Endometriosis, defined as the presence of the inner lining of the uterus in places it should not be, affects up to 10% of reproductive-age women. It causes intense pelvic pain during periods (dysmenorrhea), pain during intercourse (dyspareunia), chronic pelvic pain, irregular bleeding and infertility.
A 2007 Italian study found higher vitamin D levels in women with endometriosis than in unaffected controls. The odds ratio for endometriosis in patients with 25(OH)D levels exceeding the 75th percentile of the serum distribution was 4.8. That is, they found women with 25(OH)D levels above 27 ng/ml were almost five times more likely to have the disease than were women with the lowest 25(OH)D level. The authors also found evidence of a direct gradient; the higher the 25(OH)D, the worse the endometriosis.
The authors mentioned that two other studies found no relationship between 25(OH)D and endometriosis. They also pointed out that African Americans have a reduced incidence of endometriosis compared to Caucasians. I could not find any latitudinal or seasonal studies.
This year researchers at Harvard studied 1,385 cases of incident laparoscopically confirmed endometriosis in women in the Nurses’ Health Study.
Harris HR, Chavarro JE, Malspeis S, Willett WC, Missmer SA. Dairy-food, calcium, magnesium, and vitamin D intake and endometriosis: a prospective cohort study. Am J Epidemiol. 2013 Mar 1;177(5):420-30.
They found that women consuming more than 3 servings of total dairy foods per day were 18% less likely to be diagnosed with endometriosis than those reporting 2 servings per day. In addition, predicted vitamin D blood levels showed women in the highest quintile had a 24% lower risk of endometriosis than women in the lowest quintile (P = 0.004).
That is, they found just the opposite of the Italian study.
This month Lebanese scientists reviewed the role of vitamin D in endometriosis and concluded randomized controlled trials of vitamin D supplementation in endometriosis are needed.
Besides elaborating on a mechanistic model in which vitamin D may help quell inflammation, the Lebanese authors pointed to a randomized controlled trial of vitamin D in dysmenorrhea, which is the pain during menstrual cycles that is the hallmark of the disease.
Lasco A, Catalano A, Benvenga S. Improvement of primary dysmenorrhea caused by a single oral dose of vitamin D: results of a randomized, double-blind, placebo-controlled study. Arch Intern Med. 2012 Feb 27;172(4):366-7.
In this pain study, 20 women received a single oral dose of 300,000 IU five days before their expected menses, comparing them to 20 women getting placebo. They found a 41% reduction in the mean pain score in the vitamin D treated women (p < 0.01). The greatest reduction of pain scores was noted in women with severe pain at baseline. We covered this study in detail in the past.
What does all this mean?
For me, it means the current literature does not support a randomized controlled trial of vitamin D in treating endometriosis. Before that occurs we need case reports to see if there is evidence of a treatment effect or an ill effect. If case reports indicate vitamin D helps, then an open label trial is in order.
Have any readers with endometriosis found vitamin D is helpful? Have any readers found it makes endometriosis worse?