Abstract P161: Randomized Trial Of Magnesium Glycinate Supplementation And Blood Pressure In Middle-aged Adults

Introduction: Magnesium (Mg) intake is inversely associated with BP and hypertension risk in observational studies. However, short-term randomized trials on seated BP have been inconsistent, with few studies measuring 24-h ambulatory BP (ABP). In addition, Mg glycinate, a more easily absorbed form of supplemental Mg, has been largely untested in randomized trials and may serve as a first-line approach for BP reduction among those with elevated, untreated, BP. Methods: We conducted a randomized, double-blind, placebo-controlled trial (NCT03688503) testing 480 mg/d of elemental Mg glycinate versus placebo for 12 weeks among 59 otherwise healthy participants aged 30-74 y with elevated seated BP (systolic BP (SBP) 120-149 mmHg and/or diastolic BP (DBP) 80-94 mmHg) and no history of anti-hypertensive medication use. At baseline, 6 weeks, and 12 weeks, we measured seated BP, monitored 24-h ABP, and collected blood samples. Our primary aim tested Mg glycinate on 12-week changes in seated BP and 24-h ABP, and subgroup analyses considered if sex, age, or baseline BP modified the effect of Mg on BP. Results: Baseline characteristics were equally distributed at randomization (mean age, 57.2 y; 58% men) with mean seated BP of 133.4/82.6 mmHg. Compliance was high (Mg, 87%; placebo, 96%). After 12 weeks, there was no significant effect of Mg glycinate versus placebo on seated SBP (-4.5 vs -1.6 mmHg from baseline; p=0.38) and DBP (-1.9 vs -0.9 mmHg from baseline; p=0.64), nor was there any significant effect on overall, daytime, or nighttime 24-h ambulatory SBP and DBP (all p>0.05). In subgroup analyses, the effect of Mg glycinate on seated SBP was suggestively, but non-significantly, stronger among those with baseline seated SBP ≥130 mmHg (-9.3 vs -2.7 mmHg; p=0.12; p, interaction=0.24) and among women (-9.7 vs -3.1 mmHg; p=0.26; p, interaction=0.29). Age, seated DBP, and mean 24-h ambulatory SBP and DBP did not modify the effects of Mg supplementation. Conclusions: A Mg glycinate supplement did not significantly reduce seated or 24-h BP in adults with elevated, untreated BP. Forthcoming analyses will expand on the role of serum and dietary Mg levels. Larger trials are warranted to elucidate possible effects of Mg glycinate on seated SBP among those with elevated BP and among women.