The Science Behind The Microbiome and the Skin-Brain-Gut Axis

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When you look good, you feel good. Not only does a healthy skin barrier protect you from harmful bacteria, but it also helps prevent evaporation of important molecules, to keep skin supple and hydrated. When the skin’s protective barrier is compromised and the microbiome becomes unbalanced, it can make skin vulnerable to a variety of skin issues.

What is the Microbiome?

The skin is the largest organ in the body and the first line of defence between us and our environment.  Its most important role is as a physical barrier against germs, environmental pollutants and UV radiation.   This skin is also home to trillions of bacteria, viruses, and fungi, and these are known as the microbiome. A weakened skin barrier or an unbalanced microbiome can lead to an imbalance between beneficial and harmful microorganisms, leading to many common skin problems including dry skin, sensitive skin, acne, dermatitis and psoriasis.

The microbiome is a self-sustaining ecosystem that balances perfectly with prebiotics, the food for the microorganisms to eat, probiotics, the organisms that inhabit the skin and postbiotics, the chemical byproducts of the non-living microorganism cells that act as immune regulators and enhance the skins natural defence mechanisms.

The skins microbiome is essential for both the health of the skin and the bodies overall immune health.  This comprises roughly 1000 different species, all working to regulate the skins pH levels, protect from environmental damage and boost immunity and fight infections, while keeping the skin hydrated and youthful-looking. The greater the diversity of the microbiome, the healthier the skin barrier is and the less likely the skin will be dry, red or irritated.

How Does it Benefit the skin?

The microbiome works in harmony with the immune system by keeping it regulated, training it what is and isn’t a threat and fighting pathogenic (disease-causing) organisms. The levels of healthy commensal bacteria are essential as they outcompete pathogenic bacteria for resources and provide the skin (and body) with many numerous beneficial bio-compounds.

The types of bioactive molecules produced by the microbiome that benefit the skin include:

• Hyaluronic acid a polysaccharide found in nearly every cell of the body.  It has a skin-supporting function in the dermis, maintains epidermal barrier function, immobilizes water in tissues, influences cell proliferation, and differentiation, and plays an essential role in wound healing and inflammatory responses.  The skin utilizes almost 50% of the body’s hyaluronic acid. 

• Lactic acid a component of the NMF, with antimicrobial activity against pathogenic microorganisms that helps the skin regulate the turnover of dead skin cells.

• Acetic acid an antibacterial compound used in the treatment of burns and infections.

• Diacetyl an antibacterial agent that is effective against common skin pathogens S. aureus and E. coli.

What is the Gut-Brain-Skin Axis?

The digestive system and the skin are connected in a physical and biochemical way referred to as the gut-skin axis. Both play important roles in defending the body against pathogens from the outside environment. Additionally, they are important parts of the neuroendocrine messaging system, as they both contain nerves that send and receive signals to and from the brain.

Immune connections between the skin and the gut can be seen in conditions such as celiac disease, which often presents alongside dermatitis, and/or psoriasis, where gut-associated bacteria can be more frequently found circulating in the bloodstream after escaping during the digestive process. Lipopolysaccharide (LPS) is an inflammatory toxin made by certain bacterial species that causes inflammation it is able to cross the membrane from the gut into the bloodstream, eliciting an immune response.

The gut and skin both have a neuroendocrine pathway that influences brain function. This article published in the Journal Clinics and Practice found dysbiosis of the skin and gut microbes in atopic dermatitis has been connected to mental states such as depression and anxiety.

Specific gut microbes produce a neurotransmitter called gamma-aminobutyric acid (GABA), which helps control feelings of anxiety and fear. Studies in mice have shown that certain probiotic strains can increase the production of GABA and reduce anxiety and depression-like behaviour.

This article found that Inflammatory bowel disease (IBD) has been associated with a higher risk of developing an inflammatory skin condition, such as psoriasis, atopic dermatitis, and rosacea. In a population-based study, the researchers found a significant association between IBD disorders, including both ulcerative colitis and Crohn’s disease, and inflammatory skin conditions. The same has also been found to be true for rosacea, psoriasis and ance.

What Can Cause Disruption to the Microbiome?

An imbalance in the skin microbiota composition (dysbiosis) are associated with several skin conditions, either pathological such as eczema, acne, allergies or psoriasis or non-pathological such as sensitive skin, irritated skin or dry skin.

By using skincare products with harsh ingredients designed to kill bacteria, like alcohols, preservatives, peroxides etc. we have over time changed the ecology of the skin ecosystem and caused a state of disharmony with the microbiome.  A few years ago, it was thought acne had to be treated this way, over-cleansing the skin until it was tight and dry, using astringent toners to shrink pores and dry up oil and oral antibiotics to kill the acne-causing bacteria.  Now we know this has the opposite effect by disrupting the skins pH balance and instead leads to a decrease in the diversity and numbers of helpful bacteria that are able to naturally reduce the number of C. acnes bacteria that can survive on the skin downregulating the immune response. It is now known that the best way to treat any skin condition is to address the underlying cause, by rebuilding the skins natural ecosystem and healing any gut imbalance.

How to Repair Disbiosis:

By using gentle products that nurture the microbiome and create an environment that is the optimal pH for the health of the skin and its many inhalants, we are able to allow the skin to naturally heal and repair itself for lifelong healthy skin that doesn’t need lots of expensive products, just happy skin that can do everything it needs to work at its optimum level. By topically supplementing the skin with probiotics, prebiotics and postbiotic molecules, they can be incorporated into the skin where they are recognized as their own.  This gives skin the ability to improve its barrier function and the ability to look and act like young, healthy, happy skin.

Prebiotics and the Skin:

Take care of your intestinal health by eating healthy, prebiotic and fibre-rich foods that can boost the skin’s ability to fight off bad bacteria and help improve the overall health of the skin and body. If you are unsure if your skin’s microbiome is healthy, or if you have some skin issues that you think could be solved with an improved diet, consider looking at the foods you are consuming. It is proposed that due to the important relationship between the skin and gut microbiome and the observed positive impact a plant-based diet has on gut health, plant-based topicals in cosmetics may also act as a healthy source of nutrients for the skin microbiome and perhaps overall health. Another approach is using post-biotic skincare. Bacteria that have been grown and then killed or attenuated are referred to as lysates and they serve as a nutritional source for the resident, helpful bacteria that naturally colonize healthy skin.  This helps reduce inflammation within the skin in the same way that has been shown by taking oral probiotic strains

To encourage microbial diversity by promoting healthy gut bacteria try increasing healthy foods. Focus on foods that contain prebiotics (like nuts, seeds, onions, leeks, garlic, apples, bananas and legumes) as well as foods with probiotics (like yogurt, kimchi, sauerkraut or kefir) which have been shown to stimulate beneficial skin bacteria and address acne. Probiotic supplements are also helpful, as research published in Critical Reviews in Food Science and Nutrition shows that they may help prevent and treat skin diseases.

Sources:

• Gut Microbiota’s Effect on Mental Health: The Gut-Brain Axis. Clinics and Practice, 2017.
• Health effects of probiotics on the skin. Critical Reviews in Food Science and Nutrition, 2015.
• Revealing the secret life of skin – with the microbiome, you never walk alone.  International Journal of Cosmetic Science, 2020.
• Topical use of probiotics: The natural balance.  Porto Biomedical Journal, 2017.
• Bioactive from probiotics for dermal health: function and benefit. Journal of Applied Microbiology, 2013.
• The gut-skin axis in health and disease: A paradigm with therapeutic implications. Bioessays, 2016.
• Inflammatory bowel disease is associated with an increased risk of inflammatory skin diseases: A population-based cross-sectional study. Journal of the American Acadamy of Dermatology, 2017.
• nfluence of pH values on the growth of Staphylococcus epidermidis, Staphylococcus aureus and Propinobacterium acnes in continuous culture. International Journal of Hygiene and Environmental Medicine, 1992.
• Location-related differences in structure and function of the stratum corneum with special emphasis on these of the facial skin. International Journal of Cosmetic Science, 2008.
• Inhibiting bacteria and skin pH in hemiplegia: effects of washing hands with mineral water. American Journal of Physical Medicine & Rehabilitation, 2002.
• The effect of pH on the extracellular matrix and biofilms. Advances in Wound Care, 2014.
• Normal skin surface pH is on average below 5, which is beneficial for its resident flora. International Journal of Cosmetic Science, 2006.
• Time-dependent variations of the skin barrier function in humans. Transepidermal water loss, SC hydration, skin surface pH and skin temperature. Journal of Investigative Dermatology, 1998.
• The Neuro-endocrinological Role of Microbial Glutamate and GABA Signaling. Frontiers in Microbiology, 2016.
• Magnetic resonance spectroscopy reveals oral Lactobacillus promotion of increases in brain GABA, N-acetyl aspartate and glutamate. Neuroimage, 2016.
• The effect of probiotics on immune regulation, acne, and photoaging. International Journal of Womans Dermatology, 2015.