Magnesium bisglycinate 300 mg

The short version

What it does It releases the evening’s muscular tension: jaw, neck, legs that will not settle.

What it does not do It does not send you to sleep and does not quiet a racing mind. And if your diet is varied, you are probably not short of it.

What the studies say

The most complete review (Mah and Pitre, 3 randomised trials, 151 older adults with insomnia) finds sleep onset shortened by about 17 minutes against placebo, and 16 minutes more sleep — the second figure without reaching statistical significance. Separately, the European Union authorises several claims for magnesium: normal muscle function, reduction of tiredness, normal psychological function.

One distinction matters, and it explains why this page cites EFSA while still being rated EMERGING EVIDENCE. The European magnesium claims are so-called “functional” claims: they establish that magnesium is NECESSARY for normal muscle function. They do not say that taking more of it when you are not short improves anything. That is a different category from the phytosterol claim on cholesterol, which puts a number on an effect measured in trials. On sleep, the meta-analysis authors themselves note a moderate to high risk of bias in the three trials and rate their own level of evidence as “low to very low”. There is also a population limit: the subjects were elderly and already insomniac. You cannot infer an effect in a young adult who sleeps fine.

If your body stays tense at bedtime — jaw, neck, legs — this is the lead, and it is consistent with what we know about magnesium in muscle. If it is your mind that is racing, this is the wrong product. And if your diet is varied, you are probably not short of it.

How to take it

Relevant after 45, with a high training volume, or when stress shows up muscularly. Pointless if your diet is varied and you have no symptoms.

300 mg of ELEMENTAL magnesium a day, 60 to 90 minutes before bed. If your digestion is sensitive, split it: 150 mg at midday, 150 mg in the evening.

Give it two to three weeks. The sign of too high a dose is digestive — loose stools. If nothing changes after a month, stop: it was not your limiting factor.

What is inside

This is where everything is decided. Bisglycinate is magnesium chelated to two glycine molecules: it is better tolerated than oxide, carbonate or sulphate, which are the cheap, laxative forms. Glycine itself has its own sleep data, which makes this form consistent with the goal.

Read the dose as ELEMENTAL magnesium, never the weight of the salt: 1,000 mg of bisglycinate only provides around 140 mg of elemental magnesium. It is the most common labelling trap in the whole aisle. Be wary of “buffered” bisglycinates, which are blends with oxide.

Magnesium oxide, if you want anything other than a laxative effect: your body absorbs almost none of it. Contraindicated in kidney failure. Leave 2 hours around certain antibiotics.

Cautions

• Kidney failure
• Interacts with certain antibiotics (leave 2 h)