24-25-dihydroxyvitamin-d2 and Vitamin-D-Deficiency

Interactions between calcium and vitamin D may have implications for the regulation of serum 25-hydroxyvitamin D [25(OH)D] and its catabolism and, consequently, the vitamin D dietary requirement.. We investigated whether different calcium intakes influenced serum 25(OH)D and indexes of vitamin D activation and catabolism during winter and in the context of both adequate and inadequate vitamin D intakes.. A 15-wk winter-based, randomized, placebo-controlled, double-blind vitamin D₃ intervention (20 μg/d) study was carried out in free-living men and women aged ≥50 y (n = 125) who were stratified according to calcium intakes [moderate-low (<700 mg/d) or high (>1000 mg/d) intake]. The serum 25(OH)D concentration was the primary outcome, and serum calcium, parathyroid hormone (PTH), 1,25-dihydroxyvitamin D [1,25(OH)₂D], 24,25-dihydroxyvitamin D [24,25(OH)₂D], the ratio of 24,25(OH)₂D to 25(OH)D, vitamin D-binding protein, and free 25(OH)D were exploratory outcomes.. A repeated-measures ANOVA showed there was no significant (P = 0.2) time × vitamin D treatment × calcium intake grouping interaction effect on the mean serum 25(OH)D concentration over the 15-wk intervention period. Serum 25(OH)D concentrations increased (P ≤ 0.005) and decreased (P ≤ 0.002) in vitamin D₃ and placebo groups, respectively, and were of similar magnitudes in subjects with calcium intakes <700 mg/d (and even <550 mg/d) compared with >1000 mg/d. The response of serum PTH, 1,25(OH)₂D, 24,25(OH)₂D, the ratio of 24,25(OH)₂D to 25(OH)D, and free 25(OH)D significantly differed in vitamin D₃ and placebo groups but not by calcium intake grouping.. We found no evidence of a vitamin D sparing effect of high calcium intake, which has been referred to by some authors as "vitamin D economy." Thus, recent dietary vitamin D requirement estimates will cover the vitamin D needs of even those individuals who have inadequate calcium intakes.

Topics: 24,25-Dihydroxyvitamin D 3; 25-Hydroxyvitamin D 2; Aged; Aged, 80 and over; Aging; Calcifediol; Calcitriol; Calcium; Calcium, Dietary; Cholecalciferol; Dietary Supplements; Double-Blind Method; Ergocalciferols; Female; Humans; Ireland; Male; Middle Aged; Nutritional Requirements; Seasons; Vitamin D Deficiency

We previously showed that a single high dose of oral (po) cholecalciferol (D₃) sharply increases serum 25-hydroxyvitamin D [25(OH)D].. We evaluated the long-term bioavailability and metabolism of a single po or intramuscular (im) high dose of ergocalciferol (D₂) or D₃.. This was a prospective intervention study.. The study was conducted in an ambulatory care setting.. Participants were 24 subjects with hypovitaminosis D.. A single dose of 600,000 IU of po or im D₂ or D₃ was administered.. Serum 25(OH)D and 1,25-dihydroxyvitamin D [1,25(OH)₂D] were measured at baseline and at days 30, 60, 90, and 120 by RIA. Serum 1,25(OH)₂D₂, 1,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃], 24,25-hydroxyvitamin D₂ [24,25(OH)D₂], and 24,25-hydroxyvitamin D₃ [24,25(OH)D₃] were measured by liquid chromatography-tandem mass spectrometry in a subgroup of patients receiving the po formulations.. The areas under the curve of 25(OH)D after D₃ were significantly higher than those after D₂ (P < .0001). Serum 25(OH)D basal difference significantly increased at day 30 with po D₂ and D₃ (P < .01 and P < .0001) and up to day 90 with po D₃ (P < .01). The im formulations produced a slow increased, and values peaked at day 120 relative to the other time points (P < .0001). We found a decrease in 1,25(OH)₂D at day 30 (P < .05) and up to day 120 (P < .001) and an increase in 1,25(OH)₂D₂ at day 30 (P < .01) and up to day 120 (P < .01) after po D₂. Oral D₂ and D₃ produced increases in 24,25(OH)D₂ and 24,25(OH)D₃, respectively, at day 30 (P < .001).. A po dose of 600,000 IU of D₂ or D₃ is initially more effective in increasing serum 25(OH)D than the equivalent im dose and is rapidly metabolized. Our RIA assay for 1,25(OH)₂D may not recognize 1,25(OH)₂D₂.

Topics: 24,25-Dihydroxyvitamin D 3; 25-Hydroxyvitamin D 2; Administration, Oral; Aged; Biological Availability; Biotransformation; Calcifediol; Cholecalciferol; Chromatography, High Pressure Liquid; Ergocalciferols; Female; Humans; Injections, Intramuscular; Male; Middle Aged; Radioimmunoassay; Reproducibility of Results; Spectrometry, Mass, Electrospray Ionization; Tandem Mass Spectrometry; Vitamin D Deficiency

In 13 of 17 infants (aged 10.5 +/- 4.3; mean +/- SD mo) with iron-deficiency anemia, the serum 24,25-dihydroxyvitamin D concentration was below the normal range and in 9 of these 13 the serum 25-hydroxyvitamin D concentration was below the normal range despite the fact that these infants received 10 micrograms vitamin D/d from the age of 1 mo. The infants were treated with intramuscular iron dextran (Imferon). The iron-dextran treatment increased the hemoglobin and serum iron concentrations as well as 25-hydroxyvitamin D and 24,25-dihydroxyvitamin D concentrations. It is known that iron deficiency impairs fat and vitamin A intestinal absorption. Therefore, it is suggested that absorption of vitamin D may also be impaired. This may contribute to the development of vitamin D deficiency. Iron supplementation may have improved the absorption of vitamin D in the small intestine and hence increased the vitamin D concentration in the plasma.

Topics: 25-Hydroxyvitamin D 2; Anemia, Hypochromic; Ergocalciferols; Humans; Infant; Israel; Prevalence; Vitamin D Deficiency