Magnesium · Evidence
Each point below summarizes specific sources, linked by number to the reference list at the bottom. Where the research is thin or mixed, we say so.
The NIH fact sheet describes magnesium as a cofactor in more than 300 enzyme systems, including ones for protein synthesis, muscle and nerve function, blood sugar control and blood pressure. It is also needed for energy production, bone structure, and making DNA and RNA.[1]
According to the fact sheet, small studies found magnesium aspartate, citrate, lactate and chloride are absorbed more completely than magnesium oxide and sulfate. The fact sheet doesn’t discuss glycinate. This site compares products by the elemental magnesium on the Supplement Facts panel, not the weight of the whole compound.[1]
Grouped by how much research backs each outcome. A stronger group means more consistent results across more studies, not a bigger effect.
The NIH fact sheet says trials suggest magnesium only marginally lowers blood pressure. A Cochrane review of 12 trials (545 people with high blood pressure) found diastolic pressure fell by 2.2 mmHg. A meta-analysis of 22 studies (1,173 adults) found systolic pressure fell 3 to 4 mmHg and diastolic 2 to 3 mmHg. The FDA calls the evidence for a blood pressure claim inconsistent and inconclusive.[1]
Three of four small, short placebo-controlled trials found modest reductions in how often migraines happened with up to 600 mg of magnesium a day. A guideline cited by the fact sheet says magnesium is probably effective for preventing migraine.[1]
A meta-analysis found 3 randomized trials comparing oral magnesium with placebo in 151 older adults. People taking magnesium fell asleep 17.36 minutes faster than with placebo. Total sleep time rose by 16.06 minutes, but that was not statistically significant. The authors rated the trials at moderate-to-high risk of bias, called the evidence low to very low quality, and said it is not good enough for doctors to make well-informed recommendations.[2]
Trial results are mixed, and the fact sheet reports the American Diabetes Association’s view that there isn’t enough evidence to support routine magnesium for blood sugar control in people with diabetes.[1]
The NIH fact sheet lists a Recommended Dietary Allowance of 400 to 420 mg a day for adult men and 310 to 320 mg for adult women, from all sources combined.[1]
The upper limit for adults is 350 mg a day of magnesium from supplements and medications. It does not include magnesium in food. Above it, supplements can cause diarrhea, nausea and abdominal cramping.[1]
The fact sheet says very high doses can cause magnesium toxicity, with low blood pressure, vomiting, trouble breathing, irregular heartbeat and, rarely, cardiac arrest. The risk rises with reduced kidney function or kidney failure, because the body can’t clear the extra magnesium. Toxicity has been linked to laxative or antacid doses, typically over 5,000 mg a day.[1]
The fact sheet lists interactions with osteoporosis drugs (bisphosphonates) and some antibiotics (tetracyclines and quinolones), which should be taken hours apart from magnesium; diuretics, which can raise or lower magnesium; and long-term use of acid-reducing proton pump inhibitors, which can cause low magnesium.[1]