Background: Vitamin D (vD) deficiency in pregnancy is a global health problem and the amount of vD supplementation to prevent vD deficiency is controversial. Objective: The objective of the study was to determine effectiveness and safety of prenatal 2000 IU and 4000 IU/d compared with 400 IU/d vD3 supplementation in a randomized controlled trial in population in which vD deficiency is endemic. Design/Methods: Arab women were randomized at 12–16 weeks of gestation to 400, 2000, and 4000 IU/d vD3, which were continued to delivery. Serum 25-hydroxyvitamin D [25(OH)D] concentrations were measured during pregnancy and at delivery. The primary outcome was the maternal and cord blood 25(OH)D, and the secondary outcomes were the achievement of sufficient serum 25(OH)D of 32 ng/mL or greater (≥80 nmol/L) at delivery. Setting: The locations were primary care and tertiary perinatal care centers. Results: Of 192 enrolled, 162 (84%) continued to delivery. Mean serum 25(OH)D of 8.2 ng/mL (20.5 nmol/L) at enrollment was low. Mean serum 25(OH)D concentrations at delivery and in cord blood were significantly higher in the 2000 and 4000 IU than the 400 IU/d group (P < .001) and was highest in the 4000 IU/d group. The percent who achieved 25(OH)D greater than 32 ng/mL and greater than 20 ng/mL concentrations in mothers and infants was highest in 4000 IU/d group. Safety measurements were similar by group and no adverse event related to vD supplementation. Conclusions: Vitamin D supplementation of 2000 and 4000 IU/d appeared safe in pregnancy, and 4000 IU/d was most effective in optimizing serum 25(OH)D concentrations in mothers and their infants. These findings could apply to other populations in which vD deficiency is endemic.

Perspective on the paper by Dijkstra et al (see page 750)

There are increasing reports of rickets and vitamin D deficiency worldwide. Breastfeeding without adequate sunlight exposure and vitamin D supplementation are the major risk factors. In view of the drive to promote and increase the rate of exclusive breastfeeding, the relationship among maternal vitamin D status, vitamin D concentration of human milk, and hence vitamin D status of breastfeeding infants deserves reassessment. This review provides current information on the interrelationship between maternal vitamin D status and the vitamin D status of the breastfeeding infant. It also reviews the results of ongoing research on the effect of high-dose maternal vitamin D supplementation alone as a possible option to prevent vitamin D deficiency in the breastfeeding mother-infant dyad.

Despite its discovery a hundred years ago, vitamin D has emerged as one of the most controversial nutrients and prohormones of the 21st century. Its role in calcium metabolism and bone health is undisputed but its role in immune function and long-term health is debated. There are clear indicators from in vitro and animal in vivo studies that point to vitamin D’s indisputable role in both innate and adaptive immunity; however, the translation of these findings to clinical practice, including the care of the pregnant woman, has not occurred. Until recently, there has been a paucity of data from randomized controlled trials to establish clear cut beneficial effects of vitamin D supplementation during pregnancy. An overview of vitamin metabolism, states of deficiency, and the results of recent clinical trials conducted in the U.S. are presented with an emphasis on what is known and what questions remain to be answered.

Background: We previously found a high prevalence of vitamin D deficiency and low medication regimen compliance in Arab and East Indian women residing in the United Arab Emirates (UAE). The appropriate dosing regimen for improving vitamin D status in this population is not known. Objective: We aimed to determine the efficacy of daily and monthly supplementation with vitamin D₂, the only high-dose calciferol available in the UAE, in lactating and nulliparous women. Design: Healthy lactating (n = 90) and nulliparous (n = 88) women were randomly assigned to consume 2000 IU vitamin D₂/d or 60 000 IU vitamin D₂/mo for 3 mo. Serum 25-hydroxyvitamin D [25(OH)D] concentrations were measured by radioimmunoassay at baseline and every month. Results: Most women had vitamin D deficiency [ie, 25(OH)D < 50 nmol/L] at study entry. Mean ± SD 25(OH)D concentrations at 3 mo were significantly higher than baseline in both lactating (39.8 ± 12.4 and 25.2 ± 10.7 nmol/L, respectively) and nulliparous (40.4 ± 23.4 and 19.3 ± 12.2 nmol/L, respectively) women (P < 0.001 for both). In total, vitamin D supplementation was effective in achieving serum 25(OH)D concentrations of ≥50 nmol/L in 21 (30%) of 71 women at endpoint. Conclusions: Oral vitamin D₂ supplementation with 2000 IU/d or 60 000 IU/mo for 3 mo was safe, and it increased serum 25(OH)D concentrations significantly; however, only a small proportion of the women studied achieved concentrations of ≥50 nmol/L. This suggests that, when sunlight exposure is limited, doses of vitamin D₂ higher than those currently studied may be needed. Monthly dosing appears to be a safe and effective alternative to daily dosing.