Calcium Intake and Iron Status in Human Studies: A Systematic Review and Dose-Response Meta-Analysis of Randomized Trials and Crossover Studies

Iron Metabolism, Calcium, Magnesium and Trace Elements: A Review

Iron (Fe) is fundamental to life on earth. In the human body, it is both essential and harmful if above threshold. A similar balance applies to other elements: calcium (Ca), magnesium (Mg), and trace elements including copper (Cu), zinc (Zn), lead (Pb), cadmium (Cd), mercury (Hg), and nickel (Ni). These elements share some proteins involved in the absorption and transport of Fe. Cu and Cd can inhibit Fe absorption, while excess of Fe may antagonize Cu metabolism and reduce ceruloplasmin (Cp). Excessive Fe can hinder Zn absorption and transferrin (Trf) can bind to both Zn and Ni. Ca is able to inhibit the divalent metal transporter 1 (DMT1) in a dose-dependent manner to reduce Fe absorption and low Mg concentrations can exacerbate Fe deficiency. Pb competitively inhibits Fe distribution and elevated Cd absorption reduces Fe uptake. Exposure to Hg is associated with higher ferritin concentrations and Ni alters intracellular Fe metabolism. Fe removal by phlebotomy in hemochromatosis patients has shown to increase the levels of Cd and Pb and alter the concentrations of trace elements in some types of anemia. Yet, the effects of chronic exposure of most trace elements remain poorly understood.

Experiences, acceptability and barriers to calcium supplementation during pregnancy in Dar es Salaam, Tanzania

Calcium supplementation in pregnancy is recommended in contexts with low dietary calcium intake to reduce the risk of pre-eclampsia and its complications. The World Health Organisation suggested high-dose calcium supplementation (1500-2000 mg/day), divided into three doses and taken at different times from daily iron-folic supplements. We conducted a mixed methods evaluation study to assess experiences, acceptability and barriers to high-dose calcium supplementation from the perspectives of pregnant women and antenatal health care providers at two public health facilities in Dar es Salaam, Tanzania. Descriptive statistics and thematic analysis were used to characterise acceptability, barriers and overall experiences of using high-dose calcium supplementation. Pregnant women in the cohort were aged 19-41 years, with 32.4% being primiparous. The proportion of pregnant women who liked calcium supplements 'a lot' decreased from 50.2% at the first visit to 31.8% at the last antenatal follow-up visit. Adherence was 71.3% (interquartile range: 50.5%, 89.3%), with only 24.0% of the participants taking 90% or more of the required supplements. Although participants expressed positive attitudes towards using calcium supplements, they also voiced concerns about the large size, side effects, the potential to forget and the burden of taking calcium supplements three times per day. Antenatal health care providers also affirmed the high burden of taking calcium supplements in addition to iron-folic acid supplements. Participants expressed the acceptability of using calcium supplements during pregnancy, but adherence to three doses per day posed challenges to pregnant women. Reducing the number of calcium supplement doses per day may improve adherence.

High prevalence of anemia and overweight among women workers in three palm plantations in Indonesia: a cross sectional study

Anemia is a disorder of decreased erythrocyte mass. Indonesia is one of the countries with the highest (31.2%) prevalence of anemia among women of childbearing age in Southeast Asia in 2019. Women currently play a dual role, not only as housewives but also play a role in the public sector namely working outside the home. Women workers in the oil palm plantation sector generally experience health problems such as maternal mortality rate, malnutrition, poor pregnancy care and delivery services, and anemia. The purpose of this study was to uncover nutrition situation among women workers in the oil palm plantation sector at company X, Central Kalimantan Province, company Y, Riau Province and company Z, South Papua Province. The study design was cross-sectional which involved 105 respondents of women workers selected purposively in the study areas. Data were obtained from field measurement of hemoglobin, semi quantitative food frequency questionnaire and other questionnaire. This study found that almost half (45.7%) of respondent were anemic and around 48.6% were overweight. Around 20% were both anemic and overweight. Low iron intake, low vitamin C intake, high calcium intake, multiparity, and poor physical environment condition were all significantly related to higher risk of anemia. Various causes of anemia should be considered in intervention or supplementation program. A combination of nutrition and other health surveillance would be suggested not only to alleviate but also to prevent the problem.

Current iron therapy in the light of regulation, intestinal microbiome, and toxicity: are we prescribing too much iron?

Iron deficiency is a widespread global health concern with varying prevalence rates across different regions. In developing countries, scarcity of food and chronic infections contribute to iron deficiency, while in industrialized nations, reduced food intake and dietary preferences affect iron status. Other causes that can lead to iron deficiency are conditions and diseases that result in reduced intestinal iron absorption and blood loss. In addition, iron absorption and its bioavailability are influenced by the composition of the diet. Individuals with increased iron needs, including infants, adolescents, and athletes, are particularly vulnerable to deficiency. Severe iron deficiency can lead to anemia with performance intolerance or shortness of breath. In addition, even without anemia, iron deficiency leads to mental and physical fatigue, which points to the fundamental biological importance of iron, especially in mitochondrial function and the respiratory chain. Standard oral iron supplementation often results in gastrointestinal side effects and poor compliance. Low-dose iron therapy seems to be a valid and reasonable therapeutic option due to reduced hepatic hepcidin formation, facilitating efficient iron resorption, replenishment of iron storage, and causing significantly fewer side effects. Elevated iron levels influence gut microbiota composition, favoring pathogenic bacteria and potentially disrupting metabolic and immune functions. Protective bacteria, such as bifidobacteria and lactobacilli, are particularly susceptible to increased iron levels. Dysbiosis resulting from iron supplementation may contribute to gastrointestinal disorders, inflammatory bowel disease, and metabolic disturbances. Furthermore, gut microbiota alterations have been linked to mental health issues. Future iron therapy should consider low-dose supplementation to mitigate adverse effects and the impact on the gut microbiome. A comprehensive understanding of the interplay between iron intake, gut microbiota, and human health is crucial for optimizing therapeutic approaches and minimizing potential risks associated with iron supplementation.

A new effect of intravenous iron treatment in pregnancy: contraction in nonstress test and timing of labor

OBJECTIVE

The aim of this study was to elucidate the cause and results of contractions occurring in term pregnant women receiving intravenous iron therapy.

METHODS

During 2019-2020, 136 pregnant women beyond 35 weeks of gestation, who received intravenous iron treatment due to iron deficiency anemia, were included through retrospective screening. Iron deficiency anemia was defined as having hemoglobin levels <10 g/dL and ferritin levels <15 ng/mL, and the pregnant women underwent nonstress test before and after treatment.

RESULTS

The average treatment week for the pregnant women was 36.82±0.74, and the presence of regular contractions in post-treatment follow-up nonstress tests was 72.1% (n=98). The average week of birth was 38.48±1.60. Pregnant women with contractions who had previous cesarean were found to have a mean delivery week of 36.82±0.67, which was statistically significant earlier than for nulliparous and multiparous women (p<0.001).

CONCLUSION

In pregnant women with iron deficiency anemia who were beyond 35 weeks, temporary regular contractions may be observed in the nonstress test following intravenous iron replacement. We think that this effect may lead to early term birth in pregnant women with a history of cesarean section. It needs to be confirmed by further prospective studies and animal studies.

Acid-suppressive drugs: A systematic review and network meta-analysis of their nocturnal acid-inhibitory effect

BACKGROUND AND AIMS

Acid-suppressive drugs (ASDs) are widely used in many gastric acid-associated diseases. Nocturnal acid breakthrough has been a common problem of many ASDs, such as proton-pump inhibitors (PPIs) and H2 -receptor antagonists (H2RAs). Potassium-competitive acid blockers (P-CABs) are expected to solve this continuing conundrum. This article examined major ASDs and compared them with placebo in terms of nocturnal acid-inhibitory effects, using a network meta-analysis of randomized controlled trials (RCTs).

METHODS

To compare the effectiveness of major ASDs, a Bayesian network meta-analysis (NMA) was applied to process data extracted from RCTs. The plausible ranking for each regimen and some subgroups were assessed by surface under the cumulative ranking curves (SUCRA).

RESULTS

Fifty-five RCTs were conducted with 2015 participants. In terms of nocturnal acid-inhibitory effects, the overall results showed that tegoprazan (SUCRA 91.8%) and vonoprazan (SUCRA 91.0%) had the best performance, followed by new PPIs (including tenatoprazole and ilaprazole) (SUCRA 76.6%), additional H2RAs once at bedtime (AHB) (SUCRA 61.3%), isomer PPIs (including esomeprazole and dexlansoprazole) (SUCRA 38.6%), revaprazan (SUCRA 34.7%), traditional PPIs (including omeprazole, rabeprazole, pantoprazole, lansoprazole) (SUCRA 32.6%), H2RAs (SUCRA 23.1%), and placebo (SUCRA 0.3%). In some subgroups, the nocturnal acid-inhibitory effect of vonoprazan or tegoprazan was better than most of the other regimens, even new PPIs and AHB.

CONCLUSIONS

This is the first study to compare the effect of ASDs on inhibiting nocturnal acid breakthrough. Overall, in terms of nocturnal acid-inhibitory effect, vonoprazan and tegoprazan had an advantage against other regimens including H2RAs, isomer PPIs, traditional PPIs, AHB, and new PPIs. Even in some subgroups, such as language classification (English), types of study design (crossover-RCT), age (≤40 years), BMI (18.5-24.9 kg/m2 ), continent (Asia and North America), disease status (health), the duration of therapy (2 weeks), and time of administration (at daytime or at night-time), the nocturnal acid-inhibitory effect of vonoprazan or tegoprazan were better than most regimens, even AHB and new PPIs.

Factors affecting iron absorption and the role of fortification in enhancing iron levels

Iron is an important micronutrient required for a number of biological processes including oxygen transport, cellular respiration, the synthesis of nucleic acids and the activity of key enzymes. The World Health Organization has recognised iron deficiency as the most common nutritional deficiency globally and as a major determinant of anaemia. Iron deficiency anaemia affects 40% of all children between the ages of 6 and 59 months, 37% of mothers who are pregnant and 30% of women between the ages of 15 and 49 years worldwide. Dietary iron exists in two main forms known as haem iron and non-haem iron. Haem iron is obtained from animal sources such as meat and shows higher bioavailability than non-haem iron, which can be obtained from both plant and animal sources. Different components in food can enhance or inhibit iron absorption from the diet. Components such as meat proteins and organic acids increase iron absorption, while phytate, calcium and polyphenols reduce iron absorption. Iron levels in the body are tightly regulated since both iron overload and iron deficiency can exert harmful effects on human health. Iron is stored mainly as haemoglobin and as iron bound to proteins such as ferritin and hemosiderin. Iron deficiency affects individuals at increased risk due to factors such as age, pregnancy, menstruation and various diseases. Different solutions for iron deficiency are applied at individual and community levels. Iron supplements and intravenous iron can be used to treat individuals with iron deficiency, while various types of iron-fortified foods and biofortified crops can be employed for larger communities. Foods such as rice, flour and biscuits have been used to prepare fortified iron products. However, it is important to ensure the fortification process does not exert significant negative effects on organoleptic properties and the shelf life of the food product.

Calcium-Deficit Diet Improves Iron Content in Ovariectomized Rats

In women, menopause is associated with disorders related to calcium and iron content, which may increase the risk of osteoporosis. This study aimed to determine the effect of calcium deficiency on the iron content in ovariectomized rats. This study included 30 3-month-old female rats, which were divided into three groups: group C (n = 10)-control group fed the standard diet; group O-ovariectomized rats fed the standard diet; and group D-ovariectomized rats fed the calcium-deficit diet. After 3 months of experimental intervention, the weight of the rats was measured, and blood and tissue samples were collected. Morphological parameters were analyzed in whole blood, and serum levels of leptin, estrogen and C-reactive protein, and total antioxidant status were determined. The iron content was measured in tissues, and histological analysis was performed in the femur. The results obtained demonstrated that ovariectomy significantly decreased the iron content in bones, hair, spleen, liver, and kidneys. The calcium-deficit diet increased the iron content in tissues and the hemoglobin level in ovariectomized rats and also enhanced the number of osteoblasts in bones compared with the O group. In conclusion, calcium deficiency improved the iron content in ovariectomized rats in this 12-week study.

Dietary Iron Intake and HIV-Related Outcomes Among Adults Initiating Antiretroviral Therapy in Tanzania

OBJECTIVE

Anemia is highly prevalent among people living with HIV (PLWHIV) and is often due to iron deficiency. This study evaluated the relationship of dietary iron intake levels and sources with mortality and clinical outcomes among adults initiating HAART.

DESIGN

We conducted a secondary analysis of a multivitamin supplementation trial among 2293 PLWHIV initiating HAART in Dar es Salaam, Tanzania.

METHODS

Dietary iron intake was assessed with a food frequency questionnaire at HAART initiation, and participants followed until death or censoring. Total, animal-, and plant-sourced iron were categorized into quartiles. Intake of food groups was categorized into 0-1, 2-3, and ≥4 servings/wk. Cox proportional hazards models estimated hazard ratios for mortality and incident clinical outcomes.

RESULTS

There were 175 deaths (8%). Red meat intake was associated with a lower risk of all-cause mortality (HR: 0.54; 95% CI: 0.35 to 0.83), AIDS-related mortality (HR: 0.49; 95% CI: 0.28 to 0.85), and severe anemia (HR: 0.57; 95% CI: 0.35 to 0.91), when intake ≥4 servings/wk, compared with 0-1 servings/wk. Legume intake was a lower risk of associated with all-cause mortality (HR: 0.49; 95% CI: 0.31 to 0.77) and AIDS-related mortality (HR: 0.37; 95% CI: 0.23 to 0.61), when intake ≥4 servings/wk, compared with 0-1 servings/wk. Although total dietary iron and overall plant-sourced iron intake were not associated with the risk of mortality or HIV-related outcomes, the highest quartile of animal-sourced iron intake was associated with a lower risk of all-cause mortality (HR: 0.56; 95% CI: 0.35 to 0.90) and a lower risk of AIDS-related mortality (HR: 0.50; 95% CI: 0.30 to 0.90), compared with the lowest quartile.

CONCLUSION

Intake of iron-rich food groups may be associated with a lower risk of mortality and critical HIV-related outcomes among adults initiating HAART.

TRIAL REGISTRATION

The parent trial was registered at Clinicaltrials.gov . Identifier: NCT00383669.

Including calcium-fortified water or flour in modeled diets based on local foods could improve calcium intake for women, adolescent girls, and young children in Bangladesh, Uganda, and Guatemala

Adequate calcium intake is essential for health, especially for infants, children, adolescents, and women, yet is difficult to achieve with local foods in many low- and middle-income countries. Previous analysis found it was not always possible to identify food-based recommendations (FBRs) that reached the calcium population recommended intake (PRI) for these groups in Bangladesh, Guatemala, and Uganda. We have modeled the potential contribution of calcium-fortified drinking water or wheat flour to FBR sets, to fill the remaining intake gaps. Optimized diets containing fortified products, with calcium-rich local foods, achieved the calcium PRI for all target groups. Combining fortified water or flour with FBRs met dietary intake targets for adolescent girls in all geographies and allowed a reduction from 3-4 to the more feasible 1-2 FBRs. Water with a calcium concentration of 100 mg/L with FBRs was sufficient to meet calcium targets in Uganda, but higher concentrations (400-500 mg/L) were mostly required in Guatemala and Bangladesh. Combining calcium-fortified wheat flour at 400 mg/100 g of flour and the FBR for small fish resulted in diets meeting the calcium PRI in Bangladesh. Calcium-fortified water or flour could improve calcium intake for vulnerable populations, especially when combined with FBRs based on locally available foods.

Dietary intake and socio-economic predictors of inadequate energy and nutrient intake among women of childbearing age in Karamoja sub-region of Uganda

BACKGROUND

Karamoja sub-region is the most food insecure part of Eastern Africa. The poor status of food security in the sub-region is reflected in the high rate of undernutrition among women of childbearing age (WCBA) and children under 5 years (CUFY). The sub-region is unique in Uganda in terms of cultural diversity, agro-ecology and rainfall pattern and agricultural practices. However, the influence of these unique characteristics on dietary intake of WCBA in the sub-region is less understood. Therefore, this study examined dietary intake and socio-economic predictors of inadequate energy and nutrient intake among WCBA in Karamoja sub-region.

METHODS

A longitudinal study design was used involving 755 WCBA in the harvesting season where 635 were followed-up in the planting season. Data were collected using 24-h recall, dietary diversity and socio-economic and demographic questionnaires.

RESULTS

Intake of energy and nutrients were generally significantly higher (p < 0.05) during the planting season than in the harvesting season. Irrespective of the district, physiological status and season, household consumption of plant-based foods was far higher than intake of animal-based foods dominated by starchy stables (76-100%), dark green leafy vegetables (70-100%) and legumes, nuts and seeds (22-97%) depending on the district. Majority of the respondents had two meals (breakfast: 65-100%; supper: 90-100%) with up to 45% of WCBA who consumed alcohol across meal times. .Overall on average, 57.7, 66.6, 78.5, 60.3, 67.7 and 93.7% of WCBA did not meet the recommended daily allowance (RDA) for energy, protein, calcium, iron, zinc and folic acid, respectively. Binary logistic regression revealed that inadequate intake of energy and nutrients significantly increased (p < 0.05) with the status of being lactating/breastfeeding and was influenced by age of WCBA, number of women married, education level and occupation of the household head depending on season.

CONCLUSIONS

This study demonstrated that dietary intake of WCBA in Karamoja sub-region was inadequate. Age of WCBA, number of women married, education level and occupation of the household head and spouse and being a lactating/breastfeeding mother were the key socio-economic and demographic factors that influenced inadequate intake of energy and nutrients among WCBA.

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.

Vegan nutrition: a preliminary guide for health professionals

Since the beginning of the 21st century, interest in vegan diets has been rapidly increasing in most countries. Misconceptions about vegan diets are widespread among the general population and health professionals. Vegan diets can be health-promoting and may offer certain important advantages compared to typical Western (and other mainstream) eating patterns. However, adequate dietary sources/supplements of nutrients of focus specific to vegan diets should be identified and communicated. Without supplements/fortified foods, severe vitamin B12 deficiency may occur. Other potential nutrients of focus are calcium, vitamin D, iodine, omega-3 fatty acids, iron, zinc, selenium, vitamin A, and protein. Ensuring adequate nutrient status is particularly important during pregnancy, lactation, infancy, and childhood. Health professionals are often expected to be able to provide advice on the topic of vegan nutrition, but a precise and practical vegan nutrition guide for health professionals is lacking. Consequently, it is important and urgent to provide such a set of dietary recommendations. It is the aim of this article to provide vegan nutrition guidelines, based on current evidence, which can easily be communicated to vegan patients/clients, with the goal of ensuring adequate nutrient status in vegans.

Screening, Treatment, and Monitoring of Iron Deficiency Anemia in Pregnancy and Postpartum

Iron deficiency anemia is the most prevalent form of anemia worldwide. In the United States, clinicians routinely screen for iron deficiency anemia upon initiation of prenatal care, at the start of the third trimester, and prior to birth. Treatment of iron deficiency anemia generally begins with oral supplementation of elemental iron, which is associated with adverse gastrointestinal effects. These adverse effects can decrease adherence, leading to subtherapeutic treatment. Newer evidence highlights the benefits of early screening for iron deficiency before the onset of anemia, as well as the use of intravenous iron to expedite the treatment of iron deficiency anemia. More research is needed on the potential consequences of over-supplementation and iron deficiency without anemia to guide treatment. This article reviews the evidence for best practices for screening, treatment, and continued monitoring of iron deficiency anemia during pregnancy and postpartum. Maternal, fetal, and neonatal implications are reviewed, as well as the risks and benefits of treatment options. Finally, an evidence-based algorithm is proposed to guide clinicians on continued monitoring after treatment.

Calcium supplementation for the prevention of hypertensive disorders of pregnancy: current evidence and programmatic considerations

Most low- and middle-income countries present suboptimal intakes of calcium during pregnancy and high rates of mortality due to maternal hypertensive disorders. Calcium supplementation during pregnancy is known to reduce the risk of these disorders and associated complications, including preeclampsia, maternal morbidity, and preterm birth, and is, therefore, a recommended intervention for pregnant women in populations with low dietary calcium intake (e.g., where ≥25% of individuals in the population have intakes less than 800 mg calcium/day). However, this intervention is not widely implemented in part due to cost and logistical issues related to the large dose and burdensome dosing schedule (three to four 500-mg doses/day). WHO recommends 1.5-2 g/day but limited evidence suggests that less than 1 g/day may be sufficient and ongoing trials with low-dose calcium supplementation (500 mg/day) may point a path toward simplifying supplementation regimens. Calcium carbonate is likely to be the most cost-effective choice, and it is not necessary to counsel women to take calcium supplements separately from iron-containing supplements. In populations at highest risk for preeclampsia, a combination of calcium supplementation and food-based approaches, such as food fortification with calcium, may be required to improve calcium intakes before pregnancy and in early gestation.

Interventions to improve calcium intake through foods in populations with low intake

Calcium intake remains inadequate in many low- and middle-income countries, especially in Africa and South Asia, where average intakes can be below 400 mg/day. Given the vital role of calcium in bone health, metabolism, and cell signaling, countries with low calcium intake may want to consider food-based approaches to improve calcium consumption and bioavailability within their population. This is especially true for those with low calcium intake who would benefit the most, including pregnant women (by reducing the risk of preeclampsia) and children (by reducing calcium-deficiency rickets). Specifically, some animal-source foods that are naturally high in bioavailable calcium and plant foods that can contribute to calcium intake could be promoted either through policies or educational materials. Some food processing techniques can improve the calcium content in food or increase calcium bioavailability. Staple-food fortification with calcium can also be a cost-effective method to increase intake with minimal behavior change required. Lastly, biofortification is currently being investigated to improve calcium content, either through genetic screening and breeding of high-calcium varieties or through the application of calcium-rich fertilizers. These mechanisms can be used alone or in combination based on the local context to improve calcium intake within a population.