Their analysis of almost 500 psoriasis cases showed a linear relationship between increasing psoriasis severity and decreasing vitamin D levels, measured through blood tests, according to Rachel Lim ’21 MD’25, who presented the findings at the annual meeting of the American Society for Nutrition in July.

“Topical synthetic vitamin D creams are emerging as new therapies for psoriasis, but these usually require a doctor’s prescription,” Lim said. “Our results suggest that a vitamin D-rich diet or oral vitamin D supplementation may also provide some benefit to psoriasis patients.”

The research team was led by Eunyoung Cho, ScD, an associate professor of dermatology who studies the role of nutrition and environmental factors in skin cancer and inflammatory skin diseases.

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 says.

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.

Lim says only one previous, smaller study had examined the relationship between psoriasis and vitamin D. “We were able to add more recent data, which more than tripled the number of psoriasis cases analyzed, making our results more up-to-date and statistically powerful than previously available data,” she says.

Although dietary vitamin D toxicity is rare, the researchers advise people with psoriasis to consult their physicians and dermatologists before taking supplements.