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Vitamin D Supplementation May Help Primary Dysmenorrhea (your average case of menstrual cramps, not caused by endometriosis) By Dr Tori Hudson, ND

Primary dysmenorrhea is defined as menstrual pain without any pelvic pathology. This is the most common menstrual symptom in adolescent girls and young women. The onset of menstrual pain usually occurs just before or at the first onset of the menstrual flow and typically lasts 0.5-3 days. Some women have additional symptoms such as headache, fatigue, and even nausea/vomiting and diarrhea.

The current double-blind, randomized, placebo-controlled clinical trial in Iran included women aged 18 to 32 years, with regular menstrual cycles and with a pain score of 4 or more out of an 11-point rating scale. These women also had a laboratory value of 25-hydroxyvitamin D < 30 ng/mL which means some were insufficient (20-30 ng/mL) and some were deficient (< 20 ng/mL). There were 58 participants in the vitamin D supplement group and 58 in the placebo group. Women received vitamin D3 capsules 50,000 IU once weekly for 8 consecutive weeks or placebo.

Results: The serum level of 25 (OH)D significantly increased from 20 to 37 ng/mL in the vitamin D group and no significant changes in the placebo group. Even with this robust dosing of vitamin D for 8 weeks, 24% of the women receiving vitamin D supplements still showed low levels of 25(OH)D < 30 ng/mL at week 8. A significant change in pain intensity was found in the vitamin D group and no significant change in the placebo group. The significant reduction in pain intensity was measurable at week 4 (the first menstrual period), as well as week 8. The average pain intensity at baseline was 7.0 +/- 1.7, 6/3 +/- 1.7 at week 4 and 5.6 +/- 1.7 at week 8. There was also a significant change in the number of days with pain in the vitamin D group and no significant change in the placebo group. By week 8, the reduction in number of days went from 2 at baseline and 1 at week 8. Even the number of pain relief medications used per day was reduced in the vitamin D group by half vs no significant change in the placebo group. Lastly, there were even improvements in the systemic symptoms associated with their dysmenorrhea in the vitamin D group, including headache severity and diarrhea with no significant change in the placebo group.

Commentary: One of the things I was curious about was whether or not there was an association between the increase in serum vitamin D level and the improvement in pain intensity. The researchers found no such correlation and surprisingly, there wasn’t even a difference in pain intensity in the vitamin D group with those who did achieve normal serum levels (> 30 ng/mL) and those who did not achieve that.

A suggested mechanism causing primary dysmenorrhea is the increased production of prostaglandins in the endometrium (line of the uterus). This rise in prostaglandins in women with primary dysmenorrhea increases uterine tone and high-amplitude contractions. Both upregulation of cyclooxygenase activity and prostaglandin synthesis are generally observed in women with primary dysmenorrhea. Consequently, whether herbal or pharmaceutical, those non-steroidal anti-inflammatories that inhibit the expression of cyclooxygenase enzyme that is involved in the synthesis of prostaglandin should be considered first line options for treating acute primary dysmenorrhea. Ginger root has some nice published research for this purpose.

Given the frequency of vitamin D insufficiency or vitamin D deficiency, insufficient levels should be considered as a possible role of causing or exacerbating primary dysmenorrhea.

Rahnemaei F, Gholamrezaei A, Afrakhteh M, et al. Vitamin D supplementation for primary dysmenorrhea: a double-blind, randomized, placebo-controlled trial. Obstetrics Gyn Sci. 2021, May 18 (epub ahead of print).

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