Magnesium for premenstrual symptoms

What the research shows

• A clinical evidence review identified only two placebo-controlled magnesium trials and judged both to be of low precision because of small numbers and short treatment duration. In a trial of 28 women, total menstrual distress scores fell; in a second, there was a small reduction in fluid-retention symptoms at two months but no difference in total score. Its conclusion: insufficient evidence to recommend magnesium.
• A 2001 review of complementary therapies describes a magnesium oxide crossover trial in 38 women over two cycles, and a magnesium pyrrolidone carboxylic acid trial reporting reduced negative affect scores. Both were small.
• An older review notes that among minerals, calcium is the only supplement shown to be of significant benefit in a large, rigorous placebo-controlled trial; it adds that magnesium may also be useful but that further research is needed.
• A meta-analysis of observational studies reports that findings on blood magnesium levels in women with PMS have been inconclusive. Such data show association, not treatment effect.

One point is worth noting: a substantial share of the studies covered in Magnesium, stress and anxiety were also carried out in women with premenstrual symptoms, and four of seven reported positive results. So the signal is not absent — but it rests on a narrow literature of small trials.

What is known about the mechanism

The honest answer is: little. A 2017 review notes studies reporting a positive relationship between magnesium administration and relief of these symptoms, while also stating that data on the pharmacological mechanism are few and unsystematic. It would be wrong to speak with confidence in an area where the mechanism is poorly understood.

Magnesium’s authorised roles

There is no authorised claim specific to PMS. The authorised claims for magnesium include contributions to normal muscle function, to the normal functioning of the nervous system and to normal psychological function — general functional claims, not claims about a particular complaint.

When to see a doctor

If symptoms stop you going to work or school, cause a marked drop in mood, or come with very painful or irregular periods, this is not a supplement question. Premenstrual dysphoric disorder, endometriosis, thyroid disorders and iron deficiency produce similar pictures, and each has its own diagnosis and treatment.

Frequently asked

The questions most often searched on this topic, answered as they are.

Related reading

• Magnesium, stress and anxiety — authorised claims and the evidence
• Magnesium intake and deficiency — why intake falls short, and food sources
• Magnesium forms compared — absorption, tolerance and timing
• All guides