Vitamin D Status May Affect Uterine Fibroid Risk

Good vitamin D status may be linked to a reduced risk of uterine fibroids, according to a study.

Uterine fibroids are tumors, or growths, made up of muscle and other tissues that grow in the uterus. They may develop in the uterine wall, inside the lining of the uterus, or outside of the uterus. They occur in 20-25 percent of women of childbearing age, and up to 80 percent of women will suffer from fibroids at some point in their lives. A single fibroid may develop or several may develop in groups. Fibroids range in size from less than one inch to larger than the size of a grapefruit. Many women with fibroids do not experience any symptoms and are unaware that they have fibroids. However, about one in four women may have heavy bleeding, pain, and urinary problems that require treatment. Fibroids are almost always benign (not harmful) and very rarely develop into cancer. Fewer than 0.1 percent of fibroid cases become cancerous. Other complications may include infertility, pregnancy problems, and anemia. Any woman can develop fibroids; they are most common among African American women. The cause is unknown and there are no known ways to prevent them.

Vitamin D has been studied as a potential way to help reduce uterine fibroid risk. Vitamin D is found in many dietary sources, such as fish, eggs, fortified milk, and cod liver oil. The sun also contributes significantly to the daily production of vitamin D, and as little as 10 minutes of exposure is thought to be enough to prevent deficiencies. The term "vitamin D" refers to several different forms of this vitamin. Two forms are important in humans: ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3). Vitamin D2 is synthesized by plants. Vitamin D3 is synthesized by humans in the skin when it is exposed to ultraviolet B (UVB) rays from sunlight. Foods may be fortified with vitamin D2 or D3.

In the current study, scientists enrolled women between the ages of 35 and 49 to participate in the National Institute of Environmental Health Sciences Uterine Fibroid Study from 1996-1999. A total of 620 black women and 416 white women underwent ultrasound screening to determine fibroid status. The research team also evaluated the subjects' vitamin D status and sun exposure.

The results showed that only 10 percent of black women and 50 percent of white women in the study had sufficient vitamin D status. Women with higher vitamin D status had an estimated 32 percent lower risk of fibroids, compared to those with lower vitamin D status. This association was found to be similar regardless of race. Sun exposure of at least one hour daily was also linked to reduced fibroid risk.

These findings may suggest a potential benefit of vitamin D in terms of reducing the risk of uterine fibroids, according to the researchers. Further study is needed before firm conclusions can be made.

Peony is another integrative therapy that has been studied for use in cases of uterine fibroids. However, there is unclear or conflicting evidence for this purpose and more research is required.

For more information about vitamin D, please visit Natural Standard's Foods, Herbs & Supplements Database.

References

1. Baird DD, Hill MC, Schectman JM, et al. Vitamin d and the risk of uterine fibroids. Epidemiology. 2013 May;24(3):447-53. doi: 10.1097/EDE.0b013e31828acca0. 
   
2. Natural Standard: The Authority on Integrative Medicine.