Magnesium

Magnesium is involved in over 300 enzyme systems and is one of the most heavily marketed supplements in the UK, often with claims that outrun the underlying evidence. The 20 entries in this section cover what the published research shows about forms compared (glycinate, citrate, malate, threonate, oxide, taurate), dose, timing, sleep, blood pressure, migraine prophylaxis, muscle cramps, and where the evidence is strong versus where it is weaker than supplement marketing suggests.

Magnesium sits in an unusual position in supplement evidence: there is good clinical research for some applications, modest research for others, and notably weaker evidence for some of the strongest claims that drive consumer marketing. The published literature is strongest for migraine prophylaxis (Level B evidence per the American Academy of Neurology and American Headache Society), blood pressure reduction in hypertensive patients, and constipation. It is moderate to mixed for sleep quality and stress. It is weaker than commonly claimed for nocturnal leg cramps in adults, where the most authoritative review (Cochrane 2020) concluded magnesium is unlikely to provide a meaningful benefit.

The forms question accounts for much of the consumer confusion. Magnesium glycinate, citrate, malate, threonate, oxide, and taurate differ in absorption, gastrointestinal tolerability, and the applications they are best suited to. Magnesium L-threonate is the only form with published evidence for raising brain magnesium concentration via a glucose-transporter-mediated mechanism; the others largely act systemically. Magnesium oxide is poorly absorbed for systemic effect but still useful as an osmotic laxative. Magnesium glycinate is the form most often recommended for sleep and stress because of its tolerability and the calming properties attributed to glycine, not because it has been proven superior in head-to-head trials against other forms.

The questions covered include:

• Forms compared: glycinate vs citrate vs malate vs threonate vs oxide vs taurate, and the evidence behind common form-to-application pairings
• Dose tiers: dietary adequacy (RDA 310-420 mg/day per NIH ODS), modest supplementation, and therapeutic dosing for specific applications
• Timing: morning vs night, and why the answer depends on what the supplement is intended to do
• Sleep: what the trials actually show, and where the evidence has limits
• Migraine prophylaxis: the dose with the strongest published support, and the typical 2-3 month timeline to assess response
• Blood pressure: the consistent but modest effect across meta-analyses, and the populations who benefit most
• Muscle cramps: where the evidence is weaker than supplement marketing suggests
• Interactions: with blood pressure medications, calcium, and other supplements
• Compound patterns: how stress, caffeine, and poor sleep create a self-reinforcing magnesium depletion cycle

The marketing claims around magnesium are frequently overstated. Where the evidence is strong, the entries say so. Where it is not, they say that too.