Magnesium: Forms, Absorption & Why Most People Are Low
Magnesium is involved in over 600 enzymatic reactions and is essential for energy production, DNA synthesis, muscle and nerve function, blood sugar regulation, and blood pressure control. Despite its importance, subclinical magnesium deficiency is estimated to affect 50% or more of the population in industrialized countries.
Why Deficiency Is So Common
Several factors converge to create widespread magnesium insufficiency. Soil depletion has reduced magnesium content in crops over the past century. Water softening and purification remove magnesium from drinking water. Processed food diets are inherently low in magnesium. Stress, alcohol, caffeine, and certain medications (PPIs, diuretics, some antibiotics) increase magnesium excretion or impair absorption.
Standard blood tests (serum magnesium) are poor indicators of total body magnesium because less than 1% of total magnesium is in the blood. You can have normal serum levels while being significantly depleted at the tissue and bone level.
Forms of Magnesium Supplements
| Form | Bioavailability | Notes |
|---|---|---|
| Magnesium glycinate | High | Well-tolerated, less laxative effect, may support sleep |
| Magnesium threonate | Moderate | Researched for brain penetration and cognitive effects |
| Magnesium taurate | Moderate-high | Combined with taurine, researched for cardiovascular support |
| Magnesium citrate | Moderate-high | Good absorption but can have laxative effect at higher doses |
| Magnesium oxide | Low (~4%) | Cheapest form, primarily used as a laxative |
| Magnesium malate | Moderate-high | May support energy production (malic acid is a Krebs cycle intermediate) |
Food Sources
Pumpkin seeds, dark chocolate (70%+ cacao), spinach, Swiss chard, almonds, black beans, avocado, and whole grains are good sources. Hard water can contribute meaningfully depending on mineral content. Cooking vegetables in large amounts of water leaches magnesium.
Interactions
Magnesium works closely with calcium (they balance each other in muscle contraction/relaxation), vitamin D (magnesium is required to convert D to its active form), and B6 (they share neurotransmitter pathways). Magnesium is also critical as an enzyme cofactor and is essential for ATP function — ATP is biologically active only when bound to magnesium. For more on how magnesium form affects what you absorb, see the Bioavailability Guide.
External resources: NIH — Magnesium Fact Sheet