Does magnesium help with poor sleep and muscle cramps, and which form should you take?
Magnesium may modestly speed up falling asleep in older adults with insomnia, but the evidence is small-scale and of limited quality. The available studies say nothing concrete about muscle cramps or the best form of magnesium.
Magnesium may modestly speed up falling asleep in older adults with insomnia. A meta-analysis of three small studies (151 participants combined) showed that magnesium reduced the time to fall asleep by an average of 17 minutes compared with a placebo. Total sleep duration increased slightly, but that difference was not statistically convincing. The researchers themselves described the evidence as low to very low. Treat this as an early positive signal, not a firm conclusion.1
A separate study in 290 people with diabetes found that magnesium significantly reduced perceived insomnia and had a favourable effect on the sleep hormones melatonin and cortisol. However, the study was single-blind: the research team knew who received what. And the results apply specifically to people with diabetes, not automatically to everyone.2
Large population studies show an association between good magnesium status and better sleep, but do not prove cause and effect. For example, people with signs of magnesium deficiency reported sleep apnoea almost three times as often in a study of more than 20,000 people. Ordinary insomnia or insufficient sleep was not associated with magnesium status in that research.3,4,5,6
Nothing evidence-based can be said about muscle cramps. There are simply no controlled studies on magnesium for muscle cramps available, so this question remains unanswered.
Which form is best to choose -- citrate, glycinate or oxide -- is not addressed by the studies. The RCTs do not specify a preference. What is known is that doses of less than one gram taken three times daily caused no serious side effects in older participants. Higher doses can cause diarrhoea. Animal research suggests that magnesium combined with apigenin (a compound found in chamomile) promotes sleep more strongly than either substance alone, but whether this also applies to humans is unknown.1,7
Sleep: one meta-analysis (3 small studies, 151 participants combined), one single-blind study in humans (290 participants), multiple observational studies (more than 25,000 participants combined), one animal experiment and one narrative review. The meta-analysis itself rates the evidence as low to very low. Muscle cramps: no relevant studies available, cannot be answered.