Regular exposure to sunlight can drive down a woman’s risk of rheumatoid arthritis, according to Harvard School of Public Health researchers. Their research focused on older women, but almost all of us could benefit from more — and the right kind of — sunlight. Here’s why.
Sunshine and Vitamin D
Natural food sources of vitamin D are rare, but we can produce vitamin D ourselves with exposure to sunshine. Ultraviolet B radiation from the sun triggers a cholesterol in the skin to synthesize vitamin D from the sunlight, producing all our bodies need — if we get enough UVB ray exposure.
Unfortunately, catching enough UVB rays can be hard for many of us, especially in the winter. UVB light only exists from about 10:30 a.m. to late afternoon, when many people are burrowed away indoors at work. And when we are in the sun, we’ve been conditioned to always wear sunscreen — but this tends to block our absorption of UVB. The end result is that many people could be deficient in vitamin D.
Vitamin D Deficiency
What is vitamin D for anyway? Our bodies actually use vitamin D — which functions as a hormone throughout the body — in a lot of different ways. It helps regulate blood sugar levels, modulate gene expression, boost immune system functioning and allow the absorption of other important nutrients, like calcium and phosphorous.
Vitamin D deficiency is famously known for causing Rickets. But too little vitamin D is also linked to calcium deficiency, osteoporosis, depression, muscle weakness, inflammatory bowl disease, multiple sclerosis and, yes, rheumatoid arthritis.
Harvard Study on Sunshine & Arthritis
In this new study, published in the journal Annals of Rheumatic Diseases, researchers used data from the U.S. Nurses Health Study, which began in 1976. Ultimately, they looked at about 235,000 women who took part in one of two phases of the study (1976-2008 or 1989-2009).
By 2009, 1,314 of the women had developed rheumatoid arthritis. Among those in the first phase of the study, women with the highest estimated levels of UVB light exposure were 21% less likely to develop rheumatoid arthritis than those with the lowest exposure levels.
“Our study adds to the growing evidence that exposure to UV-B light is associated with decreased risk of rheumatoid arthritis,” wrote the researchers. “The mechanisms are not yet understood, but could be mediated by the (skin’s) production of vitamin D and attenuated by use of sunscreen or sun avoidant behavior.”
According to HealthDay, the nurses’ UVB exposure was estimated based the states where they lived while taking part in the study; estimates of their UV-B exposure at birth and by age 15 were also included.
Surprisingly, there was no significant link between sun exposure and arthritis in the second phase study group. The authors say “differences in sun-protective behaviors (eg, greater use of sun block in younger generations) may explain the disparate results.”