illuminating light

Australian researchers have shown for the first time that laser therapy can be used to alter the population of gut bacteria in mice. The findings, if confirmed in humans, could help in the treatment of diseases such as diabetes.

Our guts are home to millions of microscopic bacteria collectively called the gut microbiome. Some of these bacteria are essential for our well-being by helping us digest the food we eat and store energy. These friendly bacteria can help regulate our metabolism and therefore protect us against diseases such as diabetes and IBS.

Studies have shown that certain gut bacterial species are strongly associated with protection against these diseases. Because of this, scientists have been trying to uncover different methods to change the gut environment and increase the abundance of these beneficial bacteria.  So far, changing one’s diet remains the most effective method of achieving this but other more drastic methods such as faecal oral transplants and drugs (such as berberine and metformin) have also been used.

Photomodulation (also known as PBMt or laser therapy) has also been used to treat several diseases that have been traditionally associated with imbalances in the gut microbiome composition. These include diabetes, cardiac diseases, and neurological disorders. The technique involves applying low levels of laser light to the subject which changes the metabolism of cells leading to tissue repair and anti-inflammatory effects. However, whether laser therapy also asserts its effects by influencing the gut bacteria was not known.

To address this question, a team of researchers from Australia sought to examine whether laser therapy could change the gut microbiome composition in mice.

The team separated healthy laboratory mice into several groups for their experiment. In the first group, the mice were exposed to multiple doses of infrared laser light while a second group was only given a single dose. Another group of mice was exposed to red light instead of infrared light as some studies have suggested that different types of light might vary in their effectiveness. The final group of mice was used as a control group where the laser light was not turned on.

The researchers then analysed the gut microbiome composition of the mice by collecting their faeces after 14 days of treatment and analysing DNA from each sample using a technique called pyrosequencing. This technique allows researchers to “read” the DNA that is present in the sample and identify the bacteria species by matching sample DNA to a DNA database. This process is akin to the way police identify suspects by matching their fingerprints to a police database. Using pyrosequencing also allowed the researches to quantify how much of a particular species of bacteria is present in the sample.

When the team compared the different mice groups, they found that the diversity of the bacteria was significantly different in almost all the treated groups when compared to the control group. The team then examined the relative abundance of individual bacterial species to determine which particular bacteria were increased in the treated samples. Surprisingly, they found that the levels of a bacteria called Allobaculum stercoricanis was at least 400-fold higher in mice treated with multiple doses of infrared compared to untreated mice. This observation confirmed, for the first time, that laser-therapy can indeed influence the gut microbiome.

How does laser therapy bring about changes in the gut microbiome?

The team thinks that the laser is unlikely to be affecting the bacteria directly because of the long treatment time (14 days) that was needed to detect significant changes in bacterial numbers. Instead, the researchers think that the infrared light might be influencing the mice cells to secrete molecules that encourage the growth of certain bacteria.

The increase in Allobaculum abundance after laser therapy also has important health-related implications. Mice studies have shown that increased levels of Allobaculum are associated with higher physical activity, fibre intake, and weight loss. On the contrary, mice that are obese tend to have lower levels of the bacteria. The bacteria also produce molecules called short-chain fatty acids that are thought to strengthen the mice gut lining and protect against inflammation.

The researchers caution that the results are still preliminary and more studies are needed to see if the therapy also increases the levels of ‘good’ bacteria in humans but the therapy shows promise, according to them.

“If this is confirmed in humans, the possibility exists for PBMt to be used as an adjunct therapy in the treatment of obesity and other lifestyle-related disorders, as well as cardiovascular and neurodegenerative diseases.” Bicknell and co-authors wrote in the paper.


Article source:

Bicknell, B., Liebert, A., Johnstone, D., & Kiat, H. (2018). Photobiomodulation of the microbiome: implications for metabolic and inflammatory diseases. Lasers in medical science, 1-11.

Link for the article:


by Andrew Liew, PhD