In all species tested, except humans, biological differences between vitamins D2 and D3 are accepted as fact. To test the presumption of equivalence in humans, we compared the ability of equal molar quantities of vitamin D2 or D3 to increase serum 25-hydroxyvitamin D [25(OH)D], the measure of vitamin D nutrition. Subjects took 260 nmol (approximately 4000 IU) vitamin D2 (n=17) or vitamin D3 (n=...

The major role of 24-hydroxylase (CYP24A1) is to maintain 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) homeostasis. Recently, it has been discovered that CYP24A1 also catalyses the hydroxylation of 20(OH)D3, producing dihydroxy-derivatives that show very effective antitumorigenic activities. Previously we showed a negative correlation of vitamin D receptor (VDR) and CYP27B1 expression with progressio...

One-day-old chicks were depleted of vitamin D. At 3 weeks their right tibiae, and those of a control group given vitamin D3, were fractured and pinned. After fracture the controls were kept on vitamin D3. Another group was left vitamin D-deficient. The remaining depleted chicks, divided into four groups, were given vitamin D3, 24,25-dihydroxyvitamin D3 [24,25(OH)2D3], 1,25-dihydroxyvitamin D3 [...

An experiment was conducted to elucidate the effect of graded levels of vitamin D3 in White Leghorn (WL) layer breeders on egg production, shell quality, hatchability of eggs and juvenile performance of offspring during their late laying period (7288 wk). White Leghorn breeder females were randomly divided into 5 groups of 50 each and were housed in individual California cages in an open-side h...

OBJECTIVE Supplementing lactating mothers with high doses of vitamin D3 can adequately meet vitamin D requirements of the breastfed infant. We compared the effect of bolus versus daily vitamin D3 dosing in lactating mothers on vitamin D3 catabolism. We hypothesized that catabolism of 25(OH)D3 to 24,25(OH)2D3 would be greater in the bolus than in the daily dose group. DESIGN, SETTING AND PATIE...

We aim to evaluate whether calcium and vitamin D intake is associated with 25-hydroxyvitamin D (25-OH-Vitamin D3) and parathyroid hormone (PTH) serum concentrations or is associated with either the phalangeal dual energy X-ray absorptiometry (pDXA) or the quantitative bone ultrasound (QUS) in independent elderly men. Serum PTH and 25-OH-Vitamin D3 were measured in 195 healthy elderly men (mean ...

OBJECTIVE To determine whether serum vitamin D levels are correlated with serum levels of alkaline phosphatase or not. STUDY DESIGN Cross-sectional, observational study. PLACE AND DURATION OF STUDY Multi-centre study, conducted at Liaquat National Hospital and Medical College, National Medical Centre and Medicare Hospital, Karachi, from January to October 2009. METHODOLOGY Patients attend...

Dietary intake of vitamin D includes vitamin D3 (vitD3), 25-hydroxyvitamin D3 (25OH-D3), and vitamin D2 (vitD2). However, the bioactivity of the different species has not been scientifically established. The hypothesis in this study was that vitD3, 25OH-D3, and vitD2 have an equal effect on 25-hydroxyvitamin D in serum (vitamin D status). To test our hypothesis, we performed a randomized, cross...

BACKGROUND Even though vitamin D is mainly produced by exposure to sunlight, little is known regarding vitamin D levels in populations living in sub-Arctic areas with little or no daylight during winter. OBJECTIVE We describe distributions of vitamin D3 and the prevalence of adequate levels in a population living above 63 °N. DESIGN We sampled 1,622 randomly selected subjects, aged 25-74 ye...