential to profoundly impact how someone uses the technology. When a company provides evidence-based education that teaches consumers why, how, and when to use a product, devices can be used to better support healing. Look for products with accompanying education and instructions for use, whether in printed and/or digital formats. You can also look for companies that provide support by phone or email to current or prospective customers.


Hippocrates is credited with stating that “All disease begins in the gut”. While today’s science does not yet support that level of conviction, we do know that gut health is intimately associated with the overall health of the human body. We also know that “what happens in the gut doesn’t stay in the gut”, but rather influences other organs and systems through complex communication networks. The gut microbiome is inextricable from our own human gut, and both are important for optimal health.

When using light therapy for gut health, it’s important to also engage in other gut-friendly activities. These include eating a gut healthy diet, staying hydrated, exercising regularly, and limiting stress. It’s advisable to work with a health care provider with expertise in this area and who can provide appropriate support.

Many questions remain about how light therapy can be used to support gut health, but preliminary pre-clinical and clinical evidence supports the use of RL and NIRL both to induce healthy shifts in the gut microbiome and to decrease inflammation. Since RL and NIRL also have other effects, such as increasing energy and decreasing ROS production, many other benefits are likely to be observed. This is certain to be an area of active research interest, especially given the amazing safety profile of light therapy and the increasing availability of at-home devices.

Dr. Genevieve Newton, DC, PhD  spent close to 20 years as a researcher and educator in the field of nutritional sciences before joining Fringe as its Scientific Director. Gen’s job is to “bring the science” that supports Fringe’s products and education. She is passionate about all things Fringe, and is a deep believer in healing body, mind and spirit using the gifts of the natural world. 

The contents in this blog; such as text, content, graphics are intended for educational purposes only. The Content is not intended to substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your healthcare provider.

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