Effects of calcium supplementation on fetal growth in mothers with deficient calcium intake: a randomised controlled trial

Differential effects of RYGB surgery and best medical treatment for obesity-diabetes on intestinal and islet adaptations in obese-diabetic ZDSD rats

Modification of gut-islet secretions after Roux-En-Y gastric bypass (RYBG) surgery contributes to its metabolic and anti-diabetic benefits. However, there is limited knowledge on tissue-specific hormone distribution post-RYGB surgery and how this compares with best medical treatment (BMT). In the present study, pancreatic and ileal tissues were excised from male Zucker-Diabetic Sprague Dawley (ZDSD) rats 8-weeks after RYGB, BMT (daily oral dosing with metformin 300mg/kg, fenofibrate 100mg/kg, ramipril 1mg/kg, rosuvastatin 10mg/kg and subcutaneous liraglutide 0.2mg/kg) or sham operation (laparotomy). Insulin, glucagon, somatostatin, PYY, GLP-1 and GIP expression patterns were assessed using immunocytochemistry and analyzed using ImageJ. After RYGB and BMT, body weight and plasma glucose were decreased. Intestinal morphometry was unaltered by RYGB, but crypt depth was decreased by BMT. Intestinal PYY cells were increased by both interventions. GLP-1- and GIP-cell counts were unchanged by RYGB but BMT increased ileal GLP-1-cells and decreased those expressing GIP. The intestinal contents of PYY and GLP-1 were significantly enhanced by RYGB, whereas BMT decreased ileal GLP-1. No changes of islet and beta-cell area or proliferation were observed, but the extent of beta-cell apoptosis and islet integrity calculated using circularity index were improved by both treatments. Significantly decreased islet alpha-cell areas were observed in both groups, while beta- and PYY-cell areas were unchanged. RYGB also induced a decrease in islet delta-cell area. PYY and GLP-1 colocalization with glucagon in islets was significantly decreased in both groups, while co-staining of PYY with glucagon was decreased and that with somatostatin increased. These data characterize significant cellular islet and intestinal adaptations following RYGB and BMT associated with amelioration of obesity-diabetes in ZDSD rats. The differential responses observed and particularly those within islets, may provide important clues to the unique ability of RYGB to cause diabetes remission.

Adverse maternofoetal outcomes associated with ionised calcaemia, total calcaemia, albuminaemia, and calcium supplementation in pregnancy: Analysis from a resource-limited setting

Introduction

Disorders of total calcium (tCa) in pregnancy have been associated with adverse maternofoetal outcomes. However, studies evaluating this from the viewpoint of ionised calcaemia are practically inexistent. This study estimates the prevalence of some adverse maternal and foetal outcomes and the potential effect of ionised calcium (iCa), tCa, albumin and calcium supplementation on some maternofoetal outcomes.

Methods

A cross-sectional study was conducted among 1074 pregnant women in late pregnancy from four health facilities in the Nkongsamba Health District. Data were collected by interview, analysis of maternal blood samples and measurement of maternal and foetal parameters. Total calcaemia and albuminaemia were measured by atomic absorption spectrophotometry, while iCa and pH were measured using ion-selective potentiometry. Associations were measured using the odds ratio in simple and multiple logistic regression.

Results

The prevalence of low birth weight, macrosomia, and hypertension in pregnancy was 6.27 [4.97–7.89]%, 4.78 [3.65–7.89]%, 10.24 [8.57–12.20]%, respectively. Following multiple logistic regression, women with iCa levels ≤ 1.31mmol/L had significantly increased odds of hypertension in pregnancy (AOR = 2.47 [1.63–3.74], p-value = 0.000), having babies with low birth weight (AOR = 2.02[1.33–3.61], p-value = 0.002), low birth length (AOR = 2.00 [1.34–2.99], p-value = 0.001), low brachial circumference (AOR = 1.41[1.10–1.81], p-value = 0.007), first minute Apgar score < 7 (AOR = 3.08[1.70–5.59], p-value = 0.000) and fifth minute Apgar score < 7 (AOR = 2.86[1.32–6.16], p-value = 0.007). Ionised calcaemia had no significant association with maternal body mass index immediately after birth and the head circumference of the baby. Total calcaemia was found to have no significant association with any of the selected outcomes, while women with total albuminaemia ≤ 30mg/L had significantly higher odds of having babies with low birth weight (AOR = 3.40[1.96–5.91], p-value = 0.000), and Apgar scores < 7 at the first (AOR = 2.07[1.16–3.70], p-value = 0.013). Calcium supplementation showed no significant association with any of the selected outcomes except for the first (OR = 0.42[0.24–0.72], p-value = 0.002) and fifth minute Apgar score (OR = 0.25[0.12–0.50], p-value = 0.000).

Conclusion

The prevalence of low birth weight, macrosomia, and hypertension in pregnancy was 6.27 [4.97–7.89]%, 4.78 [3.65–7.89]%, 10.24 [8.57–12.20]%, respectively. Maternal iCa levels ≤ 1.31mmol/L significantly increase the odds of having babies with low birth weight, low birth length, low brachial circumference at birth, low Apgar scores at the first and fifth minutes and maternal hypertension in pregnancy. Low maternal albuminaemia is significantly associated with low birth weight, and Apgar score < 7 at the first minute. None f the selected maternofoetal outcomes directly depend on total calcaemia, given that none of the associations was statistically significant. Even though iCa levels remain relatively normal in normal pregnancies, it remains the strongest predictor of foetal outcomes. Calcium supplementation significantly improves the Apgar scores at the first and fifth minute. Routine pregnancy follow-up should include evaluating maternal calcaemic states, particularly the ionised fraction, to detect the low-normal concentrations likely to impact maternal and foetal outcomes. Normal iCa levels for pregnant women need revisiting.

No effect of maternal calcium intake and bone resorption during pregnancy on offspring bone mineral density at age 5 years

Maternal nutrition during pregnancy plays a role in offspring bone health. In a prospective cohort study, offspring bone mineral density at 5 years was not associated with maternal calcium intake or maternal bone resorption during pregnancy.

PURPOSE

Suboptimal bone mineral density in childhood can result in osteoporosis later in life. We reported previously that lower calcium intake during pregnancy was associated with higher maternal bone resorption during pregnancy and that lower maternal dietary calcium and higher maternal bone resorption in pregnancy were associated with lower maternal bone mineral density (BMD) 5 years later. The current study sought to investigate the effect of both maternal dietary calcium intake and maternal bone resorption during pregnancy on offspring BMD at 5 years.

METHODS

Data collected as part of the ROLO longitudinal cohort study (n = 103, mother-child dyads) were used in the current analysis. ROLO started as a randomised controlled trial of a low glycemic index diet during second pregnancy in women with macrosomia in first pregnancy in order to prevent recurrence of macrosomia. Maternal dietary intakes were assessed using 3-day food diaries completed during each trimester of pregnancy. Bone resorption in early and late pregnancy was calculated through urinary excretion of cross-linked N-telopeptides (uNTX). Offspring whole-body BMD at 5 years was measured using dual-energy X-ray absorptiometry.

RESULTS

Offspring BMD at 5 years correlated with offspring body mass index (r = .385; p < .001) and offspring BMD was higher in boys than girls (t = 2.91; p = .004). Offspring BMD at 5 years was not associated with either maternal calcium intake or uNTX during pregnancy, after controlling for offspring body mass index and offspring sex.

CONCLUSION

Offspring BMD at 5 years is not associated with either maternal calcium intake or maternal bone resorption during pregnancy.

Effects of vitamin and mineral supplementation during pregnancy on maternal, birth, child health and development outcomes in low- and middle-income countries: A systematic review

Background

Almost two billion people who are deficient in vitamins and minerals are women and children in low- and middle-income countries (LMIC). These deficiencies are worsened during pregnancy due to increased energy and nutritional demands, causing adverse outcomes in mother and child. To reduce micronutrient deficiencies, several strategies have been implemented, including diet diversification, large-scale and targeted fortification, staple crop bio-fortification and micronutrient supplementation.

Objectives

To evaluate and summarize the available evidence on the effects of micronutrient supplementation during pregnancy in LMIC on maternal, fetal, child health and child development outcomes. This review will assess the impact of single micronutrient supplementation (calcium, vitamin A, iron, vitamin D, iodine, zinc, vitamin B12), iron-folic acid (IFA) supplementation, multiple micronutrient (MMN) supplementation, and lipid-based nutrient supplementation (LNS) during pregnancy.

Search Methods

We searched papers published from 1995 to 31 October 2019 (related programmes and good quality studies pre-1995 were limited) in CAB Abstracts, CINAHL, Cochrane Central Register of Controlled Trials, Embase, International Initiative for Impact Evaluations, LILACS, Medline, POPLINE, Web of Science, WHOLIS, ProQuest Dissertations & Theses Global, R4D, WHO International Clinical Trials Registry Platform. Non-indexed grey literature searches were conducted using Google, Google Scholar, and web pages of key international nutrition agencies.

Selection Criteria

We included randomized controlled trials (individual and cluster-randomized) and quasi-experimental studies that evaluated micronutrient supplementation in healthy, pregnant women of any age and parity living in a LMIC. LMIC were defined by the World Bank Group at the time of the search for this review. While the aim was to include healthy pregnant women, it is likely that these populations had one or more micronutrient deficiencies at baseline; women were not excluded on this basis.

Data Collection and Analysis

Two authors independently assessed studies for inclusion and risk of bias, and conducted data extraction. Data were matched to check for accuracy. Quality of evidence was assessed using the GRADE approach.

Main Results

A total of 314 papers across 72 studies (451,723 women) were eligible for inclusion, of which 64 studies (439,649 women) contributed to meta-analyses. Seven studies assessed iron-folic acid (IFA) supplementation versus folic acid; 34 studies assessed MMN vs. IFA; 4 studies assessed LNS vs. MMN; 13 evaluated iron; 13 assessed zinc; 9 evaluated vitamin A; 11 assessed vitamin D; and 6 assessed calcium. Several studies were eligible for inclusion in multiple types of supplementation. IFA compared to folic acid showed a large and significant (48%) reduction in the risk of maternal anaemia (average risk ratio (RR) 0.52, 95% CI 0.41 to 0.66; studies = 5; participants = 15,540; moderate-quality evidence). As well, IFA supplementation demonstrated a smaller but significant, 12% reduction in risk of low birthweight (LBW) babies (average RR 0.88, 95% CI 0.78 to 0.99; studies = 4; participants = 17,257; high-quality evidence). MMN supplementation was defined as any supplement that contained at least 3 micronutrients. Post-hoc analyses were conducted, where possible, comparing the differences in effect of MMN with 4+ components and MMN with 3 or 4 components. When compared to iron with or without FA, MMN supplementation reduced the risk of LBW by 15% (average RR 0.85, 95% CI 0.77 to 0.93; studies = 28; participants = 79,972); this effect was greater in MMN with >4 micronutrients (average RR 0.79, 95% CI 0.71 to 0.88; studies = 19; participants = 68,138 versus average RR 1.01, 95% CI 0.92 to 1.11; studies = 9; participants = 11,834). There was a small and significant reduction in the risk of stillbirths (average RR 0.91; 95% CI 0.86 to 0.98; studies = 22; participants = 96,772) and a small and significant effect on the risk of small-for-gestational age (SGA) (average RR 0.93; 95% CI 0.88 to 0.98; studies = 19; participants = 52,965). For stillbirths and SGA, the effects were greater among those provided MMN with 4+ micronutrients. Children whose mothers had been supplemented with MMN, compared to IFA, demonstrated a 16% reduced risk of diarrhea (average RR 0.84; 95% CI 0.76 to 0.92; studies = 4; participants = 3,142). LNS supplementation, compared to MMN, made no difference to any outcome; however, the evidence is limited. Iron supplementation, when compared to no iron or placebo, showed a large and significant effect on maternal anaemia, a reduction of 47% (average RR 0.53, 95% CI 0.43 to 0.65; studies = 6; participants = 15,737; moderate-quality evidence) and a small and significant effect on LBW (average RR 0.88, 95% CI 0.78 to 0.99; studies = 4; participants = 17,257; high-quality evidence). Zinc and vitamin A supplementation, each both compared to placebo, had no impact on any outcome examined with the exception of potentially improving serum/plasma zinc (mean difference (MD) 0.43 umol/L; 95% CI -0.04 to 0.89; studies = 5; participants = 1,202) and serum/plasma retinol (MD 0.13 umol/L; 95% CI -0.03 to 0.30; studies = 6; participants = 1,654), respectively. When compared to placebo, vitamin D supplementation may have reduced the risk of preterm births (average RR 0.64; 95% CI 0.40 to 1.04; studies = 7; participants = 1,262), though the upper CI just crosses the line of no effect. Similarly, calcium supplementation versus placebo may have improved rates of pre-eclampsia/eclampsia (average RR 0.45; 95% CI 0.19 to 1.06; studies = 4; participants = 9,616), though the upper CI just crosses 1.

Authors' Conclusions

The findings suggest that MMN and vitamin supplementation improve maternal and child health outcomes, including maternal anaemia, LBW, preterm birth, SGA, stillbirths, micronutrient deficiencies, and morbidities, including pre-eclampsia/eclampsia and diarrhea among children. MMN supplementation demonstrated a beneficial impact on the most number of outcomes. In addition, MMN with >4 micronutrients appeared to be more impactful than MMN with only 3 or 4 micronutrients included in the tablet. Very few studies conducted longitudinal analysis on longer-term health outcomes for the child, such as anthropometric measures and developmental outcomes; this may be an important area for future research. This review may provide some basis to guide continual discourse around replacing IFA supplementation with MMN along with the use of single micronutrient supplementation programs for specific outcomes.

Calcium supplementation during pregnancy for preventing hypertensive disorders and related problems

BACKGROUND

Pre-eclampsia and eclampsia are common causes of serious morbidity and death. Calcium supplementation may reduce the risk of pre-eclampsia, and may help to prevent preterm birth. This is an update of a review last published in 2014.

OBJECTIVES

To assess the effects of calcium supplementation during pregnancy on hypertensive disorders of pregnancy and related maternal and child outcomes.

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (18 September 2017), and reference lists of retrieved studies.

SELECTION CRITERIA

We included randomised controlled trials (RCTs), including cluster-randomised trials, comparing high-dose calcium supplementation (at least 1 g daily of calcium) during pregnancy with placebo. For low-dose calcium we included quasi-randomised trials, trials without placebo, trials with cointerventions and dose comparison trials.

DATA COLLECTION AND ANALYSIS

Two researchers independently assessed trials for inclusion and risk of bias, extracted data and checked them for accuracy. Two researchers assessed the evidence using the GRADE approach.

MAIN RESULTS

We included 27 studies (18,064 women). We assessed the included studies as being at low risk of bias, although bias was frequently difficult to assess due to poor reporting and inadequate information on methods.High-dose calcium supplementation (≥ 1 g/day) versus placeboFourteen studies examined this comparison, however one study contributed no data. The 13 studies contributed data from 15,730 women to our meta-analyses. The average risk of high blood pressure (BP) was reduced with calcium supplementation compared with placebo (12 trials, 15,470 women: risk ratio (RR) 0.65, 95% confidence interval (CI) 0.53 to 0.81; I² = 74%). There was also a reduction in the risk of pre-eclampsia associated with calcium supplementation (13 trials, 15,730 women: average RR 0.45, 95% CI 0.31 to 0.65; I² = 70%; low-quality evidence). This effect was clear for women with low calcium diets (eight trials, 10,678 women: average RR 0.36, 95% CI 0.20 to 0.65; I² = 76%) but not those with adequate calcium diets. The effect appeared to be greater for women at higher risk of pre-eclampsia, though this may be due to small-study effects (five trials, 587 women: average RR 0.22, 95% CI 0.12 to 0.42). These data should be interpreted with caution because of the possibility of small-study effects or publication bias. In the largest trial, the reduction in pre-eclampsia was modest (8%) and the CI included the possibility of no effect.The composite outcome maternal death or serious morbidity was reduced with calcium supplementation (four trials, 9732 women; RR 0.80, 95% CI 0.66 to 0.98). Maternal deaths were no different (one trial of 8312 women: one death in the calcium group versus six in the placebo group). There was an anomalous increase in the risk of HELLP syndrome in the calcium group (two trials, 12,901 women: RR 2.67, 95% CI 1.05 to 6.82, high-quality evidence), however, the absolute number of events was low (16 versus six).The average risk of preterm birth was reduced in the calcium supplementation group (11 trials, 15,275 women: RR 0.76, 95% CI 0.60 to 0.97; I² = 60%; low-quality evidence); this reduction was greatest amongst women at higher risk of developing pre-eclampsia (four trials, 568 women: average RR 0.45, 95% CI 0.24 to 0.83; I² = 60%). Again, these data should be interpreted with caution because of the possibility of small-study effects or publication bias. There was no clear effect on admission to neonatal intensive care. There was also no clear effect on the risk of stillbirth or infant death before discharge from hospital (11 trials, 15,665 babies: RR 0.90, 95% CI 0.74 to 1.09).One study showed a reduction in childhood systolic BP greater than 95th percentile among children exposed to calcium supplementation in utero (514 children: RR 0.59, 95% CI 0.39 to 0.91). In a subset of these children, dental caries at 12 years old was also reduced (195 children, RR 0.73, 95% CI 0.62 to 0.87).Low-dose calcium supplementation (< 1 g/day) versus placebo or no treatmentTwelve trials (2334 women) evaluated low-dose (usually 500 mg daily) supplementation with calcium alone (four trials) or in association with vitamin D (five trials), linoleic acid (two trials), or antioxidants (one trial). Most studies recruited women at high risk for pre-eclampsia, and were at high risk of bias, thus the results should be interpreted with caution. Supplementation with low doses of calcium reduced the risk of pre-eclampsia (nine trials, 2234 women: RR 0.38, 95% CI 0.28 to 0.52). There was also a reduction in high BP (five trials, 665 women: RR 0.53, 95% CI 0.38 to 0.74), admission to neonatal intensive care unit (one trial, 422 women, RR 0.44, 95% CI 0.20 to 0.99), but not preterm birth (six trials, 1290 women, average RR 0.83, 95% CI 0.34 to 2.03), or stillbirth or death before discharge (five trials, 1025 babies, RR 0.48, 95% CI 0.14 to 1.67).High-dose (=/> 1 g) versus low-dose (< 1 g) calcium supplementationWe included one trial with 262 women, the results of which should be interpreted with caution due to unclear risk of bias. Risk of pre-eclampsia appeared to be reduced in the high-dose group (RR 0.42, 95% CI 0.18 to 0.96). No other differences were found (preterm birth: RR 0.31, 95% CI 0.09 to 1.08; eclampsia: RR 0.32, 95% CI 0.07 to 1.53; stillbirth: RR 0.48, 95% CI 0.13 to 1.83).

AUTHORS' CONCLUSIONS

High-dose calcium supplementation (≥ 1 g/day) may reduce the risk of pre-eclampsia and preterm birth, particularly for women with low calcium diets (low-quality evidence). The treatment effect may be overestimated due to small-study effects or publication bias. It reduces the occurrence of the composite outcome 'maternal death or serious morbidity', but not stillbirth or neonatal high care admission. There was an increased risk of HELLP syndrome with calcium supplementation, which was small in absolute numbers.The limited evidence on low-dose calcium supplementation suggests a reduction in pre-eclampsia, hypertension and admission to neonatal high care, but needs to be confirmed by larger, high-quality trials.

Potential Hormone Mechanisms of Bariatric Surgery

PURPOSE OF REVIEW

In recent years, the role of the gastrointestinal (GI) tract in energy homeostasis through modulation of the digestion and absorption of carbohydrates and the production of incretin hormones is well recognized.

RECENT FINDINGS

Bariatric surgery for obesity has been a very effective method in substantially improving weight, and numerous studies have focused on intestinal adaptation after bariatric procedures. A number of structural and functional changes in the GI tract have been reported postsurgery, which could be responsible for the altered hormonal responses. Furthermore, the change in food absorption rate and the intestinal regions exposed to carbohydrates may affect blood glucose response. This review hopes to give new insights into the direct role of gut hormones, by summarising the metabolic effects of bariatric surgery.

The effect of bariatric surgery on gastrointestinal and pancreatic peptide hormones

Bariatric surgery for obesity has proved to be an extremely effective method of promoting long-term weight reduction with additional beneficial metabolic effects, such as improved glucose tolerance and remission of type 2 diabetes. A range of bariatric procedures are in common use, including gastric banding, sleeve gastrectomy and the Roux-en-Y gastric bypass. Although the mechanisms underlying the efficacy of bariatric surgery are unclear, gastrointestinal and pancreatic peptides are thought to play an important role. The aim of this review is to summarise the effects of different bariatric surgery procedures upon gastrointestinal and pancreatic peptides, including ghrelin, gastrin, cholecystokinin (CCK), glucose-dependent insulinotropic hormone (GIP), glucagon-like peptide 1 (GLP-1), peptide YY (PYY), oxyntomodulin, insulin, glucagon and somatostatin.

Calcium Plus Vitamin D Supplementation During the Third Trimester of Pregnancy in Adolescents Accustomed to Low Calcium Diets Does Not Affect Infant Bone Mass at Early Lactation in a Randomized Controlled Trial

BACKGROUND

Pregnancy and lactation in adolescents with low calcium intake may impair fetal growth and infant bone mass.

OBJECTIVE

We investigated the effects of calcium plus vitamin D supplementation during pregnancy in Brazilian adolescent mothers consuming low calcium diets (∼600 mg/d) on fetal biometry and infant bone mass, and the relation between infant and maternal bone mass during early lactation.

METHODS

Infants of mothers who received calcium (600 mg/d) plus cholecalciferol (200 IU/d) supplementation (n = 30) or placebo (n = 26) from 26 wk of gestation until parturition were studied. Fetal biometric measurements at 23 and 36 wk of gestation were obtained from medical records. Infant anthropometric and total body bone measurements [bone mineral content (BMC), bone area (BA), and bone mineral density (BMD)] at 5 wk postpartum were assessed by dual-energy X-ray absorptiometry. Maternal BMD z scores for total body, lumbar spine, total hip, and femoral neck at 5 wk postpartum were obtained. Group comparisons were adjusted for significant covariates.

RESULTS

Maternal mean serum 25-hydroxyvitamin D was 59 nmol/L at baseline in both groups. No differences in fetal measurements at 36 wk of gestation were observed between the groups, except for body weight and its increment from 23 to 36 wk, which were higher in the supplemented group (6.8%, P = 0.014 and 10.5%, P = 0.07, respectively). Infant BMC (61.1 ± 21.7 g), BA (167 ± 79 cm(2)), and BMD (0.385 ± 0.069 g/cm(2)) did not significantly differ between the groups. In the placebo group, infant BMC and BA were negatively correlated with maternal BMD z scores for total body (r = -0.40 and r = -0.47; P < 0.05) and hip (r = -0.41 and r = -0.46; P < 0.05). In contrast, no correlations were observed in the supplemented group.

CONCLUSIONS

Calcium and vitamin D supplementation of the adolescents studied resulted in higher fetal body weight at 36 wk of gestation and had no effect on infant bone mass at 5 wk postpartum. Because correlations between maternal and infant bone mass were evident only in the placebo group, infant bone mass appeared to be more dependent on maternal skeletal mass when calcium intake was low. This trial was registered at clinicaltrials.gov as NCT01732328.

Calcium supplementation (other than for preventing or treating hypertension) for improving pregnancy and infant outcomes

BACKGROUND

Maternal nutrition during pregnancy is known to have an effect on fetal growth and development. It is recommended that women increase their calcium intake during pregnancy and lactation, although the recommended dosage varies among professionals. Currently, there is no consensus on the role of routine calcium supplementation for pregnant women other than for preventing or treating hypertension.

OBJECTIVES

To determine the effect of calcium supplementation on maternal, fetal and neonatal outcomes (other than for preventing or treating hypertension) as well as any possible side effects.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (30th September 2014).

SELECTION CRITERIA

We considered all published, unpublished and ongoing randomised controlled trials (RCTs) comparing maternal, fetal and neonatal outcomes in pregnant women who received calcium supplementation versus placebo or no treatment. Cluster-RCTs were eligible for inclusion but none were identified. Quasi-RCTs and cross-over studies were not eligible for inclusion.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion and risk of bias, extracted data and checked them for accuracy.

MAIN RESULTS

Twenty-five studies met the inclusion criteria, but only 23 studies contributed data to the review. These 23 trials recruited 18,587 women, with 17,842 women included in final analyses. There were no statistically significant differences between women who received calcium supplementation and those who did not in terms of reducing preterm births less than 37 weeks' gestation (risk ratio (RR) 0.86, 95% confidence interval (CI) 0.70 to 1.05; 13 studies, 16,139 women; random-effects model) or less than 34 weeks' gestation (RR 1.04, 95% CI 0.80 to 1.36; four trials, 5669). Most studies were of low risk of bias. We conducted sensitivity analysis for the outcome of preterm birth less than 37 weeks by removing two trials with unclear risk of bias for allocation concealment; the results then favoured treatment with calcium supplementation (RR 0.80, 95% CI 0.65 to 0.99; 11 trials, 15,379 women). There was no significant difference in infant low birthweight between the two treatment groups (RR 0.93, 95% CI 0.81 to 1.07; six trials, 14,162 infants; random-effects model). However, when compared to the control group, women in the calcium supplementation group gave birth to slightly heavier birthweight infants (mean difference 56.40, 95% CI 13.55 to 99.25; 21 trials, 9202 women; random-effects model).Three outcomes were chosen for assessment with the GRADE software: preterm birth less than 37 weeks; preterm birth less than 34 weeks; and low birthweight less than 2500 g. Evidence for these outcomes was assessed as of moderate quality.

AUTHORS' CONCLUSIONS

This review indicates that there are no clear additional benefits to calcium supplementation in prevention of preterm birth or low infant birthweight. While there was a statistically significant difference of 56 g identified in mean infant birthweight, there was significant heterogeneity identified, and the clinical significance of this difference is uncertain.

Differential expression of calcium transport genes caused by COMT inhibition in the duodenum, kidney and placenta of pregnant mice

Preeclampsia is a pregnancy-specific disease characterized by concurrent development of hypertension, proteinuria, and oxidative stress in the placenta. Preeclampsia-like genetic models were also developed by modification of preeclampsia-related genes, such as catechol-O-methyltranferase (COMT). In this study, we induced COMT inhibition in mice during pregnancy in order to reproduce physiological conditions associated with preeclampsia. Expression of the gene known as hypoxia biomarker, HIF-1α, was highly induced in the placenta of this model. The over-expression of HIF-1α demonstrates that our experimental conditions were similar to those of preeclampsia. We measured the expression of several calcium transport genes (CTGs; TRPV5, TRPV6, PMCA1 and CaBP-9k) in the placenta, duodenum and kidney after COMT inhibition on gestation day 17.5 (GD 17.5). In addition, we evaluated the calcium transporters in the kidney, duodenum of non-pregnant female mice. Placental TRPV5, TRPV6 and PMCA1 expressions were down-regulated by COMT inhibitor (ro41-0960). In addition, the reduced PMCA1 expression in the placenta was reversed by calcium supplementation. Duodenal expressions of TRPV5, TRPV6, and PMCA1 were decreased in COMT-inhibited mice, and recovered slightly after calcium supplementation. Renal expression of TRPV5, TRPV6, and PMCA1 was also decreased by COMT inhibition, while it was reversed by calcium supplementation to the level of control. Duodenal- and renal calcium transporting genes, TRPV5, TPRV6, PMCA1 and CaBP-9k, were down-regulated by COMT treatment in female mice. Taken together, these results indicate that physiological changes observed in COMT inhibition were similar to symptoms of preeclampsia, which may be related to disturbance of calcium metabolism during pregnancy.

Calcium revisited: part II calcium supplements and their effects

Calcium supplements were tested in pregnancy and lactation, in childhood and adolescence, in pre- and postmenopausal women and in elderly persons with various effects on bone density and fracture incidence. They must be properly chosen and adequately used. In this case, the reported minor negative side-effects do not restrict their use. All these aspects are reviewed here.

Calcium supplementation during pregnancy for preventing hypertensive disorders and related problems

BACKGROUND

Pre-eclampsia and eclampsia are common causes of serious morbidity and death. Calcium supplementation may reduce the risk of pre-eclampsia, and may help to prevent preterm birth.

OBJECTIVES

To assess the effects of calcium supplementation during pregnancy on hypertensive disorders of pregnancy and related maternal and child outcomes.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (28 March 2013) and contacted study authors for more data where possible. We updated the search in May 2014 and added the results to the 'Awaiting Classification' section of the review.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing high-dose (at least 1 g daily of calcium) or low-dose calcium supplementation during pregnancy with placebo or no calcium.

DATA COLLECTION AND ANALYSIS

We assessed eligibility and trial quality, extracted and double-entered data.

MAIN RESULTS

High-dose calcium supplementation (≥1 g/day)We included 14 studies in the review, however one study contributed no data. We included 13 high-quality studies in our meta-analyses (15,730 women). The average risk of high blood pressure (BP) was reduced with calcium supplementation compared with placebo (12 trials, 15,470 women: risk ratio (RR) 0.65, 95% confidence interval (CI) 0.53 to 0.81; I² = 74%). There was also a significant reduction in the risk of pre-eclampsia associated with calcium supplementation (13 trials, 15,730 women: RR 0.45, 95% CI 0.31 to 0.65; I² = 70%). The effect was greatest for women with low calcium diets (eight trials, 10,678 women: average RR 0.36, 95% CI 0.20 to 0.65; I² = 76%) and women at high risk of pre-eclampsia (five trials, 587 women: average RR 0.22, 95% CI 0.12 to 0.42; I² = 0%). These data should be interpreted with caution because of the possibility of small-study effect or publication bias.The composite outcome maternal death or serious morbidity was reduced (four trials, 9732 women; RR 0.80, 95% CI 0.65 to 0.97; I² = 0%). Maternal deaths were not significantly different (one trial of 8312 women: calcium group one death versus placebo group six deaths). There was an anomalous increase in the risk of HELLP (haemolysis, elevated liver enzymes and low platelets) syndrome (two trials, 12,901 women: RR 2.67, 95% CI 1.05 to 6.82; I² = 0%) in the calcium group, however, the absolute number of events was low (16 versus six).The average risk of preterm birth was reduced in the calcium group (11 trials, 15,275 women: RR 0.76, 95% CI 0.60 to 0.97; I² = 60%) and amongst women at high risk of developing pre-eclampsia (four trials, 568 women: average RR 0.45, 95% CI 0.24 to 0.83; I² = 60%), but no significant reduction in neonatal high care admission. There was no overall effect on the risk of stillbirth or infant death before discharge from hospital (11 trials 15,665 babies: RR 0.90, 95% CI 0.74 to 1.09; I² = 0%).One study showed a reduction in childhood systolic BP greater than 95th percentile among children exposed to calcium supplementation in utero (514 children: RR 0.59, 95% CI 0.39 to 0.91). In a subset of these children, dental caries at 12 years old was also reduced (195 children, RR 0.73, 95% CI 0.62 to 0.87). Low-dose calcium supplementation (< 1 g/day)We included 10 trials (2234 women) that evaluated low-dose supplementation with calcium alone (4) or in association with vitamin D (3), linoleic acid (2), or antioxidants (1). Most studies recruited women at high risk for pre-eclampsia, and were at high risk of bias, thus the results should be interpreted with caution. Supplementation with low doses of calcium significantly reduced the risk of pre-eclampsia (RR 0.38, 95% CI 0.28 to 0.52; I² = 0%). There was also a reduction in hypertension, low birthweight and neonatal intensive care unit admission.

AUTHORS' CONCLUSIONS

Calcium supplementation (≥ 1 g/day) is associated with a significant reduction in the risk of pre-eclampsia, particularly for women with low calcium diets. The treatment effect may be overestimated due to small-study effects or publication bias. It also reduces preterm birth and the occurrence of the composite outcome 'maternal death or serious morbidity'. We considered these benefits to outweigh the increased risk of HELLP syndrome, which was small in absolute numbers. The World Health Organization recommends calcium 1.5 g to 2 g daily for pregnant women with low dietary calcium intake.The limited evidence on low-dose calcium supplementation suggests a reduction in pre-eclampsia, but needs to be confirmed by larger, high-quality trials. Pending such results, in settings of low dietary calcium where high-dose supplementation is not feasible, the option of lower-dose supplements (500 to 600 mg/day) might be considered in preference to no supplementation.

Calcium intake in health maintenance - a systematic review

Background

Calcium (Ca) is an essential nutrient for the human body. Despite lively research, there is uncertainty about Ca requirements in terms of desirable health outcomes including an upper intake level above which the potential for harm increases.

Objectives

The aim was to conduct a review to update requirements and desirable or harmful health effects of Ca on the current scientific evidence.

Methods

We searched Medline and Swemed from January 2000 to December 2011 and included all systematic reviews that reported Ca supplementation or usual Ca intake on health outcomes. Meta-analyses, randomized clinical trials and cohort studies were included in the second search between May 2009 and March 2011 and an additional search covering studies till the end of 2011. This review concentrated on studies reporting independent effects of Ca, although a few recent trials report sole effects of Ca on health outcomes, most trials use Ca in combination with vitamin D vs. placebo.

Results

In total, we reviewed 38 studies addressing the effects of Ca on bone, pregnancy-related outcomes, cancers, cardiovascular outcomes, obesity, and mortality. There was a lot of heterogeneity in the study protocols, which made it difficult to draw any strong conclusions. According to the literature, high Ca intake seems to have a small positive effect on bone mineral content (BMC) or bone mineral density (BMD) in children and postmenopausal women. We did not find any consistent evidence on the effects of Ca on bone health in premenopausal women or men. Also, the evidence that Ca supplementation reduces fracture incidence is scarce and inconsistent. Maternal diet may influence the peak bone mass of offspring but more studies are required. There was no overall effect of Ca intake on cancers. Ca was associated with a decreased risk of breast cancer and a slightly increased risk of prostate cancer in two of the three studies. No associations were found with other cancers. We found no consistent association between cardiovascular outcomes and Ca intake except for blood pressure. A small decrease of 2–4 mmHg in systolic blood pressure was found in pregnant and in hypertensive subjects with Ca supplementation. Reviewed studies did not show consistent evidence relating Ca intake to either mortality or obesity.

Conclusion

Based on this evidence, there is no need to change the Nordic recommendations for Ca intake. However, due to heterogeneity in the studies it is difficult to interpret the results and provide single summary statement.

Change of genes in calcium transport channels caused by hypoxic stress in the placenta, duodenum, and kidney of pregnant rats

Preeclampsia is a pregnancy-specific disease characterized by concurrent development of hypertension, proteinuria, and oxidative stress in the placenta. In this study, we induced hypoxic stress in rats during pregnancy to reproduce physiological conditions associated with preeclampsia. The maternal weight of hypoxic pregnant rats was lower than that of normoxic animals. The level of calcium ions were also increased in urine collected from the hypoxic animals. In contrast, urinary concentrations of sodium, chloride, and potassium ions declined in hypoxic rats, and developed to proteinuria. The expression of genes known as two biomarkers, sFLT1 (for preeclampsia) and HIF-1alpha (for hypoxia), were highly induced in the placenta, duodenum, and kidney by hypoxic stress. The overexpression of sFLT1 and HIF-1alpha demonstrated that our experimental conditions closely mimicked ones that are associated with preeclampsia. In the present study, we measured the expression of calcium transporters (TRPV5, TRPV6, PMCA1, NCKX3, NCX1, and CaBP-9k) in the placenta, duodenum, and kidney under hypoxic conditions on Gestational Day 19.5 in rats. Placental TRPV5, TRPV6, and PMCA1 expression was up-regulated in the hypoxic rats, whereas the levels of NCX1 and CaBP-9k were unchanged. In addition, NCKX3 expression was increased in the placenta of hypoxic rats. Duodenal expression of CaBP-9k, TRPV5, TRPV 6, and PMCA1 was decreased in the hypoxic rats, whereas levels of NCXs were not altered. Renal expression of NCKX3 and TRPV6 was increased, whereas NCX1 was decreased in the hypoxic rats compared to the normoxic controls. Taken together, these results indicate that physiological changes observed in the hypoxic rats were similar to ones associated with preeclampsia. Expression of calcium transport genes in the placenta, duodenum, and kidney perturbed by hypoxic stress during pregnancy may cause calcium loss in the urine, and thereby induce calcium-deficient characteristics of preeclampsia.

Role of calcium during pregnancy: maternal and fetal needs

Although the demand for additional calcium during pregnancy is recognized, the dietary reference intake for calcium was lowered for pregnant women in 1997 to amounts recommended for nonpregnant women (1,000 mg/day), and recently (November 2010) the Institute of Medicine report upheld the 1997 recommendation. It has been frequently reported that women of childbearing age do not consume the dietary reference intake for calcium and that calcium intake in the United States varies among ethnic groups. Women who chronically consume suboptimal amounts of calcium (<500 mg/day) may be at risk for increased bone loss during pregnancy. Women who begin pregnancy with adequate intake may not need additional calcium, but women with suboptimal intakes (<500 mg) may need additional amounts to meet both maternal and fetal bone requirements. The objective of this review is to elucidate the changes in calcium metabolism that occur during pregnancy as well as the effect of maternal calcium intake on both maternal and fetal outcomes.

Calcium supplementation (other than for preventing or treating hypertension) for improving pregnancy and infant outcomes

BACKGROUND

Maternal nutrition during pregnancy is known to have an effect on fetal growth and development. It is recommended that women increase their calcium intake during pregnancy and lactation, although the recommended dosage varies among professionals. Currently, there is no consensus on the role of routine calcium supplementation for pregnant women other than for preventing or treating hypertension.

OBJECTIVES

To determine the effect of calcium supplementation on maternal, fetal and neonatal outcomes (other than for preventing or treating hypertension) as well as any possible side effects.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (17 March 2011).

SELECTION CRITERIA

We considered all published, unpublished and ongoing randomised controlled trials (RCTs) comparing maternal, fetal and neonatal outcomes in pregnant women who received calcium supplementation versus placebo or no treatment. We excluded quasi- and pseudo-RCTs.

DATA COLLECTION AND ANALYSIS

Two review authors identified studies for inclusion and extracted the data. Two review authors performed data analysis.

MAIN RESULTS

This review includes data from 21 studies (involving 16,602 women). There were no statistically significant differences between women who received calcium supplementation and those who did not in terms of reducing preterm births (less than 37 weeks' gestation) (risk ratio (RR) 0.90; 95% confidence interval (CI) 0.73 to 1.11; 12 studies, 15615 women; random-effects model) and also in less than 34 weeks' gestation (RR 1.11; 95% CI 0.84 to 1.46; three trials, 5145 women). There was no significant difference in infant low birth weight between the two groups (RR 0.91; 95% CI 0.72 to 1.16; four trials, 13449 infants; random-effects). However, compared to the control group, women in the calcium supplementation group gave birth to slightly heavier birth weight infants (mean difference (MD) 64.66 g; 95% CI 15.75 to 113.58; 19 trials, 8287 women; random-effects).

AUTHORS' CONCLUSIONS

Calcium supplementation is associated with a significant protective benefit in the prevention of pre-eclampsia, and should be used for this indication according to a previous review. This review indicates that there are no additional benefits for calcium supplementation in prevention of preterm birth or low infant birth weight. While there was a statistically significant difference of 80 g identified in mean infant birth weight, there was significant heterogeneity identified, and the clinical significance of this difference is uncertain.

Association between calcium in cord blood and newborn size in Bangladesh

Ca status in the uterus during pregnancy has been suggested to affect fetal growth and size at birth. In Bangladesh, low Ca levels in pregnant women and low birth weight in infants are common. The present study explored the association between Ca levels in cord blood and newborn size at birth (birth weight and birth length) in Bangladesh. Samples and data included 223 women with live-born singleton deliveries in rural Bangladesh. Newborn weight and length were measured at birth. From cord blood obtained at delivery, Ca, 25-hydroxy vitamin D, bone-specific alkaline phosphatase and intact parathyroid hormone levels were determined. An association between size at birth and Ca levels in cord blood was found (birth weight, P = 0.022; birth length, P = 0.001). Associations between Ca and newborn size were further analysed using multivariate regression analyses. After adjusting for several covariates of characteristics in mothers and newborns (gestational weeks at birth, sex of newborn, socio-economic status, maternal height, BMI, age and season at birth), birth length still exhibited a significant relationship with Ca levels in cord blood (birth length, P = 0.030). The present study indicates that Ca status in cord blood might be associated with the birth length of newborns. Ca levels during gestation may affect fetal growth.

Calcium supplementation during pregnancy for preventing hypertensive disorders and related problems

BACKGROUND

Pre-eclampsia and eclampsia are common causes of serious morbidity and death. Calcium supplementation may reduce the risk of pre-eclampsia through a number of mechanisms, and may help to prevent preterm birth.

OBJECTIVES

To assess the effects of calcium supplementation during pregnancy on hypertensive disorders of pregnancy and related maternal and child outcomes.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (May 2010) and contacted study authors.

SELECTION CRITERIA

Randomised trials comparing at least 1 g daily of calcium during pregnancy with placebo.

DATA COLLECTION AND ANALYSIS

We assessed eligibility and trial quality, extracted and double-entered data.

MAIN RESULTS

We included 13 studies of good quality (involving 15,730 women). The average risk of high blood pressure was reduced with calcium supplementation rather than placebo (12 trials, 15,470 women: risk ratio (RR) 0.65, 95% confidence interval (CI) 0.53 to 0.81). There was also a reduction in the average risk of pre-eclampsia associated with calcium supplementation (13 trials, 15,730 women: RR 0.45, 95% CI 0.31 to 0.65). The effect was greatest for high-risk women (five trials, 587 women: RR 0.22, 95% CI 0.12 to 0.42), and those with low baseline calcium intake (eight trials, 10,678 women: RR 0.36, 95% CI 0.20 to 0.65).The average risk of preterm birth was reduced in the calcium group overall (11 trials, 15,275 women: RR 0.76, 95% CI 0.60 to 0.97) and amongst women at high risk of developing pre-eclampsia recruited to four small trials (568 women: RR 0.45, 95% CI 0.24 to 0.83).There was no overall effect on the risk of stillbirth or death before discharge from hospital (11 trials 15,665 babies; RR 0.90, 95% CI 0.74 to 1.09). The composite outcome maternal death or serious morbidity was reduced (four trials, 9732 women; RR 0.80, 95% CI 0.65 to 0.97). Most of the women in these trials were low risk and had a low calcium diet. Maternal deaths were reported in only one trial. One death occurred in the calcium group and six in the placebo group, a difference which was not statistically significant (RR 0.17, 95% CI 0.02 to 1.39).Blood pressure in childhood has been assessed in two studies, only one of which is currently included: childhood systolic blood pressure greater than 95th percentile was reduced (514 children: RR 0.59, 95% CI 0.39 to 0.91).

AUTHORS' CONCLUSIONS

Calcium supplementation appears to approximately halve the risk of pre-eclampsia, to reduce the risk of preterm birth and to reduce the rare occurrence of the composite outcome 'death or serious morbidity'. There were no other clear benefits, or harms.