13.5 Magnesium

Magnesium is an electrolyte, but that is not considered its major function in the body. Green leafy vegetables, beans, nuts, seeds, and whole grains are good sources of magnesium1,2. 40-60% of consumed magnesium is absorbed at normal levels of intake. Magnesium is excreted primarily in urine3.

55-60% of magnesium in the body is found in bone3. Some (30%) of this bone magnesium is believed to be exchangeable, or can be used to maintain blood concentrations, similar to how calcium in bones can be used to maintain blood concentrations.

Magnesium helps to stabilize ATP and nucleotides by binding to phosphate groups. Magnesium plays a role in over 300 enzymes in the body. Here is a list of some of the physiological processes that magnesium participates in3:


TCA cycle

Fatty acid oxidation (beta-oxidation)

DNA and RNA transcription

Nucleotide synthesis

Muscle contraction

Magnesium deficiency is rare, but can be caused by prolonged diarrhea or vomiting. Symptoms include1:

Irregular heartbeat

Muscle spasms





Magnesium toxicity is also rare but can occur from excessive use of antacids or laxatives. Symptoms include3:




Double vision

Slurred speech



Magnesium supplements differ in percent of magnesium in the different forms, as shown below.

Figure 13.51 Percent magnesium in oral supplements

The bioavailability of magnesium oxide is significantly lower than magnesium chloride, magnesium lactate, and magnesium aspartate. The latter 3 are equally bioavailable4.

References & Links

1. Byrd-Bredbenner C, Moe G, Beshgetoor D, Berning J. (2009) Wardlaw’s perspectives in nutrition. New York, NY: McGraw-Hill.

2. McGuire M, Beerman KA. (2011) Nutritional sciences: From fundamentals to food. Belmont, CA: Wadsworth Cengage Learning.

3. Gropper SS, Smith JL, Groff JL. (2008) Advanced nutrition and human metabolism. Belmont, CA: Wadsworth Publishing.

4. http://www.health-choices-for-life.com/magnesium_supplements.html