Humans have an innate relationship with the sun. Ancient civilizations worshipped it. Our 365-day calendar was created around it. And when bare skin is exposed to its ultra violet rays, the human body produces an essential nutrient—vitamin D.
Decades of studies have shown how vitamin D receptors are found in almost every cell of the body, influencing different levels of tissue and organ function. And now, emerging research is pinpointing how vitamin D, and more specifically sunlight exposure, may offer protection from chronic conditions like uterine fibroids.
Vitamin D, Sun Exposure, and Fibroids
A study published in Epidemiology evaluated 620 African American women and 416 Caucasian women, ages 35-49, in the National Institute of Environmental Health Sciences Uterine Fibroid Study.
Researchers determined participant vitamin D status by analyzing 25-hydroxy vitamin D levels (the precursor to active vitamin D) from collected blood samples. Ultrasound examinations were performed to establish the presence or absence of uterine fibroids. Additionally, data from a survey on self-reported sun exposure was gathered. Utilizing each piece of the puzzle, the authors then investigated whether vitamin D levels were associated with fibroid status in women.
Results of the study showed that women who had sufficient serum 25-hydroxy vitamin D levels, deemed as 20ng/mL or higher, had a 32% reduced risk of having fibroids when compared to those who had lower levels. Additionally, those who reported at least one hour per day of sun exposure also had a reduced risk.
Further investigation is needed, but these findings are consistent with results from previous in vitro studies and animal studies where treatment with active vitamin D metabolites slowed the growth of cultured uterine fibroid tissue. The authors concluded that “the consistency of [the current] findings provide evidence that sufficient vitamin D is associated with a reduced risk of uterine fibroids.”
How Much Sun Do I Need?
Exact recommendations are not easy to make. Individuals make vitamin D at different rates due to factors like skin pigment, age, season, and location in proximity to the equator. A person in Miami, Florida, for example, would need less time outside to receive the same sunshine benefits than someone in Boston, Massachusetts.
If you aren’t able to get enough sun or if you’re concerned about skin damage, a vitamin D supplement is another viable option. There are vitamin D food sources like fatty fish and egg yolks, but these foods probably won’t provide enough vitamin D.
The recommended daily allowance of vitamin D for adults 19-70 years of age is 600 IU. After 70, this amount increases to 800 IU. Although vitamin D shows promise and may naturally reduce the risk of fibroids, it’s still important to first discuss supplementation with your physician.
