You may already know that vitamin D fortifies bones and muscle strength, or that it increases immunity and reduces inflammation. Recently, researchers have found a possible cause-effect relationship between low vitamin D levels and greater risk for fibroids.
Fibroids are smooth muscular tumors, usually benign, that grow in the muscle layer of the uterus. About 40% of premenopausal women develop uterine fibroids, and it is estimated that 70 to 80% of women develop fibroids by age 50.
While most fibroids are asymptomatic, they can grow and cause heavy and painful vaginal bleeding, pain during sex, and urinary or bowel symptoms. In the United States, fibroids are among the major reasons why women get hysterectomy.
A number of recent studies suggest that vitamin D deficiency may be a cause of fibroid tumors.
Deficiency Links to Higher Risks
In March 2012, researchers from the Center for Women's Health Research at Nashville's Meharry Medical College, lead by Dr Sunil K Halder, reported that in rats, intravenous vitamin D3 inhibited the growth of fibroid cells, shrank fibroid tumors, and reduced production of tissues and enzymes known to fuel fibroid growth.1
Later, scientists from Meharry Medical College and Egypt's Sohag University conducted a study in 154 premenopausal women, including 50 fibroid-free controls.
After measuring vitamin D3 levels in all 154 women, the Nashville-Egypt team found that women with fibroids were significantly more likely to have low vitamin D levels. In African American, women with the lowest vitamin D levels had the largest fibroid tumors, while those with the highest vitamin D levels had the smallest tumors.2
As the researchers wrote, these associations support the possibility of a cause-effect relation: "Vitamin D deficiency is a possible risk factor for the occurrence of [uterine fibroids]."
New Study Affirms Link
In May 2013, researchers from US National Institute of Environmental Health Sciences (NIEHS), led by Dr. Donna Baird, published the results of a new epidemiological study, which affirms the Nashville-Egypt team's findings.
The researchers tested 1,036 American women, aged 35-49, for vitamin D levels. Based on U.S. Institute of Medicine guidelines, vitamin D (in form of 25-hydroxy vitamin D) blood levels above 20 ng/mL are defined as sufficient by the team. (Note: many health and medical experts define sufficiency as a blood level of 30 ng/mL or above. IMI's Founding Director Graeme Bradshaw recommends an optimal blood level of at 40 ng/mL year-round.)
Dr Baird and her collaborators then used ultrasound to look for uterine fibroids. After comparing the participants' vitamin D levels and fibroid status, the women who had sufficient vitamin D levels were 32% less likely to develop fibroids, compared to women with insufficient vitamin D levels.3
While there hasn't been a clinical trial to prove vitamin D can prevent or shrink fibroid tumors in human, it is a good idea to make sure we—men and women—are getting enough vitamin D, given the broad benefits.
A study conducted in Asia concluded that low vitamin D level is a common but largely-ignored health problem in Hong Kong. Test results showed 63% of the subjects had vitamin D below 30 ng/mL.
If you don't spend a considerable amount of time under direct sun exposure, or you are over the age of 50, you are likely to be vitamin D deficient.4,5
Graeme Bradshaw recommends 2,000 IU of vitamin D taken as a supplement daily for those women who avoid the sun or whom always use sunscreen when outdoors.
Have a blood text to check your levels, so as not to be guessing about the amount of vitamin D supplementation you need.
1. Halder SK, Sharan C, Al-Hendy A. 1,25-dihydroxyvitamin D3 treatment shrinks uterine leiomyoma tumors in the Eker rat model. Biol Reprod. 2012 Apr 19;86(4):116.
2. Sabry M, Halder SK, Allah AS, Roshdy E, Rajaratnam V, Al-Hendy A. Serum vitamin D3 level inversely correlates with uterine fibroid volume in different ethnic groups: a cross-sectional observational study. Int J Womens Health. 2013;5:93-100. Epub 2013 Feb 27.
3. Baird DD, Hill MC, Schectman JM, Hollis BW. Vitamin D and the risk of uterine fibroids. Epidemiology. 2013 May;24(3):447-53.
4. Vieth R, et al. The urgent need to recommend an intake of Vitamin D that is effective. Am J Clin Nutr 2007; 85:649-650.
5. Wat WZ, Leung JY, Tam S, Kung AW. Prevalence and impact of vitamin D insufficiency in southern Chinese adults, Ann Nutr Metab 2007; 51(1):59-64.