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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="Dave Barry" data-source="post: 28159" data-attributes="member: 117"><p><strong>"There are very few trials examining the effect of dietary calcium intake on serum 25(OH)D response to vitamin D supplementation, and the results are mixed</strong> (<a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4516990/table/nutrients-07-05111-t001/" target="_blank">Table 1</a>). Most dose-response and efficacy trials administer calcium supplements alongside vitamin D supplements to ensure daily calcium intake of 1200–1500 mg and to minimize the confounding effect of dietary calcium intake on response to supplementation. Goussous <em>et al.</em> (2005) assigned elderly men and women with baseline calcium intake of ≤600 mg/d (diet plus supplements) to receive both 800 IU vitamin D3 and 1000 mg calcium or 800 IU vitamin D3 and placebo per day for three months [<a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4516990/#B42-nutrients-07-05111" target="_blank">42</a>]. Circulating 25(OH)D concentrations increased significantly in both groups, and the mean increase was comparable in both groups (+16.2 ± 14.8 nmol/L in the calcium group and +16.6 ± 17.4 nmol/L in control group, <em>p</em> > 0.05).</p><p>In another study, however, Bell, Shaw and Turner (1987) showed that the addition of 2000 mg calcium per day to daily 100,000 IU vitamin D for four days resulted in a significantly lower increase in mean 25(OH)D concentration [<a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4516990/#B51-nutrients-07-05111" target="_blank">51</a>]. The increment in calcium group was less than half of that observed in the control group (63% <em>vs.</em> 133%, respectively; <em>p</em> < 0.02). It should be noted that the dose of vitamin D was not anywhere near a physiologically normal dose.</p><p>Thomas, Need and Nordin (2010), in contrast, showed that supplementation with 1000 mg calcium for one week with additional 1000 IU vitamin D daily for 7 weeks raised the mean 25(OH)D concentration more effectively than vitamin D or calcium alone [<a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4516990/#B57-nutrients-07-05111" target="_blank">57</a>]. Similar results were reported in dose-response trials conducted to determine the effect of different dosages of vitamin D supplement on 25(OH)D concentrations [<a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4516990/#B53-nutrients-07-05111" target="_blank">53</a>]. Using a multivariate model, Gallagher <em>et al.</em> (2013) [<a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4516990/#B53-nutrients-07-05111" target="_blank">53</a>] showed that total calcium intake (diet plus supplement) was a significant covariate. Every 1000 mg increase in calcium intake was associated with a 9.5 nmol/L increase in 25(OH)D concentrations in vitamin D deficient postmenopausal African American women supplemented with vitamin D.</p><p>Increased intake of calcium is associated with a slight increase in serum calcium levels and with lower levels of serum PTH [<a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4516990/#B57-nutrients-07-05111" target="_blank">57</a>]. The decrease in PTH levels results in a decrease in production of 1,25(OH)2D by the kidneys, and an increase in the levels of 25(OH)D in the circulation [<a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4516990/#B18-nutrients-07-05111" target="_blank">18</a>].The increase in 25(OH)D levels could be explained by several mechanistic pathways: (1) inhibition of 25-hydroxylase by 1,25(OH)2D as a result of negative feedback loop (2) decrease in the use of 25(OH)D as a substrate; and (3) delayed metabolic clearance of 25(OH)D in the liver [<a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4516990/#B57-nutrients-07-05111" target="_blank">57</a>]."</p></blockquote><p></p>
[QUOTE="Dave Barry, post: 28159, member: 117"] [B]"There are very few trials examining the effect of dietary calcium intake on serum 25(OH)D response to vitamin D supplementation, and the results are mixed[/B] ([URL="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4516990/table/nutrients-07-05111-t001/"]Table 1[/URL]). Most dose-response and efficacy trials administer calcium supplements alongside vitamin D supplements to ensure daily calcium intake of 1200–1500 mg and to minimize the confounding effect of dietary calcium intake on response to supplementation. Goussous [I]et al.[/I] (2005) assigned elderly men and women with baseline calcium intake of ≤600 mg/d (diet plus supplements) to receive both 800 IU vitamin D3 and 1000 mg calcium or 800 IU vitamin D3 and placebo per day for three months [[URL="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4516990/#B42-nutrients-07-05111"]42[/URL]]. Circulating 25(OH)D concentrations increased significantly in both groups, and the mean increase was comparable in both groups (+16.2 ± 14.8 nmol/L in the calcium group and +16.6 ± 17.4 nmol/L in control group, [I]p[/I] > 0.05). In another study, however, Bell, Shaw and Turner (1987) showed that the addition of 2000 mg calcium per day to daily 100,000 IU vitamin D for four days resulted in a significantly lower increase in mean 25(OH)D concentration [[URL="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4516990/#B51-nutrients-07-05111"]51[/URL]]. The increment in calcium group was less than half of that observed in the control group (63% [I]vs.[/I] 133%, respectively; [I]p[/I] < 0.02). It should be noted that the dose of vitamin D was not anywhere near a physiologically normal dose. Thomas, Need and Nordin (2010), in contrast, showed that supplementation with 1000 mg calcium for one week with additional 1000 IU vitamin D daily for 7 weeks raised the mean 25(OH)D concentration more effectively than vitamin D or calcium alone [[URL="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4516990/#B57-nutrients-07-05111"]57[/URL]]. Similar results were reported in dose-response trials conducted to determine the effect of different dosages of vitamin D supplement on 25(OH)D concentrations [[URL="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4516990/#B53-nutrients-07-05111"]53[/URL]]. Using a multivariate model, Gallagher [I]et al.[/I] (2013) [[URL="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4516990/#B53-nutrients-07-05111"]53[/URL]] showed that total calcium intake (diet plus supplement) was a significant covariate. Every 1000 mg increase in calcium intake was associated with a 9.5 nmol/L increase in 25(OH)D concentrations in vitamin D deficient postmenopausal African American women supplemented with vitamin D. Increased intake of calcium is associated with a slight increase in serum calcium levels and with lower levels of serum PTH [[URL="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4516990/#B57-nutrients-07-05111"]57[/URL]]. The decrease in PTH levels results in a decrease in production of 1,25(OH)2D by the kidneys, and an increase in the levels of 25(OH)D in the circulation [[URL="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4516990/#B18-nutrients-07-05111"]18[/URL]].The increase in 25(OH)D levels could be explained by several mechanistic pathways: (1) inhibition of 25-hydroxylase by 1,25(OH)2D as a result of negative feedback loop (2) decrease in the use of 25(OH)D as a substrate; and (3) delayed metabolic clearance of 25(OH)D in the liver [[URL="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4516990/#B57-nutrients-07-05111"]57[/URL]]." [/QUOTE]
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Vitamin D Absorption is Decreased By Co-Administration of Calcium
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