Evidence Trace, complete trial record
In plain terms
In plain terms: Magnesium shows early signals in human research but the evidence is limited -- small trials, surrogate endpoints, or not yet independently replicated. It is an emerging area, not yet a proven one.
Magnesium
C
Limited: small, mixed or unreplicated trials
The endpoint this grade is based on: Surrogate biomarker endpoint, Use-specific. Sleep quality in primary insomnia: Grade C on three small self-report trials pooled at low to very low certainty. Cardiovascular events and all-cause mortality: Grade D, because no randomized trial has tested it; the evidence is observational dietary data. Deficiency is common and correcting a deficiency is not the same claim as supplementing when replete.
The evidence as the record states it
Mah et al. (BMC Complement Med Ther, 2021; PMID 33865376): systematic review/meta-analysis of oral magnesium for insomnia in older adults: low-quality evidence, sleep-onset benefit only. Abbasi et al. (2012; PMID 23853635): component RCT in elderly primary insomnia. Guasch-Ferré et al. (2014; PMID 24259558): dietary magnesium inversely associated with mortality (observational). Regraded to C: no single use reaches B on current human evidence.
PMID 33865376 PMID 23853635 PMID 24259558
Evidence by specific use
Sleep quality in primary insomnia (older adults)
Grade C
Mah et al. (BMC Complementary Medicine and Therapies, 2021; PMID 33865376) pooled three RCTs (151 older adults): sleep onset latency ~17 min shorter than placebo, but total sleep time was not significant and all trials were at moderate-to-high risk of bias with low-to-very-low GRADE certainty. The component trial (Abbasi 2012; PMID 23853635) cannot outrank the pooled analysis that contains it. Graded C.
PMID 33865376 PMID 23853635
Cardiovascular events and all-cause mortality
Grade D
PREDIMED (Guasch-Ferre et al., Journal of Nutrition, 2014; PMID 24259558) found the highest tertile of DIETARY magnesium intake associated with roughly 34% lower all-cause mortality (HR 0.66, 95% CI 0.45-0.95). It is an observational analysis: nobody was randomized to magnesium, and it measures dietary intake rather than supplementation. People who eat more magnesium eat more vegetables, nuts and whole grains. EBL excludes observational data from grades under the same rule applied to the Finnish sauna cohorts and to the resistance-training mortality association.
PMID 24259558 PMID 23520480
Why Grade C and not Grade B
Grade C reflects early or limited human evidence -- small trials, surrogate endpoints, or preliminary findings not yet independently replicated. The evidence points in a promising direction but does not yet meet the standard for Grade B. A single well-powered, independently replicated trial with a meaningful endpoint would move this to Grade B or higher.
What this grade covers and what it does not
Grade C on sleep (Mah 2021 meta-analysis; pooled evidence is low-to-very-low quality by GRADE). Grade C on cardiovascular and mortality (observational, excluded from carrying a grade). No use reaches B on current human evidence.
What would move this grade
A well-powered randomized trial with an objective, clinically meaningful primary endpoint and at least one independent replication would support Grade B or higher.
How to track whether this is working
RBC magnesium (serum is unreliable for tissue stores), sleep quality, muscle cramps, blood pressure