Magnesium: bisglycinate, citrate or oxide, which one is really absorbed?
Magnesium is the 4th most studied ingredient in our PubMed count, with 3,367 human clinical trials, and one of the best sellers in pharmacies. Yet every brand asks the same question: which form to choose? Here is what the studies measure, what the label can say and how we manufacture it, from the Irati Production R&D team.
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- In comparative studies, organic salts (citrate, bisglycinate, lactate) are better absorbed than oxide; the measured gap ranges from a few points to a factor of three depending on the protocol.
- Oxide remains the most concentrated: 60% elemental magnesium, against 16% for citrate and about 14% for bisglycinate. The more absorbable the form, the bulkier the capsule.
- In France the maximum daily dose in supplements is 300 mg; EFSA sets the safe upper level at 250 mg of added magnesium, a threshold ANSES recommends adopting.
- Ten authorised claims, including "contributes to a reduction of tiredness and fatigue" and "to normal functioning of the nervous system", from 56 mg per serving.
- Irati Production manufactures magnesium as capsules, tablets, powder in stick packs or doypacks and pectin-based gummies, in Saumur, France.
What the studies actually measured
The most cited comparison dates from 1990: Lindberg and colleagues gave 25 mmol of citrate or oxide to volunteers and measured urinary magnesium. Citrate was 55% water-soluble, oxide almost insoluble, and urinary excretion after intake was clearly higher with citrate. In 2003, Walker compared citrate, an amino acid chelate and oxide over 60 days in 46 adults: both organic forms raised urinary magnesium more, and oxide was no different from placebo on salivary magnesium.
The absorbed fraction of oxide is often summarised as 4%, after Firoz and Graber (2001), against about 12% for citrate, lactate or chloride. These figures come from short urinary studies, criticised for their method, and the review by Schuchardt and Hahn (2017) recalls that the ingested dose and the person's magnesium status weigh more than the salt. In 2024, a crossover trial in 40 adults at 375 mg found no difference in plasma area under the curve between oxide, citrate and bisglycinate. The honest conclusion: organic forms have a probable but modest advantage, and oxide is not useless, especially in divided doses.
Bisglycinate: the tolerance argument more than the absorption argument
Magnesium bisglycinate, or glycinate, binds one magnesium atom to two glycine molecules. Its best documented advantage is digestive: in Schuette's 1994 study in patients with intestinal resection, the chelate caused 2.4 stools per 24 hours against 3.7 for oxide, with an earlier absorption peak. The hypothesis of absorption through dipeptide transporters remains to be demonstrated in humans, but the smaller amount of free magnesium in the gut explains the good tolerance.
This is why bisglycinate dominates premium launches, especially for sleep and stress: a gentle form, taken in the evening, with no laxative effect. Its drawback is bulk: at 14% elemental magnesium, 300 mg of magnesium means more than 2 g of bisglycinate, three size 00 capsules or a powder. Citrate (16%) raises the same issue. Oxide (60%) fits in a single capsule, and so does marine magnesium, a blend of oxide and hydroxide.
How much can go in, and what can the label say?
The regulatory frame is precise:
- Maximum dose in France: 300 mg of magnesium a day in a food supplement (order of 9 May 2006). EFSA sets the safe upper level at 250 mg of added magnesium a day, because of the laxative effect of dissociable salts, and ANSES recommended in 2024 that this threshold be adopted in the future order.
- Nutrient reference value: 375 mg. From 56 mg per serving (15% of the NRV), the product is a "source of magnesium" and may carry the claims.
- Authorised claims (Regulation (EU) No 432/2012): magnesium contributes to a reduction of tiredness and fatigue, to electrolyte balance, to normal energy-yielding metabolism, to normal functioning of the nervous system, to normal muscle function, to normal protein synthesis, to normal psychological function, to the maintenance of normal bones and teeth; it has a role in the process of cell division.
- What is forbidden: "anti-stress", "anti-cramp", "against insomnia". Irati Production's regulatory team writes the exact wording.
Which form to manufacture, for which positioning?
The choice crosses dose, tolerance, bulk and price:
- Bisglycinate capsules: the sleep, stress and premium pharmacy positioning; 2 to 3 capsules a day for 300 mg, often with vitamin B6 and taurine. See magnesium manufacturer.
- Oxide or marine magnesium tablets: the full dose in one unit, the lowest cost, for essential ranges and multivitamins.
- Citrate or bisglycinate powder in stick packs: the rising format, with electrolytes or for the evening routine, exact dose and good dispersion in water.
- Pectin-based gummies: a gentle dose per gummy, for people who do not swallow capsules; the "source of magnesium" claim remains within reach.
Why magnesium never goes out of fashion
In the SU.VI.MAX study, 77% of women and 72% of men had magnesium intakes below the recommended level. Tiredness, stress and sleep are cited by 41 to 45% of supplement consumers in the 2026 Synadiet barometer, and among 18 to 34-year-olds, 59% say their sleep is often a problem. Magnesium is one of the few ingredients able to answer these expectations with authorised claims. It combines with vitamin B6, taurine, zinc, low-dose melatonin or evening botanicals in our standard formulas.
Your magnesium, made in Saumur, France
Irati Production manufactures magnesium as capsules, tablets, powder and pectin-based gummies in its Saumur unit, ISO 22000 certified, HACCP approach and FDA-registered.
- Bisglycinate, citrate, oxide, marine or malate depending on your positioning
- Capsule sizes 1, 0 and 00, tablets up to 2 g, stick packs and doypacks, pectin-based gummies
- Standard formulas with vitamin B6, taurine, zinc or botanicals
- Small batches available on standard formulas
- Dose per unit and claims checked
Our answers on magnesium forms
Which form of magnesium is best absorbed?
Comparative studies favour organic salts (citrate, bisglycinate, lactate) over oxide, but the gap depends on the protocol: clearly higher in short urinary studies, not significant in a 2024 crossover trial at 375 mg. Dose, divided intake and magnesium status matter as much as the salt.
Why is magnesium bisglycinate so popular?
For its digestive tolerance: less free magnesium in the gut, so less laxative effect, which makes it the form of sleep and stress products taken in the evening. Its drawback is bulk: at 14% elemental magnesium, more than 2 g are needed for 300 mg of magnesium.
What is the maximum magnesium dose in a food supplement in France?
300 mg a day under the order of 9 May 2006. EFSA sets the safe upper level at 250 mg of added magnesium a day, and ANSES recommended in 2024 that this threshold be adopted when the order is revised.
Which claims can a magnesium supplement carry?
Ten claims authorised by Regulation (EU) No 432/2012, from 56 mg per serving: reduction of tiredness and fatigue, electrolyte balance, energy-yielding metabolism, nervous system, muscle function, protein synthesis, psychological function, bones, teeth, cell division. Irati Production checks the exact wording for each formula.
How much elemental magnesium does each form contain?
About 60% for oxide, 41% for hydroxide, 16% for citrate, 15% for malate and 14% for bisglycinate. Marine magnesium, a blend of oxide and hydroxide, is around 55%.
Who manufactures private label magnesium in France?
Irati Production manufactures private label magnesium in its Saumur unit, as capsules, tablets, powder in stick packs or doypacks and pectin-based gummies, on standard or custom formulas.
The information in this article is general and does not constitute regulatory advice. Each formula undergoes a technical and regulatory feasibility study.