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Zhang X.,Indiana University | Li Y.,Beijing Pinggu Hospital | Del Gobbo L.C.,Stanford University | Rosanoff A.,Center for Magnesium Education and Research | And 3 more authors.

The antihypertensive effect of magnesium (Mg) supplementation remains controversial. We aimed to quantify the effect of oral Mg supplementation on blood pressure (BP) by synthesizing available evidence from randomized, double-blind, placebo-controlled trials. We searched trials of Mg supplementation on normotensive and hypertensive adults published up to February 1, 2016 from MEDLINE and EMBASE databases; 34 trials involving 2028 participants were eligible for this meta-analysis. Weighted mean differences of changes in BP and serum Mg were calculated by random-effects meta-analysis. Mg supplementation at a median dose of 368 mg/d for a median duration of 3 months significantly reduced systolic BP by 2.00 mm Hg (95% confidence interval, 0.43-3.58) and diastolic BP by 1.78 mm Hg (95% confidence interval, 0.73-2.82); these reductions were accompanied by 0.05 mmol/L (95% confidence interval, 0.03, 0.07) elevation of serum Mg compared with placebo. Using a restricted cubic spline curve, we found that Mg supplementation with a dose of 300 mg/d or duration of 1 month is sufficient to elevate serum Mg and reduce BP; and serum Mg was negatively associated with diastolic BP but not systolic BP (all P<0.05). In the stratified analyses, a greater reduction in BP tended to be found in trials with high quality or low dropout rate (all P values for interaction <0.05). However, residual heterogeneity may still exist after considering these possible factors. Our findings indicate a causal effect of Mg supplementation on lowering BPs in adults. Further well-designed trials are warranted to validate the BP-lowering efficacy of optimal Mg treatment. © 2016 American Heart Association, Inc. Source

Rosanoff A.,Center for Magnesium Education and Research
Magnesium Research

USDA food surveys from 1977 through 2007-8 show a rising food Ca:Mg ratio for all USA adult age-gender groups. Food Ca:Mg intake ratios rose from 2.3-2.9 in 1977 to 2.9-3.5 in 2007-8. The % rise in mean Mg intakes compared closely with % rise in mean energy intakes while % rise in mean Ca intakes were substantially higher in all groups, suggesting the rising Ca:Mg comes from higher Ca intakes via food selections, rising food Ca contents or both. Original intake data from these surveys need to be accessed to calculate each individual's Ca:Mg for statistical assessment of this ratio rise. Ca:Mg rose from largely below 3.0 in 1994-5 to generally above or approaching 3.0 after 2000, coinciding with a sharp 2% rise in type 2 diabetes incidence and prevalence in the USA population and a 1994-2005 rise in colorectal cancer incidence among young white, non-Hispanic adult men and women in the USA. The intracellular Ca activation response to low Mg is discussed as a possible mechanism linking metabolic and inflammatory syndromes with low dietary Mg and rising dietary Ca:Mg ratio. Adequacy of both Ca and Mg as well as the Ca:Mg ratio are important in assessing study outcomes. Health consequences should be considered for the USA's 64-67% adults not meeting their Mg requirement from foods, many also consuming below their Ca requirements, and their increasing Ca:Mg ratio from foods. Source

Rosanoff A.,Center for Magnesium Education and Research
Magnesium Research

Nutritional magnesium intake from foods in the United States of America (USA) is widely below individual daily requirements [1]. Magnesium in USA has been called the "orphan nutrient" by Robert Heaney due to its lack of attention by the USA nutrition research community during the 20th century - a time of prolific and varied nutrition research progress. USA's Dept. of Agriculture (USDA) first published food values for Ca, P and Fe in 1945; Mg content did not appear regularly in these large food tables until after 1977. Beyond its large study of USA population's serum Mg, 1971-74, NHANES does not measure or make available to researchers any blood or urinary Mg values among its vast array of measurements on a representative sampling of USA humans. Standard medical laboratory assessments do not routinely include serum, red blood cell (RBC) or urinary magnesium. Source

Sun X.,Shanghai JiaoTong University | Sun X.,Nanjing Agricultural University | Rosanoff A.,Center for Magnesium Education and Research | Liu C.,Shanghai JiaoTong University | And 2 more authors.
Crop and Pasture Science

Potassium (K), calcium (Ca) and magnesium (Mg) are three macro-elements essential for plants and animals. The ratios K:Mg or K:(Ca+Mg) are viewed as indices of physiological status in livestock animals. In plants, Ca, Mg and K concentrations can vary with climate in terrestrial ecosystems. Here, with a widespread tree species (Chinese cork oak, Quercus variabilis Blume) and an acorn predator (the weevil Curculio davidi Fairmaire), we investigate how K, Ca and Mg vary in soils, plant tissues (leaves and acorns) and a consumer (herbivore insects) with climatic variables induced by latitude (LAT) across the temperate-subtropical areas of eastern China. Concentrations of K, Ca and Mg in soils, leaves, acorns and weevil larvae showed different degrees of variation across the study area, but only Mg concentration increased significantly with rising LAT across all four trophic levels, albeit with varying slopes. With rising mean annual temperature (MAT) and precipitation (MAP), soil Ca significantly decreased, as did leaf and acorn K concentrations, whereas all four tropic levels showed significant decreases in Mg content with both MAT and MAP (P<0.05-0.001). Leaf and acorn Ca:Mg showed significant relationships with LAT and MAT (P<0.05-0.01). The K:(Mg+Ca) ratio in soils and weevil larvae increased linearly with MAP (P<0.05), and acorn K:(Mg+Ca) ratio varied in a concave manner (P<0.001). Our results suggest that variations of Ca, Mg and K in plant tissues and weevil larva across a study area of 20° LAT range were largely driven by climatic factors, and that Mg concentration changes in all four trophic levels with climate (and LAT) largely drive changes in soil, plant and consumer ratios between Mg, Ca and/or K. These results provide information on possible effects of climate change on nutrient dynamics in terrestrial ecosystems. © CSIRO 2015. Source

Zhang X.,Indiana University | Del Gobbo L.C.,Stanford University | Hruby A.,Harvard University | Rosanoff A.,Center for Magnesium Education and Research | And 5 more authors.
Journal of Nutrition

Background: Accurate determination of Mgstatus is important for improving nutritional assessment and clinical risk stratification. Objective: We aimed to quantify the overall responsiveness of Mg biomarkers to oral Mg supplementation among adults without severe diseases and their dose- and time responses using available data from randomized controlled trials (RCTs). Methods: We identified 48 Mg supplementation trials (n = 2131) through searches of MEDLINE and the Cochrane Library up to November 2014. Random-effects meta-analysis was used to estimate weighted mean differences of biomarker concentrations between intervention and placebo groups. Restricted cubic splines were used to determine the dose- and time responses of Mg biomarkers to supplementation. Results: Among the 35 biomarkers assessed, serum, plasma, and urineMg were most commonlymeasured. ElementalMg supplementation doses ranged from 197 to 994 mg/d. Trials ranged from 3 wk to 5 y (median: 12 wk).Mg supplementation significantly elevated circulating Mg by 0.04 mmol/L (95% CI: 0.02, 0.06) and 24-h urine Mg excretion by 1.52 mmol/24 h (95% CI: 1.20, 1.83) as compared to placebo. Circulating Mg concentrations and 24-h urine Mg excretion responded to Mg supplementation in a dose- and time-dependent manner, gradually reaching a steady state at doses of 300 mg/d and 400 mg/d, or after ~20 wk and 40 wk, respectively (all P-nonlinearity ≤ 0.001). The higher the circulating Mg concentration at baseline, the lower the responsiveness of circulating Mg to supplementation, and the higher the urinary excretion (all Plinearity < 0.05). In addition, RBC Mg, fecal Mg, and urine calcium were significantly more elevated byMg supplementation than by placebo (all P-values < 0.05), but there is insufficient evidence to determine their responses to increasingMg doses. Conclusions: This meta-analysis of RCTs demonstrated significant dose- and time responses of circulating Mg concentration and 24-h urine Mg excretion to oral Mg supplementation. Source

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