LONDON — Psoriasis has long been linked with poor nutrition, high body mass index and metabolic disorders, and new research suggests a reduced sense of taste and smell, caused by inflammation, may be part of the explanation why.
The link between psoriasis and higher rates of obesity has generally been attributed to obesity being a risk factor for psoriasis. Metabolic disorders that affect the body’s ability to process food into energy and increased body mass index are common in psoriasis and may result from the inflammatory characteristics of the disease or unbalanced diet.
It is already known that patients’ sense of smell and taste can be impaired in chronic inflammatory bowel diseases; this can change the food a patient eats, but diet returns to normal once the disease has been successfully treated. As psoriasis is also an immune-mediated disease, a research team at Erlangen University in Germany decided to test whether patients’ sense of smell and taste were similarly affected in psoriasis.
For the study 50 patients with psoriasis were asked to complete taste and olfactory tests to try to identify sweet, sour, salty, bitter and umami. They were asked to identify the tastes of solutions sprayed onto the back of the tongue, and a range of sniffing sticks. The results were compared with those in a group of healthy volunteers.
The psoriasis patients had a mean age of 50.74 years (21-85), a mean Psoriasis Area and Severity Index (PASI) of 8 (0.8-27) and mean C-reactive protein (CRP) of 5.4ng/ml (0.2 – 29.1); there were 26 women and 24 men. The healthy volunteers had a mean age of 62.82 years (26-81).
The results, presented at the Psoriasis: From Gene to Clinic International Congress in London, from November 30 through December 2, suggest a distinct impairment of taste and smell was found in patients with psoriasis. While all psoriasis patients could detect sweet taste, bitter could not be tasted by 33 patients and umami by 15 patients. With the sniffer sticks, 2 vs 23 patients showed hyposmia with results off the 10% vs 50% percentile of normal volunteers.
The findings suggest that inflammation impairs the sense of smell and taste, which may influence food uptake and adequate nutrition resulting in a raised average BMI compared to the rest of the population.
Michael Sticherling M.D., one of the researchers from the Department of Dermatology at University Hospitals Erlangen in Germany, said: “Patients with psoriasis commonly have issues with nutrition, which can have an impact on their overall health. We wanted to explore in greater detail the reasons for this. Our results show that psoriasis patients may have greater difficulty identifying tastes than the general population, with the exception of sweet flavours. It’s possible that this is part of the reason for nutrition issues amongst people with the disease. More study is needed before we can say this for sure, but in the meantime there is compelling evidence that inflammation does have an impact on our ability to taste and smell things.”
Impairment of gustatory and olfactory senses in plaque psoriasis. Rüter, P. Grünthaler V, Zopf Y, Sticherling M. P007. Psoriasis: From Gene to Clinic International Congress, London 30th November - 2nd December 2017. http://psoriasisg2c.com/wp-content/uploads/2017/11/Online-Psoriasis-G2C-Programme-2017.pdf (page 74)