Vitamin D Absorption is Decreased By Co-Administration of Calcium

[Nelson Vergel]

Effect of Vitamin D or Activated Vitamin D on Circulating 1,25-Dihydroxyvitamin D Concentrations: A Systematic Review and Metaanalysis of Randomized Controlled Trials
Clinical Chemistry December 2015 vol. 61 no. 12
[h=2]Abstract[/b]BACKGROUND: Evidence is accumulating that circulating 1,25-dihydroxyvitamin D [1,25(OH)[SUB]2[/SUB]D] concentrations are inversely related to overall mortality.

METHODS: 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.

RESULTS: 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 P < 0.001, 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; P = 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; P = 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; P = 0.04). Again, there was evidence for significant heterogeneity among studies (Cochran Q = 85.4; P < 0.001; 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.

CONCLUSIONS: 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.

 

[Dave Barry]

"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 (Table 1). 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 et al. (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 [42]. 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, p > 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 [51]. The increment in calcium group was less than half of that observed in the control group (63% vs. 133%, respectively; p < 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 [57]. 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 [53]. Using a multivariate model, Gallagher et al. (2013) [53] 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 [57]. 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 [18].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 [57]."

 

[Nelson Vergel]

Thanks Dave! Glad to see you back, buddy

Can you add the reference to that good info? Thanks

 

[Nelson Vergel]

In February, the United States Preventive Services Task Force recommended that postmenopausal women refrain from taking supplemental calcium and vitamin D. After reviewing more than 135 studies, the task force said there was little evidence that these supplements prevent fractures in healthy women.

Moreover, several studies have linked calcium supplements to an increased risk of heart attacks and death from cardiovascular disease. Others have found no effect, depending on the population studied and when calcium supplementation was begun.
The resulting controversy has left countless people, especially postmenopausal women, wondering whether they should be taking calcium. Given the conditional evidence currently available, the answer is not likely to be greeted enthusiastically by anyone other than dairy farmers, who supply the foods and drinks that are the country's richest dietary sources of calcium.

The one indisputable fact is that the safest and probably the most effective source of calcium for strong bones and overall health is diet, not supplements. But few American adults, and a decreasing proportion of children and teenagers, consume enough dairy foods to get the recommended intakes of this essential mineral.


Thinking Twice About Calcium Supplements

 

[Re-Ride]

Nelson, Dave thanks for these Vit D updates. I agree, source nutrients from real food wherever possible. Most are aware that magnesium, zinc, B vitamins and possibly boron are considered likely co-factors in Vit D absorption and metabolism. A balanced diet should include nuts, seeds, seafood or poultry,veggies and dairy. Serum tests help guide the need for supplements. Many will need to supplement Mg.

Cultured grass fed lactose-free organic may be the ticket for those with symptoms of lactose intolerance ( gas, bloating, cramps, diarrhea ). Originally I was drawn to a local organic dairy's kefir for it's unique cultures and digestive benefit. Only one of the organic kefirs available in my market met all of these the criteria: grass fed, organic, lactose free.

Daily intake of Grass Valley Organics kefir coincided with my finally being able to raise Vit D serum to 40 ng/ml ( ref 30- 100 ) after being in the single digits for years despite intensive Rx supplementation first with ergocalciferol (D2) then cholcalciferol (D3).

Too many variables prevent me from attributing the kefir intake to the improvement with any certainty. Coincidentally, a chronic skin condition all but disappeared. For those wanting to try this I take 1/4 of one serving or 2 oz AM w/ D3 drops and 1 gm Lovaza then more with each meal and bedtime up to 6 oz/day tot.

Green Valley Organics lactose-free Kefir has a store locator on it's site.

http://greenvalleylactosefree.com/farm/organic.php

label facts, G.V. plain low fat variety, $1.50 /serving, 4 servings per $6 quart:
calories 90
tot fat 2.5g
cholesterol 10mg
carbs 10g
protein 8g
calcium 30% DV
Vit A 15%
live active species 10