Magnesium

Description

Three forms under one listing: magnesium glycinate at 400mg, magnesium L-threonate at 2000mg, and magnesium citrate as a 500g powder. Pick the option by name at checkout. The reason magnesium glycinate is the default choice for most people is tolerability rather than potency, and the reason all three carry different numbers is that each salt holds a different fraction of actual magnesium by weight.

The three options

Why 400mg on a magnesium glycinate label is ambiguous

Across this industry that figure is used two different ways. Some labels mean 400 mg of elemental magnesium, which takes roughly 2,800 mg of the glycinate chelate to deliver. Others mean 400 mg of the compound, which carries nearer 56 mg of magnesium. The same number on two bottles can differ sevenfold.

So our panel gives the elemental amount in the main column with the compound weight beneath it, for every option. That convention runs across the whole minerals page, because comparing mineral salts by compound weight produces nonsense answers.

The elemental fractions, form by form

Magnesium oxide is around 60 percent elemental magnesium by mass and is the cheapest form on any shelf. Citrate sits near 16 percent. Glycinate is closer to 14 percent, which is why a glycinate capsule is physically large and why gram scale servings end up as powders.

Higher elemental percentage is not better. Oxide is dense in magnesium and poorly absorbed, which is why it turns up in cheap multivitamins and in laxatives. A magnesium glycinate capsule carries less magnesium per milligram of compound and is the form most people tolerate at a daily serving.

Why the threonate option costs more per milligram

Magnesium L-threonate is about 8 percent elemental magnesium, so 2,000 mg of the compound delivers roughly 144 mg of the mineral. It is the most expensive magnesium on this page per milligram of elemental content, and the published work on it is a small number of trials rather than a large literature.

The citrate powder, and what the 500g means

Five hundred grams of magnesium citrate powder, measured by the scoop rather than swallowed in capsules, because gram quantities of a 16 percent salt do not fit into capsules sensibly. Citrate is also the form with the most pronounced laxative effect at higher servings, which is a tolerability fact rather than a criticism.

What the research administered

Trials have used 200 to 400 mg of elemental magnesium a day across a range of endpoints, measuring serum and red cell magnesium concentrations, sleep questionnaire scores and blood pressure readings, with the form varying between studies. The threonate work measured cognitive task performance at 1.5 to 2 grams of compound. Those are the amounts administered and the instruments read, not claims about these bottles.

Which magnesium glycinate option to start with

For most people the glycinate, since magnesium glycinate has the mildest gastrointestinal reputation of the three at a daily serving. The citrate powder is the cheapest per milligram of elemental magnesium and the most likely to loosen the bowels. The threonate is the dearest and carries the smallest published literature behind it.

We stock all three rather than recommending one. The magnesium glycinate option is simply the one most buyers choose, and each lot of each option carries its own certificate, so the elemental figure you pay for has been measured rather than assumed from a textbook.

Reference intakes

Adult recommended intakes run 310 to 420 mg a day of elemental magnesium depending on age and sex, and the upper limit for supplemental magnesium is 350 mg, which is lower than many bottles on the market. The NIH magnesium fact sheet has the full table and the food sources alongside it.

Testing

Every lot of every option is assayed for elemental magnesium by an independent laboratory and screened for lead, cadmium and arsenic, which matters because mineral salts are mined material. Under strength lots are withdrawn and the failing certificate stays published, as explained in why we publish the batch that failed.