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RCT discovers vitamin D may alleviate painful menstrual cramps

Posted on: May 10, 2016   by  Amber Tovey



Primary dysmenorrhea refers to painful menstrual cramps. Symptoms vary in severity and may include nausea, back pain, hip pain, vomiting and diarrhea. Dysmenorrhea is extremely common, affecting up to 90% of women who are of reproductive age.

Painful cramps begin to occur after the uterus produces high amounts of prostaglandins. Prostaglandins cause the uterine muscles to contract and help the uterus shed the lining. Excessive amounts of prostaglandins can cause the uterine to contract too strongly or too frequently, leading to pain. Therefore, most primary dysmenorrhea medications aim to suppress prostaglandin synthesis. These medications include contraceptives and non-steroidal anti-inflammatory drugs (NSAIDs).

Since past research has found that vitamin D reduces the production of prostaglandins, researchers recently conducted a study to evaluate the effects of vitamin D supplementation on primary dysmenorrhea in women with vitamin D deficiency. The researchers enrolled sixty women with primary dysmenorrhea aged 18-30 years, having at least four recent consecutive painful menstrual cycles during the past six months and low vitamin D status (< 30 ng/ml). Women were excluded if they had taken contraceptives within the past two months, since contraceptives would affect the pain severity caused by dysmenorrhea.

The participants were randomly divided into two groups of either treatment or placebo. The treatment group received a 50,000 IU vitamin D3 supplement weekly, and the placebo group received identical placebo weekly for a total of eight weeks.

The researchers assessed vitamin D levels, pain severity and the use of NSAIDS at baseline, after 8 weeks and one month after the end of treatment. The visual analog scale (VAS) measured pain severity. VAS is a 0-10 scale pain rank with zero indicating no pain and a 10 indicating very severe pain. Here is what the researchers found:

  • A total of 50 out of the 60 women completed the study. Among the 50 women, 31 had severe vitamin D deficiency (< 10 ng/ml) and 19 had moderate vitamin D deficiency (10-19 ng/ml).
  • Baseline characteristics were not significantly different between the treatment and placebo groups.
  • After two months of treatment, vitamin D status significantly increased in the treatment group from a mean of 9.7 ng/ml to 55.4 ng/ml; whereas the vitamin D status of the placebo group did not significantly increase.
  • At baseline, in the vitamin D group, pain was mild in 3 patients (13%), moderate in 16 patients (69.6%) and severe in 4 patients (17.4%). After treatment, 95.7% of patients had mild pain, 1 (4.3%) had moderate pain and none of them had severe pain (p < 0.001).
  • Pain intensity reduced significantly in the vitamin D group after 8 weeks of treatment and one month after the end of treatment (p < 0.001).
  • The number of NSAID used by the patients was not significantly different between the two groups at baseline. At the end of treatment, the number of tablets used by the women in the vitamin D group decreased significantly, and there was a significant difference between the two groups (p < 0.001).

The researchers concluded,

“Based on the study findings, it seems that vit D supplementation with a weekly dose of 50,000 IU for eight weeks could improve pain intensity and decrease the need for using NSAID in patients with primary dysmenorrhea and vit D deficiency.”

While the study presents promising results, the small sample size and the short duration of treatment limited the study’s findings. Therefore, further randomized controlled clinical trials with greater sample size, longer duration and daily dosing of vitamin D are needed to confirm the efficacy of vitamin D for treatment of primary dysmenorrhea.  However, if you have dysmenorrhea, take at least 5,000 IU/day of vitamin D3. Heavier women may need 10,000 IU/day.


Moini A, Ebrahimi T, Hosseini R, et al. The effect of vitamin D on primary dysmenorrhea with vitamin D deficiency: a randomized double-blind controlled clinical trial. Gynecological Endocrinology, 2016.

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