A new study has suggested that switching from a high fat and sugar diet to a more balanced diet may help to reduce inflammation in skin and joints.
A new study, led by UC Davis Health researchers, has demonstrated that diets with high amounts of sugar and fat lead to an imbalance in the gut’s microbial culture and may contribute to inflammatory skin diseases such as psoriasis.
Published in the Journal of Investigative Dermatology, the study suggests that switching to a more balanced diet restores gut health and suppresses skin inflammation.
High sugar and fat diets
Food is one of the major modifiable factors regulating the gut microbiota, and eating a diet which is high in fat and sugar can cause rapid change to the gut’s microbial community and its functions. This disruption – known as dysbiosis – contributes to gut inflammation.
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.
Sam T. Hwang, Professor and Chair of Dermatology at UC Davis Health and senior author on the study, said: “Earlier studies have shown that Western diet, characterised by its high sugar and fat content, 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.”
The team used a mouse model to study the effect of diet on psoriasis and psoriatic arthritis – injecting the mice with Interleukin-23 (IL-23) minicircle DNA – a protein generated by the immune cells responsible for many inflammatory autoimmune reactions – to induce a response mimicking psoriasis-like skin and joint diseases. They 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.
“There is a clear link between skin inflammation and changes in the gut microbiome due to food intake. The bacterial balance in the gut disrupted shortly after starting a Western diet, and worsened psoriatic skin and joint inflammation,” Hwang said.
One critical 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.
Reversing the damage
To see if the damage from a high sugar and fat diet can be reversed, the team fed mice this Western diet for six weeks before giving them an IL-23-inducing agent to trigger psoriasis and psoriatic arthritis features. The mice were then randomly divided into two groups consisting of one that continued the Western diet for another four weeks, and another that switched to a balanced diet for the same duration.
The team found that eating the diet high in sugar and fat for ten weeks predisposed mice to skin and joint inflammation, and that 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 also indicates a short-term impact of the Western diet on skin inflammation.
The team highlight that these findings suggest that changes in diet could partially reverse the proinflammatory effects and alteration of gut microbiota caused by a high sugar and fat diet.
Zhenrui Shi, Visiting Assistant Researcher in the UC Davis Department of Dermatology and lead author on the study, said: “It was quite surprising that a simple diet modification of less sugar and fat may have significant effects on psoriasis. These findings reveal that patients with psoriatic skin and joint disease should consider changing to a healthier dietary pattern.”