Study shows link between vitamin D levels and psoriasis

US researchers have discovered a linear relationship between severity of psoriasis — a condition in which skin cells build up and form itchy dry patches — and decreasing vitamin D levels measured through blood tests, in one of the largest studies in this area to date. Their findings were presented last month at NUTRITION 2023, the annual flagship meeting of the American Society for Nutrition.

The research team was led by Eunyoung Cho, an associate professor at Brown University who studies the role of nutrition and environmental factors in skin cancer and inflammatory skin diseases such as psoriasis. Vitamin D is thought to influence the development of skin diseases by affecting the body’s immune response and through direct effects on the cells involved in skin repair.

“With growing public interest in vitamin supplementation, we wanted to further examine the connection between vitamin D levels and psoriasis severity,” Cho said. “Few studies have looked for this association in groups of people, especially in large US populations, or examined this relationship through a clinical nutrition lens.”

For the new study, the researchers identified 491 psoriasis cases from more than 40,000 participants in the US National Health and Nutrition Examination Survey (NHANES), with 162 cases from 2003–2006 and 329 from 2011–2014. They also extracted data on vitamin D levels, self-reported psoriasis-affected body surface area and other factors including age, gender, race, body mass index and smoking status.

After adjusting for lifestyle factors such as smoking, the analysis showed that lower vitamin D levels and vitamin D deficiency were significantly associated with greater psoriasis severity. The researchers also found that patients with the least amount of body surface affected by psoriasis had the highest average vitamin D levels, while those with the greatest affected area had the lowest average levels of vitamin D.

“Only one previous study, published in 2013, has used NHANES data to analyse the relationship between vitamin D and psoriasis,” said Brown University researcher Rachel K Lim. “We were able to add more recent data, which more than tripled the number of psoriasis cases analysed, making our results more up-to-date and statistically powerful than previously available data.”

According to Lim, the results suggest that a vitamin D-rich diet or oral vitamin D supplementation may benefit psoriasis patients, providing a treatment option outside of topical synthetic vitamin D creams that usually require a doctor’s prescription. The researchers do however advise people with psoriasis to consult their physicians and dermatologists before taking supplements.

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