Magnesium Forms Compared: Citrate, Bisglycinate, Oxide, and Co.

Magnesium oxide: high content, low absorption

Magnesium oxide is the cheapest and most common form available at drugstores and has the highest magnesium content per capsule. The catch: it is very poorly absorbed. In studies, the absorbed amount was only around four percent, significantly less than with organic forms. To reiterate: only 4% of what you ingest actually reaches the bloodstream. The majority remains in the intestines, attracts water, and thus has a laxative effect.

This does not make oxide worthless, but it explains its use: as an inexpensive remedy for constipation. To replenish a deficiency or reliably supply the nervous system and muscles, it is the worst choice.

Magnesium citrate: the well-absorbable all-rounder

Magnesium citrate is an organic compound and is absorbed significantly better than oxide. In direct comparative studies, citrate performed better both in blood and in excretion. It is highly soluble, fairly priced, and for most people, a solid standard choice for daily supplementation.

In higher doses, citrate has a mild laxative effect because it osmotically binds water. Those prone to loose stools should spread the dosage throughout the day, while those already prone to constipation often find this a pleasant side effect.

Magnesium Bisglycinate: gentle on the stomach

In bisglycinate, also called glycinate, magnesium is bound to the amino acid glycine. This chelated form is considered to be well absorbed and, above all, particularly gentle on the stomach, which is why it is often recommended when citrate or oxide cause digestive issues. The data on superior tolerability is predominantly based on smaller studies and empirical evidence, plausible, but less rigorously proven than the absorption advantage over oxide.

Bisglycinate is often advertised for sleep and relaxation, as glycine is said to have a calming effect. Caution is advised here: such an effect is not substantiated as a health claim. What applies is the benefit of magnesium itself, namely its contribution to normal psychological function and the function of the nervous system, and this is independent of the form.

L-Threonate, Malate, and Taurate: the specialized forms

Magnesium L-Threonate is specifically marketed for brain and cognition. Animal studies are interesting, but the few human studies are small, short, and some are funded by manufacturers. A proven benefit for memory or mental performance does not yet exist; furthermore, the magnesium content is low and the price is high. Malate and taurate, on the other hand, are well-tolerated, well-absorbed organic forms, but the evidence for their advertised special effects on energy or cardiovascular health is thin.

Why many good supplements combine several forms

In practice, you don't have to commit to a single form. Many high-quality supplements combine several well-absorbed organic forms, such as bisglycinate, malate, and citrate, in a complex. The idea behind this: the strengths complement each other, good absorption meets good tolerability, instead of relying on the weaknesses of a single form. The crucial thing remains that these are organic, well-resorbable forms and not cheap oxide.

Important: The benefit applies to magnesium, not to the form

This is the point that advertising often blurs. The approved claims for magnesium, such as its contribution to the normal function of the nervous system, to normal psychological function, to the reduction of fatigue, and to normal muscle function, apply to magnesium as a nutrient once the necessary dose is reached. They apply equally to citrate, bisglycinate, or oxide. A form may therefore advertise better absorption or tolerability, but not a stronger effect. This is a shame, as there are indeed forms that work better. But now you know that.

Conclusion: Citrate or bisglycinate for most people

For daily supplementation, citrate and bisglycinate are the most suitable forms: easily absorbable, well-tolerated, and reasonably priced. Citrate is the all-rounder, while bisglycinate is the primary, albeit more expensive, choice for sensitive stomachs or higher doses. Oxide, which is usually cheap and available in drugstores, is primarily useful as a laxative, and the expensive specialized forms have not yet lived up to their promises.

However, the most important thing remains: that you get enough magnesium in a form that your body absorbs, and in an appropriate dose. To find out if your symptoms are related to a magnesium deficiency, read our article on Magnesium Deficiency in Women.