Gut-skin axis: Ditching sugary and fatty diets may reduce skin and joint inflammation

24 Jun 2021 --- A diet rich in sugar and fat leads to an imbalance in the gut’s microbial culture and may contribute to inflammatory skin diseases such as psoriasis and joint inflammation, according to a study from the University of California Davis (UC Davis).

“There is a clear link between skin inflammation and changes in the gut microbiome due to food intake,” Sam Hwang, professor and chair of dermatology at UC Davis Health and senior author on the study, tells NutritionInsight.

“The bacterial balance in the gut disrupted shortly after starting a diet high in sugar and fat, and worsened psoriatic skin and joint inflammation.”

Ditching Western diets
The research, published in the Journal of Investigative Dermatology, suggests that switching to a more balanced diet restores the gut’s health and suppresses skin inflammation.

Switching to a more balanced diet restores the gut’s health and suppresses skin inflammation, the study supports.Hwang explains that Western diets, characterized by their high sugar and fat content, appear to have an effect on inflammation in the body and not just skin alone. 

“Patients really need to be aware of this since the other sites (like joints) may be far less amenable to repair and recovery compared to the skin. One surprising aspect to me was how rapidly the proinflammatory effects of Western diet can go away if the diet is changed to a normal one.”

“Earlier studies have shown that Western diets can lead to significant skin inflammation and psoriasis flares. Despite having powerful anti-inflammatory drugs for the skin condition, our study indicates that simple changes in diet may also have significant effects on psoriasis.

Improving treatment
The findings have broad clinical implications as physicians may be able to tell their patients that changing their diets can lead to fairly rapid beneficial effects. This will make their current treatments more effective in a relatively short period of time if the results of the study apply to humans, Hwang adds.

Psoriasis is a skin condition linked to the body’s immune system. When immune cells mistakenly attack healthy skin cells, they cause skin inflammation and the formation of scales and itchy red patches.

Up to 30 percent of patients with psoriasis also have psoriatic arthritis with symptoms such as morning stiffness and fatigue, swollen fingers and toes, pain in joints and changes to nails.

Food as medicine
Food is one of the major modifiable factors regulating the gut microbiota, the community of microorganisms living in the intestines. 

There is a clear link between skin inflammation and changes in the gut microbiome due to food intake, the study says.Since bacteria in the gut may play key roles in shaping inflammation, the researchers wanted to test whether intestinal dysbiosis affects skin and joint inflammation. 

They injected mice with Interleukin-23 (IL-23) minicircle DNA to induce a response mimicking psoriasis-like skin and joint diseases.

IL-23 is a protein generated by the immune cells responsible for many inflammatory autoimmune reactions, including psoriasis and inflammatory bowel disease (IBD).

Hwang and his colleagues found that a short-term Western diet appears sufficient to cause microbial imbalance and to enhance susceptibility to IL-23 mediated psoriasis-like skin inflammation.

Another important finding of their work was identifying the intestinal microbiota as a pathogenic link between diet and the displays of psoriatic inflammation. The study also found that antibiotics block the effects of the Western diet, reducing skin and joint inflammation.

Is the damage reversible?
The researchers wanted to test if switching to a balanced diet can restore the gut microbiota, despite the presence of IL-23 inflammatory proteins. 

They found that eating a diet high in sugar and fat for 10 weeks predisposed mice to skin and joint inflammation. Mice that were switched to a balanced diet had less scaling of the skin and reduced ear thickness than mice on a Western diet. 

The improvement in skin inflammation for mice taken off the Western diet indicates a short-term impact of the Western diet on skin inflammation.

This suggests that changes in diet could partially reverse the proinflammatory effects and alteration of gut microbiota caused by the Western diet.

By Kristiana Lalou