California [US]: According to a study by UC Davis Health researchers, inflammatory skin conditions like psoriasis may be caused by a Western diet saturated high in fat and sugar.
According to the study, which was written up in the Journal of Investigative Dermatology, dietary factors rather than obesity itself may be responsible for skin inflammation and the onset of psoriasis.
Psoriasis is a common chronic skin condition that generates scales and red patches of skin that are irritating and occasionally painful. Obesity is a risk factor for the onset or progression of psoriasis, according to earlier research.
The rising incidence of obesity around the world has been attributed to the Western diet, which is characterised by a high dietary consumption of saturated fats and sugar and a low intake of fibre.
‘In our study, we found that short-term exposure to Western diet is able to induce psoriasis before significant body weight gain,’ said Sam T. Hwang, professor and chair of dermatology at UC Davis and senior author on the study.
For the UC Davis Health study, which used a mouse model, Hwang and his colleagues found that a diet containing both high fat and high sugar (mimicking the Western diet in human) was required to induce observable skin inflammation. In four weeks only, mice on Western diet had significantly increased ear swelling and visible dermatitis compared to mice fed a controlled diet and those on high-fat diet alone.
‘Eating an unhealthy diet does not affect your waistline alone, but your skin immunity too,’ said Zhenrui Shi, visiting assistant researcher in UC Davis Department of Dermatology and lead author on the study.
The study detailed the mechanisms by which inflammation happens following a Western diet. It identified bile acids as key signaling molecules in the regulation of skin immunity. Bile acids are produced in the liver from cholesterol and metabolized in the intestine by the gut microbiota. They play an important role in dietary lipid absorption and cholesterol balance in the blood.
The study found that cholestyramine, a drug used to lower cholesterol levels by binding to bile acids in the intestine, helped reduce the risk of skin inflammation. The finding suggests that bile acids mediate the development of psoriasis. The binding of cholestyramine to bile acids in the gut and its subsequent release through the stool allows for lowering of skin inflammation