What causes psoriasis? Beer or vitamin D deficiency?

Drinking non-light beer may boost risk of psoriasis in women, a study published in the December 2010 issue of Archives of Dermatology suggests.

Psoriasis is a chronic, autoimmune disease that occurs on the skin when the immune system emits wrong signals that speed up the growth of skin cells.

The study, led by Abrar A. Qureshi, M.D., M.P.H., of Brigham and Women's Hospital and Harvard Medical School, Boston, found that women who drank five or more non-light beers per week were 2.3 times as likely to be diagnosed with psoriasis as were their non-drinking counterparts.

In their report, the authors of the study state that alcoholic beverages have long been suspected of being a potential risk for both psoriasis onset and worsening of the condition. Alcohol drinkers are known to be more likely to suffer from the disease; alcohol may also exacerbate the severity of the ailment.

For the study, researchers surveyed 82,860 women aged 27 to 44 who participated in the Nurses' Health Study II.  They questioned the women on the type of alcohol they regularly consumed through biennial questionnaires; participants were also asked whether or not they had psoriasis.

Women who had an average of 2.3 drinks or more each week were 72 percent more likely than those who did not drink alcohol to report they suffered psoriasis, the study found.

Women who drank five or more non-light beers per week were found to have a 1.8 times higher risk for the disease compared to those who did not consume these beers. 

When only confirmed cases of psoriasis were considered, the risk for the condition was 2.3 times higher for those who drank five or more non-light beers per week compared to those who did not drink beer.

Light beer, wine and liqueurs, on the other hand, were not linked to an increased psoriasis risk.

The researchers suggested that malted barley, the main ingredient found in non-light beer, may be the culprit for the elevated psoriasis risk.

According to the researchers, barley contains gluten, which some women with psoriasis have shown sensitivity to. Light beers contain lower amounts of barley while non-light or dark beers contain higher amounts of the ingredient.

The authors suggested that women at a high risk of psoriasis should consume only light beer.

Still, a health observer suggests that the relationship between consumption of non-light beer and an elevated risk of psoriasis may not be causal.

He cited an article circulated over the internet saying that people tend to drink more dark beers in the winter when vitamin D deficiency is more common than it is in the summer.

Vitamin D has been known to be a variable in immune system health; deficiency of this sunshine vitamin can cause a wide spectrum of diseases including autoimmune diseases, according to the Vitamin D Council. So, it is possible that vitamin D deficiency is directly linked to an increased risk of psoriasis.

In fact, vitamin D products are used to ease symptoms of psoriasis.

According to a study reported in the Aug 2009 issue of Journal of Drugs in Dermatology, calcitriol ointments can be used to improve symptoms of psoriasis. The efficacy of these ointments may be boosted by ultraviolet B phototherapy.

Calcitriol is the naturally occurring active form of vitamin D3. Ultraviolet B can induce the vitamin when the skin is exposed to the UV ray.

In another report, the author, whose name remains unknown in the pubmed database, says the U.S. Food and Drug Administration has actually approved one such ointment to treat psoriasis.

In light of these other factors, it remains unknown whether avoiding non-light beer would directly reduce psoriasis risk.

By David Liu and editing by Rachel Stockton

Photo credit: wikipedia