Magnesium

Magnesium is an essential dietary nutrient and is one of the most abundant minerals in the body. Magnesium acts as an electrolyte and is a cofactor for more than 300 enzymes. Magnesium is required for energy (ATP) production, glucose metabolism, DNA and protein synthesis, nerve conduction, bone health, and cardiovascular regulation, among other functions. It also plays a crucial role in the synthesis and activation of vitamin D.

Dietary sources of magnesium include dark green leafy vegetables, nuts and seeds, legumes, whole grains, and meat/fish such as salmon, chicken, and beef.^[4] Many foods such as breakfast cereals and bread are fortified with magnesium. It appears that approximately 20%–40% of the dietary magnesium that enters the body becomes bioavailable.^[5][6][7]

More than half of adults may not meet the recommended daily intake of magnesium,^[4] likely because Western diets tend to be very low in magnesium-rich foods and high in processed foods and refined grains, which are magnesium-poor. As such, magnesium deficiency — which elevates the risk of obesity, diabetes, cardiovascular disease, metabolic syndrome, and osteoporosis — is a major public health concern, especially for older adults.^[8][9]

Low magnesium levels are associated with a higher risk of diabetes, and supplementation with magnesium has been shown to reduce blood glucose and improve insulin sensitivity,^[10][11][12] especially in people who are insulin resistant and/or magnesium deficient^{[13][14][15][16]} and/or in women with gestational diabetes.^[12][17]

Supplemental magnesium also appears to lower blood pressure in people who are deficient in magnesium^[18][19] and in those who have elevated blood pressure (hypertension).^[20][21][22] The average reduction in blood pressure after magnesium supplementation is 2–4 mmHg for systolic blood pressure and 2 mmHg for diastolic blood pressure,^[23][24] though the reductions may be greater for individuals with type 2 diabetes (6–8 mmHg and 2–3 mmHg for systolic and diastolic blood pressure, respectively.^[25][26]

There is some indication that magnesium supplementation may normalize age-related changes in sleep patterns or improve sleep in people who have insomnia or who are magnesium deficient,^[27][28][29] reduce the frequency and intensity of migraine headache,^[30][31][32] and attenuate premenstrual symptoms in women.^[33][34][35]

Magnesium supplementation that is not excessive is well tolerated and probably won’t cause side effects, and it’s difficult to ingest too much magnesium from food sources alone. Excess magnesium in the body is eliminated by the kidneys, so the risk of magnesium toxicity from food is quite low for healthy people.^[36]

Supplementing with high doses and certain magnesium salts (i.e., magnesium carbonate, magnesium chloride, magnesium gluconate, magnesium hydroxide, and magnesium oxide) can have a laxative effect — though some people choose to take certain forms of magnesium for this reason.^[2][4] Unabsorbed magnesium salts have an osmotic effect in the intestinal tract and can increase gastric motility. In one study, 12% of participants experienced diarrhea with a 1,000 mg dose of magnesium oxide,^[37] but this form of magnesium is poorly absorbed, and the dose is well above the tolerable upper limit (UL) for magnesium of 350 mg for healthy adults.^[38] Nausea, diarrhea, and abdominal cramping are also occasional side effects reported from supplemental magnesium.

Magnesium supplements can also interfere with the absorption of certain medications, including bisphosphonates (used for treating osteoporosis) and antibiotics — to avoid these interactions, individuals who are taking these types of medications should talk to their healthcare provider about how to space out and time their supplemental magnesium.^[4]

Many observations related to magnesium’s effect on reducing disease risk are likely due to correction of a deficiency. In other words, it may not be the case that supplemental magnesium is beneficial per se; instead, magnesium deficiency may lead to several health problems, many of which may be related to chronic low-grade inflammation.^[39] There is also the possibility of reverse causation because many modern diseases (i.e., obesity and diabetes) may lead to a magnesium deficiency.

Nonetheless, there are well-documented mechanisms that explain why magnesium may benefit health.

For one, magnesium plays a role in beta-cell activity in the pancreas, influencing insulin secretion and, therefore, our ability to regulate blood glucose. Magnesium deficiency can lead to impaired insulin secretion, impaired glucose utilization, and insulin resistance — all of which contribute to the development of type 2 diabetes.^[40]

In the cardiovascular system, magnesium regulates calcium concentrations, which enhances vascular relaxation and inhibits vasoconstriction, leading to healthy vascular tone and protecting against high blood pressure (hypertension). Magnesium also improves endothelial function by directly stimulating the release of nitric oxide(NO).^[41]

In the brain, magnesium binds to and blocks the actions of NMDA receptors, thereby preventing glutamate-dependent transmission of cortical spreading depression — one mechanism involved in the pathogenesis of migraine headache. Magnesium is also a GABA agonist. Magnesium affects the function of serotonin receptors, influences platelet aggregation, and regulates the synthesis and release of several neurotransmitters. These mechanisms explain magnesium’s benefit for migraine, as well as the potential for magnesium to improve sleep and other aspects of neurological health.^[42][43]