§.01The study, in one paragraph.
74 adults with type 2 diabetes (78% male, median age 72) with documented peripheral medial arterial calcification (MAC) and high baseline arterial stiffness (cfPWV ≥ 12.0 m/s) were randomized to either 350 mg/day of oral magnesium citrate or placebo for 6 months. Outcomes were measured by carotid-femoral pulse wave velocity (the gold standard for arterial stiffness) and nephelometry-based serum calciprotein crystallization (a marker of how readily calcium phosphate precipitates in serum, which links to MAC). It was double-blind, placebo-controlled, and registered with the Dutch trial registry and ISRCTN.
§.02What the numbers actually show.
Six months of 350 mg/day magnesium citrate did not reduce calciprotein crystallization. It did not reduce arterial stiffness. Both outcomes were statistically indistinguishable from placebo. The authors conclude that, "Daily supplementation of 350 mg appears to be ineffective in this population, possibly attributable to normomagnesemia and preserved renal function."
That last bit is the key piece. The study population was not magnesium-deficient at baseline — their renal function was preserved, their serum magnesium was normal. So adding more magnesium to a system that already has enough did not move arterial calcification.
§.03What it means for your magnesium routine.
This is a clean negative trial, and it lands in a specific lane: older diabetic patients with already-normal magnesium status do not get cardiovascular benefit from adding more magnesium. It does not say magnesium is useless — it says the population that already has enough magnesium will not see arterial calcification regress from extra supplementation.
Where the magnesium cardiovascular story still holds:
- People with low serum or red-cell magnesium (measured deficiency)
- Diabetics with proteinuria or renal magnesium wasting
- Adults on chronic PPI therapy (depletes magnesium)
- People with mild hypertension where magnesium has shown 2-3 mmHg systolic reduction
For everyone else taking magnesium daily: the rationale is not arterial calcification reversal. It is everything else magnesium does well — sleep, stress, muscle cramps, daily mineral adequacy.
§.04Limitations the authors flagged.
- Sample size (n=74): the trial was powered to detect a moderate effect. A very small effect could be hiding in the noise.
- Duration (6 months): arterial calcification is slow-moving. A 12 or 24-month trial might show different results.
- Form used (citrate at 350 mg/day): different forms or higher doses were not tested. Glycinate or chelated forms might absorb differently.
- Population was magnesium-replete at baseline: the study cannot answer what happens in a deficient population (where the prior probability of benefit is higher).
§.05Where it fits in the broader evidence.
This is the cleanest negative trial on magnesium + arterial stiffness to date. It fits with the broader pattern: most magnesium intervention trials show benefit primarily in populations with measurable deficiency. The Zhang 2016 meta-analysis on magnesium and blood pressure showed a modest 2-3 mmHg systolic effect overall, but the larger effects were in deficient subgroups.
The takeaway is consistent with our editorial position: measure first, supplement to correct. Magnesium is not a generic "more is better" intervention. It is a corrective tool for specific situations. Generic daily supplementation for "heart health" via this mechanism is not supported by AJCN-quality evidence.
§.99The bottom line.
Six months of 350 mg/day magnesium citrate did not move arterial stiffness or calciprotein crystallization in older diabetic adults who started with normal magnesium status. That is useful information. It does not contradict the reasons most people take magnesium — sleep, stress, cramps, daily mineral adequacy — but it does push back on the broader 'magnesium for cardiovascular calcification' narrative. If your goal is sleep or stress, glycinate at 200-400 mg/day stays a reasonable choice. If your goal is arterial health via supplementation, AJCN says: not from this protocol.
Magnesium glycinate, 90 capsules — at the apothecary.
§.RXThe study.
Author group, AJCN 2026 — The American Journal of Clinical Nutrition, 2026 May
Reviewed by Dr. Marthe Janssen, PharmD on May 21, 2026. We summarize peer-reviewed research without making medical claims.
Disclaimer: this article is educational only and not medical advice. Statements about supplements have not been evaluated by the FDA. Always discuss new supplements with your prescriber.