Factors Associated with Serum 25-Hydroxyvitamin D Concentration in Two Cohorts of Pregnant Women in Southern Ontario, Canada

Zinc Supplementation Trial in Pediatric Chronic Kidney Disease: Effects on Circulating FGF-23 and Klotho

Background

Zinc status, its role in bone metabolism and efficacy of deficiency correction has not been well studied in children with chronic kidney disease (CKD).

Objectives

The primary objective was to investigate whether 3 months of oral zinc supplementation corrects zinc deficiency in children with CKD who have native or transplanted kidneys. The secondary objective was to compare circulating intact FGF-23 (iFGF-23), c-terminal FGF-23 (cFGF-23), and Klotho between zinc-sufficient and zinc-deficient children with CKD and to assess the relationship between circulating zinc, iFGF-23, cFGF-23, Klotho, bone biomarkers, copper, and phosphate excretion pre-supplementation and post-supplementation of zinc.

Methods

Forty-one children (25 male and 16 female, age 12.94 ± 4.13 years) with CKD in native or transplanted kidneys were recruited through 2 pediatric nephrology divisions in Ontario, Canada. Of those, 14 patients (9 native CKD, 5 transplant CKD) with identified zinc deficiency (64% enrollment rate) received zinc citrate supplement for 3 months: 10 mg orally once (4-8 years) or twice (9-18 years) daily.

Results

Zinc deficiency (plasma concentration < 11.5 µmol/L) was found in 22 patients (53.7%). A linear regression model suggested that zinc concentration reduced by 0.026 µmol/L (P = .04) for every 1-unit of estimated glomerular filtration rate (eGFR) drop. Zinc deficiency status was associated with higher serum iFGF-23; however, this was predominantly determined by the falling GFR. Zinc deficient and sufficient children had similar circulating c-FGF-23 and alpha-Klotho. Normalization of plasma zinc concentration was achieved in 8 (5 native CKD and 3 transplant CKD) out of 14 treated patients rising from 10.04 ± 1.42 to 12.29 ± 3.77 μmol/L (P = .0038). There were no significant changes in other biochemical measures in all treated patients. A statistically significant (P = .0078) rise in c-FGF-23 was observed only in a subgroup of 11 children treated with zinc but not receiving calcitriol.

Conclusions

Zinc status is related to kidney function and possibly connected to bone metabolism in patients with CKD. However, it plays a minor role in fine-tuning various metabolic processes. In this exploratory non-randomized study, 3 months supplementation with zinc corrected deficiency in just over half of patients and only modestly affected bone metabolism in asymptomatic CKD patients.

Individualized high dairy protein + walking program supports bone health in pregnancy: a randomized controlled trial

BACKGROUND

Pregnancy induces bone mineral mobilization, which may be further compromised if diet and physical activity are suboptimal.

OBJECTIVES

We aimed to determine the effects of a Nutrition + Exercise intervention during pregnancy on maternal calciotropic and bone biomarker profiles throughout pregnancy and the postpartum.

METHODS

In the Be Healthy in Pregnancy (BHIP) randomized controlled trial, 203 of 225 participants who consented to the bone health substudy were, randomly assigned at 12-17 weeks gestation to receive either usual care (control) or a structured and monitored Nutrition + Exercise plan (intervention) providing an individualized high dairy protein diet and a walking program throughout pregnancy. Maternal serum total procollagen type 1 N-terminal propeptide (P1NP; bone formation), C-terminal telopeptide of type I collagen (CTX; bone resorption), and insulin-like growth factor-1 (IGF-1) were measured by ELISA, and vitamin D metabolites by ultra-performance LC tandem MS at early and late pregnancy, 6 mo postpartum, and in cord blood.

RESULTS

In 187 participants completing all measures, significantly higher intakes were observed in the intervention than in the control group for total protein (P < 0.0001), protein intake from dairy foods (P < 0.0001), and calcium (P < 0.0001), whereas vitamin D intake was similar between treatment groups in both the second and third trimesters. The intervention group had significantly lower serum CTX at end of pregnancy (mean ± SD: 0.78 ± 0.31 ng/mL; n = 91 compared with 0.89 ± 0.33 ng/mL; n = 96, P = 0.034) and in cord serum (0.58 ± 0.13 ng/mL; n = 31 compared with 0.69 ± 0.18 ng/mL; n = 22, P < 0.025). Serum concentrations of P1NP rose significantly (P < 0.02) from early pregnancy to 6 mo postpartum for the intervention group only. Serum 25-hydroxyvitamin D status was >50 nmol/L for 97% of all participants.

CONCLUSIONS

Higher maternal dietary protein and calcium intakes than usual care in concert with normal vitamin D status minimized bone resorption and maintained bone formation and may protect bone health during pregnancy.This trial was registered at clinicaltrials.gov as NCT01689961.

Vitamin D-Related Risk Factors for Maternal Morbidity and Mortality during Pregnancy: Systematic Review and Meta-Analysis

Vitamin D deficiency (serum 25-hydroxyvitamin D [25(OH)D] levels <20 ng/mL in serum) is a common health condition among pregnant women, especially in high-risk groups. Evidence has connected vitamin D levels with many health-related problems during pregnancy, including gestational diabetes and preeclampsia. Because of vitamin D’s effect on both mother and fetus, we systematically review the association between 25(OH)D level and its health effects. From a total of 143 studies, 43 came from PubMed, 4 from Cochrane, and 96 from EMBASE. After screening, we identified 38 studies as candidates for inclusion. Ultimately, we limited this review to 23 articles originating from 12 countries, written in English or Spanish, and conducted between 2010 and 2022. We conducted this review according to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines and evaluated the quality and strength of the evidence by using the Navigation Guide Systematic Review Methodology (SING). These systematic reviews summarize findings that support vitamin D’s role in reducing risks of multiple outcomes and the possible contribution of adequate vitamin D levels to a healthy pregnancy.

Disparities in Vitamin D Status of Newborn Infants from a Diverse Sociodemographic Population in Montreal, Canada

BACKGROUND

Vitamin D status at birth is reliant on maternal-fetal transfer of vitamin D during gestation.

OBJECTIVES

We aimed to examine the vitamin D status of newborn infants in a diverse population and to subsequently identify the modifiable correlates of vitamin D status.

METHODS

In this cross-sectional study, healthy mother-infant dyads (n = 1035) were recruited within 36 h after term delivery (March 2016-March 2019). Demographic and lifestyle factors were surveyed. Newborn serum 25-hydroxyvitamin D [25(OH)D] was measured (standardized chemiluminescence immunoassay) and categorized as deficient [serum 25(OH)D <30 nmol/L] or adequate (≥40 nmol/L). Serum 25(OH)D was compared among categories of maternal characteristics using ANOVA; each characteristic was tested in a separate model. Subgroups (use of multivitamins preconception and continued in pregnancy compared with during pregnancy only) were matched (n = 352/group) for maternal factors (ancestry, age, income, education, parity, and prepregnancy BMI) using propensity scores; logistic regression models were generated for odds of deficiency or adequacy.

RESULTS

Infants' mean serum 25(OH)D was 45.9 nmol/L (95% CI: 44.7, 47.0 nmol/L) (n = 1035), with 20.8% (95% CI: 18.3%, 23.2%) deficient and 60.7% (95% CI: 55.2%, 66.2%) adequate. Deficiency prevalence ranged from 14.6% of white infants to 41.7% of black infants. Serum 25(OH)D was higher (P < 0.0001) in infants of mothers with higher income, BMI < 25 kg/m2, exercise and sun exposure in pregnancy, and use of multivitamins preconception. In the matched-subgroup analysis, multivitamin supplementation preconception plus during pregnancy relative to only during pregnancy was associated with lower odds for vitamin D deficiency (ORadj: 0.55; 95% CI: 0.36, 0.86) and higher odds for adequate vitamin D status (ORadj: 1.47; 95% CI: 1.04, 2.07).

CONCLUSIONS

In this study most newborn infants had adequate vitamin D status, yet one-fifth were vitamin D deficient with disparities between population groups. Guidelines for a healthy pregnancy recommend maternal use of multivitamins preconception and continuing in pregnancy. An emphasis on preconception use may help to achieve adequate neonatal vitamin D status.This trial was registered at clinicaltrials.gov as NCT02563015.

Longitudinal Assessment of Vitamin D Status across Trimesters of Pregnancy

BACKGROUND

The evolution of vitamin D status across pregnancy trimesters and its association with prepregnancy body mass index (ppBMI; in kg/m2) remain unclear.

OBJECTIVES

We aimed to 1) assess trimester-specific serum total 25-hydroxyvitamin D [25(OH)D] concentrations, 2) compare those concentrations between ppBMI categories, and 3) examine associations between 25(OH)D concentrations, ppBMI, and vitamin D intake.

METHODS

As part of a prospective cohort study, 79 pregnant women with a mean age of 32.1 y and ppBMI of 25.7 kg/m2 were recruited in their first trimester (average 9.3 weeks of gestation). Each trimester, vitamin D intake was assessed by 3 Web-based 24-h recalls and a Web questionnaire on supplement use. Serum total 25(OH)D was measured by LC-tandem MS. Repeated-measures ANOVA was performed to assess the evolution of 25(OH)D concentrations across trimesters of pregnancy and comparisons of 25(OH)D concentrations between ppBMI categories were assessed by 1-factor ANOVAs. Stepwise regression analyses were used to identify determinants of 25(OH)D concentrations in the third trimester.

RESULTS

Mean ± SD serum total 25(OH)D concentrations increased across trimesters, even after adjustments for ppBMI, seasonal variation, and vitamin D intake from supplements (67.5 ± 20.4, 86.5 ± 30.9, and 88.3 ± 29.0 nmol/L at mean ± SD 12.6 ± 0.8, 22.5 ± 0.8, and 33.0 ± 0.6 weeks of gestation, respectively; P < 0.0001). In the first and third trimesters, women with a ppBMI ≥30 had lower serum total 25(OH)D concentrations than women with a ppBMI <25 (P < 0.05); however, most had concentrations >40nmol/L by the second trimester. Vitamin D intake from supplements was the strongest determinant of third-trimester serum total 25(OH)D concentrations (r2 = 0.246, β = 0.51; P < 0.0001).

CONCLUSIONS

There was an increase in serum total 25(OH)D concentrations across trimesters, independent of ppBMI, seasonal variation, and vitamin D intake from supplements. Almost all women had serum total 25(OH)D concentrations over the 40- and 50-nmol/L thresholds, thus our study supports the prenatal use of a multivitamin across pregnancy.

Early prenatal use of a multivitamin diminishes the risk for inadequate vitamin D status in pregnant women: results from the Maternal-Infant Research on Environmental Chemicals (MIREC) cohort study

BACKGROUND

Reports on the adequacy of vitamin D status of pregnant women are not available in Canada.

OBJECTIVES

The objectives of this study were to examine vitamin D status across pregnancy and identify the correlates of vitamin D status of pregnant women in Canada.

METHODS

Pregnant women (≥18 years) from 6 provinces (2008-2011) participating in a longitudinal cohort were studied. Sociodemographic data, obstetrical histories, and dietary and supplemental vitamin D intakes were surveyed. Plasma 25-hydroxyvitamin D (25OHD) was measured using an immunoassay standardized to LC-MS/MS from samples collected during the first (n = 1905) and third trimesters (n = 1649) and at delivery (n = 1543). The proportion of women with ≥40 nmol/L of plasma 25OHD (adequate status) was estimated at each time point, and factors related to achieving this cut point were identified using repeated-measures logistic regression. Differences in 25OHD concentrations across trimesters and at delivery were tested a using repeated-measures ANOVA with a post hoc Tukey's test.

RESULTS

In the first trimester, 93.4% (95% CI: 92.3%-94.5%) of participants had 25OHD ≥40 nmol/L. The mean plasma 25OHD concentration increased from the first to the third trimester and then declined by delivery (69.8 ± 0.5 nmol/L, 78.6 ± 0.7 nmol/L, and 75.7 ± 0.7 nmol/L, respectively; P < 0.0001). A lack of multivitamin use early in pregnancy reduced the odds of achieving 25OHD ≥40 nmol/L (ORadj = 0.33; 95% CI: 0.25-0.42) across all time points. Factors associated with not using a prenatal multivitamin included multiparity (ORadj = 2.08; 95% CI: 1.42-3.02) and a below-median income (ORadj = 1.39; 95% CI: 1.02-1.89).

CONCLUSIONS

The results from this cohort demonstrate the importance of early multivitamin supplement use to achieve an adequate vitamin D status in pregnant women.

Vitamin D Status and Its Determinants in Mexican Pregnant Women from a Rural and an Urban Area: A Comparative Study

BACKGROUND

During pregnancy, vitamin D requirements are higher due to fetal growth and development. Vitamin D production occurs mainly through sunlight exposure, which is affected by geographic location and lifestyle factors.

METHODS

This was a case-control study nested within two cohorts of adult pregnant women (n = 298): urban (Mexico City) and rural (Cuetzalan). To reduce confounding, pairs were selected by age, pregestational body mass index, and pregnancy trimester. Generalized linear models were used to assess the two groups according to their vitamin D status.

RESULTS

A total of 298 adult women were studied: 149 from a rural area and 149 from an urban area. Vitamin D deficiency and insufficiency were observed in 28% and 38.2% of women, respectively. A trend for higher 25(OH)D concentrations was observed in women from the rural area (27.5 ng/mL vs. 25.8 ng/mL), probably related to the type of job, where women with partial jobs showing less probability of having vitamin D deficiency (OR = 0.26; CI = 0.06-1.16; p = 0.08) and vitamin D insufficiency (OR = 0.24; CI = 0.06-0.99; p = 0.05). Women whose Last Menstrual Period occurred in spring showed lower vitamin D concentration compared to those whose LMP occurred in winter (p < 0.01).

CONCLUSIONS

A high prevalence of vitamin D deficiency was observed in both rural and urban areas. Women living in rural areas tended to have higher 25(OH)D concentrations, probably related to more sunlight exposure associated with their type of job.

Vitamin D Deficiency in Mexican Pregnant Women: Is Supplementation with ≤400 IU/day Enough?

Controversy remains surrounding vitamin D routine supplementation in healthy pregnancy, and the doses are unclear. The aim of this study was to describe maternal vitamin D status throughout pregnancy in a group of Mexican women and evaluate the effect of frequently prescribed doses of vitamin D3 on longitudinal 25-OH-D concentrations, adjusting for obesity, season, and other factors. We conducted a cohort study (Instituto Nacional de Perinatología-INPer) (2017-2020)) of healthy pregnant women without complications. Pregestational overweight/obesity (body mass index ≥ 25), vitamin D3 supplementation (prescribed by physician; 0-250, 250-400, and >400 IU/day), and serum 25-OH-D concentrations (ELISA) were evaluated in each trimester of pregnancy. Vitamin D deficiency or insufficiency was computed (<20 and <30 ng/mL, respectively). We studied 141 adult women; 58.5% had pregestational obesity or overweight. In the first trimester, 45.8% of the women were supplemented with vitamin D3; 51.4% had vitamin D insufficiency and 37.3%, deficiency. In the third trimester, 75.4% of the women were supplemented, and 20% of them still had deficiency. The final general mixed linear model showed that 25-OH-D significantly increased throughout pregnancy (p < 0.001); the highest increase was observed in the third trimester in women with doses >400 IU/day of vitamin D3 (+4 ng/mL, 95% CI: 1.72-8.11 ng/mL). In winter/autumn, 25-OH-D concentrations were also lower (p ≤ 0.05). In this group of pregnant Mexican women, the prevalence of vitamin D deficiency and insufficiency was high. A higher increase in 25-OH-D concentrations during pregnancy was observed when the women were supplemented with >400 IU/day. Common supplementation doses of 250-400 IU/day were insufficient for achieving an adequate maternal vitamin D status.

Summer Season and Recommended Vitamin D Intake Support Adequate Vitamin D Status throughout Pregnancy in Healthy Canadian Women and Their Newborns

BACKGROUND

Vitamin D deficiency in pregnancy is reported as a prevalent public health problem.

OBJECTIVES

We aimed to evaluate, in pregnant Canadian women, 1) vitamin D intake, 2) maternal and cord serum 25-hydroxycholecalciferol [25(OH)D] and maternal 1,25-dihydroxycholecalciferol [1,25(OH)2D], and 3) factors associated with maternal serum 25(OH)D.

METHODS

Women (n = 187; mean prepregnancy BMI 24.4 kg/m2, mean age 31 y) recruited to the Be Healthy in Pregnancy study provided fasting blood samples and nutrient intake at 12-17 (early) and 36-38 (late) weeks of gestation, and cord blood. Vitamin D intakes (Nutritionist Pro™) and serum 25(OH)D and 1,25(OH)2D concentrations (LC-tandem MS) were measured.

RESULTS

Vitamin D intake was comparable in early and late pregnancy [median (IQR) = 586 (459, 859) compared with 689 (544, 974) IU/d; P = 0.83], with 71% consumed as supplements. Serum 25(OH)D was significantly higher in late pregnancy (mean ± SD: 103.1 ± 29.3 nmol/L) than in early pregnancy (82.5 ± 22.5 nmol/L; P < 0.001) and no vitamin D deficiency (<30 nmol/L) occurred. Serum 1,25(OH)2D concentrations were significantly higher in late pregnancy (101.1 ± 26.9 pmol/L) than in early pregnancy (82.2 ± 19.2 pmol/L, P < 0.001, n = 84). Cord serum 25(OH)D concentrations averaged 55% of maternal concentrations. In adjusted multivariate analyses, maternal vitamin D status in early pregnancy was positively associated with summer season (est.β: 13.07; 95% CI: 5.46, 20.69; P < 0.001) and supplement intake (est.β: 0.01; 95% CI: 0.00, 0.01; P < 0.001); and in late pregnancy with summer season (est.β: 24.4; 95% CI: 15.6, 33.2; P < 0.001), nonmilk dairy intake (est.β: 0.17; 95% CI: 0.02, 0.32; P = 0.029), and supplement intake (est.β: 0.01; 95% CI: 0.00, 0.01; P = 0.04).

CONCLUSIONS

Summer season and recommended vitamin D intakes supported adequate vitamin D status throughout pregnancy and in cord blood at >50 nmol/L in healthy Canadian pregnant women. This trial was registered at clinicaltrials.gov as NCT01693510.

Vitamin D Status in Pregnant Women in Southern China and Risk of Preterm Birth: A Large-Scale Retrospective Cohort Study

Background

The influence of maternal vitamin D on pregnancy outcomes, including preterm birth (PTB), is unclear due to different experimental designs and study populations (patient race and sample size) of previous studies. We aimed to investigate the relationship between 25-hydroxyvitamin D (25[OH] D) levels and PTB among pregnant women in southern China.

Material/Methods

A total of 11 641 pregnant women were retrospectively enrolled between January 2016 and April 2019. Vitamin D concentrations were evaluated by electrochemiluminescence immunoassay. Logistic regression analysis was used to analyze the association between vitamin D and PTB.

Results

The average 25(OH) D concentration was 59.3±21.5 nmol/L; 34.8% of patients were vitamin D deficient, 43.0% were vitamin D insufficient (25[OH] D <50 nmol/L and 50–74.9 nmol/L, respectively). In total, 3.6% of newborns were born prematurely. Comparing the pre-term and full-term groups, 45.7% versus 42.9% and 29.8% versus 35% were vitamin D deficient and insufficient, respectively These differences were not significant (P>0.05). However, the mean vitamin D status was significantly different between the pre-term and full-term groups (61.3±21.3 and 59.1±21.5 nmol/L, respectively). No association was found between vitamin D deficiency/insufficiency and PTB in unadjusted or adjusted models, compared with vitamin D sufficiency (adjusted odds ratio, 1.016; 95% confidence interval, 0.794–1.301 and 0.842; 0.641–1.106, respectively).

Conclusions

Low maternal 25(OH) D levels are common in southern China. However, low vitamin D status in pregnant women appears to be unrelated to PTB. Measuring vitamin D level alone is therefore not sufficient to predict PTB.