What does your gut tell you about your skin?

Healthy skin comes from more than just staying hydrated and eating the right foods. As it turns out, it also depends on the trillions of microbes that live on (and in) our bodies.

This complex community of bacteria, fungi and viruses is collectively called the microbiome. Research shows that an imbalance in the skin’s microbiome can trigger conditions like acne, psoriasis, and eczema.

But our microbiomes do not operate in isolation. The gut microbiome is seemingly in constant communication with the skin microbiome. This is why when something goes haywire in your digestive system, it often manifests on your face or body.

But scientists are only beginning to unravel these complex microbial interactions. Understanding this could help treat and manage skin conditions and bad body odour.

Home to trillions

The skin is the largest organ of the body, and it houses trillions of bacteria, fungi, and yeasts. These microorganisms are beneficial as they act as a physical barrier to pathogens (disease-causing organisms) that may enter the body.

When the skin barrier is broken or if there is an imbalance (dysbiosis as opposed to symbiosis) between the ‘good’ microbes and pathogens, our skin could have issues. Sometimes, it could have adverse effects.

Chris Callewaert is a microbiologist from the University of Ghent in Belgium. He says, “Everything in the body works when there is a balance, and this hold true for the microbiome as well. An imbalance or dysbiosis can bring about a host of problems including medical conditions that impact health.”

Callewaert, who goes by ‘Dr Armpit’, further explains that the microbes on our skin help break down sweat and sebum, maintain the correct pH of the skin and ward off unwanted bacteria.

The skin microbiome also primes the skin cells, known as keratinocytes, to produce certain antimicrobial compounds. These help kick off the body’s response to the bad bugs, especially in skin infections. “Many skin disorders have a dysbiosis in the skin microbiome. And if our microbiome is off, then so is the immune system,” Callewaert points out.

Link between GI conditions and the skin

There are numerous studies that support the association between gastrointestinal (GI) disorders and cutaneous diseases. For instance, 10-25 per cent of individuals with GI conditions, such as ulcerative colitis, Crohn’s disease, and celiac disease, also experience skin conditions like psoriasis and cutaneous ulcers. However, the precise mechanisms on how this happens is still not quite understood.

It has been hypothesised that inflammation, originating either in the gut, may be initiated by intestinal microbial dysbiosis. It suggests that gut microbiota is a potential origin for skin disease.

Interestingly, Bruce A Vallance, a professor of gastroenterology in the University of British Columbia, Canada and his team found that skin microbiome imbalance can also indirectly affect the gut. In a study on vitamin D activation, they found that when skin dysbiosis occurs, it may impair vitamin D production in ways that disrupt intestinal health. Vallace adds, “Research suggests that adequate vitamin D levels may be associated with a lower risk of developing atopic dermatitis, which is a common inflammatory skin condition.”

This highlights how the skin-gut dialogue flows both ways – microbial disturbances on the surface can worsen inflammation and nutrient deficiencies inside the body too.

There are specific changes in the gut microbiome that have been associated with skin conditions. However, we cannot yet be sure if it is causation; that will take more clinical studies and research. Here are some links established between skin issues and gut health.

Microbiome and body odour

Our choice of foods also impacts how we smell says Callewaert, adding that body odour is a great example of the gut-skin axis.

“The advantage of our skin is we know when something is off, we feel it, smell and can see it too,” he says.

He has dedicated his research solely to the study of the microbiome of the armpit, a site where bacterial species like Corynebacterium, Staphylococcus and Cutibacterium reside, giving rise to good or bad odour depending on their numbers.

“People that consume more fast foods, smell worse because they have more of the smellier bacteria like Corynebacterium on the skin,” says Callewaert. In contrast, he says that people that consume more vegetables smell better and have more good bacteria in their underarms.

Eating your way to healthy skin

Some dermatologists already consider diet a key part of any skin health regimen. Raja Sivamani, an adjunct associate professor of dermatology at University of California, Davis says that he regularly discusses diet with those who come in for a skin consultation. “For example, if my patient has acne, I discuss the need to reduce high glycemic load foods and dairy. Diet on its own won’t cure a skin condition, but it is greatly helpful when it is part of a holistic plan,” he explains.

Vallance too stresses on the importance of a healthy diet in treating skin conditions, especially cutting out excess fat intake. “This [excess fat in diet] can increase the escape of inflammatory bacteria from the GI tract such that they spread to the bloodstream and reach the skin,” says Maira Jimenez Sanchez, a graduate student in Vallance’s lab.

What Sanchez is referring to here is a barrier in the gut that is made up of mucous and keeps the microbes in their own space. The skin too has one which needs to be maintained. If either of the barriers is off or very thin, then bacteria can start leeching in, causing local inflammation.

“As we learn more about the microbiome, we’ll understand there are ways to individualise treatment – like what probiotics, supplements, and foods better support our unique imbalances,” says Sivamani.

The aim is to lower the inflammation state in the body. “Having a microbiome that produces short chain fatty acids like butyrate and propionate is really good in doing that,” says Callewaert.

However, the road to changing our skin microbiome has a long way to go as we still do not have definite answers. And yet, it is the beginning of a more holistic approach to health matters, particularly where skin and gut issues are concerned.