About one in two menstruating women suffer cramps – a condition called dysmenorrhea – just before and during their periods.
The discomfort ranges from annoying to agonizing, and can interfere with everyday activities for several days every month.
Fish fit the vitamin D bill; Sockeye salmon stand out
In addition to getting vitamin D from supplements, certain fish rank among the very few substantial food sources of vitamin D, far outranking milk and other D-fortified foods.
Among fish, wild Sockeye Salmon may be the richest source of all, with a single 3.5 ounce serving surpassing the US RDA of 400 IU by about 70 percent:
Vitamin D per 3.5 ounce serving*
Sockeye Salmon 687 IU
Albacore Tuna 544 IU
Silver Salmon 430 IU
King Salmon 236 IU
Sardines 222 IU
Sablefish 169 IU
Halibut 162 IU
*For our full test results, click here.
Menstrual cramps may be caused by identifiable problems, such as endometriosis or uterine fibroids. Otherwise, cramps tend to diminish and often disappear once a woman has given birth.
The pain is thought to be sparked by excessive production of prostaglandins that control vasoconstriction and uterine contractions.
Prostaglandins are ephemeral, hormone-like compounds made from omega-3 and omega-6 fatty acids, and affect many aspects of metabolism.
The problematic prostaglandins that cause cramps when produced in excess are made from omega-6 fatty acids, just before the onset of menses.
Thus, menstrual cramps may belong in the growing list of health problems linked to the average American's excessive intake of omega-6 fats from vegetable oils and foods made with them. (See “America's Sickening Omega Imbalance.”)
Vitamin D experts
provide helpful perspective
We thought it would be informative to present an excerpt from Dr. John Cannell's article on the study, found at the Vitamin D Council website.
As we noted, the safe upper intake limit set by the U.S. Institute of Medicine now stands at 4,000 IU (raised from 2,000 IU in 2010) … see “Vitamin D RDAs Raised Substantially.”
Here's Dr. Cannell's account of his interview with a vitamin D researcher from Harvard (Cannell J 2012):
Approached for comment, Clifford Lo, M.D., Ph.D., Director, Harvard Human Nutrition Program, and Medical Education Coordinator, Harvard Medical School Division of Nutrition, said that although the numbers were small, there was a convincing difference between the placebo and vitamin D groups in the study.
However, although it is plausible that vitamin D affects prostaglandins, the study did not specify which prostaglandin or which pain site might be involved, said Dr. Lo, whose research interests include vitamin D metabolism.
The study proposes an interesting possible mechanism, “but that's certainly not good enough for me to say that this is a good treatment for pain,” said Dr. Lo. “It's very premature to say it's something we should use.”
Pain associated with dysmenorrhea is generally subjective and not easily measured, he added. It is difficult to make conclusions about the effect an agent will have on pain when there is "no convincing biomarker" for the pain, as was the case with this study, said Dr. Lo.
The 300,000 IU dose of vitamin D used in the study is probably harmless if taken every month or two, and even perhaps every week, but it could cause hypercalcemia [excess calcium in bones] if taken daily, said Dr. Lo. The typical vitamin D dose is 400 to 1000 IU/day.
Dr. Lo pointed out that because the participants in the study had vitamin D levels below 45 ng/mL, they were not exactly deficient in vitamin D to begin with. “Most people would say that you're not deficient until you're below 20 ng/ml,” he said. “I would say that half the American population is below 30 ng/mL.”
Now, the outcomes of a small clinical trial suggest that women who take a single high dose of vitamin D suffer much less menstrual pain and have no need of pain medications for any reason for up to 2 months (Lasco A et al. 2012).
The study authors proposed that vitamin D may suppress the expression of key genes involved in producing the problematic prostaglandins, and thereby act as an anti-inflammatory agent.
Clinical trial finds high-dose D eases menstrual cramps
The small placebo-controlled trial was the first such study ever conducted, and it comes from a team at Italy's University of Messina, led by Dr. Antonino Lasco.
They tested the effect of a single, high oral dose of vitamin D3 (cholecalciferol) – 300,000 international units (IU) – in 40 women aged 18 to 40.
All of the women had experienced at least four consecutive painful menstrual periods in the past six months and had a vitamin D blood level below the upper limit of peers whose vitamin D levels fell in the lowest quarter (below 45 ng/mL).
They were not taking calcium, vitamin D, oral contraceptives, or other medications, and had not used an intrauterine contraceptive device during the previous six months.
The participants could use other birth control methods and take nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin or ibuprofen as needed, but had to report their use.
The women were randomly assigned to receive a single oral dose of 300,000 IUs of vitamin D (cholecalciferol) or placebo five days before the time they expected to begin their next menstrual period.
The primary measures of efficacy were the intensity of menstrual pain and the use of NSAIDs.
After two months, the scores for perceived pain fell by 41 percent among women in the vitamin D group … but there was no change in pain scores among the women taking placebo pills.
The greatest reduction in pain was among women in the vitamin D group who had the most severe pain at the outset of the study.
During the two-month study, none of the women in the vitamin D group needed NSAIDs to manage pain, whereas 40 percent of those in the placebo group used an NSAID at least once.
Editorialists urge more research
Two expert commenters – Elizabeth R. Bertone-Johnson, ScD, from the University of Massachusetts, and JoAnn E. Manson, M.D., from Brigham and Women's Hospital and Harvard – said the study provides support for larger clinical trials testing vitamin D against cramps and related gynecological pains.
As they noted, chronic widespread pain and fibromyalgia syndromes are more prevalent in women, “likely owing to the influence of sex steroid hormones.” (Bertone-Johnson ER, Manson JE 2012)
This future research, they write, must explore how long the pain reductions would persist and how often treatment would need to be repeated.
They also pointed out that each dose would need to be effective for a lengthy period for average daily intake to remain below the current recommended upper intake limit of 4,000 IU per day.
Because many women suffer dysmenorrhea for several years until menopause, follow-up of participants in future vitamin D trials must be extended to better evaluate the effects and compare risks and benefits.
The editorialists also noted that it remains unknown whether vitamin D would improve dysmenorrhea pain in women with higher 25(OH)D [vitamin D] levels.
Overall, they expressed cautious hope:
“If these findings are confirmed in future randomized trials, vitamin D supplementation may become an important new treatment option for women who experience menstrual pain disorders.” (Bertone-Johnson ER, Manson JE 2012)
And they urged women to maintain adequate vitamin D intake until we know more:
“In the meantime, encouraging all women to obtain the recommended dietary allowance for vitamin D (600 IU/day or more for women of reproductive age), as well as screening for low serum 25(OH)D [vitamin D] levels among women with other risk factors for vitamin D deficiency, would be a rational interim approach.” (Bertone-Johnson ER, Manson JE 2012)
Dr. Mason noted that if 300,000 IU is required every two months, “... this would equate to approximately 5000 IU per day, considerably higher than the tolerable upper intake level set by the Institute of Medicine of 4000 IU per day.”
To help ensure optimal health, most researchers involved in vitamin D studies recommend minimum blood levels ranging from 90 to 120 nmol/L (36 to 48 ng/mL).
However, leading vitamin D researcher Ronald Vieth, M.D., notes that normal human blood levels of vitamin D extend above 200 nmol/L or 80 ng/mL (Vieth R 2004).
Dr. Vieth points out that vitamin D blood levels above 120 nmol/L pose no risk and may confer additional benefits, up to the upper reaches of the normal human range (i.e., 200 nmol/L).
Though the official safe upper intake limit is 4,000 IU per day, vitamin D intake of 10,000 IU per day is proven safe. This is 16 times the current RDA for adults 51 or older (600 IU).
Most experts – such as Professor Michael Holick, M.D., Ph.D., of Boston University –recommend taking 2,000 IU to 4,000 IU per day ... unless you have a light complexion and most of your skin is exposed to 20 to 30 minutes of strong sunlight per day, in which case 600 IU daily is usually enough.
Darker skinned people, whose greater amount of skin pigment blocks the UV rays that make vitamin D, need more sun exposure or more oral vitamin D.
Bertone-Johnson ER, Manson JE. Vitamin d for menstrual and pain-related disorders in women: comment on "improvement of primary dysmenorrhea caused by a single oral dose of vitamin d". Arch Intern Med. 2012 Feb 27;172(4):367-9.
Cannell J. New study: vitamin D eases menstrual cramps. Vitamin D Council. February 27, 2012. Accessed at http://www.vitamindcouncil.org/new-study-vitamin-d-eases-menstrual-cramps/
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.
Vieth R. Why the optimal requirement for Vitamin D3 is probably much higher than what is officially recommended for adults. J Steroid Biochem Mol Biol. 2004 May;89-90(1-5):575-9. Review.