If Your Supplement Bottle Claims "500 mg of Magnesium Glycinate in 1 Capsule," Chemistry Says It’s Lying to You: Inside Our NIH DSLD Label Audit
Pure chelated magnesium bisglycinate is only 14.1% elemental magnesium by molecular weight—meaning a standard Size-00 capsule can physically hold at most ~100–120 mg of real elemental magnesium. Here is how brands sneak cheap, laxative Magnesium Oxide into the bottle.
Here is the hard law of chemistry from our audit of the NIH Dietary Supplement Label Database (DSLD): pure magnesium bisglycinate has a molecular weight of 172.31 g/mol, and two big glycine amino acid molecules make up 85.9% of that weight. Only 14.1% of the powder is actual elemental magnesium . That means to get 400 mg of real elemental magnesium, you need 2,837 mg of powder—which physically takes 3 to 4 large Size-00 capsules to hold! Any bottle claiming 400–500 mg in a single capsule is either quoting the total weight of the powder (giving you only 70 mg of actual magnesium) OR secretly spiking the capsule with cheap Magnesium Oxide (which absorbs at ~4% in human trials, PMID 11794633, and acts like a laxative) .