Is my psoriasis caused by the gut?
Psoriasis affects 2-3% of people in the UK and 120 million people worldwide, making it the most common autoimmune disease. Its exact cause has never been pinned down, but clinical research suggests the gut might have a key role to play.
Psoriasis is an autoimmune disease. This means the immune system mistakenly launches an attack against the body’s own tissues, triggering an inflammatory response. In psoriasis, this response causes skin cell production to go into overdrive. Excess skin cells build up in patches called plaques. Plaques are usually red, flaky, crusty and covered in silvery scales. They’re often sore and itchy, too. The condition can also affect the joints, causing swelling, stiffness and pain (known as psoriatic arthritis).
There are many possible triggers of psoriasis and reasons why it flares in some people. Everyone is different. Infection, injury, medication, diet, alcohol, smoking and hormonal changes are all known triggers. It is also accepted that stress can both trigger psoriasis and make existing psoriasis worse.
How is this connected to the gut?
The human gut is much more than a tube through which our food is processed. Often called the ‘second brain’, the gut is involved in a bewildering range of processes including immune defence, energy and water harvesting, lipid metabolism, cell signalling, synthesis of vitamins, insulin sensitivity, hormone release, suppression of harmful bacteria, and maintenance of the gut epithelial barrier.
Overall, 100 trillion bacteria live on, or in, our bodies, meaning that we are home to more bacteria than our own cells!1 Gut microbiota is the name we give to the trillions of these microorganisms living in the human gut. Gut microbiota is made up of 5,000 different species, which have a combined 316 million genes2. We have a mutually beneficial relationship with our gut microbiota. We are dependent upon them for our health and they need us for food and shelter.
Our unique gut microbiota started life with us on the day we were born – or even when we were in our mother’s womb. According to some studies3, it can be influenced by lifestyle factors, such as antibiotic use, stress, smoking, exercise, obesity and diet, as well as the normal ageing process4. A growing body of evidence suggests that disruptions to gut microbiota can cause autoimmune diseases, such as psoriasis5, as well as increased infection risk, constipation, diarrhoea, irritable bowel syndrome, cancer, type 2 diabetes and obesity.
Gut health and nutrition
Taking care of our gut microbiota through wise diet and lifestyle choices translates into increased diversity of bacteria, and a shift toward more friendly types.
The food we eat comes into direct contact with our gut microbiota so the macronutrients, vitamins, minerals, fibre, microorganisms and plant bioactive compounds from our diet are incredibly important.
But of particular note is the role of a cuppa when it comes to sorting our gut microbiota. New research reveals that four to five cups of tea per day could boost ‘friendly’ gut bacteria. The good news is that a range of different teas including black tea, green tea, oolong and pu-erh, can contribute to a positive shift in our gut microbiota. This positive shift can help avoid gut dysbiosis, in which gut bacteria composition becomes detrimental.
And the secret lies in tea’s rich array of polyphenols – natural flavonoid compounds found in the tea plant. Tea is one of the richest sources of flavonoid polyphenols in the diet of many global diets, demonstrating a prebiotic effect and rebalancing our gut microbiota towards more favourable strains including Lactobacillus, Faecalibacteria and Bacteroides.
A 10-day study where participants drank four to five cups of green tea daily instead of water, also showed increased levels of Bifiobacterium, a healthy bacteria strain.
Studies further proved that green and black tea polyphenols increased Bacteriodetes phyla and reduced Firmicutes. Green, oolong, black and pu-erh teas also increased bacterial diversity; important for strengthening immunity – vital for those with psoriasis – and also something particularly relevant in the current global situation.
Foods to help psoriasis
A change in diet can have an effect in as little as one or two days6 – so it’s worth eating more healthily from today.
- High fibre diets have been linked with improved microbiota balance7.
- Polyphenols are organic compounds found naturally in plants especially tea, fruits, vegetables, cocoa, wine, soya, spices and nuts. In general8, polyphenol-rich diets boost levels of beneficial bacteria and decrease more harmful species. Tea is one of the main sources of polyphenols in the British diet.
- Vitamin A, vitamin D and long-chain omega-3 fatty acids all have roles in gut health.
- Fermented foods and probiotic drinks contain live ‘good’ bacteria. If these are able to survive the pH extremes of the stomach and small intestine, the bacteria travel to the large intestine where they become established. A recent review9 examined evidence from 19 studies to assess the effect of fermented foods on the human gut microbiota. Promising findings were reported, but no overall conclusion.
- Prebiotics are non-digestible carbohydrates, which can change the gut microbiota towards healthier species. They are found in various fruit and vegetables, such as tomatoes, onions, garlic, leeks, asparagus and bananas. Recent evidence suggests that tea can now also be considered a prebiotic. Prebiotics are relatively stable and, unlike probiotics, can be relied on to arrive relatively unchanged in the gut, despite digestive enzymes.
- Avoid ultra-processed foods, which tend to be low in fibre and high in fat. They have been linked with inflammation and gut dysbiosis10.
In addition to taking responsibility for improving our gut microbiota, there is also a wide range of effective treatments for psoriasis. These range from over-the-counter moisturisers and emollients to prescription creams, ointments and medicines.
Finding the most effective therapy is often a matter of trial and error and new products are being introduced all the time, such as medicated tapes with a fixed dose of steroid. It’s important to keep going back to your doctor, or dermatologist, for advice if you are not happy.
At home, try and ensure you eat a balanced diet and make two to three cuppas part of that daily diet to help good gut health.
If you need support with your gut health, use the advanced search to find a nutrition professional who’s right for you.
Dr Tim Bond is a chemist, natural health expert and tea scientist. Dr Tim is part of the Tea Advisory Panel, a novel health group that conducts scientific studies into the healthy role of black tea in diets.
- Thursby E & Juge E., (2017) doi: 10.1042/BCJ20160510)
- Thomas AM & Segata N (2019) Multiple levels of the unknown in microbiome research. BMC Biol 17:48.
- D’Argenio V (2018) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6306741/
- Nagpal R et al. (2018) https://www.ncbi.nlm.nih.gov/pubmed/29951588
- Scher JU, Ubeda C, Artacho A, et al. Decreased bacterial diversity characterizes the altered gut microbiota in patients with psoriatic arthritis, resembling dysbiosis in inflammatory bowel disease. Arthritis Rheumatol. 2015;67(1):128-139. doi:10.1002/art.38892
- David LA et al. (2014) Diet rapidly and reproducibly alters the human gut microbiome. Nature 505: 559-563.
- Leeming ER et al. (2019) https://www.ncbi.nlm.nih.gov/pubmed/31766592
- Valdes A et al. (2018) https://www.bmj.com/content/361/bmj.k2179
- Stiemsma LT et al. (2020) https://academic.oup.com/jn/advance-article-abstract/doi/10.1093/jn/nxaa077/5814068?redirectedFrom=fulltext
- Zinöcker MK & Lindseth IA (2018) https://www.ncbi.nlm.nih.gov/pubmed/29562591