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General Health & Fitness
Nutrition and Supplements
Vitamin D Absorption is Decreased By Co-Administration of Calcium
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<blockquote data-quote="Nelson Vergel" data-source="post: 28144" data-attributes="member: 3"><p><strong>Effect of Vitamin D or Activated Vitamin D on Circulating 1,25-Dihydroxyvitamin D Concentrations: A Systematic Review and Metaanalysis of Randomized Controlled Trials</strong></p><p>Clinical Chemistry<strong> December 2015 </strong>vol. 61 no. 12 </p><p>[h=2]Abstract[/b]<strong>BACKGROUND:</strong> Evidence is accumulating that circulating 1,25-dihydroxyvitamin D [1,25(OH)[SUB]2[/SUB]D] concentrations are inversely related to overall mortality.</p><p></p><p><strong>METHODS:</strong> We searched PubMed, Embase and ISI Web of Science for randomized controlled trials with a control group receiving a placebo instead of vitamin D/activated vitamin D and performed a metaanalysis to evaluate the effect of oral vitamin D/activated vitamin D on circulating 1,25(OH)[SUB]2[/SUB]D concentrations using a random effects model.</p><p></p><p><strong>RESULTS:</strong> We included 52 vitamin D intervention groups (4796 individuals) and 14 intervention groups with activated vitamin D (668 individuals). Vitamin D supplements increased circulating 1,25(OH)[SUB]2[/SUB]D by 12.2 pmol/L (95% CI, 7.8–16.5 pmol/L) and 18.8 pmol/L (95% CI, 9.2–28.4 pmol/L) if only studies with a low risk of bias in study design and reporting were considered (n = 18). There was significant heterogeneity among studies (Cohran's Q <em>P</em> < 0.001, <em>I</em>[SUP]2[/SUP] = 91%). The incremental effect was larger in studies using vitamin D alone compared with coadministration of calcium supplements (18.6 pmol/L; 95% CI, 12.7–24.4 pmol/L vs 4.9 pmol/L; 95% CI, −0.4 to 10.2 pmol/L; <em>P</em> = 0.001), and if quantification was performed with RIA vs other methods (17.1 pmol/L; 95% CI, 11.1–23.1 pmol/L vs 6.9 pmol/L; 95% CI, 1.0–12.8 pmol/L; <em>P</em> = 0.02). Activated vitamin D increased the mean circulating 1,25(OH)[SUB]2[/SUB]D by 20.5 pmol/L (95% CI, 8.3–32.7 pmol/L; <em>P</em> = 0.04). Again, there was evidence for significant heterogeneity among studies (Cochran Q = 85.4; <em>P</em> < 0.001; <em>I</em>[SUP]2[/SUP] = 87%), but subgroup analysis did not identify parameters significantly influencing the increment in 1,25(OH)[SUB]2[/SUB]D concentrations.</p><p></p><p><strong>CONCLUSIONS:</strong> Both vitamin D and activated vitamin D significantly increase circulating 1,25(OH)[SUB]2[/SUB]D concentrations, but in vitamin D users this increase is suppressed by calcium coadministration.</p></blockquote><p></p>
[QUOTE="Nelson Vergel, post: 28144, member: 3"] [b]Effect of Vitamin D or Activated Vitamin D on Circulating 1,25-Dihydroxyvitamin D Concentrations: A Systematic Review and Metaanalysis of Randomized Controlled Trials[/b] Clinical Chemistry[B] December 2015 [/B][I][/I]vol. 61 no. 12 [h=2]Abstract[/b][B]BACKGROUND:[/B] Evidence is accumulating that circulating 1,25-dihydroxyvitamin D [1,25(OH)[SUB]2[/SUB]D] concentrations are inversely related to overall mortality. [B]METHODS:[/B] We searched PubMed, Embase and ISI Web of Science for randomized controlled trials with a control group receiving a placebo instead of vitamin D/activated vitamin D and performed a metaanalysis to evaluate the effect of oral vitamin D/activated vitamin D on circulating 1,25(OH)[SUB]2[/SUB]D concentrations using a random effects model. [B]RESULTS:[/B] We included 52 vitamin D intervention groups (4796 individuals) and 14 intervention groups with activated vitamin D (668 individuals). Vitamin D supplements increased circulating 1,25(OH)[SUB]2[/SUB]D by 12.2 pmol/L (95% CI, 7.8–16.5 pmol/L) and 18.8 pmol/L (95% CI, 9.2–28.4 pmol/L) if only studies with a low risk of bias in study design and reporting were considered (n = 18). There was significant heterogeneity among studies (Cohran's Q [I]P[/I] < 0.001, [I]I[/I][SUP]2[/SUP] = 91%). The incremental effect was larger in studies using vitamin D alone compared with coadministration of calcium supplements (18.6 pmol/L; 95% CI, 12.7–24.4 pmol/L vs 4.9 pmol/L; 95% CI, −0.4 to 10.2 pmol/L; [I]P[/I] = 0.001), and if quantification was performed with RIA vs other methods (17.1 pmol/L; 95% CI, 11.1–23.1 pmol/L vs 6.9 pmol/L; 95% CI, 1.0–12.8 pmol/L; [I]P[/I] = 0.02). Activated vitamin D increased the mean circulating 1,25(OH)[SUB]2[/SUB]D by 20.5 pmol/L (95% CI, 8.3–32.7 pmol/L; [I]P[/I] = 0.04). Again, there was evidence for significant heterogeneity among studies (Cochran Q = 85.4; [I]P[/I] < 0.001; [I]I[/I][SUP]2[/SUP] = 87%), but subgroup analysis did not identify parameters significantly influencing the increment in 1,25(OH)[SUB]2[/SUB]D concentrations. [B]CONCLUSIONS:[/B] Both vitamin D and activated vitamin D significantly increase circulating 1,25(OH)[SUB]2[/SUB]D concentrations, but in vitamin D users this increase is suppressed by calcium coadministration. [/QUOTE]
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General Health & Fitness
Nutrition and Supplements
Vitamin D Absorption is Decreased By Co-Administration of Calcium
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