Magnesium
Preliminary· human dataFixing a shortfall can help sleep and cramps; a boost when you're replete is weak.
What it is
Magnesium is an essential mineral involved in hundreds of processes, including muscle and nerve function and sleep. Mild shortfalls are fairly common, which is where supplementing can have a role.
What the evidence shows
Fixing a deficiency (sleep, cramps). Preliminary· human data If you're genuinely low, correcting magnesium may help sleep quality and muscle cramps. The evidence is stronger for people who were short to begin with than for everyone.
A benefit when you're already replete. Preliminary· human data Topping up someone who already gets enough has not been shown to reliably improve sleep, performance or recovery. Much of the "magnesium for sleep" marketing overstates this.
Strength and testosterone claims. Marketing claim Not supported beyond, again, correcting a deficiency.
Who it suits
People with a likely shortfall (low intake of greens, nuts, seeds, legumes and wholegrains) or troubled sleep worth investigating. Food first; supplement to fill a real gap.
Practical notes
Choose a well-absorbed form — citrate, glycinate or malate — over magnesium oxide, which absorbs poorly and is the most likely to cause loose stools (see the safety box). It pairs conventionally with zinc in ZMA.
Sources
Frequently asked questions
- Does magnesium improve sleep?
- If you're low in magnesium, correcting it may help sleep and muscle cramps. The evidence for a sleep benefit in people who already get enough is weaker and often overstated.
- Which form is best?
- Well-absorbed forms like magnesium citrate, glycinate or malate are preferable to magnesium oxide, which is poorly absorbed and most likely to cause loose stools.
- Will it help my performance?
- Mainly by fixing a deficiency. Topping up someone who is already replete has not been shown to reliably boost strength or endurance.
- Can I just get it from food?
- Often yes — leafy greens, nuts, seeds, legumes and wholegrains are good sources. Food first, supplement to fill a genuine gap.
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Written and reviewed by Mathew Beale — MSc Biotechnology, University of Reading.
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