Magnesium, explained properly.

What magnesium actually is

Magnesium is the fourth most abundant mineral in the human body and the second most abundant intracellular cation (after potassium). An adult body contains ~25 g of magnesium — about 60% locked in bones, 27% in muscle, and the rest distributed in soft tissue and blood serum. Only 1% circulates in serum, which is why serum magnesium testing is a poor marker of total body stores.

Magnesium is essential — meaning the body cannot make it, you must consume it. Modern food systems have stripped ~25-30% of the magnesium content out of wheat, rice, and vegetables compared to mid-20th century levels, mostly due to soil depletion and food processing. Coffee, alcohol, and high-stress lifestyles further deplete it through urinary excretion.

How magnesium works in the body

Magnesium is a cofactor for more than 300 enzyme systems — more than any other mineral. The clinically-relevant effects trace to a handful of these reactions:

1. ATP energy production. ATP (the energy currency of every cell) must be bound to Mg²⁺ to be biologically active. Every metabolic process — walking, thinking, contracting a muscle — consumes Mg-ATP. Low magnesium → fatigue, exercise intolerance.
2. NMDA receptor modulation. Magnesium blocks the NMDA glutamate receptor at normal serum levels. Low magnesium disinhibits NMDA → hyperexcitability → anxiety, insomnia, and (in severe cases) seizures.
3. Muscle contraction/relaxation. Calcium contracts muscle fibers; magnesium is the natural antagonist that allows them to relax. Low Mg → chronic muscle tension, eye twitches, nighttime leg cramps.
4. Blood pressure regulation. Magnesium acts as a natural calcium channel blocker in vascular smooth muscle. The Del Gobbo 2013 meta-analysis (44 trials, 1,978 participants) found 400-1000 mg/day reduces systolic BP by 2-4 mmHg in hypertensive adults — a clinically meaningful effect.
5. Blood sugar control. Required for insulin receptor signaling and GLUT4 translocation. Meta-analyses show 250-450 mg/day improves insulin sensitivity by 10-15% in pre-diabetics (Veronese 2016).
6. DNA and protein synthesis. Required for over 600 transcription factors and every ribosomal protein synthesis step.
7. Bone health. ~60% of bodily magnesium is stored in bone, where it modulates vitamin D activation and parathyroid hormone signaling.

The 7 forms of magnesium, compared

All magnesium supplements are eventually Mg²⁺ in the body, but the anion bound to it (glycinate, citrate, oxide, etc.) affects absorption, gut tolerance, and clinical effect. This is the most important decision you make when choosing a magnesium supplement.

Why so many people are low on magnesium

The 2011-2012 Australian Health Survey found 1 in 3 adults below the EAR for magnesium. The reasons are structural:

• Soil depletion: 50-80 years of intensive agriculture has stripped ~25% of the magnesium from wheat, rice, and vegetables compared to mid-20th century levels.
• Food processing: white rice, white flour, and refined sugar have 80-95% of the magnesium removed compared to whole grain versions.
• High caffeine and alcohol intake: both increase renal magnesium excretion.
• Chronic stress: cortisol-driven urinary Mg loss. People with high-stress jobs often have the lowest serum levels.
• PPIs (omeprazole, pantoprazole): long-term use (>1 year) impairs intestinal Mg absorption. FDA issued a safety warning in 2011.
• Type 2 diabetes and insulin resistance: insulin resistance causes renal Mg wasting.
• High-sugar diets: fructose in particular increases renal Mg excretion.

How much magnesium do you actually need?

Per the US Institute of Medicine (IOM 1997) and the Australian NHMRC. The RDA is the daily amount needed by 97-98% of healthy adults. The UL is the upper limit from supplements (not diet).

Source: NIH ODS Magnesium Fact Sheet. The RDA can be met from food + supplements combined; the UL applies only to supplements because dietary magnesium is much less efficiently absorbed at high doses.

Choosing by use case

What to pair with magnesium (and what to avoid)

Frequently asked questions

References & sources

1. NIH Office of Dietary Supplements — Magnesium Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/
2. Del Gobbo LC, et al. (2013). Circulating and dietary magnesium and risk of cardiovascular disease: a systematic review and meta-analysis of prospective studies. American Journal of Clinical Nutrition 98(1):160-173. doi.org/10.3945/ajcn.112.053132
3. Slutsky I, et al. (2010). Enhancement of learning and memory by elevating brain magnesium. Neuron 65(2):165-177. doi.org/10.1016/j.neuron.2009.12.026
4. Veronese N, et al. (2016). Effect of magnesium supplementation on glucose metabolism in people with or at risk of diabetes: a systematic review and meta-analysis of double-blind randomized controlled trials. European Journal of Clinical Nutrition 70(12):1354-1359. doi.org/10.1038/ejcn.2016.154
5. Barbagallo M, Dominguez LJ. (2015). Magnesium and aging. Current Pharmaceutical Design 21(17):2244-2249. doi.org/10.2174/1381612821666150312142300
6. Examine.com — Magnesium research review. examine.com
7. Australian Health Survey 2011-2012 — Usual Nutrient Intakes. Australian Bureau of Statistics. abs.gov.au
8. Chemist Warehouse AU, iHerb, Amazon, Swisse AU, Blackmores AU, BioCeuticals AU, Ethical Nutrients, Herbs of Gold, Nature's Own, Vistra TH, Mega We Care, Thorne, Interpharma — product pages and price snapshots cited per row in the magnesium comparison table.