Brain-Gut-Skin Axis

Focus on the Brain-Gut-Skin Axis

Have you ever wondered why your face flushes when you drink wine?
Or why your love of chocolate makes your skin blotchy?
Well, the science is in.

The gut and the skin share many common functions as they are both an interface between the external environment. They both have a protective layer, a unique microbiome and well-organised immune and neuroendocrine systems through which they communicate. These systems form the basis of the Gut-Skin axis. In addition, both the gut and the skin are under the influence of neuroendocrine signals from the brain – thus forming the Brain-Gut-Skin Axis.

The exact mechanisms of this tri-directional communication are still uncertain, however the bi-directional communication between the gut and brain is well established. Stress has been shown to change microbial composition within hours, and dysbiosis is strongly associated with psychological conditions such as anxiety. Both stress and dysbiosis have been linked to rashes, psoriasis, acne, dermatitis, hair loss and rosacea. What is uncertain is whether stress is able to cause these skin changes directly or whether it occurs indirectly through the microbiome. Either way, gut disorders such as Coeliac disease and Inflammatory Bowel Disease (e.g. Crohn’s disease and Ulcerative Colitis) have been well researched and found to be associated with a range of skin symptoms or conditions such as dermatitis, psoriasis and rosacea


How it’s all connected…

When the gut is healthy, the microbiome produces a variety of metabolites that regulate immune function to produce an anti-inflammatory response throughout the body. It also produces neurotransmitters, vitamins and peptides that have widespread benefits. Combined, these metabolites help to maintain healthy skin function and appearance. (See left side of the image below).

In states of dysbiosis, microbial metabolites are altered due to a reduction in beneficial bacteria and an increase of pathogenic ones. Metabolites deriving from pathogenic species have been linked to increased permeability of the gut wall (leaky gut), which then allows antigens to pass through. In addition, these metabolites – alongside antigens from the gut lumen - produce a potent inflammatory response and disrupt metabolic and neuroendocrine signals. The detrimental effects of these signalling molecules extend well beyond the gut and have been found to disrupt the function of distal organs such as the liver, fatty tissue, brain and skin. These are the mechanisms through which pathological changes in the gut have been linked to pathological changes within the skin. (See right side of the image below)


The molecular pathways towards skin dyshomeostasis

Research has found that certain gut bacteria are able to trigger specific immune responses within the gut that are associated with either skin homeostasis (balance) or dyshomeostasis (imbalance).

These immune pathways involve the activation of specific T cells (lymphocytes) and their subsequent differentiation into either regulatory T cells (Treg) which have an anti-inflammatory effect, or T-helper cells – which are pro-inflammatory. The most common T-helper cells involved in cellular and organ dysfunction are Th1, Th2 and Th17, which, when activated, produce an inflammatory, allergic or autoimmune response, respectively (see image below). Whether a Treg or T-helper cell response is activated depends on the individual’s microbial composition, the signalling molecules produced by these bacteria and genetic predisposition. The image below shows the specific T-cell pathways that are associated with a range of skin outcomes. It’s important to note that these pathways can - and often do -coexist, which means acne, psoriasis and eczema can be present at the same time.


Another thing to note is that all of these pathways lead to inflammation in the skin. This causes oxidative stress which disrupts cellular regeneration and repair and ultimately leads to accelerated ageing and wrinkles. The connection between inflammation and ageing has been termed “inflammageing” and you can find more information on the topic here

Foods that contribute to skin disorders

There is no doubt that diet and medications (especially antibiotics) have the greatest impact on the gut microbiome. Fortunately, these are modifiable factors. The microbiome changes from meal to meal, which means we have the ability to restore it to a more health-promoting profile.

Diets that are high in sugars and saturated fats have been linked to dysbiosis and skin conditions such as acne, rosacea, psoriasis and general skin reactivity. In addition, they change the way our body manages carbohydrates – termed glycaemic control. If unchecked, poor glycaemic control leads to excess glucose in the bloodstream and eventually insulin resistance. In the skin, excess glucose triggers inflammation and accelerated skin ageing. It also increases lipid production and bacterial colonisation – signs that are synonymous with acne. Hence the link between chocolate and botchy skin.

Insulin resistance also changes testosterone levels within hair follicles, leading to hair loss on scalp, but an increase in facial hair (termed hirsutism). This means that a high carbohydrate diet, may cause masculinisation in a female.

Dysbiosis and leaky gut have also been linked to food intolerances due to activation of the allergy pathways within the gut immune system (Th2). And again, this activity extends to distal organs, such as the skin. It is estimated that up to 40% of individuals will have antibodies against one or more food proteins or constituents (such as histamine). This is wine, which is naturally high in histamine, may cause facial flushing or a rash. Similar skin responses may be seen with collagen powders and fermented foods – both high in histamine. Consuming these so-called “gut-healing foods” can actually do more harm than good in up to 40% of the population. (More information on fermented foods here ).

How to reduce skin symptoms and reactivity

If you want to improve the health and appearance of your skin, you need to take care of your gut and brain.

If you have any skin signs or symptoms - or any chronic condition – there are no quick fixes. It will take a degree of commitment to see an improvement and there are no blanket recommendations. Everyone has a unique baseline microbiota, a specific food tolerance profile and different genetics. A systematic learning approach is needed so that you understand how to identify your needs at any given time. This is what BiomeMD® provides as a kickstart towards optimising your physiology.

If you’re not ready for that level of commitment, then here are some tips to help you get started:

  1. Avoid processed foods and foods that are high in sugars, saturated fats and additives.

  2. Avoid foods that are high in histamines (fermented foods, vinegar, wine, protein powders).

  3. Avoid any foods that cause symptoms such as bloating, cramping, flatulence, fluid retention, fatigue, headaches, skin symptoms, cravings, joint pain, mood swings or brain fog.

  4. Avoid grains, dairy, alcohol and caffeine until symptoms resolve, particularly if you have any autoimmune or inflammatory conditions.

  5. Switch to an unprocessed diet that is high in leafy greens and brightly coloured vegetables, add plenty of healthy fats (olive oil, avocado, flaxseed oil) plus small amounts of fish and low-sugar fruit.

  6. Incorporate some positive lifestyle changes – like allocating rest time, stress management and ensuring that you get enough sleep. More on that here

These changes are likely to make a big difference to the quality and function of your gut, skin and brain. REFERENCES:

  1. Salem I, Ramser A, Isham N, Ghannoum MA. The Gut Microbiome as a Major Regulator of the Gut-Skin Axis. Front Microbiol. 2018;9:1459. Published 2018 Jul 10. doi:10.3389/fmicb.2018.01459

  2. Thevaranjan, N. et al. Age-Associated Microbial Dysbiosis Promotes Intestinal Permeability, Systemic Inflammation, and Macrophage Dysfunction. Cell Host & Microbe. 21, 455–466; April 12, 2017

  3. O'Neill CA, Monteleone G, McLaughlin JT, Paus R. The gut-skin axis in health and disease: A paradigm with therapeutic implications. Bioessays. 2016 Nov;38(11):1167-1176. doi: 10.1002/bies.201600008.

  4. Comas-Basté O, Sánchez-Pérez S, Veciana-Nogués MT, Latorre-Moratalla M, Vidal-Carou MDC. Histamine Intolerance: The Current State of the Art. Biomolecules. 2020;10(8):1181. Published 2020 Aug 14. doi:10.3390/biom10081181

  5. Alexandra R Vaughn, et al. Skin-gut axis: The relationship between intestinal bacteria and skin health. World J Dermatol. Nov 2, 2017; 6(4): 52-58. doi: 5314/wjd.v6.i4.52

  6. Rodrigo L, Beteta-Gorriti V & Alvarez N, et al. Cutaneous and Mucosal Manifestations Associated with Celiac Disease. Nutrients. 2018 Jun 21;10(7):800. doi: 10.3390/nu10070800.

  7. Parodi, A., Paulino, S & Greco, A. (2008) Small Intestinal Bacterial Overgrowth in Rosacea: Clinical Effectiveness of Its Eradication. Clin Gast and Hep. 6 (7), 759-764

  8. Zheng, D., Liwinski, T. & Elinav, E. Interaction between microbiota and immunity in health and disease. Cell Res30, 492–506 (2020).

  9. Kim, J. & Kim, H. Microbiome of the Skin and Gut in Atopic Dermatitis (AD): Understanding the Pathophysiology and Finding Novel Management Strategies. Clin. Med.2019, 8(4), 444;

  10. Lee, N., Kim, W. Microbiota in T-cell homeostasis and inflammatory diseases. Exp Mol Med49, e340 (2017).

  11. Flannigan, KL & Denning, T. Segmented filamentous bacteria‐induced immune responses: a balancing act between host protection and autoimmunity. Jour Cel Mol Sys & Tech. 2018. doi/10.1111/imm.12950

  12. Leeming ER, Johnson AJ, Spector TD, Le Roy CI. Effect of Diet on the Gut Microbiota: Rethinking Intervention Duration. Nutrients. 2019;11(12):2862. Published 2019 Nov 22. doi:10.3390/nu11122862

  13. Karl JP, Hatch AM, Arcidiacono SM, et al. Effects of Psychological, Environmental and Physical Stressors on the Gut Microbiota. Front Microbiol. 2018;9:2013. Published 2018 Sep 11. doi:10.3389/fmicb.2018.02013

  14. Smith RP, Easson C, Lyle SM, et al. Gut microbiome diversity is associated with sleep physiology in humans. PLoS One. 2019;14(10):e0222394. Published 2019 Oct 7. doi:10.1371/journal.pone.0222394

  15. Mitchell CM, Davy BM, Hulver MW, Neilson AP, Bennett BJ, Davy KP. Does Exercise Alter Gut Microbial Composition? A Systematic Review. Med Sci Sports Exerc. 2019 Jan;51(1):160-167. doi: 10.1249/MSS.0000000000001760. PMID: 30157109.