The gut-skin axis

The gut and the skin are organs with crucial immune and neuro-endocrine roles and are uniquely related in purpose and function. The intimate relationship between these organs is referred to as the “skin-gut axis” and numerous studies have linked gastrointestinal (GI) health to skin homeostasis.

The relationship between the gut microbiome and skin health

One of the main regulators in the skin-gut axis is how the gut microbiota communicates with the skin and it does this mostly via intricate interactions with the immune system to regulate systemic and local inflammation.

In addition to this mode of communication, research suggests that the gut microbiota can affect the skin more directly. In the case of an impaired intestinal barrier, intestinal bacteria as well as their metabolites can enter the bloodstream, accumulate in the skin and disrupt the skin microbiome [1].

GI disorders are often accompanied by skin manifestations and the gut microbiome appears to play a key role in the development of many inflammatory disorders of the skin.

Altered gut function and associated skin disorders

Intestinal dysbiosis, a state of microbial imbalance, has the potential to negatively impact the skin microbiome and its basic function. This can contribute to common skin disorders such as acne, psoriasis, atopic dermatitis (eczema) and rosacea.

Research suggests a potential relationship between rosacea and Helicobacter pylori, a pathogenic bacteria found in the stomach and small intestine. A recent study demonstrates a significantly higher prevalence of H.pylori infection in those with rosacea when compared to controls and irradication of the bacteria led to a significant improvement in skin symptoms [2].

It is well established that the microbiome can regulate the immune response through multiple interactions with the immune system. In the case of atopic dermatitis, it is believed that lack of microbiome diversity during the early stages of life can affect the maturation of innate and adaptive immunity leading to chronic inflammation. Research has shown infants with atopic dermatitis to have low quantities of bifidobacterium and bacteroides [6, 10].

Although acne is caused by many factors, gut microbiome can play a key role in the progression and severity of the disease. The emotional stress that accompanies acne can impair the gut microbiome, most notably Lactobacillus and Bifidobacterium species. Psychological stress can cause intestinal microbes to produce neurotransmitters that can enter the bloodstream through the intestinal barrier, resulting in systemic inflammation [1, 7].

The skin microbiome

The skin microbiota, like the microbes present in the gut are able to interact with the immune system, helping to maintain skin homeostasis by inhibiting the growth of pathogenic bacteria found on the skin and decreasing inflammation. Dysregulation of the skin immune response can be seen in skin disorders such as psoriasis and atopic dermatitis [3, 8, 12].

The gut microbiome appears to have an influence on the skin microbiome. Short chain fatty acids (SCFAs) resulting from fiber fermentation in the gut can promote the growth of certain skin microbes, which influence immune defence and regulate skin inflammation [11].

Altering the gut microbiome to prevent and treat disease has been well established while the effect of skin microbiome on disease is still a developing and exciting area of research.

The role of probiotics in skin health

Recent research has suggested that probiotic supplementation presents promising potential in the role of prevention and management of various skin disorders.

An example of this can be seen in acne cases. Probiotics can suppress Propionibacterium acnes (P. acnes), the bacteria responsible for acne breakouts. They do this by secreting an antibacterial protein, which inhibits the growth of P. acnes [11].

There are of course many strains of bacterial species available as probiotics however the important ones to consider in the context of skin health are Lactobacillus species and Bifidobacterium. In a recent human study, after taking Lactobacillus.brevis oral supplementation for 12 weeks, a significant decrease in water loss across the skin epidermis and increased skin hydration was observed [9]. Another study also demonstrated a marked improvement in skin elasticity and increased skin hydration after 12 weeks of oral supplementation with Lactobacillus. Plantarum [11].

Diet is widely recognised as a key factor that mediates the function of the gastrointestinal microbiome. Dietary fiber goes through a process of bacterial fermentation in the GI tract, producing short chain fatty acids that promote a healthy colon. Studies have shown that a greater dietary fiber intake is associated with increased gut microbe diversity [5].

The recommended daily intake of fiber is 30g per day however in the UK we are getting roughly 14g per day. Good sources of dietary fiber include: oats, chia seeds, flax seed, all beans and pulses, grains, vegetables, avocado, apple, banana, nuts and seeds.

Consumption of probiotic foods are a great way to ensure you’re getting a wide diversity of the beneficial strains to promote skin health and help to maintain a healthy gut microbiome. Try to include a portion of the following foods daily:

Sauerkraut, kimchi, kefir, miso, tempeh, kombucha or even natural live yogurt

Consumption of prebiotic foods will also help to maintain a healthy balance gut microbiome. Prebiotics work in a similar way to fiber, acting as a source of fuel / food for the beneficial bacteria, allowing them to flourish in the gut and perform their health promoting functions. Although all prebiotics are fiber, not all fiber is prebiotic!

Probiotics in skincare

As the skin microbiome has become a widely studied area, the cosmetics industry has in recent years placed a lot of focus around topically applied probiotics in creams and serums.

Topical probiotics have shown efficacy in several clinical trials, particularly those involving the treatment of acne, atopic dermatitis and rosacea [4]. Whilst topical probiotics are promising therapeutic options for inflammatory skin conditions there is still a great deal of research that needs to be carried out to demonstrate large scale effectiveness.

In summary

There is an undeniable relationship between the gut microbiome and the skin and although this is not a new area of research, it has become an important topic in dermatology and gastroenterology alike. It is evident that many environmental factors such as diet and psychological stress can influence the gut microbiome, which can directly or indirectly affect skin health. With the use of probiotics supplements and consumption of probiotic foods showing great promise in the management of skin disorders, they should be widely considered as a therapeutic approach to address these concerns.

Gut health, as part of any nutritional intervention is getting a lot of attention and skin health is no exception to this. Look after your gut microbiota and your skin will flourish.

Find out more microbiome-friendly choices in an article by Nutritional Therapist, Laura MacDonald.

Reference list:

1. Bowe, WP. Logan, AC. (2011). ‘Acne vulgaris, probiotics and the gut-brain-skin axis – back to the future?’, Gut Pathogens, 2011 (3), 1. [Online]. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3038963/?report=reader
2. Gravina, AG. Federico, A. Romano, M. (2015). ‘Helicobacter pylori infection but not small intestinal bacterial overgrowth may play a role in rosacea’, United European Gastroenterology Journal, 3 (1), pp.17-24. [Online]. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4315682/
3. Grice, EA. Segre, JA. (2011). ‘The skin microbiome’, Nature reviews. Microbiology, 9 (4), pp. 244-253. [Online]. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3535073/
4. Griffin, LR. Melody, M. Aleksi, HJ. et al. (2019). ‘Topical probiotics: the unknowns behind their rising popularity’, Dermatology Online Journal, 25 (5):5. [Online]. Available at: https://escholarship.org/uc/item/2v83r5wk
5. Holscher, HD. (2017). ‘Dietary fiber and prebiotics and the gastrointestinal microbiota’, Gut Microbes, 8 (2), pp. 172-184. [Online]. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5390821/
6. Kim, JE. Kim, HS. (2019). ‘Microbiome of the Skin and Gut in Atopic Dermatitis (AD): Understanding the Pathophysiology and Finding Novel Management Strategies’, Journal of Clinical Medicine, 8 (4), 444. [Online]. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6518061/
7. Lee, YB. Byun, EJ. Kim, HS. (2019). ‘Potential Role of the Microbiome in Acne: A comprehensive review’, Journal of Clinical Medicine, 8 (7), pp.987. [Online]. Available at: https://www.mdpi.com/2077-0383/8/7/987/htm.
8. Nguyen, AV. Soulika, AM. (2019). ‘The Dynamics of the Skins Immune System’, International Journal of Molecular Sciences, 20 (8), pp.1811. [Online]. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6515324/
9. Ogawa, M. Saiki, A. Nakamura, T. (2016). ‘Effects of oral intake of heat-killed Lactobacillus brevis SBC8803 (SBL88) on dry skin conditions: A randomised, double-blind, placebo-controlled study’, Experimental and Therapeutic Medicine, 12 (6), pp. 3863-3872. [Online]. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5228549/?report=reader
10. Pascal, M. Perez-Gordo, M. Mayorga, C. (2018). ‘Microbiome and Allergic Diseases’, Frontiers in Immunology, 2018 (9), 1584. [Online]. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6056614/#!po=1.31579
11. Salem, I. Ramser, A. Ghannoum, MA. (2018). ‘The Gut Microbiome as a Major Regulator of the Gut-Skin Axis’, Frontiers in Microbiology, (9), pp.1459. [Online]. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6048199/#!po=2.77778
12. Vollmer, DL. West, VA. Lephart, ED. (2018). ‘Enhancing Skin Health: By Oral Administration of Natural Compounds and Minerals with implications to the Dermal Microbiome’, International Journal of Molecular Sciences, 19 (10), pp.3059. [Online]. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6213755/.