Magnesium aspartate

A US Supplement Facts panel declares the element, not the salt. Magnesium aspartate has a molar mass of 288.5 against magnesium's 24.305, so 8.42% of its mass is magnesium.

A size 00 capsule holds about 730 mg of powder at powder density 0.6–0.8 g/mL; a size 000 about 1,100 mg.

Counted only for capsule labels naming this salt alone. Full method and the corpus-wide figure: label mass-budget audit.

Absorption is a separate question from mass, and a contested one. Below is what each study did, on whom, and what it measured — with the original linked. See the full literature page for why results conflict.

These entries report what each study measured and on whom. They are not advice, not a ranking, and not a claim about any product on this site. Every reference links to its PubMed record so the original can be read in full.

1. Study of magnesium bioavailability from ten organic and inorganic Mg salts in Mg-depleted rats using a stable isotope approach

   Magnesium Research · 2005 · PMID 16548135

   Design

   Eighty male Wistar rats fed a magnesium-depleted diet for three weeks, then randomised into ten groups, each receiving a different magnesium salt labelled with a stable isotope.

   What it measured

   Stable isotopes allow absorption and retention to be traced directly rather than inferred from urine, across ten salts at once — the widest head-to-head comparison in the literature.

   Limits

   Rats, not people, and magnesium-depleted rats at that: depletion itself raises absorption. The breadth of the comparison is its value; the species is its limit.

2. Bioavailability of US commercial magnesium preparations

   Magnesium Research · 2001 · PMID 11794633

   Design

   Four commercially available US preparations given to healthy volunteers; bioavailability measured as the increment in urinary magnesium excretion.

   What it measured

   The study set out to test the claim that organic magnesium salts are more easily absorbed than inorganic ones, using urinary excretion as the read-out.

   Limits

   Healthy volunteers, small sample, urinary excretion as a proxy for absorption rather than a direct measurement of retention.

Compare aspartate with other salts

13 published comparisons include magnesium aspartate as of 2026-09-13; each row gives the other salt's magnesium fraction and compound mass for 100 mg elemental magnesium from the chemistry model.

• Magnesium aspartate vs magnesium citrate: 11.3–16.16% magnesium by mass; 619–885 mg compound per 100 mg elemental magnesium.
• Magnesium aspartate vs magnesium glycinate: 11.83–14.1% magnesium by mass; 709–845 mg compound per 100 mg elemental magnesium.
• Magnesium aspartate vs magnesium oxide: 60.32% magnesium by mass; 166 mg compound per 100 mg elemental magnesium.
• Magnesium aspartate vs magnesium malate: 13.2–15.54% magnesium by mass; 644–758 mg compound per 100 mg elemental magnesium.
• Magnesium aspartate vs magnesium carbonate: 24.78–28.83% magnesium by mass; 347–404 mg compound per 100 mg elemental magnesium.
• Magnesium aspartate vs magnesium gluconate: 5.86% magnesium by mass; 1,706 mg compound per 100 mg elemental magnesium.
• Magnesium aspartate vs magnesium chloride: 11.96–25.53% magnesium by mass; 392–836 mg compound per 100 mg elemental magnesium.
• Magnesium aspartate vs magnesium taurate: 8.85% magnesium by mass; 1,130 mg compound per 100 mg elemental magnesium.
• Magnesium aspartate vs magnesium hydroxide: 41.68% magnesium by mass; 240 mg compound per 100 mg elemental magnesium.
• Magnesium aspartate vs magnesium l-threonate: 8.25% magnesium by mass; 1,212 mg compound per 100 mg elemental magnesium.
• Magnesium aspartate vs magnesium orotate: 7.27% magnesium by mass; 1,376 mg compound per 100 mg elemental magnesium.
• Magnesium aspartate vs magnesium lactate: 12.01% magnesium by mass; 833 mg compound per 100 mg elemental magnesium.
• Magnesium aspartate vs magnesium sulfate: 9.86–20.19% magnesium by mass; 495–1,014 mg compound per 100 mg elemental magnesium.

Excipients most common in aspartate labels

5 published excipient facets below have the highest frequencies among 46 labels mentioning magnesium aspartate in the NIH DSLD records, counted 2026-09-13; each label enters an ingredient count once.

• silicon dioxide: 28 of 46 labels.
• magnesium stearate: 24 of 46 labels.
• stearic acid: 16 of 46 labels.
• microcrystalline cellulose: 15 of 46 labels.
• cellulose: 14 of 46 labels.