Study of magnesium bioavailability from ten organic and inorganic Mg salts in Mg-depleted rats using a stable isotope approach.
Level 5 - mechanism / opinion, no new human data
Preclinical animal study in rats
What was done
Eighty male Wistar rats (6 weeks old) were fed a magnesium-depleted diet for 3 weeks and then randomized into 10 groups receiving a magnesium-repleted diet (550 mg Mg/kg) for 2 weeks containing one of 10 magnesium salts: oxide, chloride, sulphate, carbonate, acetate, pidolate, citrate, gluconate, lactate, or aspartate. After 10 days of repletion, the rats were given 1.8 mg of oral 26Mg stable isotope. Feces and urine were collected for 4 consecutive days to measure isotope ratios, absorption, urinary excretion, and retention.
What was found
Magnesium absorption varied from 50% to 67% across all forms, with organic salts slightly more available than inorganic salts, and magnesium gluconate exhibiting the highest bioavailability. Urinary 26Mg excretion ranged from 0.20 mg to 0.33 mg, with higher urinary excretion observed from organic pidolate, citrate, gluconate, and aspartate salts than inorganic salts. Magnesium retention was higher in rats receiving organic salts such as gluconate, lactate, and aspartate compared to inorganic salts.
Why it matters
The study directly compares 10 common magnesium formulations under identical isotopic conditions, demonstrating modest absorption and retention advantages for organic magnesium salts over inorganic forms.
Limits
The study was conducted entirely in magnesium-depleted male rats (n = 8 per group) and findings may not reflect human bioavailability or non-depleted states. Individual numerical absorption and retention values for each specific salt, along with statistical variance and significance metrics, were not reported in the abstract.
Cited by
- context Organic magnesium salts like citrate, glycinate, taurate, and malate are more bioavailable and raise plasma magnesium better than inorganic forms like oxide, chloride, and sulfate.