Skin Concerns
The Link Between Gut Health and Skin Health
BY
Anjali Tiscia
Aug 14, 2024
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Gut health, gut health, gut health. I am sure we have all heard about the importance of gut health for our overall health. With links to chronic disease prevention, improved mental health outcomes, reduced autoimmune risk and improved overall well-being. However, the link between gut health and skin health - often referred to as the gut-skin axis - is a fascinating area of research that shows our environment and behaviours can either positively or negatively impact our gut health and, as a result, the health and appearance of our skin. In this post we will explore the current findings about this gut-skin axis, how it impacts us and what we can do to improve our skin through our gut.
What is the Gut-Skin Axis?
Our bodies may seem like a collection of separate systems and organs, but it is becoming clear that these systems are constantly communicating through chemical and physical messengers like hormones, neurotransmitters and motor signals. Every part of our body is interconnected and they let each other know when things are good or not so good. The types of signals sent - whether positive or negative - therefore depends largely on the health of each system.
Ongoing research is exploring the connections between the gut and other parts of the body, such as the brain, lungs, and skin. The 'gut-skin axis' refers to the two-way communication between our gut and skin. It is believed that the state of the gut can impact the health and appearance of our skin and vice versa. Many skin concerns, like acne, psoriasis and eczema, occur more frequently in individuals with gut concerns. There is a particular link between an imbalanced gut microbiome, known as dysbiosis, and various inflammatory skin conditions.
The Gut Microbiome and Skin Health:
The gut microbiome is a collection of trillions of microbes living in our intestines, playing a crucial role in our health and longevity. These microbes can be either harmful or helpful, affecting not just the gut but also our skin and overall health. The beneficial gut microbes have a number of important roles in the body. They help to protect against harmful invading microbes, support metabolism, break down toxins and drugs, and produce essential vitamins, hormones and metabolites needed for our health.
One group of these beneficial metabolites are the short chain fatty acids (SCFAs), like butyrate. These SCFAs strengthen the gut lining and reduce the permeability of our intestinal barrier, preventing harmful substances and microbes that may enter into our gut from escaping into the bloodstream, which could lead to systemic health issues, including skin concerns.
The beneficial gut microbes can also help to make important plant polyphenols more bioavailable and these have tremendous benefits on our skin and overall health. From certain polyphenols (primarily ellagic acid and ellagitannins in pomegranates, walnuts, strawberries and raspberries), the gut microbiome produces metabolites called urolithins. They are said to have anti-inflammatory effects and help to improve mitochondrial activity in ageing tissues.
A healthy microbiome and the beneficial compounds and metabolites they produce can therefore positively impact the skin by providing both anti-ageing and anti-inflammatory benefits. However, when harmful microbes overgrow in the gut - a condition known as dysbiosis - it can lead to various gut and skin concerns, which we will explore in more detail below.
In addition to the gut microbiome, which directly impacts the health of our skin, we also have a skin microbiome that likely interacts with the gut microbiome. The skin microbiome is also a collection of beneficial and harmful microbes that live on our skin. Many skin conditions have been linked to an imbalance in the skin microbiome, where harmful microbes outnumber the beneficial ones. For example, atopic dermatitis has been shown to have decreased skin bacterial diversity and an increased presence of the harmful, Staphylococcus aureus. However, it is still unclear whether this imbalanced skin microbiome causes the skin condition or is a result of it.
Can Our Skin Influence Our Gut Microbiome?
The gut-skin axis works both ways: just as our gut and gut microbiome affect our skin, our skin also influences our gut microbiome. For example, when our skin is exposed to ultraviolet light (UVB rays specifically), it produces vitamin D. This increase in vitamin D leads to greater diversity in the gut microbiome - a marker that is linked to improved health outcomes. Interestingly, there is also a connection between skin health and food allergies. An impaired skin barrier, such as in the case of atopic dermatitis, might sensitise people to a peanut allergy.
Do Skin Conditions Start in the Gut?
When our gut lining is damaged and the gut microbiome is imbalanced, this can negatively impact the health of our skin. Studies have shown that the presence (or absence) of certain gut microbes is linked to skin conditions like rosacea, psoriasis, atopic dermatitis and acne vulgaris. While it is not yet clear whether these gut imbalances are the cause or consequence of the skin conditions (or if there is merely a correlation), there is strong evidence that gut dysbiosis is linked to inflammatory diseases throughout the body. So, it is reasonable to suggest that these inflammatory skin conditions are at least partly influenced by the health of our gut.
There are numerous examples of these gut-skin associations. For instance, people with acne tend to have fewer Firmicutes and more Bacteroides in their gut compared to those without acne. In atopic dermatitis, there are higher levels of gut Faecalibacterium prausnitzii, Clostridium and Eschericia and lower levels of beneficial Akkermansia, Bacteroidetes and Bifidobacterium. Rosacea has been linked to Small Intestinal Bacterial Overgrowth (SIBO) and ~7-11% of individuals with Inflammatory Bowel Disease (IBD) such as Crohn’s Disease and Ulcerative Colitis also have psoriasis, compared with 1-2% of the general population. This link between IBD and psoriasis likely has both genetic and immune-related causes.
Let’s explore some of the proposed mechanisms for this link between gut and skin conditions:
Dysbiosis and Skin Inflammation:
As we have discussed, an imbalanced gut microbiome, or dysbiosis, is linked to inflammation throughout the body, including the skin. Good gut microbes produce beneficial substances like short chain fatty acids (SCFAs), which strengthen the gut lining and have anti-inflammatory effects. A reduction of these beneficial bacteria, and in turn, of SCFAs is associated with conditions like IBD, and as mentioned above, IBD has associations with psoriasis.
On the other hand, an overgrowth of harmful microbes can cause inflammation. They produce reactive oxygen species (ROS) which damage tissues and accelerate ageing. These harmful microbes also produce toxins and metabolites that trigger the production of pro-inflammatory cytokines, which are found in greater amounts in individuals with certain skin conditions like atopic dermatitis.
Dysbiosis also causes premature ageing by increasing the activity of enzymes called Matrix Metalloproteinases (MMPs). These enzymes break down collagen and elastin - key structural proteins that keep our skin firm and elastic.
Increased Intestinal Permeability:
Increased intestinal permeability, or increased gut ‘leakiness’ occurs when the gut lining becomes compromised allowing for substances that enter into the gut, like harmful bacteria and toxins, to sneak into the bloodstream. A healthy gut lining acts as a barrier, keeping these substances out. When they do enter the bloodstream, they can cause systemic inflammation and this is thought to be linked with inflammatory skin conditions. In one study, they found bacterial DNA in the blood of patients with psoriasis, with E. coli as the primary source, suggesting their origin in the gut. These bacterial DNA fragments are associated with increased levels of inflammatory cytokines.
Certain dietary components, alcohol, specific gut conditions and dysbiosis can increase intestinal permeability. However, beneficial bacteria like Faecalibacterium prausnitzii produce SCFAs which help to protect the gut lining.
The Gut-Brain-Skin Axis:
The gut and skin are in constant communication, but the brain is also involved in this connection. Stress can trigger flare-ups in gut conditions like IBD and skin issues like psoriasis and acne, likely because of this brain-gut-skin link.
Interestingly, many key neurotransmitters, which are chemical messengers for the nervous system, are produced by gut microbes. These include GABA, dopamine, acetylcholine, and serotonin. While these neurotransmitters can influence skin function through the nervous system, we still don’t fully understand how they impact the skin but this is an exciting area of research.
What Positively Influences Gut and Skin Health?
We have covered a lot about dysbiosis, gut 'leakiness' and how certain gut bacteria are good while others are linked to certain skin conditions. We also touched on the benefits of SCFAs for overall health. But I'm sure what most of you really want to know is how to achieve a healthy gut and glowing skin - and what steps you can take to get there. I do need to mention though, if you have a skin condition already, this may require a more targeted and individualised approach. These suggestions are more general and are still absolutely safe to implement, however, you should consult with your health professional to develop a plan to help manage your specific concern.
Varied Plant-Based Diet:
No, this does not mean you need to be vegan or vegetarian but without a doubt, one of the best things you can do to improve your gut and skin health is to eat more plants! This means including more vegetables, legumes, fruits, wholegrains, nuts, seeds, herbs and spices. The key is diversity - a diverse plant-based diet leads to a more diverse (and healthier) gut microbiome. The “magic number” is 30 or more different plants per week, based on findings from the American Gut Project, which showed that those who hit this number had the most diverse and healthy gut microbiomes.
Similarly, the PREDICT study found 15 species of beneficial gut microbes that were linked with healthier diets and markers of overall health. People with these gut microbes were better at processing sugar and fat in foods and had less inflammatory markers. Unsurprisingly, they also consumed more fibre from a wide variety of plant foods.
Physical Activity:
Physical activity does not have to mean spending hours at the gym. It includes any form of movement that burns energy, like walking, swimming or pilates. Beyond weight loss, stress management and disease prevention, it appears from the research that physical activity also benefits gut and skin health by positively impacting the gut microbiome.
A systematic review looking at the effects of exercise on gut health found that a number of studies consistently showed increases in Bacteroides and Roseburia bacterial species in response to exercise. Bacteroides and Roseburia are key species involved in the production of the beneficial SCFAs that support gut health.
In another study, researchers found that aerobic exercise altered the microbiome within 2 weeks of exercise and achieved a stable new composition between 6 and 8 weeks. Interestingly, resistance training alone didn’t show the same effects. Also, it seems that whilst 2-3 times per week of physical activity can bring some changes to the gut microbiome, working out 5 or more days a week is needed for more significant diversity improvements.
Adequate Sleep:
We all know the importance of getting enough "beauty sleep" for weight management, reduced disease risk, and better mental health. But did you know that sleep also plays a key role in gut and skin health?
Our gut follows the body’s internal clock, known as the circadian rhythm. Disruptions to this rhythm through shift work, erratic sleep schedules, frequent travel or bright light exposure at night has been shown to negatively impact our gut microbiome. One study found that just two days of partial sleep deprivation in healthy young men led to changes in their gut microbiome, increasing the Firmicutes:Bacteroidetes ratio, a measure that is linked with metabolic diseases. They also had increased Coriobacteriaceae and Erysipelotichaceae, bacteria that have been found in higher proportions in humans that are morbidly obese.
Besides the indirect effects of poor sleep on the skin through the gut, a study commissioned by Estée Lauder found that poor sleepers also had more visible signs of ageing and slower recovery from external stressors like ultraviolet radiation. In a skin barrier stressor test, they found that after 72 hours, good sleepers had a 30% higher recovery than poor quality sleepers, highlighting the importance of sleep for faster skin recovery.
Stress Management Strategies:
Before we talk about the different stress management strategies and their benefits for gut and skin health, let’s first understand why chronic stress is so harmful. As we mentioned earlier, the brain communicates with the gut and the skin through chemical messengers. When we are stressed, the brain signals the release of stress hormones, which leads to inflammation, nerve sensitivity and changes in the gut microbiome. This can cause gut dysfunction, alter bowel movements, weaken the gut barrier and negatively impact the skin. For instance, stress is a reported trigger and aggravator for conditions like psoriasis.
Stress management techniques like meditation, deep breathing, yoga and spending time in nature can reduce these negative effects on the gut and skin. In one study comparing the faecal microbiome of Buddhist monks who practiced long-term meditation with control subjects, they found that the monks had more beneficial bacteria present in their stool, including Prevotella and Bacteroides, which are linked with better health. While the study involved only 56 participants and focused on the faecal microbiome, which may not fully represent the gut microbiome, it still highlights the importance of stress management for overall health and well-being.
Safe Sun Exposure:
As mentioned earlier, when our skin is exposed to UVB radiation from sunlight, it triggers the production of vitamin D, which not only benefits overall health but also improves gut microbiome diversity. However, excessive exposure to the sun can have harmful effects and actually end up damaging the skin. It is super important to be sun safe - learn more about that here!
Probiotics:
Probiotics are living microbes that can offer health benefits when consumed in the right amounts. You can find them in supplements or fermented foods like yoghurt, kimchi, and sauerkraut. Since a diverse gut microbiome is linked to better gut and skin health, adding these beneficial microbes to your diet seems like a smart choice. However, it's not that simple—probiotics vary, and finding the right strains for each person and condition can be tricky.
Still, some studies show promising results for gut and skin health. For example, in one study conducted on 45 acne patients, they found that patients treated with a combination of antibiotics (Minocycline) and probiotics saw better improvements in the total number of acne lesions, compared to those taking antibiotics alone.
A meta-analysis summarising the effect of probiotics on atopic dermatitis found that probiotic supplementation can reduce the severity of skin lesions in atopic dermatitis by improving gut permeability and reducing inflammatory markers. Also, a study on dandruff showed that a group taking probiotics with the Lactobacillus paracasei strain had a significant reduction in the severity and symptoms of dandruff compared to a control group.
What Negatively Influences Gut and Skin Health?
Just as important as knowing what can improve gut and skin health is understanding what might harm them. In this section, we’ll explore some of the factors that can negatively impact your gut and skin, often because they lead to gut dysbiosis, loss of beneficial microbes, and increased gut permeability.
High Fat and High Protein Diet:
Fat and protein are essential macronutrients, but consuming too much from certain sources can harm gut and skin health. Industrial trans fats and refined oils (like canola, vegetable, and soybean) as well as red and processed meats are linked to gut inflammation, which can also manifest on the skin.
High-fat diets have been shown to increase Firmicutes and reduce Bacteroidetes, a microbiome imbalance associated with metabolic issues, like obesity, insulin resistance and type 2 diabetes, as well as inflammation.
When we eat a lot of animal protein, our gut microbiome produces Trimethylamine N-oxide (TMAO), a molecule linked to inflammatory conditions like atherosclerosis and psoriasis. While moderation is fine, problems arise when these foods are consumed excessively without enough fibre.
Alcohol:
Excessive alcohol consumption has a significant impact on overall health, and so it is no surprise that it negatively affects gut and skin health too. Alcohol has been shown to disrupt the gut microbiome and increase gut "leakiness”.
A study examining the microbiomes of 48 alcoholics (with and without alcoholic liver disease) compared to 18 healthy people found that the alcoholics had lower levels of beneficial Bacteroidetes and higher levels of harmful Proteobacteria. This imbalance promotes inflammation and disease. Even after stopping alcohol, the dysbiosis persisted in both active drinkers and those who were now sober, suggesting that the effects of alcohol consumption are not temporary but long-lasting.
In skin directly, alcohol consumption appears to be a risk factor for certain skin conditions like acne and atopic dermatitis. In a cross-sectional study looking at a Dutch general population, they found that heavy drinking (>2 alcoholic drinks per day) is linked to moderate-severe atopic dermatitis, whilst low-moderate drinking (≤2 alcoholic drinks per day) was not linked to the condition, however this quantity and frequency can still have harmful effects on the body. Alcohol has also been shown to slow down skin wound healing due to increased inflammation in both the skin and gut. Finally, in people with rosacea, flare-ups of symptoms are frequently attributed to alcohol consumption.
Antibiotics:
Antibiotics work by killing harmful bacteria that cause infections, but they also affect the beneficial bacteria in our gut. While antibiotics are often necessary and life-saving for acute infections, the problem comes with overuse or when they are not appropriate or the best approach, such as in the treatment of viral infections. For example, oral administration of the antibiotic, Vancomycin for the treatment of skin wounds reduced bacterial diversity in the gut, potentially slowing down wound-healing.
Importantly though, antibiotics are often also used in the management of skin conditions like acne because they can kill harmful bacteria that contribute to acne. However, this isn't the only way to manage acne, and antibiotics should be used with caution due to their impact on gut health. It’s often a good idea to explore lifestyle changes first, in consultation with your healthcare provider. Also, as we mentioned under ‘probiotics’ above, if you are taking antibiotics for acne, pairing them with a good quality probiotic can improve acne and mitigate impacts on the gut.
Hygiene Hypothesis:
The hygiene hypothesis suggests that conditions like asthma, allergies, atopic dermatitis, and autoimmune diseases may arise from being too clean. The theory is that exposure to microbes, especially in childhood, helps strengthen the immune system. This doesn’t mean you should skip basic hygiene, but rather that overuse of sanitisers and antibacterial products, and avoiding natural exposure to things like dirt and animals, may not be beneficial.
Interestingly, studies show that children exposed to farms or stables are less likely to develop these atopic conditions, and this exposure even helps in conditions that impact the gut, like Inflammatory Bowel Disease (IBD). In one study, patients with Crohn’s Disease who were given ova from a pig parasite (Trichuris suis) over a 6 month period saw symptom improvements in 72% of cases.
This connection is likely related to the gut and skin microbiomes. Over-sanitising can kill beneficial bacteria, while exposure to a variety of microbes, such as those found on animals, supports microbiome diversity - key to better health.
Artificial Sweeteners:
Artificial sweeteners like aspartame, saccharin, sucralose, and acesulfame-K are popular calorie-free sugar alternatives, often found in sugar-free products and touted as better for blood sugar control. However, new research suggests they may negatively impact our gut microbiomes.
In a study of 120 healthy adults, different groups were given various artificial sweeteners, and researchers found noticeable changes in both their stool and oral microbiomes.
While the direct link to gut and skin health isn’t fully clear yet, animal studies have shown that these changes in the microbiome may increase the risk of obesity and type 2 diabetes.
