I received the following question from an SGU listener:

Recently when I visited a neurologists with my daughter to seek help for her migraines the doctor prescribed something that caught me off guard and in my research since the visit I still have not convinced myself of the validity. The doctor told my daughter she should start taking magnesium supplements. The doctor told her this would serve as a natural muscle relaxant.
I have been listening to your podcast for about 6 months now and enjoy it very much. I enjoy the entire crew and would really like your team’s take on the Migraine and Magnesium relation.

This is an excellent question, and reinforces the notion that science-based medicine is not about a list of acceptable beliefs or modalities – it is about method. There is nothing inherently implausible or unscientific about using vitamins, minerals, or other nutrients to address diseases or symptoms. All that matters is the science.

However, the current state of loose regulation did result in an explosion of the supplement industry, with a multiplication of dubious claims. This had the additional consequence of drowning out legitimate nutritional advice with all the nonsense, in a “boy who cried wolf” phenomenon. Now the skeptical consumer is and should be wary of any and all supplement claims.

Magnesium for migraine is a plausible hypothesis. Magnesium can affect both regulation of blood flow and neuronal function – both of which are physiological factors important in migraine. There is evidence that magnesium deficiency is common, and is more common in migraine patients than non-migraine sufferers.

But the basic science is complex, and there is evidence that low magnesium in brain tissue may be a side effect, and not a cause, of the physiological mechanisms of migraine. So the bottom line is that magnesium as a treatment for migraine is plausible, but there are still unknowns.

The clinical evidence needs to be divided into specific clinical claims: magnesium as a treatment for children vs adults, migraine with aura vs migraine without aura, acute treatment of migraine attacks vs migraine prophylaxis, and treatment of menstrual migraines.

Here is my quick summary of the evidence: There is preliminary evidence only in children, and more research is needed. Treatment of acute attacks with IV magnesium sulfate has mixed evidence, but more positive than negative. One study showed, however, that it can decrease the effectiveness of medication for nausea, often given to treat the nausea of severe migraines.

There is more evidence for migraine with aura than without, but probably not enough to make a critical difference. The best evidence is for menstrual migraines.

Overall the evidence for prophylaxis shows a small but significant effect. Evidence is still preliminary, and large definitive trials are needed to fully settle the question.The effect seems to be smaller than for other nutritional interventions for migraine, specifically vitamin B2 and Coenyzme Q10, and all the supplements are less effective than the best prescription medications.

As a neurologist who treats migraine frequently, I also have experience using magnesium. This is how I put it all together: Most of my patients have not noticed a significant improvement with magnesium. While it is safe, in the doses used for migraines (400-600mg per day) diarrhea can be a significant side effect, and many of my patients stopped using it or had to decrease the dose for that reason.

While the evidence is preliminary, it tends to be positive and so magnesium is a plausible and generally benign treatment option  (if you don’t get diarrhea). It may have a role more as adjunctive treatment (in addition to other treatment) rather than stand-alone treatment because the effect is modest.

Typically I will check the magnesium level in patients with migraine and supplement magnesium if it is low. These patients may represent a subset that responds to magnesium, and in any case they are low in magnesium and probably should be supplemented anyway.

Overall magnesium has a minor role to play in the management of migraine. We could benefit from larger studies to more definitively clarify its role in the various clinical situations I outlined above, primarily because it is inexpensive and relatively benign.

I do not think that the evidence supports using magnesium as a primary treatment for migraine before other more effective treatments. However, some patients may wish to give it a try in the hopes of avoiding medication, and that is reasonable.

The use of magnesium in migraine is a good example of how a science-based practitioner might incorporate benign and plausible treatments but with only preliminary evidence into their practice.