The Gut-Skin Axis
What You Put on Your Plate Shows Up on Your Skin
Illustration © D. Yael Bernhard
Your skin is the largest organ in your body. It forms a protective barrier against heat, cold, moisture, chemicals, pathogens, and ultraviolet sunlight. It’s also an interface between the outside world and the inside of your body, acting as a sensory organ and releasing sweat, oil, and toxins. Your skin produces pigment, grows hair, and cushions muscles and bones. It has several layers which must constantly regenerate as well as maintain elasticity.
As your protective outer layer or integument, your skin is a major part of your microbiome. It hosts a large microbial community – up to 1200 different species of bacteria, fungi, parasites, phages (beneficial viruses that kill harmful bacteria), and more.1 These microbes are your friends. Crowding out the bad guys with good microbes is more effective than killing the bad ones – and the good ones – with chemicals and drugs. Maintaining a healthy skin microbiome is essential for maintaining strong immunity. Excessive washing and using antibacterial soaps, gels, and wipes damages your skin microbiome. Walking barefoot, gardening, eating minimally-rinsed fruits and vegetables direct from farms, and petting animals that come in contact with the earth are all effective ways to replenish it. It’s also crucial to eat fermented foods on a regular basis. In some cases, applying them externally may be soothing, such as dabbing plain yogurt or the brine of kimchi or sauerkraut on an itchy yeast infection. It’s important to remember, however, that the underlying cause of yeast infections comes from the gut.
It’s midsummer as I write this article, and especially at this time of year, overexposure to sunlight comes to mind as a major cause of skin damage and cancer. Fortunately, there are several ways to protect yourself. Fruits and vegetables rich in antioxidant polyphenols also help protect skin against the harmful effects of ultraviolet radiation. Examples include catechins found in green tea; ellagitannins in pomegranates; anthocyanidins in blue and red berries; isoflavones in edamame soybeans; stilbene in the skins of grapes; and silymarin in milk thistle seed. These antioxidants are anti-mutagenic and chemoprotective, reducing inflammation, repairing DNA damage, and modulating the body’s immune response. Studies have shown great promise in these polyphenols to “prevent, delay or completely halt the process of photocarcinogenesis.”2
While commercial sunscreens may be better than nothing, many are loaded with harmful ingredients that are absorbed through the skin. They’re also expensive, inconvenient, and messy. EWG.org puts out a review of safe sunscreen products each year. But my personal favorite is homemade: St. John’s Wort oil – that is, fresh flowers of Hypericum perforatum infused into olive or avocado oil. This remarkable plant produces hypericin to protect itself from the sun. I gather the bright yellow flowers each year in June and July, fill a small jar, fill the jar again with oil, and wait six weeks. It’s that simple. It costs almost nothing, has no toxic chemicals, spreads easily, and may be applied in advance of exposure to the sun. Hypericum oil also makes an effective and soothing remedy for sunburn. Its unfounded reputation for causing sun sensitivity and other adverse effects is based on improper use of the plant in dried form (powders, pills, and teas).
Collagen and elastin play a crucial role in skin health, derived from the proteins you eat. Collagen is made within the body. Collagen supplements may be broken down into the raw materials for building more collagen, but do not provide it directly. Collagen is harmed by glycation, a process which makes it rigid and less elastic, contributing to wrinkles. AGES, or advanced glycation end products, are created when sugars and proteins fuse together in high heat cooking methods such as broiling, grilling, frying, air-frying, and smoking. Glycation is what makes French fries crispy and toasted bagels crunchy. AGES cause aging by way of inflammation, dehydration, and oxidative stress, not only aging your skin but also contributing to cancer. You can reduce glycation by using “low and slow” cooking techniques such as poaching, simmering, and stewing; by marinating meats in liquid before cooking; and by cutting out sugar. Chicken soup, for example, is much healthier than fried chicken coated in bread crumbs, which break down into sugar.
Chronic skin disorders such as acne, eczema, rosacea, and psoriasis are also directly affected by the gut – not just what you eat, but the state of your microbiome. But wait, you might ask, how can a rash be the result of diet? Doesn’t bad food cause digestive upset? Won’t a dairy allergy show up as a stomachache? If you have bad gut bacteria, won’t it cause intestinal uproar?
Not necessarily. For some people, not at all; for others it’s the “new normal” they no longer notice. The body works in mysterious ways. If you have an intestinal barrier that is damaged by gluten, or a gut microbiome that’s been wiped out by antibiotics, it may produce obvious symptoms, or be intermittently disruptive, or show up elsewhere in the body. Inflammation in your gut may be silent, causing no obvious digestive symptoms for months or years – but on a cellular level, changes are taking place in far-flung tissues such as your eyes, your brain, your thyroid, nerves, and skin. It’s all connected. Thus, food poisoning may cause a headache; excess alcohol may aggravate painful joints; and a food sensitivity or dairy intolerance may underlie a chronic skin condition.
The “gut-skin axis” is a term that describes an alliance between your gut and your skin. It has the word “gut” first and “skin” second to imply cause and effect. I prefer to think of it as many axes that radiate outward from your gut to your skin, like the life-giving rays of the sun. Your gut microbiome is your internal interface with the outside world, comprised of millions of microbes that live inside you. It’s lined with “gut associated lymphatic tissue” (GALT), which produces 2/3 of your immune system. Like a marionette master who controls the strings, this internal ecosystem governs nearly every chronic condition in your body, whether good or bad. It’s up to you how you populate your microbial community, which far outnumbers your own cells. If you have too many bad microbes, or too few good ones, this results in a dysfunctional gut-skin axis. Bad gut bacteria thrive on sugar and ultra-processed foods; good ones love prebiotic fiber from fruits and vegetables.
An unhealthy microbiome results in inflammation and damage to the intestinal walls. Zonulin, a protein that weakens the gut lining, is triggered in response to harmful foods, particularly gluten. After years of exposure to zonulin, your gut may literally be torn and leaking, like frayed cheesecloth, allowing unwanted particles and substances to pass into your bloodstream, such as undigested food; endotoxins from bad bacteria; yeast; casein proteins from cow milk; solanines from nightshade vegetables; and any number of chemical additives. Your body perceives these antigens as a threat, and launches cellular soldiers to attack the invaders. In doing so, the body may also attack itself. This is an inflammatory autoimmune response, a/k/a food sensitivity. Less severe than food allergies (which may be life-threatening) but along the same spectrum, food sensitivities may be more insidious and difficult to detect. “Atopic dermatitis,” another term for eczema, means “inflamed allergy.” The inflammation is chronic, but when provoked by stress or certain foods, may also flare from low-grade into an acute condition.
The gut-skin axis governs this chain of cause and effect. The greater the degradation of the protective mucosal lining of the gut, the more severe the eczema.3 Autoimmune reactions may also surface along a different axis – such as in the lungs as asthma; in the joints as psoriatic or rheumatoid arthritis; in the thyroid as Hashimoto’s disease; in the gut as Crohn’s disease or ulcerative colitis – and so on. All arise in the gut, and cause the body’s immune system to mistakenly attack its own healthy tissue.
Chronic internal inflammation may also manifest externally as acne. Consuming too much sugar and toxins may cause the natural turnover of skin cells to accelerate beyond what the skin can handle, causing external inflammation. Like all skin conditions, acne is an inside job that shows up on the outside.
Establishing a healthy microbiome and repairing a leaky gut are crucial to healing these conditions. The two go hand in hand – for your probiotic pals are the ones who repair their own habitat. Fermented foods and plenty of fiber are the key to a good internal neighborhood. Full-fat yogurt and kefir, kimchi and sauerkraut, probiotic pickles, natto, kombucha, and miso are all excellent sources of the beneficial bacteria that build a healthy gut barrier, and along with it, clear skin. Judicious use of probiotic supplements may be helpful in certain cases, but live foods almost always trump pills and powders. The goal is a healthy ratio of good to bad, so that your bacterial buddies dominate the bullies in your belly. This means eating fermented foods daily, in different forms, not always the same kind or even the same brand. Mix it up! The more the merrier – probiotic bacteria join their molecular hands and work as a team to strengthen the tight junctions that control gut permeability and restore the delicate mucosal lining of the gut. Prebiotic foods – insoluble fibers that feed gut bacteria – are also important. Examples include Jerusalem artichokes, asparagus, cold cooked potatoes, jicama, dandelion greens, chicory root, onions, plantains, and more.
Food is information. The food you eat not only provides the raw material of your flesh and bones, but also sends signals to every cell in your body. As the earth circles the sun, your health revolves around your gut. This is where you take in the world and make it part of your body. We are holobionts – living, walking hosts for the organisms we house.
If we treat these organisms well, they pay dividends in the form of precious short-chain fatty acids (SCFAs), the “postbiotics” produced by good gut bacteria. Among these, butyrate is currently the most well-known for its ability to impede cancer. Research on postbiotics is already merging with the field of immunology, as specific strains of bacteria are harnessed to produce these healing compounds. Among these are Akkermansia muciniphila, Clostridia butyricum, Faelcalibacterium prausnitzii, and Roseburia spp. These intestinal allies repair a leaky gut, calm inflammation, quiet the immune system, and benefit your liver. SCFAs are also the preferred energy source of your enterocytes (intestinal cells), to fuel their digestive work.
“Severity of atopic disease inversely correlates with intestinal microbiota diversity and butyrate-producing bacteria.”4
In addition to fermented foods, medicinal herbs have a healing effect on chronic skin conditions. Burdock root has been used for centuries to heal skin problems ranging from blemishes to tumors. Infuse the root in boiled water for at least 8 hours, or try a liquid alcohol-based extract. The fresh root may also be cooked and eaten as a vegetable. Dandelion root is a supreme ally of the liver and lymphatic system, helping to detoxify the entire body, including your skin. Liquid extract is probably the most convenient form. Chaga tea or liquid extract, made from a hard fungal conk that grows on birch trees, is also renowned for its powerful antioxidants and medicinal effect on both intestines and skin.
Certain foods are especially beneficial to the skin. Bone broth is nutrient-dense, and rich in gut-sealing collagen and other amino acids. Whether made from chicken, beef, or fish bones, bone broth is healing to the gut and beneficial to the skin.5 Seaweed helps support healthy skin and hair, as well as detoxifying heavy metals, increasing bone density, mitigating the effects of radiation, and other health benefits.6 Seaweed contains beneficial histidines, which help produce natural moisturizing factors (NMFs) in the skin; and alginate and chitin, which help to seal up a leaky gut.7 You don’t need much – a small handful of dry seaweed crumbled into any savory soup, stir-fry, or stew is sufficient. Coconut oil contains lauric acid, a fatty acid which helps the body produce a skin-friendly protein called filaggrin. Some people with eczema are genetically deficient in this protein.8Curcumin from turmeric is also believed to help the formation of both filaggrin and collagen. Its antioxidant, anti-inflammatory properties make it a good choice. Turmeric is best combined with a little black pepper for greater absorption.
For severe or chronic skin or gut problems, colostrum supplements may be helpful. Colostrum heals the gut barrier and provides immunological support, which in turn benefits the skin.9 It also contains lactoferrin, a glycoprotein that supports a healthy microbiome.10
Chronic skin conditions are multifactorial, and it may take several changes and some trial and error to achieve your goal of clear, healthy skin. A naturopathic or functional dermatologist may be necessary in order to determine the root cause. No matter where you are on this journey, good nutrition is a great start. As you improve your diet, your skin will become healthier.
Once you understand the gut-skin axis, it all makes perfect sense. What you put on your plate and pour in your cup shows up on your skin. Everything shines from the inside.
To your good health –
Yael Bernhard
Certified Integrative Health & Nutrition Coach
Have you seen my other Substack, Image of the Week? Check it out here, and learn about my illustrations and fine art paintings, and the stories and creative process behind them.
Yael Bernhard is a writer, illustrator, book designer and fine art painter with a lifelong passion for nutrition and herbal medicine. She was certified by Duke University as an Integrative Health Coach in 2021 and by Cornell University in Nutrition & Healthy Living in 2022. For information about private health coaching or nutrition programs for schools, please respond directly to this newsletter, or email dyaelbernhard@protonmail.com. Visit her online gallery of illustration, fine art, and children’s books here.
Information in this newsletter is provided for educational – and inspirational – purposes only.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3288507/
Addressing the Root Cause of Eczema: The Gut Microbiome
Youtube: watch?v=QU8nWOm-wB8
Ibid.
Axe, Josh Dr., Eat Dirt: Why Leaky Gut May Be the Root Cause of Your Health Problems, Harper Wave, 2016; pp 107-108.
Weed, Susun, Abundantly Well, Ashtree Publishing, 2020, pg.106.
https://www.skinnutritioninstitute.com/blog/filaggrin-diet-eczema
https://www.medicalnewstoday.com/articles/323154
https://chriskresser.com/colostrum-liquid-gold-for-gut-and-immune-health/
https://chriskresser.com/the-gut-and-immune-health-benefits-of-lactoferrin/