Magnesium is involved in over 300 enzymatic reactions in the human body. It's required for ATP (energy) synthesis, DNA replication and repair, protein synthesis, neurotransmitter regulation, blood pressure control, and insulin signaling. And despite all of that, an estimated 40–50% of Americans don't get enough from food alone.
The reason is partly agricultural: magnesium content in soil — and therefore in crops — has declined substantially over the past 50 years due to industrial farming practices. The foods that were once reliable magnesium sources (leafy greens, nuts, whole grains) contain meaningfully less magnesium than they did in 1970.
The supplement market hasn't helped: magnesium products are everywhere, but most people buy magnesium oxide — the worst-absorbed, most laxative form available — because it's the cheapest and most common.
Magnesium glycinate is magnesium chelated (bound) to glycine, an amino acid. The chelation dramatically improves absorption compared to inorganic magnesium salts. Glycine itself has additional benefits: it's calming, supports sleep quality, and acts as an inhibitory neurotransmitter in the nervous system.
Crucially, magnesium glycinate causes significantly less GI distress than other high-absorption forms. At therapeutic doses (200–400mg elemental), it doesn't cause the loose stool or cramping common with citrate or the non-absorption problem of oxide.
When to take: 200–400mg elemental magnesium 30–60 minutes before bed. The glycine component adds to sleep quality enhancement. Morning dosing works too but the sleep-specific benefit is lost.
View Magnesium Glycinate on Amazon →Magnesium citrate is well-absorbed and widely available. Its main limitation is osmotic laxative effect at doses above ~200mg elemental — it pulls water into the gut. For people who need a gentle digestive nudge, this is a feature; for everyone else, it's a reason to use glycinate instead.
Good for: constipation-prone individuals who also want magnesium supplementation benefits.
Magnesium bound to malic acid, a compound involved in the Krebs cycle (cellular energy production). Some evidence for fibromyalgia symptom reduction and energy support. Slightly energizing — better taken in the morning than at night. Good for athletes or those with chronic fatigue complaints.
Developed at MIT specifically to cross the blood-brain barrier. Animal models show significant increases in brain magnesium levels and cognitive improvements. Human trial data exists but is limited. At 3–4x the price of glycinate, it's hard to justify unless specifically targeting cognitive function. Evidence promising but needs more large-scale human RCTs.
Magnesium oxide has approximately 4% absorption rate in some studies. Despite being the most common form sold (because it's cheapest to manufacture), most of a magnesium oxide dose passes through the GI tract without absorption — acting primarily as a laxative. The "500mg magnesium" on the label sounds impressive; the ~20mg you actually absorb is not. Don't buy this for magnesium repletion.
| Goal | Form | Dose (elemental Mg) | Timing |
|---|---|---|---|
| General repletion + sleep | Glycinate | 200–400mg | Before bed |
| Migraine prevention | Glycinate or Citrate | 400–600mg | Split AM/PM |
| Athletic performance | Malate | 300–500mg | Morning + pre-workout |
| Cognitive support | L-Threonate | 2,000mg (144mg elemental) | Split doses |
| Constipation | Citrate | 200–400mg | Before bed |
Note: "elemental magnesium" is the actual magnesium content — the amount matters, not the total capsule weight. Check the label for elemental Mg.
The label will say something like "Magnesium Glycinate 500mg — provides 100mg elemental magnesium." The 500mg is the total weight of the compound. The 100mg is what matters — the actual magnesium. Aim for 200–400mg elemental magnesium daily.
Reputable brands with third-party testing: Thorne (most rigorous), Pure Encapsulations, NOW Foods, Life Extension. All available on Amazon with the affiliate links below.
View Thorne Magnesium on Amazon →Magnesium is a Tier 1 foundation supplement. See how it fits with everything else in your protocol — personalized to your age, goal, and budget.
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