psoriasis microbiome gut bacteria

Psoriasis is a common immune-mediated condition affecting between 1% and 4% of the population. (1)

The defining characteristic of psoriasis is a unique patchy skin rash. The rash is made up of one or more individual “psoriatic plaques”, which are areas of thickened, inflamed skin covered by a layer of silvery-white flakes. (1)

These plaques burn, sting and itch. In some cases, the itching is severe enough to cause people to scratch the plaques open. The resulting wounds may bleed, ooze, scar or even become infected. (1)

In addition to these serious skin symptoms, psoriasis has many less visible effects. These include (1, 2, 3, 4, 5, 6):

  • social ostracization by those who believe psoriasis is contagious
  • changes in personal and intimate relationships
  • loss of a healthy social life
  • development of chronic joint inflammation (“psoriatic arthritis”)
  • development of clinical depression, anxiety, & suicidal thoughts
  • increased risk for metabolic syndrome (obesity, diabetes, high blood pressure)
  • increased risk for inflammatory bowel disease (Crohn’s disease, ulcerative colitis)
  • severely decreased quality of life

Current Psoriasis Treatments

Thankfully, there are many treatment options available to help people manage the many symptoms of psoriasis. Light treatments, medicated ointments, steroid creams, prescription pills and injections can all be effective in helping minimize psoriasis’ effects on a person’s life. (1)

However, none of these treatment options is without its downsides.

Topical skin treatments aren’t always strong enough to really heal psoriatic plaques and can’t address non-skin symptoms. (1, 7)

Immune-modulating pills and injections are more effective when the skin rash is severe and they can provide relief for whole body symptoms. But they can also cause serious side effects and can cost a small fortune. (1, 8, 9, 10)

These downsides have left patients and researchers looking for more effective, safer and cheaper options. (4)

Recently, there has been growing hope that efforts to support healthy gut bacteria might provide just that. (11, 12, 13, 14)

Where has this hope come from?

To understand the answer to this question, it is useful to take a quick step back and review exactly how psoriatic plaques develop in the first place.

Immune Dysfunction in Psoriasis

When the immune system is healthy, immune cells patrol the skin for wounds, infections and cancer. These immune cells communicate with each other, sending signals to one another to ensure that they all attack when there is danger and no one attacks when there isn’t. (15, 16, 17)  

Researchers believe that in people with psoriasis this communication between immune cells breaks down. Specifically, one group of immune system regulating cells, called T regulatory cells (Treg for short), loses its ability to control another group of inflammation-promoting immune cells, called Th17 cells. (15, 16, 17)

Treg cells regulate the immune system and keep other inflammatory immune cells like Th17 from wreaking havoc.

Th17 cells release inflammatory chemicals and oxidants into the skin around them, harming or even killing the skin cells they come into contact with. This leads to pain, swelling, redness, and itching and a build-up of silver-white dead skin cells. (15, 16, 17, 18)  

Unfortunately, once Treg cells lose control of Th17 cells, it’s difficult to ever get them under control again.

This is because the same chemicals damaging the skin also draw new Th17 to the skin and tell them to start making even more inflammatory chemicals. This creates a vicious cycle, with ever more Th17 cells arriving and overwhelming any effort by Treg cells to bring them back under control. (15, 16, 17)

Immune Regulation and Gut Microbiota

So why might changes in gut bacteria be helpful in breaking this cycle?

Well, there is growing evidence that healthy gut bacteria do something remarkable: They increase the function of Treg cells and decrease the function of Th17 cells. (19)

This is exactly what we’re looking for when trying to control an autoimmune response.

Helping Treg cells control Th17 cells while simultaneously making the Th17 cells less powerful gives Treg cells a fighting chance to get the upper hand again and stop Th17 cell attacks on the skin altogether.

Boosting Treg Function

Healthy gut bacteria provide a double boost to Tregs’ ability to stop Th17 cells. They can enhance Treg cell function directly and increase the number of Treg cells you have.

Improving Function Directly

Healthy gut bacteria make a group of chemicals called short-chain fatty acids (SCFAs) (19, 20, 21), which are powerful modulators of Treg cells. SCFAs enter the cells and make their “stop attacking” signals stay turned on, halting the attack on your skin. (19, 20, 22)

This ensures that Treg cells can produce and send tons of these regulating signals out to Th17 cells. The more signals make it to attacking Th17 cells, the more likely they can all be brought back under control.

Increasing Treg Numbers

In addition to making each Treg more efficient at producing regulatory chemicals, healthy gut bacteria also help increase the number of active Treg cells in the body.

This they do indirectly by boosting the functions of a different group of immune cells, called dendritic cells. (19, 23, 24)

Dendritic cells are responsible for sending signals to immature Treg cells that it’s time to “grow-up” and start controlling Th17 cells. (19, 24)

Remember the SCFAs that keep the “stop attacking” signal turned on in Treg cells? Well, those same SCFAs also help to send this “grow up” signal to immature Treg cells from dendritic cells.   

Interestingly, SCFAs aren’t the only molecules made by these healthy bacteria that have this boosting effect on dendritic cells — they also make a molecule called histamine, which stimulates dendritic cells to make more of the chemicals that allow Treg cells to mature. (19, 25)

Studies also show that dendritic cells are healthier, in general, when beneficial gut bacteria are around. This appears to be the result of an increased ability of dendritic cells to make their own vitamin A when healthy levels of these bacteria are in the gut. (19, 26)

Vitamin A is a powerful hormone that dendritic cells need to function properly. By increasing vitamin A levels, gut bacteria help ensure that Treg-cell stimulating dendritic cells are healthy, happy, and functioning optimally. (19, 27)

Hampering Th17 Function

The SCFAs and histamine produced by your healthy gut bacteria have another beneficial effect when it comes to controlling the autoimmune process: they slow down the production of inflammatory chemicals by Th17 cells. (19, 28, 29, 30)

These inflammatory chemicals are responsible for the swelling, pain, redness, itching, and other symptoms you get when you have psoriasis. (15, 16, 17, 18)

Healthy bacteria keep these inflammatory chemicals in check, thus keeping your skin healthy.

Getting Healthy Levels of Good Gut Bacteria

Clearly, improving the health of your microbiome can be useful in helping the immune system regain its balance and keeping psoriasis away for good.

If you’ve been diagnosed with psoriasis, I highly recommend testing your gut bacteria to see if you may have a microbiome imbalance, such as dysbiosis or small intestinal bacterial overgrowth (SIBO).

Both dysbiosis and SIBO have been linked to the development of psoriasis. In addition to this, more severely imbalanced bacteria correlates to worse psoriasis symptoms, and treating SIBO or dysbiosis is associated with improved psoriasis symptoms. (12, 31, 32)

If you have psoriasis and one of these gut bacterial imbalances, you want to find out and get it treated!

You can use a breath test to determine if you have SIBO, or a stool test to identify any bacterial colonies that are out of place in the large intestine. You can learn more about testing here.

If you discover that you have SIBO or dysbiosis, it’s very important to balance your microbiome using antimicrobial herbs, antibiotics, probiotics, prebiotics and more. This, in turn, will help to regulate your immune system!

Beyond identifying and dealing with any imbalances in your microbiome, you can also make some dietary and lifestyle changes that will help to balance your gut bacteria as well. Some of these changes include:

Increasing Probiotic Intake

Probiotics are really amazing in their ability to help regulate the immune system and have been shown to have positive effects on psoriasis symptoms and biomarkers. (33, 34)

Regularly consuming fermented foods like kimchi, sauerkraut, yogurt and kefir is a great way to get these helpful bacteria into your system. (35, 36)

You can also take a probiotic supplement to get these beneficial bacteria if you’re not a fan of fermented foods. (37)

Boosting Prebiotic and Fiber Intake

Healthy gut bacteria use prebiotics and fiber to survive, grow, thrive and make SCFAs. (38) Increasing fiber intakes can boost their levels and function in the gut within just a few days! (39)

Easy ways to increase fiber intake include loading up on fiber-rich foods, such as fruits and vegetables, or taking a fiber supplement. (37)

Getting Enough Exercise

Studies show moderate aerobic exercise can increase the health of your gut bacteria. (40) The introduction of a regular exercise routine has also been shown to be useful in easing psoriasis symptoms.  (41, 42, 43)

Drinking Enough Water

Dehydration can mess with your gut bacteria by promoting constipation. (44) Constipation slows down the movements of your intestinal wall. This can affect how well gut bacteria grow and lead to poor gut bacterial health. (45, 46)

Shifting to a Whole Foods Diet

Study after study shows that a western style diet rich in calories, fat, simple sugars, and salt and low in fruits and vegetables is harmful to healthy gut bacteria, while traditional diets rich in whole foods help these bacteria grow. (47, 48, 49, 50)

Multiple studies also show that putting individuals with psoriasis on a whole-food diet can improve their symptoms. (41, 42, 43)

The Impact of Diet on the Immune System

Diet plays a crucial role in regulating a healthy immune system and controlling psoriasis.

Evidence suggests that a shift away from processed foods towards whole foods may not only boost fiber intake, healthy gut bacteria numbers, SCFA levels and histamine levels, but it might very well provide its own direct inhibition of Th17 cells.

Th17 Function and Processed Foods

There are at least two components in processed food that may boost Th17 function: salt and advanced glycation end products.


While I’m not against a moderate amount of salt in the diet (and in fact higher levels of salt intake can be helpful in conditions like “adrenal fatigue”), research indicates that the high level of salt found in many processed foods is problematic when it comes to autoimmune disease.

Consuming large amounts of salt directly activates Th17 cells, which produce inflammatory chemicals and in turn lead to psoriasis symptoms.

Researchers have recently identified a special sensor in Th17 cells that is sensitive to the amount of salt around. If this sensor is activated by lots of salt, it causes the Th17 cells to produce more inflammatory chemicals. (51)

And this isn’t just at the cellular level. Studies show that eating diets containing lots of salt leads to worsening of symptoms of Th17-related diseases, such as asthma and multiple sclerosis. (52, 53, 54, 55)

Advanced Glycation End Products (AGEs)

Advanced glycation end products (AGEs) form when foods are heated to extreme temperatures, making them a common molecule found in broiled or fried foods like chips, french fries, chicken nuggets, fish sticks, etc. (56, 57)

Similar to how SCFAs and histamine help Treg cells mature, AGEs have been found to help inflammation-promoting Th17 cells mature. (58) This suggests that eating lots of fried junk food can increase the number of damaging Th17 cells.

Th17 Function and Whole Foods

On the other hand, replacing junk food with whole foods can help to reduce the damage from Th17 cells.


One nutrient rich in many whole foods that may play an important role in regulating immune function is potassium.

High levels of potassium trigger the kidneys to produce a group of molecules called glucocorticosteroids. (59)

These molecules are natural steroids that work just like the drugs doctors prescribe. They are powerful inhibitors of inflammatory chemicals. (60)

Bioactive Phytonutrients

Many whole plant foods contain phytonutrients that have helpful health benefits. Some of these benefits include preventing the effects of inflammatory chemicals on the body. (61, 62, 63)

Some of these anti-inflammatory phytonutrients have powerful effects against inflammatory chemicals known to be important in damaging psoriatic skin.

For example, there is a phytonutrient in turmeric root called curcumin that blocks the effects of the inflammatory chemical TNF-alpha, which plays a major role in promoting psoriasis. (64, 65) In fact, curcumin blocks TNF-alpha nearly as well as drugs we designed to block it. (66)

In addition to the anti-inflammatory nature of phytonutrients, polyphenols (a type of phytonutrient) also boost the health of your microbiome. If you’d like to learn more about that process, check out my article on the topic here.


As their name suggests, antioxidants block the effects of oxidants.

Since one of the key chemicals Th17 cells use to damage skin cells are oxidants (called reactive oxygen species (ROSs)), antioxidants from fruits, vegetables, nuts, seeds, teas and spices may be helpful in reducing psoriasis symptoms. (18, 67, 68, 69, 70)

The Bottom Line:

The evidence suggests that a whole food diet rich in foods that help promote a healthy microbiome may help prevent and reduce the symptoms of psoriasis and other autoimmune diseases.


Have you been diagnosed with psoriasis? Do you notice a difference in your symptoms when you eat well and support your microbiome? Let me know in the comment section below!

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