Clinical studies on the effects of magnesium on the functioning of the body
✔ Cardiovascular health
Numerous clinical studies have examined the effect of magnesium on blood pressure. A meta-analysis of more than 8,600 subjects showed a significant decrease in SBP (-1.25 mmHg) and DBP (-1.40 mmHg) with magnesium supplementation, especially at high doses (≥400 mg/day) and long-term treatments.pubmed.ncbi.nlm.nih.gov.
A systematic review of 49 trials suggests that the antihypertensive effect is mainly seen in hypertensive patients: only high doses (>600 mg/day) in monotherapy lowered SBP and DBP in untreated hypertensive patients, whereas at moderate doses (240–486 mg/day) the results were mixedmdpi.com.
In contrast, normotensive or controlled hypertensive subjects (under treatment) do not show a notable drop in pressure even at high doses. Overall, the effect is thereforemodest to positivein hypertensive patients (especially uncontrolled or at high doses), but oftenneutralin others.
The forms used are varied (oxide, citrate, chloride, lactate, aspartate, amino chelates, etc.); it seems that it is above all thedosethat matters, rather than the chemical form (even the poorly absorbable MgO gave results at high dosesmdpi.com).
No trials report significant effects on heart rate or other cardiovascular parameters, except for a general trend toward improvement in risk factors (insulin resistance, lipids) in some studies.mdpi.compubmed.ncbi.nlm.nih.govSupplements were well tolerated up to ~1 g/d without major adverse effects.
✔Nerve and muscle function (cramps, fatigue, stress)
Magnesium is often touted for relieving muscle cramps, but the clinical evidence is negative.
A Cochrane review of 11 trials (735 patients) concluded that there is no significant difference between magnesium and placebo on the frequency or intensity of idiopathic cramps (particularly nocturnal cramps in the elderly).pubmed.ncbi.nlm.nih.gov.
Regarding muscle function, a few small studies suggest an effectbeneficialon recovery and performance in athletes: a recent review reported that Mg supplements reduced muscle soreness and improved post-exercise recoverytranslational-medicine.biomedcentral.com.
Isolated clinical trials also show strength gains in deficient subjects (e.g. quadriceps strength or walking time in the elderly), although this is not very well documented.
Regarding fatigue, few rigorous trials exist. An early randomized trial (intramuscular route) in chronic fatigue syndrome reported subjective improvement in energy and mood with magnesiumpubmed.ncbi.nlm.nih.gov, but this data remains isolated.
In a situation ofstress, evidence suggests a positive effect: a large comparative trial showed that the combination of magnesium and vitamin B₆ reduced the perceived stress score more strongly than magnesium alone (for subjects with severe stress)pmc.ncbi.nlm.nih.gov.
In summary, for this category the results are mixed: effectneutralon cramps (no net benefit)pubmed.ncbi.nlm.nih.gov, effectmoderately positiveon post-exercise muscle recoverytranslational-medicine.biomedcentral.com, and tendency towards reduction of stress/anxiety in vulnerable people (notably with B6)pmc.ncbi.nlm.nih.govpmc.ncbi.nlm.nih.gov.
Studies have used various forms (MgO, lactate, citrate, etc.); no single form stands out clearly.
✔ Mood, sleep, anxiety, depression
Several trials suggest that magnesium supplementation improves mood and sleep.
In depression, a recent meta-analysis (7 trials, 325 depressed patients) found a significant decrease in depressive scores under magnesium (standardized mean difference ≈−0.92)frontiersin.org.
For anxiety, a systematic review (18 trials) indicates effectsbeneficial variables: in anxious subjects (or with premenstrual syndrome), almost half of the studies report an improvement in anxiety with magnesium, while no difference was noted postpartumpmc.ncbi.nlm.nih.gov.
Regarding thesleep,Clinical trials generally show an improvement in quality. For example, in 46 seniors with insomnia, 500 mg/day of MgO for 8 weeks increased sleep time and sleep efficiency and significantly decreased sleep latency.pmc.ncbi.nlm.nih.gov.
A meta-analysis (3 trials, 151 subjects ≥55 years) confirms a reduction of approximately 17 minutes in sleep latency under magnesium compared to placebobmccomplementmedtherapies.biomedcentral.com.
A small pilot crossover trial even showed subjective improvement in sleep quality and mood (with an organic supplement “Upgraded Magnesium” at 1 g/d)esmed.org.
In summary, the data generally indicate an effectpositivemagnesium on sleep and mood (better sleep, improved mood)pmc.ncbi.nlm.nih.govfrontiersin.org.
The administered forms were often magnesium oxide or citrate (e.g. MgO in the senior trialpmc.ncbi.nlm.nih.gov), but, as with blood pressure, the dose matters more than the form.
As it stands, magnesium appears promising as an adjuvant for sleep and mood disorders, although the quality of trials varies and larger studies remain desirable.
✔Metabolism (glycemic regulation, diabetes, energy)
Magnesium plays a key role in carbohydrate metabolism.
Clinical trials in type 2 diabetics show modest improvements in glycemic control with supplementation.
A dose-response meta-analysis estimated that 500 mg/d of magnesium resulted in a mean reduction in HbA1c of approximately −0.73% (p<0.01) and a slight decrease in fasting blood glucose.pubmed.ncbi.nlm.nih.gov.
Another review (18 trials) confirms a downward trend in HbA1c and especially in insulin resistance (HOMA-IR) when supplementation lasts ≥4 monthspubmed.ncbi.nlm.nih.gov.
More concretely, a pool of 24 RCTs (1325 diabetic patients) found significant reductions in fasting blood glucose (WMD ≈−0.20 mmol/L, or ~−3.6 mg/dL) and HbA1c (−0.22%) under magnesiumfrontiersin.org, as well as a marked drop in blood pressure (SBP −7.7 mmHg) in these diabetic patientsfrontiersin.org.
These effects are more pronounced in subjects with magnesium deficiency or poor initial diabetes control. Few studies specifically assess energy or general metabolic fatigue; however, magnesium is known to be an essential cofactor of ATP, suggesting an indirect role in energy levels.
Overall, the effect on carbohydrate metabolism ispositive: magnesium supplements (≥200–300 mg/d) slightly improve glycemic control and insulin sensitivitypubmed.ncbi.nlm.nih.govfrontiersin.orgThe forms used are varied (MgO, citrate, chloride, etc.); no major difference between them has been demonstrated.
In practice, doses higher than the RDA (300–400 mg/day) and treatments over several months seem necessary to observe a clinical benefitpubmed.ncbi.nlm.nih.govpubmed.ncbi.nlm.nih.gov.
✔Bone and immune health
Magnesium is essential for bone health. Available studies are few, but trends arefavorable.
In growing adolescent girls with low initial intake, 300 mg/d of MgO administered for 1 year significantly increased hip bone mineral mass (BMM) compared with placebopubmed.ncbi.nlm.nih.gov.
Observational data confirm a positive association: a meta-analysis on cohorts showed that higher dietary magnesium intake is associated with higher bone density at the femoral neck (β≈+0.03 per unit of intake, p<0.05)pubmed.ncbi.nlm.nih.gov.
There is no randomized trial in elderly osteoporotic subjects yet, but these elements suggest a beneficial effect of magnesium on bone remodeling and the prevention of osteoporosis.
As for the immune system, magnesium has effectsimmunomodulators and anti-inflammatoriesExperimental studies show that magnesium reduces the production of pro-inflammatory cytokines such as IL-6 and TNF-α (by >60% in monocytes exposed to MgSO₄ in vitro)pmc.ncbi.nlm.nih.gov.
Magnesium deficiencies are associated with increased chronic inflammation. Thus, magnesium supplementation lowers inflammatory markers in some settings and may improve the immune response (although few clinical trials have directly studied infections).
In summary, the effects on immunity arebeneficial/modulators(reduction of inflammation)pmc.ncbi.nlm.nih.gov, and on the bones ratherpositive(increased mineralization)pubmed.ncbi.nlm.nih.govpubmed.ncbi.nlm.nih.gov.
✔Final synthesis
Overall, the body of clinical studies suggests that magnesium supplementation isoverall beneficialfor several major physiological functions.
It moderately lowers blood pressure in hypertensive patients (especially at high doses or in combination with other hygiene and dietary measures)pubmed.ncbi.nlm.nih.govmdpi.com, slightly improves glycemic control in diabeticspubmed.ncbi.nlm.nih.govfrontiersin.org, and promotes sleep and moodpmc.ncbi.nlm.nih.govfrontiersin.org.
Its effects on the nervous and muscular systems are mixed: it does not appear to prevent idiopathic crampspubmed.ncbi.nlm.nih.gov, but may relieve exercise soreness and reduce stress/anxiety in some peopletranslational-medicine.biomedcentral.compmc.ncbi.nlm.nih.gov. Finally, it contributes to bone health (improved mineralization)pubmed.ncbi.nlm.nih.govpubmed.ncbi.nlm.nih.govand has anti-inflammatory/immunomodulatory propertiespmc.ncbi.nlm.nih.gov.
The observed contradictions (e.g., negative blood pressure studies or variability of effects on anxiety) often relate to the dose, the initial state of the patients (deficient or not), and the duration of treatment.
The most commonly studied forms are magnesium oxide and citrate (as well as other salts such as lactate or aspartate), but effectiveness appears to be dictated primarily by the amount of elemental magnesium ingestedmdpi.commdpi.com.
In practice, dosages of the order of 300–500 mg/day for several months are generally necessary to obtain a notable clinical effect, without serious adverse effects.
Thus, magnesium is a safe supplement whose benefits, although quite modest individually, converge towards a general improvement in cardiovascular, metabolic, bone and neurological health.pubmed.ncbi.nlm.nih.govfrontiersin.orgpubmed.ncbi.nlm.nih.gov.
Sources:Synthesis of multiple clinical trials and meta-analyses (see citations) on magnesium supplementation in humanspubmed.ncbi.nlm.nih.govmdpi.comfrontiersin.orgpubmed.ncbi.nlm.nih.govpubmed.ncbi.nlm.nih.gov.
These studies include systematic reviews and meta-analyses on blood pressure, muscle function, sleep and glycemic regulation, as well as randomized trials evaluating different dosages and forms of magnesium.
Each statement above is supported by published data (cited in the text).