The effect of calcium supplementation on blood pressure in non-pregnant women with previous pre-eclampsia: A randomized placebo-controlled study

Effectiveness of calcium supplementation in the prevention of gestational hypertension: A systematic review and meta-analysis of randomised controlled trials

BACKGROUND

Gestational hypertension and related disorders, such as preeclampsia, pose significant risks to maternal and foetal health. Calcium supplementation has been proposed as a preventive measure, but its effectiveness remains debated. This review assess the impact of calcium supplementation in prevention of gestational hypertension.

METHODS

A comprehensive literature search was conducted across multiple databases, including Scopus, EMBASE, PubMed, Web of Science, CINAHL, Cochrane CENTRAL, from inception to July 2024. Eligibility criteria included studies involving pregnant women at risk of gestational hypertension, comparing calcium supplementation to control group, and reporting on outcomes such as preeclampsia, pregnancy-induced hypertension, HELLP syndrome, preterm birth, and maternal mortality. Data were analysed using a random-effects inverse-variance model to calculate pooled risk ratios (RRs) and assess heterogeneity using Cochran's Q and I2 statistics. Publication bias was evaluated using funnel plots and Egger's test.

RESULTS

22 studies with 39,270 individuals were included. Most studies had higher risk of bias. Calcium supplementation significantly reduced the risk of preeclampsia (pooled RR = 0.606, 95 %CI: 0.483-0.761, p < 0.001) and pregnancy-induced hypertension (pooled RR = 0.870, 95 %CI: 0.759-0.996, p = 0.044). However, it showed no significant effect on HELLP syndrome, preterm birth, or mortality. Heterogeneity was moderate to substantial across outcomes, and publication bias was detected for preterm birth and pregnancy-induced hypertension.

CONCLUSION

Calcium supplementation during pregnancy significantly reduces the risk of preeclampsia and pregnancy-induced hypertension, highlighting its value as a cost-effective intervention for improving maternal health. These findings support integrating calcium supplementation into prenatal care strategies, particularly for populations with low dietary calcium intake.

Serum Calcium and Magnesium Levels in Women Presenting with Pre-eclampsia: A Systematic Review and Meta-analysis Based on Observational Studies

BACKGROUND

Multiple studies have investigated the serum concentrations of calcium (Ca) and magnesium (Mg) in preeclampsia, but the results have been contradictory. The objective of this systematic review and meta-analysis was to examine the association between serum calcium and magnesium levels in patients with preeclampsia and those in the healthy pregnancies.

MATERIALS AND METHODS

A comprehensive search was conducted in various online databases, including PubMed/Medline, Scopus, Embase, Web of Sciences, and Cochrane library to identify relevant studies on Ca and Mg levels in preeclampsia up to July 2023. Inter-study heterogeneity across the included studies was assessed using the chi-square test and I2 statistic. Pooled effect size (ES) was calculated as weighted mean differences (WMDs) with corresponding 95% confidence intervals (CI).

RESULTS

A total of 76 articles (comprising 92 studies) were included, with a combined sample size of 10,482 participants (preeclampsia: n=3,991; controls: n=6,491). The random-effects model revealed significantly lower levels of calcium (WMD=-0.807 mg/dL, 95% CI: -0.983, -0.632, P0.01) and magnesium (WMD=-0.215, 95% CI: -0.338, -0.092, P0.01) in women with pre-eclampsia compared to the control group. However, the overall pooled WMD for calcium and magnesium levels did not significantly change when individual studies were excluded one by one.

CONCLUSION

This meta-analysis demonstrates that the circulating levels of calcium and magnesium in patients with preeclampsia are significantly lower than those in the control group.

Clinical efficacy of low-dose aspirin combined with calcium in preventing preeclampsia: A systematic review and meta-analysis

OBJECTIVE

This systematic review and meta-analysis aimed to evaluate the clinical effectiveness of low-dose aspirin combined with calcium supplements for the prevention of preeclampsia.

METHODS

China National Knowledge Infrastructure, VIP, Wanfang, PubMed, EMBASE, and Cochrane Library databases were searched from inception until December 2022. Randomized controlled trials investigating the preventive use of aspirin in combination with calcium supplementation for preeclampsia in high-risk pregnant women were included. The quality of the literature was evaluated, and a meta-analysis was conducted using RevMan 5.3 software to analyze the clinical efficacy of low-dose aspirin combined with calcium supplementation in preventing preeclampsia.

RESULTS

Seven randomized controlled trials were included in this meta-analysis, and compared with the control group, the experimental group had lower incidence rates of preeclampsia with gestational hypertension (odds ratios [OR]: 0.17, 95% confidence interval [CI]: 0.11-0.28), preeclampsia (OR: 0.20, 95% CI: 0.10-0.37), gestational hypertension (OR: 0.15, 95% CI: 0.07-0.31), preterm birth (OR: 0.26, 95% CI: 0.16-0.44), postpartum hemorrhage (OR: 0.15, 95% CI: 0.08-0.27), and fetal growth restriction (OR: 0.16, 95% CI: 0.08-0.33).

CONCLUSION

Compared with aspirin alone, low-dose aspirin combined with calcium supplementation was more effective in preventing preeclampsia, reduced the risk of preterm birth and postpartum hemorrhage, and promoted fetal growth. This intervention has clinical value and should be considered for high-risk pregnant women.

Differential influences of serum vitamin C on blood pressure based on age and sex in normotensive individuals

Aim

Hypertension is among the most prevalent chronic diseases with diverse etiology, affecting over 1 billion people globally. In numerous studies, vitamin C inversely correlated with blood pressure and was suspected to have antihypertensive properties. Currently, there is conflicting evidence regarding the relationship between vitamin C and blood pressure, with most studies being conducted on hypertensive subjects. The principal objective of this project was to investigate the relationship between vitamin C and blood pressure in normotensive adult subjects.

Methods

A total of 2,533 individuals aged 20 years and above were enrolled in the present study from the National Health and Nutrition Examination Survey (NHANES) 2017-2018. Outcome variables were systolic blood pressure (SBP) and diastolic blood pressure (DBP). Serum vitamin C was regarded as an independent variable. EmpowerStats software and R (version 3.4.3) were used to examine the association between vitamin C and SBP or DBP.

Results

Vitamin C was reversely correlated with both SBP (β = −0.02, 95% CI: −0.03 to −0.00, p = 0.0306) and DBP (β = −0.02, 95% CI: −0.04 to −0.01, p = &lt;0.0011) after adjusting all covariates. This reverse relationship may be affected by a number of factors, including a person’s gender, age, race, and ethnicity. A U-shaped association between vitamin C and SBP in females and an inverted one between vitamin C and DBP in males were detected, respectively. We further calculated the inflection points at 90.3 μmol/L for females and 40 μmol/L for males. It is somewhat surprising that a reverse U-shaped distribution between vitamin C and SBP and DBP in people over 50 was detected, and the point of inflection of vitamin C were all located at 40 μmol/L.

Conclusion

Vitamin C was negatively correlated with both SBP and DBP in this cross-sectional analysis. However, a U-shaped relationship and an inverted one were also observed in certain people, which implied that, though vitamin C is considered a vital antioxidant, maintaining vitamin C at appropriate levels may be beneficial according to different populations.

Calcium for pre-eclampsia prevention: A systematic review and network meta-analysis to guide personalised antenatal care

BACKGROUND

Calcium supplementation reduces the risk of pre-eclampsia, but questions remain about the dosage to prescribe and who would benefit most.

OBJECTIVES

To evaluate the effectiveness of high (≥1 g/day) and low (<1 g/day) calcium dosing for pre-eclampsia prevention, according to baseline dietary calcium, pre-eclampsia risk and co-interventions, and intervention timing.

SEARCH STRATEGY

CENTRAL, PubMed, Global Index Medicus and CINAHL, from inception to 2 February 2021, clinical trial registries, reference lists and expert input (CRD42018111239).

SELECTION CRITERIA

Randomised controlled trials of calcium supplementation for pre-eclampsia prevention, for women before or during pregnancy. Network meta-analysis (NMA) also included trials of different calcium doses.

DATA COLLECTION AND ANALYSIS

Two independent reviewers extracted published data. The meta-analysis employed random-effects models and the NMA, a Bayesian random-effects model, to obtain direct and indirect effect estimates.

MAIN RESULTS

The meta-analysis included 30 trials (N = 20 445 women), and the NMA to evaluate calcium dosage included 25 trials (N = 15 038). Calcium supplementation prevented pre-eclampsia similarly with a high dose (RR 0.49, 95% CI 0.36-0.66) or a low dose (RR 0.49, 95% CI 0.36-0.65). By NMA, high-dose (vs low-dose) calcium did not differ in effect (RR 0.79, 95% CI 0.43-1.40). Calcium was similarly effective regardless of baseline pre-eclampsia risk, vitamin D co-administration or timing of calcium initiation, but calcium was ineffective among women with adequate average baseline calcium intake.

CONCLUSIONS

Low- and high-dose calcium supplementation are effective for pre-eclampsia prevention in women with low calcium intake. This has implications for population-level implementation where dietary calcium is low, and targeted implementation where average intake is adequate.

TWEETABLE ABSTRACT

A network meta-analysis of 25 trials found that low-dose calcium supplementation (<1 g/day) is as effective as high-dose calcium supplementation (≥1 g/day) in halving the risk of pre-eclampsia when baseline calcium intake is low.

Dietary factors that affect the risk of pre-eclampsia

Pre-eclampsia affects 3%-5% of pregnant women worldwide and is associated with a range of adverse maternal and fetal outcomes, including maternal and/or fetal death. It particularly affects those with chronic hypertension, pregestational diabetes mellitus or a family history of pre-eclampsia. Other than early delivery of the fetus, there is no cure for pre-eclampsia. Since diet or dietary supplements may affect the risk, we have carried out an up-to-date, narrative literature review to assess the relationship between nutrition and pre-eclampsia. Several nutrients and dietary factors previously believed to be implicated in the risk of pre-eclampsia have now been shown to have no effect on risk; these include vitamins C and E, magnesium, salt, ω-3 long-chain polyunsaturated fatty acids (fish oils) and zinc. Body mass index is proportionally correlated with pre-eclampsia risk, therefore women should aim for a healthy pre-pregnancy body weight and avoid excessive gestational and interpregnancy weight gain. The association between the risk and progression of the pathophysiology of pre-eclampsia may explain the apparent benefit of dietary modifications resulting from increased consumption of fruits and vegetables (≥400 g/day), plant-based foods and vegetable oils and a limited intake of foods high in fat, sugar and salt. Consuming a high-fibre diet (25-30 g/day) may attenuate dyslipidaemia and reduce blood pressure and inflammation. Other key nutrients that may mitigate the risk include increased calcium intake, a daily multivitamin/mineral supplement and an adequate vitamin D status. For those with a low selenium intake (such as those living in Europe), fish/seafood intake could be increased to improve selenium intake or selenium could be supplemented in the recommended multivitamin/mineral supplement. Milk-based probiotics have also been found to be beneficial in pregnant women at risk. Our recommendations are summarised in a table of guidance for women at particular risk of developing pre-eclampsia.

Evaluation of serum calcium differences in hypertensive crises and control patients: A randomly matched case-control study

The role of calcium in blood pressure has been widely studied among hypertensive patients; however, no study has explored the role of calcium in hypertensive crises. The primary objective of this study is to evaluate the differences in serum calcium levels between hypertensive crises patients and a 1:1 random matched controls (age‐, sex‐, race‐, diabetes, and body mass index matched). This study is a single‐center, retrospective, chart review, case‐control study of patients with hypertensive crises (case group) and patients without hypertensive crises (control group). Patients were included in the case group if they were 18 years of age or older with hypertensive crises and have a documented calcium level. The control group patients were required to be 18 years of age or older, have a documented calcium level, and have no diagnosis of hypertensive crises. The primary outcome of the study was to compare the mean serum calcium in patients with hypertensive crises vs patients without hypertensive crises. Five hundred and sixty‐six patients were included in the study: 283 patients in both the case group and control group. The primary outcome results showed that serum calcium concentration was not significantly different between the case group (8.99 ± 0.78 mg/dL) and control group (8.96 ± 0.75 mg/dL) (P = .606). This study found no significant difference in serum calcium levels in patients with hypertensive crises compared to a random matched control group. Larger observational or experimental studies may be useful to evaluate the effect of calcium on blood pressure in hypertensive crises.