Magnesium is one of the most talked-about supplements in health right now — and one of the most misunderstood. It's involved in more than 300 enzymatic reactions in the body, from energy production to muscle and nerve function. But popularity has outrun evidence in places, so this guide separates what the research supports from what it doesn't.
Why magnesium matters
Magnesium is an essential mineral your body can't make — you get it from food or supplements. It contributes to normal muscle function, normal protein synthesis, and the reduction of tiredness and fatigue, among other roles recognised by European food-safety authorities.
The catch is that a large share of people don't get enough from diet alone. A global review estimated roughly 31% of the world's population — around 2.4 billion people — fall below recommended magnesium intakes, and US survey data (NHANES) finds close to 79% of adults don't meet their recommended allowance.12 Diets high in processed food and low in leafy greens, nuts and whole grains are a large part of why.
How much do you need?
The recommended dietary allowance for adults is roughly 420 mg/day for men and 320 mg/day for women, with food the ideal first source.3 Magnesium-rich foods include leafy greens, pumpkin seeds, almonds, legumes and dark chocolate.
Which form is best? Glycinate vs citrate vs oxide
This is where the form genuinely matters, because they don't absorb equally.
- Magnesium oxide is cheap and common, but poorly absorbed. In a randomised cross-over study, magnesium citrate produced higher 24-hour urinary magnesium excretion than oxide — a marker of better bioavailability.4
- Magnesium citrate absorbs well, though it can have a mild laxative effect at higher doses.
- Magnesium glycinate (bisglycinate) is well absorbed and gentlest on the stomach, with fewer of the gastrointestinal side effects that put people off other forms.
For everyday supplementation where tolerability matters, glycinate is the form many people get on with best — which is why it's the form Proco Magnesium Glycinate uses.
What the research shows: sleep
Magnesium is heavily marketed for sleep, so it's worth being precise. A meta-analysis of three randomised controlled trials in 151 older adults found magnesium reduced the time taken to fall asleep by around 17 minutes versus placebo — a real but modest effect, and the authors judged the overall evidence limited.5 More recent trials, including one on magnesium bisglycinate in poor sleepers, add support, but the honest summary is: magnesium may modestly help some people fall asleep faster, particularly if they're short to begin with.6
What the research shows: muscle, recovery and cramps
Here the evidence splits in an important way:
- For everyday cramps, the evidence is weak. A 2020 Cochrane review of 11 trials (735 participants) concluded magnesium is unlikely to provide clinically meaningful relief for idiopathic skeletal muscle cramps.7
- For exercise recovery, results are more encouraging but the evidence base is small — a 2022 trial found 350 mg/day for 10 days reduced delayed-onset muscle soreness.7
The takeaway: magnesium plays a genuine role in normal muscle function, but supplementing it isn't a reliable cramp cure.
Who should be cautious
Magnesium is well tolerated for most healthy adults, with gastrointestinal upset (especially from oxide) the most common side effect. People with kidney disease, or anyone on medication, should speak to a doctor before supplementing, as magnesium clearance depends on kidney function.
This article is for general information and is not medical advice. Supplements are not intended to diagnose, treat, cure or prevent any disease.
The bottom line
Magnesium is a foundational mineral that a large proportion of people under-consume. A well-absorbed, well-tolerated form like glycinate is a sensible way to close that gap. The evidence for modest sleep benefit is real if limited; the evidence for cramp relief is weak. As with everything Proco publishes: useful where the science supports it, honest where it doesn't.
References
- Global Dietary Magnesium Deficiency: Prevalence, Causes, Consequences. Int. J. Vitamin & Nutrition Research. imrpress.com
- Magnesium — The Nutrition Source, Harvard T.H. Chan School of Public Health. nutritionsource.hsph.harvard.edu
- Dietary Reference Intakes (Calcium, Phosphorus, Magnesium, Vitamin D, Fluoride). NCBI Bookshelf. ncbi.nlm.nih.gov
- Higher bioavailability of magnesium citrate vs oxide. BMC Nutrition, 2017. link.springer.com
- Oral magnesium supplementation for insomnia in older adults: systematic review & meta-analysis. PMC. ncbi.nlm.nih.gov
- Magnesium Bisglycinate in Adults Reporting Poor Sleep: RCT. Nature and Science of Sleep. tandfonline.com
- Magnesium for skeletal muscle cramps. Cochrane Systematic Review, 2020. cochranelibrary.com
Proco Magnesium Glycinate is a gentle, well-absorbed form, dosed to the range used in research and third-party tested every batch. Shop Magnesium →