Supplements of vitamin D and fish oil reduce menstrual pain

Menstrual pain can be quite severe, especially among teenagers and young women, but supplementation with vitamin D seems to reduce the pain, according to a new meta-analysis that is published in Nutrients. Earlier research has shown that fish oil supplements can do the same. Vitamin D and fish oil primarily work by lowering levels of hormone-like compounds called prostaglandins that cause inflammation and are responsible for the painful cramps in the uterus.

In medical terms, painful menstrual cramps are known as dysmenorrhea. Primary dysmenorrhea especially affects teenagers and young women, and there does not seem to be an organic cause. The pain usually starts a few hours before or at the same time as the bleeding and lasts one or two days. The pain is caused by contractions (cramps) of the uterus that can be more or less severe. Secondary dysmenorrhea usually starts at the age of 30 or 40 and has an organic cause.
An estimated 45-95 percent of women in their reproductive age suffer from dysmenorrhea, and it is especially teenagers and young women with primary dysmenorrhea. Ten to 15 percent with primary dysmenorrhea experience such severe pain that they are forced to stay home from school or work one or several days each month. Dysmenorrhea is a global health problem with huge human and economic costs.
The most common treatment is to take non-steroidal anti-inflammatory drugs (NSAID) for pain relief, but these drugs are known to cause side effects such as nausea, tiredness, kidney damage, stomach bleeding, and other types of internal bleeding. NSAID drugs work by preventing the body’s production of some hormone-like compounds called prostaglandins (PGE2) that cause inflammation and cramps in the uterus. Hormone therapy is another treatment, but it may cause long-term side effects that can increase the risk of cardiovascular disease and cancer. It is therefore far better to use therapies that are natural but still able to correct the inflammatory and hormonal imbalances.

Vitamin D supplementation primarily helps against primary dysmenorrhea

The purpose of the new meta-analysis was to look closer at the effect of giving vitamin D to patients suffering from dysmenorrhea. The researchers collected randomized, controlled trials (RCTs) involving dysmenorrhea and vitamin D supplementation from databases such as the Cochrane Library, Embase, Google Scholar, Medline, and Scopus. They ended up with 11 eligible studies with a total of 687 participants. Their meta-analysis showed that supplementation with vitamin D significantly reduced pain in patients with dysmenorrhea compared with placebo. Analyses of subgroups revealed that vitamin D primarily had a pain-relieving effect with primary but not secondary dysmenorrhea. The researchers concluded that vitamin D supplementation can reduce pain intensity in patients suffering from dysmenorrhea, especially those with primary dysmenorrhea.

How does vitamin D relieve dysmenorrhea pain?

Nearly all cells in the body have vitamin D receptors (VDR). Vitamin D regulates a host of different genes, and researchers have found VDRs in the pituitary gland, the ovaries, and the uterus, suggesting that vitamin D is important for the hormone balance and fertility. Vitamin D is also important for the immune defense and for controlling the inflammatory processes involved in dysmenorrhea. Moreover, vitamin D can counteract certain pain signals from structures in the spine called dorsal root ganglia that contain sensory nerve cells. In patients with dysmenorrhea, scientists have found low vitamin D levels in the so-called luteal phase of the menstrual period (the period from ovulation to menstruation). This vitamin D deficiency can stimulate the production of inflammatory cytokines and prostaglandins (PGE2) that cause pain and cramps in the uterus.
In some of the studies, very high doses of vitamin D have been administered for a short period to correct the deficiency as fast as possible. In any case, it is essential that the supplements are able to optimize blood levels of vitamin D, which is ideally more than 75 nmol/L and preferably 100-120 nmol/L.
None of the patients experienced any side effects from taking such high doses. The official recommendation for vitamin D intake is relatively low (typically around 5-20 micrograms daily). Multiple studies have shown that supplementation with 50 micrograms of vitamin D daily is enough to optimize blood levels of the nutrient in most people. According to EFSA, the safe upper intake level for vitamin D is 100 micrograms/day. In cases where people want a more rapid effect on dysmenorrhea, they can easily begin with such a high dose for a period.

Fish oil also relieves menstrual pain

Omega-3 and omega-6 are essential fatty acids that are involved in the body’s production of different prostaglandins (PGE1, PGE2, and PGE3) that regulate many different processes. It is vital to have the correct balance between these two fatty acids. We primarily get omega-3 fatty acids by eating oily fish or taking fish oil supplements that contain the two active omega-3 fatty acids, EPA (eicosapentaenoic aid) and DHA (docosahexaenoic acid). There is also omega-3 in flaxseed oil and a few other plant sources, but this is a form of omega-3 called ALA (alpha-linolenic acid) that many people have difficulty with converting into EPA and DHA. We mainly get omega-6 from plant oils, nuts, seeds, and kernels, but modern diets contain less fish and a whole lot of plant oils from margarine, ready meals, chips, French fries, dressings, cakes, and other sources. For that reason, many people get too little omega-3 (especially EPA and DHA) and too much omega-6, which causes disturbances in the body’s production of prostaglandins. The result is a deficiency of PGE3, a prostaglandin that is able to counteract inflammation and cramps, and an excess of PGE2 that is pro-inflammatory and causes pain and cramps.
Bente Deutch, a Danish researcher from Århus University, conducted a study of 78 young women with dysmenorrhea. Her study showed that daily supplementation with two capsules containing concentrated fish oil (in the form of free fatty acids) and vitamin B12 reduced menstrual pain by regulating the prostaglandin balance. This trial supports a later meta-analysis showing that fish oil supplementation reduces pain in primary dysmenorrhea. It usually takes around a month for a fish oil supplement to work optimally, and it also lasts around a month for the effect to taper off when the supplementation is discontinued.

Referencer:

Kan-Chu Lin et al. Vitamin D Supplementation for Patients with Dysmenorrhoea: A Meta-Analysis with Trial Sequential Analysis of Randomized Controlled Trials. Nutrients 2024

Pawel Pludowsky et al. Vitamin D Supplementation: A review of the Evidence Arguing for a Daily Dose of 2000 International Units (50 µg) of vitamin D for adults in the General Population. Nutrients 2024

Bente Deutch et al: Menstrual discomfort in Danish women reduced by dietary supplements of omega-3 PUFA and B12 (fish oil or seal oil capsules). Nutrition Research. 2020

Mohammad Mehdi et al. The impact of omega-3 polysaturated fatty acids on primary dysmenorrhea: a systematic review and meta-analysis of randomized controlled trials. Eur J Clin Pharmacol 2022