Microbiome part 1: the gut-skin axis


Until recently, if I told you that there are at least as many microbes in and on your body as your own cells, you would have recoiled in disgust. But science has helped us understand the important roles these microbes (a huge collection of bacteria, viruses, fungi and other microscopic organisms - called the ‘microbiome’) play in our health.

This post deals with the gut microbiome-skin axis and how we can manipulate this with oral probiotics for optimum skin health. Part 2 of this series (next month) will deal with maintaining the skin microbiome and topical application of probiotic creams.


The gut microbiome – what we do and don’t know

Let’s focus on the gut microbiome. After decades of research we know that changes in the gut microbiome are associated with diseases like inflammatory bowel disease, obesity, autism, arthritis, some diarrhoeal infections, and the skin diseases: acne, atopic dermatitis, and psoriasis. We don’t know exactly HOW changes in our microbes cause disease, although scientists have 2 theories: (1) microbes change circulating immune system chemicals, and; (2) microbes directly produce chemicals that circulate in the blood stream. Some other things we don’t know about the microbiome: how and why the gut microbiome varies over time, why it is so personalized to individuals, or what a ‘healthy’ microbiome looks like. Clearly, there’s an enormous amount of research yet to be done, so it’s important that you ask for evidence before you believe a ‘miraculous’ microbiome-related cure.


The link between gut and skin health – the ‘gut-skin axis’

Whilst we don’t yet know the mechanism behind them, several diseases gave us a hint that there might be a relationship between the gut and skin. Certain gut conditions have manifestations in the skin: for example, 7-11% of inflammatory bowel disease patients are diagnosed with psoriasis. And it works both ways - some skin conditions are used to diagnose underlying gut diseases and malignancies. These types of associations got researchers thinking: can we manipulate gut flora easily, cheaply and safely with pre- and pro-biotics to positively impact skin health?

The rise of nutribiotics: Can we improve skin health and appearance with probiotics?

The good news is that we can! Research has shown a beneficial relationship between probiotics and skin health, and not just in lab rodents or skin cells in a dish, but in actual, real humans in well-designed, independent studies. Multiple studies have demonstrated improved skin barrier function (decreased water loss from the epidermis, increased skin hydration and decreased skin sensitivity) when human subjects were given oral probiotic supplements containing Lactobacillus and Bifidobacterium species, also called ‘Lactic Acid Bacteria’ (LAB for short). There are too many studies to detail all the findings here, but some are listed in this table, if you want to research them in more detail for yourself:

Image source: Salem, I, Ramser, A,  et al.  2018, The gut microbiome as a major regulator of the gut-skin axis.  Front Microbiol , 9:1459.

Image source: Salem, I, Ramser, A, et al. 2018, The gut microbiome as a major regulator of the gut-skin axis. Front Microbiol, 9:1459.

Of course, the mice and rats didn’t escape unscathed (sorry, that’s science) – supplementing rodents with LAB probiotics resulted in improvement in the kinds of biological processes that improve skin health and appearance. Or to put it simply – mice have shinier fur after eating probiotic yoghurt! This is yet more supporting evidence that probiotics can improve skin health - obviously not as compelling as the human studies, but you get the picture. If you want to read up on some of these studies, here they are:

Image source: Salem, I, Ramser, A,  et al.  2018, The gut microbiome as a major regulator of the gut-skin axis.  Front Microbiol , 9:1459.

Image source: Salem, I, Ramser, A, et al. 2018, The gut microbiome as a major regulator of the gut-skin axis. Front Microbiol, 9:1459.

In yet more studies, prebiotics (substances that nourish our resident intestinal bacteria, the ones you often hear described as ‘good’ bacteria) had a similar effect. I think you’ve probably had enough of reading references by now, so these are included with the others at the end of this post.

*Probiotic treatment of specific skin diseases is a complex topic, and too broad to discuss here. If you’re interested in this, contact me here and I can address it in another post. 

Click here to see which commercial probiotic contains the bacterial strains shown to improve skin health.

What about probiotics and ageing skin?

Skin ageing is a complex process involving intrinsic (hormones, genetics) and extrinsic (UV exposure, smoking, pollution) factors that all contribute to changes in cell activities and molecules. These changes accumulate and produce the outward appearance we associate with older skin: laxity, wrinkles and sagging. I’ll address all of these issues in the coming months, but for now let’s look at whether oral probiotics can positively impact ageing skin. Topical probiotics and ageing will be dealt with in Part 2 next month.

We have already seen that probiotics can improve skin moisture levels (and which of us with ageing skin don’t want that!), but let’s consider some other ageing factors: 

UV - Ultraviolet radiation is the primary external contributor to skin ageing, a process called ‘photo-ageing’ (if you know me, you’ll know I’m an SPF Nazi). Several studies have shown that Lactobacillus (strain: L. sakei) supplements can reduce photo-ageing in mice as well as human fibroblast cells in a laboratory. Fibroblasts are the cells that produce collagen and elastin precursors in our skin. UV radiation also alters skin immune responses that are associated with ageing and skin cancer development. Oral probiotics (strain: L. johnsonii La1) can prevent these UV-related changes in human skin immune cells, again only in the laboratory. More work needs to be done, but these results are promising.

 Collagen – a family of enzymes called matrix metalloproteinases (MMPs) increase in older skin. These enzymes increase collagen breakdown and decrease new collagen production in skin, resulting in an overall decrease in collagen in the skin of older people. Supplementation with a commercial probiotic formulation called VSL#3 (8 strains of Lactobacilli and Bifidobacteria plus Streptococcus salivarius subsp thermophilus) reduced MMP formation in the gut (this study wasn’t looking at the skin). Other studies show that probiotics reduce MMP in saliva. It is therefore possible that the same mechanism occurs in skin, but this is yet to be confirmed.

The take home message

I’ll admit I was sceptical when I started researching this topic, but the weight of evidence has convinced me that probiotics have a role in skin health. Will I go and find a good LAB probiotic? Well, I will definitely start searching for one that contains the skin-specific strains that have been shown to work (I found it! It’s this one).

There are a couple of caveats:

1.    Stay on top of the research as this is an emerging field and open to continuing evaluation.

2.    Most probiotic LAB don’t persist in the gut after you stop taking them. Although this probably doesn’t impact their ability to activate the immune system or produce their own chemicals, it’s important to know that any health benefits will only occur if you take them daily, and only during the period you take them.

3.    Foods containing LAB are therefore a great way to get a daily dose. These include fermented foodstuffs like yoghurt, cheese, sauerkraut, olives, kefir, tempeh, kombucha, pickles, kimchi. I already take this soluble fibre supplement (prebiotic) each day.

4.    The participants in all human studies referenced here took the probiotic (or placebo) for at least 2-3 months before the results were evaluated. So if you’re going to take a probiotic with a view to improving skin, don’t just take it for a week and decide it’s not working!

5.    I know the limitations of my qualifications - if you have an immune disorder, or anything else you’re concerned about, check with your doctor before taking any probiotics.



Cinque, B, Palumbo, P, et al. 2017, Probiotics in ageing skin. In Textbook of Ageing Skin, Farage, MA, Miller, KW, Maibach, HI (eds), pp:811-820.

Forbes, JD, Van Domselaar, G, et al. 2015, The gut microbiota in immune-mediated inflammatory diseases. Front Microbiol, 7:1081.

Frei, R, Akdis, M, et al. 2015, Prebiotics, probiotics, synbiotics, and the immune system: experimental data and clinical evidence. Curr Opin Gastroenterol, 31:153–158.

Gilbert, JA, Blaser, MJ, et al. 2018, Current understanding of the human microbiome. Nat Med, 24(4):392-400.

Guéniche, A, Philippe, D, et al. 2009, Probiotics for photoprotection. Dermato-Endocrinology, 1(5):275-279.

Lee, D-E, Huh, C-S, et al. 2015, Clinical evidence of effects of Lactobacillus plantarum HY7714 on skin aging: a randomized, double blind, placebo-controlled study. J Microbiol Biotechnol, 25(12): 2160-2168

Levkovich, T, Poutahidis, T, et al. 2013, Probiotic bacteria induce a ‘glow of health’. PLos ONE, 8(1):e53867.

Maguire, M and Maguire, G, 2017, The role of microbiota, and probiotics and prebiotics in skin health. Arch Dermatol Res, 309:411-421.

Muizzuddin, N, Maher, W, et al. 2012,  Physiological effect of a probiotic on skin. J Cosmet Sci, 63:385–395.

O’Neill, CA, Monteleone, G, et al. 2016, The gut-skin axis in health and disease: a paradigm with therapeutic implications. Bioessays, 38(11):1167-1176.

Salem, I, Ramser, A, et al. 2018, The gut microbiome as a major regulator of the gut-skin axis. Front Microbiol, 9:1459.

You, G-E, Jung, B-J, et al. 2013, Lactobacillus sakei Lipoteichoic Acid Inhibits MMP-1 Induced by UVA in Normal Dermal Fibroblasts of Human. J Microbiol Biotechnol, 23(10):1357-1364.