Fibroids are muscular tumors that grow in the wall of the uterus (womb).
They're almost always benign, and can grow as a single or multiple tumors ... as small as a seed or as big as a grapefruit ... rarely larger.
Thirty to 40 percent of premenopausal women develop uterine fibroids, and an estimated 70 to 80 percent of women develop fibroids by age 50.
Uterine fibroids cause troublesome symptoms in about 30 percent of affected women, including heavy vaginal bleeding, pelvic pressure, pelvic pain, urinary and bowel symptoms, pain during sex, lower back pain, and complications during pregnancy and labor.
Fibroids rank high among the reasons why women get hysterectomies, accounting for some 200,000 operations annually. Effective treatments remain elusive.
Certain hormone-related drugs may inhibit and even reverse the fibroid-growth process, while potential non-hormonal therapies include anti-fibrotic drugs, curcumin, and retinoic acid (a vitamin A metabolite that mediates vitamin A functions related to tissue growth).
The causes remain unknown, but researchers have suspected a combination of hormonal (estrogen/progesterone levels) and genetic factors.
Now, it's looking like vitamin D deficiency may be a cause – or co-promoter – of fibroid tumors.
Paired risk for fibroids and vitamin D deficiency present a possible clue
Uterine fibroids are the most common benign tumors in women of reproductive age, but are three to four times more common in African-American women.
And African-American women are also 10 times more likely than white women to have inadequate blood levels of vitamin D.
These coincidental characteristics of African-American women raise the possibility of a connection between vitamin D and fibroids.
Prompted by this prospect, researchers from the Center for Women's Health Research at Nashville's Meharry Medical College tested the effects of dietary vitamin D in rats with uterine fibroids.
Last year, the Meharry team reported that in rats, intravenous vitamin D3 inhibited the growth (proliferation) of fibroid cells, shrank fibroid tumors, and reduced production of tissues and enzymes known to fuel fibroid growth ... see “Vitamin D Shrank Fibroid Tumors in Rats
Then, last February, 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.
Strengthening the possibility of a cause-effect relationship between low D levels and greater risk for fibroids, the black women with the lowest vitamin D levels had the largest fibroid tumors, while those with the highest vitamin D levels had the smallest tumors.
(The link between lower vitamin D levels and larger tumors fell short of statistical significance in white women.)
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 UFs [uterine fibroids].” (Sabry M et al. 2013)
New study affirms link between fibroids and vitamin D deficiency
Last month, researchers from US National Institute of Environmental Health Sciences (NIEHS) published the results of a new epidemiological study … which echo the Nashville-Egypt team's findings (Baird DD et al. 2013).
The NIEHS group – led by Dr. Donna Baird – recruited 1,036 American women aged 35-49 for their study.
First, the NIEHS team tested the women's blood for vitamin D, and, based on U.S. Institute of Medicine guidelines, defined blood levels above 20 ng/mL as sufficient.
We should note that many experts define sufficiency as a blood level of 30 to 100 ng/mL, and consider this the optimal range (Holick MF et al. 2011; Heaney RP et al. 2011).
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 percent less likely to develop fibroids, compared to women with insufficient vitamin D levels.
The participants also answered a questionnaire on sun exposure, and those who reported spending more than one hour outside daily were about 40 percent less likely to have fibroids.
Only a controlled clinical trial can prove whether vitamin D does or does not help prevent, limit, or shrink fibroid tumors.
However, given the broad benefits of vitamin D3, it seems reasonable for women to make sure they are getting enough from sunshine, seafood, and/or supplements to ensure optimal blood levels.
The RDA for teens and adults age 70 and under is 600 IU, although doses of up to 4,000 IU daily are considered safe for children over age nine, adults, and for pregnant and breastfeeding females (ODS 2011).
- Baird DD, Hill MC, Schectman JM, Hollis BW. Vitamin D and the risk of uterine fibroids. Epidemiology. 2013 May;24(3):447-53. doi: 10.1097/EDE.0b013e31828acca0.
- 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. doi: 10.1095/biolreprod.111.098145. Print 2012 Apr.
- Office of Dietary Supplements, U.S. National Institutes of Health (ODS). Dietary Supplement Fact Sheet: Vitamin D. June 24, 2011. Accessed at http://ods.od.nih.gov/factsheets/VitaminD-QuickFacts/
- Office on Women's Health, U.S. Department of Health and Human Services (OWH/HHS). Uterine fibroids fact sheet. Accessed at http://www.womenshealth.gov/publications/our-publications/fact-sheet/uterine-fibroids.cfm
- 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. doi: 10.2147/IJWH.S38800. Epub 2013 Feb 27.