I read an interesting article in one of my medical journals (American Family Physician) about the therapeutic uses of magnesium, ranging from preeclampsia to migraines.  The article also discussed the consequences of magnesium deficiency.  Studies estimate that 75% of Americans do not get enough of the element in their diet, and that the general mineral content of our food is declining.

Early signs of magnesium deficiency are quite nonspecific and overlap with thousands of other conditions, but include loss of appetite, nausea, vomiting, fatigue, and weakness. As levels decrease further, numbness, tingling, muscle contractions, cramps, seizures, personality changes, arrhythmias, and even coronary artery spasms can occur. Severe deficiency can lead to low potassium and calcium levels, each of which can cause serious problems as well.

Conditions that have been associated with low magnesium levels include poorly-controlled diabetes, malabsorptive disorders like Crohn’s Disease and celiac disease, alcoholism, and older age.  Taking diuretics and certain antibiotics can also decrease magnesium levels in the body.  Studies have linked magnesium deficiency to heart attacks, congestive heart failure, hypertension, and angina, but evidence is still too sparse to recommend its use for these problems.

The only two clinical recommendations that carry an “A” evidence rating (consistent, good-quality patient-oriented evidence) are for using magnesium in the treatment of eclampsia and preeclampsia in pregnancy, and in the treatment of torsade de pointes and rapid atrial fibrillation, two serious heart rhythm disturbances.

Other studies have found magnesium beneficial in the treatment of acute asthma (when given intravenously in conjunction with standard bronchodilators and steroids), migraines and cluster headaches, dyspepsia and gastroesophageal reflux. If you’re wondering if you should take magnesium, talk to your doctor.  Oral magnesium supplementation can be well-tolerated, or can cause nausea, vomiting, and diarrhea in and of itself.   Overdose of magnesium can lead to thirst, dangerously low blood pressure, drowsiness, muscle weakness, respiratory depression, cardiac arrhythmia, coma and death.   Magnesium can also interfere with the absorption of other medicines, and people with poor kidney filtration may accumulate toxic levels.

As with all reductionist approaches to food and nutrition, purely focusing on individual nutrients and minerals like magnesium is too easy, and misses the bigger picture.  Like Michael Pollan says, “Eat food. Not too much. Mostly plants.”   Food sources of magnesium tend to be rather healthy foods, and include green leafy vegetables, nuts, legumes, and whole grains. The NIH has compiled this list of common magnesium-containing foods:

Table 1: Selected food sources of magnesium [5]

The USDA has a much more complete and exhaustive list, although it is sorted alphabetically and therefore requires a lot of scrolling around.

And finally, some cool facts about magnesium in the universe from Wikipedia:

Magnesium, an alkaline earth metal, is the 9th most abundant element in the universe by mass. The commonness of magnesium is related to the fact that it is easily built up in supernova stars from a sequential addition of 3 helium nuclei to carbon (which in turn is made from a single reaction between 3 helium nuclei at once). Magnesium constitutes about 2% of the Earth’s crust by mass, which makes it the 8th most abundant element in the crust. Magnesium ion’s high solubility in water helps ensure that it is the 3rd most abundant element dissolved in seawater.

Halibut with chocolate pudding and boiled spinach on top, anyone?