Magnesium

What Is Magnesium?

Magnesium is the fourth most abundant mineral in the body and the second most abundant intracellular cation after potassium. An adult body contains approximately 25 grams of magnesium: about 60 percent in bone, 39 percent in soft tissues (especially muscle), and only 1 percent in blood. This distribution means serum magnesium levels can appear normal even when total body magnesium is depleted, making deficiency difficult to detect through routine blood tests.

Key Functions

Magnesium is a cofactor for over 300 enzymatic reactions in the body. Its roles include:

• Energy production: ATP (adenosine triphosphate) must bind magnesium to be biologically active. All ATP-dependent reactions — glycolysis, oxidative phosphorylation, fatty acid oxidation — require magnesium.
• Protein synthesis: Magnesium stabilizes ribosomes and is required for DNA replication and RNA transcription.
• Muscle and nerve function: Magnesium acts as a natural calcium antagonist, regulating muscle contraction and nerve transmission. Low magnesium promotes muscle cramps and excitability.
• Blood glucose control: Magnesium is a cofactor for insulin receptor tyrosine kinase. Low magnesium impairs insulin signaling and is associated with type 2 diabetes risk.
• Blood pressure: Magnesium promotes vasodilation by stimulating nitric oxide production and antagonizing calcium-mediated vasoconstriction.

Dietary Reference Values and Food Sources

The RDA for magnesium is 400-420 mg/day for men and 310-320 mg/day for women (higher during pregnancy: 350-360 mg/day). National surveys indicate that a majority of Americans fall below these targets. The UL for supplemental magnesium is 350 mg/day due to laxative effects at higher doses. Food sources are not subject to a UL. Rich dietary sources include:

• Pumpkin seeds (roasted, 1 oz): ~156 mg
• Dark chocolate (70-85%, 1 oz): ~65 mg
• Cooked black beans (1 cup): ~120 mg
• Cooked spinach (1 cup): ~157 mg
• Almonds (1 oz): ~80 mg
• Avocado (one fruit): ~58 mg
• Brown rice (1 cup cooked): ~84 mg

Deficiency Signs

Early magnesium deficiency may present as loss of appetite, nausea, fatigue, and weakness. Progressing deficiency causes numbness and tingling, muscle cramps and spasms, abnormal heart rhythms, and in severe cases, hypocalcemia and hypokalemia (as magnesium is required to maintain these electrolytes). Suboptimal magnesium status is associated with increased risk of hypertension, type 2 diabetes, cardiovascular disease, migraine, and osteoporosis.