Over the last 15 years, research into the gut microbiome — the ecosystem of microorganisms that reside in the gut — has garnered increasing attention. With the emergence of supplements and food products that claim to improve your gut health, the term “gut microbiome” has become a familiar idea to the general public.
Both in the lab and in clinical trials, Dr. Bruce Vallance’s team at BC Children’s Hospital Research Institute (BCCHR) has been working to better understand the role that the gut microbiome plays in maintaining intestinal health and how it impacts disorders such as inflammatory bowel disease (IBD). What they’ve found is that the composition of bacteria in the gut plays a key role, not just in gut health, but also in many different diseases.
A balanced gut microbiome can promote both tissue health and a robust immune system. In contrast, an imbalanced microbiome, caused by a loss of beneficial microbes, or an overgrowth of harmful microbes, can lead to a breakdown of the barriers that line the gut, allowing bacteria and other gut contents to spill into the body. This can lead to several health complications including IBD — an umbrella term for a group of conditions, including ulcerative colitis and Crohn’s disease, where an individual’s immune system triggers inflammation in the gut, leading to cramps, pain and diarrhea. At present there are no cures for IBD, but the goal of most treatments is to reduce the inflammation that triggers symptoms.
Recently, many new studies are showing that the gut microbiota is more involved in controlling how our bodies function than we originally thought, and that the gut microbiota may “talk” with other organs, such as the skin, through shared molecular and cellular signals.
Maira Jimenez is a PhD candidate in Experimental Medicine at UBC with Dr. Vallance’s team, and is the first author on a recent review paper in the journal Gut Microbes, discussing this newfound appreciation for the “gut-skin axis.”
“The fact that the skin and gut actually talk to each other is a very new and exciting development in the gut microbiome space,” says Jimenez, who is also part of the Falling Walls Female Science Talents Intensive Track 2025. In the paper, Jimenez describes how many different biological pathways, including those of the immune system and vitamin D signaling, are involved in this “cross-talk” between the skin and the gut.
“One of the reasons why these discoveries are so fascinating is that it demonstrates how interactions between bacteria in the gut and the immune system can impact overall health, and it also means that the gut microbiota may be a key influence on a host of diseases not previously considered to be related.”
Dr. Vallance’s lab was one of the first to find that this cross-talk between the skin and gut can go in both directions. In an earlier experiment published in Frontiers in Microbiology, they showed that exposing the skin to a specific type of ultraviolet light can be beneficial to the gut microbiome and intestinal health.
Dr. Larissa Celiberto, a postdoctoral fellow in the Vallance lab and another author on the paper explained, “The sun has different rays — UVA, UVB, and UVC. But only UVB promotes vitamin D production. Using a narrow band of UVB light (NB-UVB) on the skin, we can promote vitamin D production in the body, while sparing the risk of some of the more harmful effects of the other types of UV light, such as long-term damage to the skin.”
Vitamin D has many useful functions in the body, but one of its key roles is to promote intestinal health by enhancing intestinal barrier integrity. In both the skin and the gut, vitamin D receptor activation plays a critical role in regulating the production of antimicrobial peptides which help maintain balanced microbiota and provide protection against pathogens. People who suffer from vitamin D deficiency are also more likely to have a gut with increased permeability, sometimes referred to as “leaky gut syndrome.”
Jimenez and colleague Dr. Hyungjun Yang, a research associate in the Vallance team and co-author on the review paper, are continuing this work by exploring how improving the natural production of vitamin D through NB-UVB exposure can lead to better gut health and could, eventually provide a type of treatment for people with IBD.
“Our work shows that sunlight acting on your skin can definitely change your feces,” says Jimenez. “And that might lead to new treatments for diseases like IBD.”
“Mice who are unable to make vitamin D have greatly increased inflammation in their gastrointestinal tract,” says Dr. Vallance. “If you look back at how humans evolved, their day-to-day life involved a lot of running around outside, getting exposed to sunlight. Today, most people’s jobs involve sitting inside, typically working on a computer. Unfortunately, many people spend very little time outside, and thus have very limited exposure to sunlight.”
This connection between limited UV exposure and an increased risk of IBD may be part of the reason why Canada, with its higher latitude, has one of the highest rates of IBD in the world. This is especially true for children, as vitamin D deficiency is also on the rise in younger populations due to decreased outdoor activity and changes in diet, potentially amplifying the risk. Therefore, understanding the mechanisms of gut health and inflammation, as well as potential new treatments, is increasingly important.
Dr. Vallance’s research team is one of the leading groups in the world looking into this complicated relationship between the gut microbiota, the immune system, IBD, and other diseases.
The team also draws on the expertise in gut health that they have developed to assist other researchers in exploring the impact of the gut microbiome. For the past five years, Dr. Andy Sham has been developing the technologies and protocols to measure and assess the gut microbiota “in house” with Mining for Miracles funded Gut4Health Microbiome Core Facility.
“What we are hoping to accomplish is to make the lab a one-stop shop for any microbiome-related questions,” says Dr. Sham. “Researchers who are considering whether the disease or condition that they study may involve gut health can come talk to us and we can sort out what experiments and procedures might be needed.”
In the future, Dr. Vallance’s team hopes to be able to fully model the human gut to better explore the myriad intersecting biological pathways and environmental factors that determine gut health.
“We have only just begun to appreciate the true extent of the different diseases and conditions affected by the gut and the complexity of these interactions,” says Jimenez. “Our goal is to develop innovative new treatments for children, not just those with IBD but potentially children suffering from a range of different ailments.”
