Kinetics of iron absorption from ferrous fumarate with and without galacto-oligosaccharides determined from stable isotope appearance curves in women

A review of the effect of iron supplementation on the gut microbiota of children in developing countries and the impact of prebiotics

Iron is essential for many physiological functions of the body, and it is required for normal growth and development. Iron deficiency (ID) is the most common form of micronutrient malnutrition and is particularly prevalent in infants and young children in developing countries. Iron supplementation is considered the most effective strategy to combat the risk of ID and ID anaemia (IDA) in infants, although iron supplements cause a range of deleterious gut-related problems in malnourished children. The purpose of this review is to assess the available evidence on the effect of iron supplementation on the gut microbiota during childhood ID and to further assess whether prebiotics offer any benefits for iron supplementation. Prebiotics are well known to improve gut-microbial health in children, and recent reports indicate that prebiotics can mitigate the adverse gut-related effects of iron supplementation in children with ID and IDA. Thus, provision of prebiotics alongside iron supplements has the potential for an enhanced strategy for combatting ID and IDA among children in the developing world. However, further understanding is required before the benefit of such combined treatments of ID in nutritionally deprived children across populations can be fully confirmed. Such enhanced understanding is of high relevance in resource-poor countries where ID, poor sanitation and hygiene, alongside inadequate access to good drinking water and poor health systems, are serious public health concerns.

Effect of probiotic and prebiotics supplementation on hemoglobin levels and iron absorption among women of reproductive age and children: a systematic review and meta-analysis

BACKGROUND

This review aims to assess the effect of oral administration of probiotics and/or prebiotics in children and women of reproductive age (WRA) to improve intestinal iron absorption, hemoglobin, and ferritin levels.

METHODS

Randomized controlled trials from published literature on probiotics and or prebiotics for prevention or treatment of anemia as a supplement or fortification in children or WRA till Jan 31, 2023, were included. Studies on probiotics and prebiotics in patients with anemia due to other causes were excluded. Screening and data extraction was done using Distiller SR and meta-analysis was performed using Revman 5.4.1.

RESULTS

A total of 1925 records were identified from Pubmed, Embase, and Cochrane, of which 29 were included in the systematic review (14 supplementation and 15 fortification studies; 15 studies in children and 14 studies in WRA). The major interventions included galacto-oligosaccharide, inulin, heat-killed H61, Lactobacillus plantarum 299v, Lactobacillus reuteri, Lactobacillus acidophilus. Meta-analysis of 5 studies in WRA showed that the use of prebiotics and/or probiotics with or without iron was associated with little or no effect on hemoglobin. However, there is low certainty of evidence that the intervention led to improvement in fractional absorption of iron as compared to placebo or iron [8 studies, n = 335, mean increase 0.74%, 95%CI-0.11-1.38, p = 0.02]. Meta-analysis of 6 studies in WRA using prebiotics and/or probiotics with or without iron led to a significant increase in ferritin levels in WRA (mean increase 2.45 ng/ml, 95% CI 0.61-4.3, p = 0.009, n = 320) [Moderate certainty of evidence]. In children, meta-analysis of up to 8 studies did not result in any significant change in hemoglobin, ferritin and fractional iron absorption [low or very low certainty of evidence].

CONCLUSION

There is some evidence to show that the use of prebiotics or probiotics (especially Lp299v and GOS) with or without oral iron can improve iron absorption in women and lead to improvement in ferritin levels in women. However, the current evidence does not conclusively show the benefit of these interventions in improving hemoglobin levels in women and children.

A Systematic Review of Isotopically Measured Iron Absorption in Infants and Children Under 2 Years

BACKGROUND

Iron is an essential element for critical biological functions, with iron deficiency negatively affecting growth and brain development and iron excess associated with adverse effects. The goal of this review is to provide a comprehensive assessment of up-to-date evidence on iron absorption measured isotopically in children, preterm infants, and full-term infants, up to 24 months of age.

METHODS

Search databases included Pubmed, Cochrane, Web of Science, and Scopus from a date range of 1 January 1953 to 22 July 2024. The included articles were experimental studies with iron absorption outcomes measured by isotopic techniques. The risk of bias was assessed using the Cochrane Risk of Bias Tool.

RESULTS

A total of 1594 records were identified from databases, and 37 studies were included in the quality review with a total of 1531 participants. Article results were grouped by study commonality: absorption and red blood cell incorporation, type of milk feedings, additives to improve absorption, how and when to supplement with iron, and iron forms and complimentary foods.

CONCLUSIONS

The results from this review support the current recommendations of oral iron supplementation. Iron from breast milk has high bioavailability, and unmodified cow's milk reduces iron absorption. Supplemental iron is required at 4-6 months for healthy, full-term infants and sooner for preterm infants. Ascorbic acid increases iron absorption in full-term infants and children. Lactoferrin and prebiotics are promising candidates for enhancing iron absorption, but they require further investigation. Research evidence of iron absorption mechanisms and modulating factors in preterm infants is limited and should be a research priority.

Assessing Human Iron Kinetics Using Stable Iron Isotopic Techniques

Stable iron isotope techniques are critical for developing strategies to combat iron deficiency anemia, a leading cause of global disability. There are four primary stable iron isotope methods to assess ferrokinetics in humans. (i) The fecal recovery method applies the principles of a metabolic balance study but offers enhanced accuracy because the amount of iron isotope present in feces can be directly traced back to the labeled dose, distinguishing it from endogenous iron lost in stool from shed intestinal cells. (ii) In the plasma isotope appearance method, plasma samples are collected for several hours after oral dosing to evaluate the rate, quantity, and pattern of iron absorption. Key metrics include the time of peak isotope concentration and the area under the curve. (iii) The erythrocyte iron incorporation method measures iron bioavailability (absorption and erythrocyte iron utilization) from a whole blood sample collected 2 weeks after oral dosing. Simultaneous administration of oral and intravenous tracers allows for separate measurements of iron absorption and iron utilization. These three methods determine iron absorption by measuring tracer concentrations in feces, serum, or erythrocytes after administration of a tracer. In contrast, (iv) in iron isotope dilution, an innovative new approach, iron of natural composition acts as the tracer, diluting an ad hoc modified isotopic signature obtained via prior isotope administration and equilibration with body iron. This technique enables highly accurate long-term studies of iron absorption, loss, and gain. This review discusses the application of these kinetic methods and their potential to address important questions in hematology and iron biology.

Prebiotics increase iron absorption and reduce the adverse effects of iron on the gut microbiome and inflammation: a randomized controlled trial using iron stable isotopes in Kenyan infants

BACKGROUND

Iron fortificants tend to be poorly absorbed and may adversely affect the gut, especially in African children.

OBJECTIVE

We assessed the effects of prebiotic galacto-oligosaccharides/fructo-oligosaccharides (GOS/FOS) on iron absorption and gut health when added to iron-fortified infant cereal.

METHODS

We randomly assigned Kenyan infants (n = 191) to receive daily for 3 wk a cereal containing iron and 7.5 g GOS/FOS (7.5 g+iron group), 3 g (3-g+iron group) GOS/FOS, or no prebiotics (iron group). A subset of infants in the 2 prebiotic+iron groups (n = 66) consumed 4 stable iron isotope-labeled test meals without and with prebiotics, both before and after the intervention. Primary outcome was fractional iron absorption (FIA) from the cereal with or without prebiotics regardless of dose, before and after 3 wk of consumption. Secondary outcomes included fecal gut microbiota, iron and inflammation status, and effects of prebiotic dose.

RESULTS

Median (25th-75th percentiles) FIAs from meals before intervention were as follows: 16.3% (8.0%-27.6%) without prebiotics compared with 20.5% (10.4%-33.4%) with prebiotics (Cohen d = 0.53; P < 0.001). FIA from the meal consumed without prebiotics after intervention was 22.9% (8.5%-32.4%), 41% higher than from the meal without prebiotics before intervention (Cohen d = 0.36; P = 0.002). FIA from the meal consumed with prebiotics after intervention was 26.0% (12.2%-36.1%), 60% higher than from the meal without prebiotics before intervention (Cohen d = 0.45; P = 0.007). After 3 wk, compared with the iron group, the following results were observed: 1) Lactobacillus sp. abundances were higher in both prebiotic+iron groups (P < 0.05); 2) Enterobacteriaceae sp. abundances (P = 0.022) and the sum of pathogens (P < 0.001) were lower in the 7.5-g+iron group; 3) the abundance of bacterial toxin-encoding genes was lower in the 3-g+iron group (false discovery rate < 0.05); 4) fecal pH (P < 0.001) and calprotectin (P = 0.033) were lower in the 7.5-g+iron group.

CONCLUSIONS

Adding prebiotics to iron-fortified infant cereal increases iron absorption and reduces the adverse effects of iron on the gut microbiome and inflammation in Kenyan infants. This trial was registered at clinicaltrials.gov as NCT03894358.

Unraveling the intricate connection between dietary factors and the success in long-term space missions

In recent decades of spaceflight, inadequate caloric intake has posed significant nutritional challenges, contributing to muscle degradation, weakened immune and cardiovascular systems during and after space missions. This challenge becomes more acute on longer exploration missions, where transporting all food for the entire mission becomes a logistical challenge. This places immense pressure on the food system, requiring energy-dense, varied, stable, and palatable food options. Prolonged storage can lead to nutrient degradation, reducing their bioavailability and bioaccessibility to astronauts. Research is essential not only to improve the quality and stability of space food but also to enhance nutrient bioavailability, thereby reducing weight and volume of food. Muscle and bone loss represent major risks during extended spaceflight, prompting extensive efforts to find exercise countermeasures. However, increased exercise requires additional energy intake, and finding the optimal balance between energy needs and the preservation of muscle and bone mass is challenging. Currently, there is no reliable way to measure total energy expenditure and activity-related energy expenditures in real-time. Systematic research is necessary to develop onboard technology for accurate energy expenditure and body composition monitoring. This research should aim to establish an optimal exercise regimen that balances energy requirements while maintaining astronaut strength and minimizing food transport. In summary, this overview outlines key actions needed for future exploration missions to maintain body mass and physical strength of space travellers. It addresses the requirements for food processing and preservation, considerations for space food formulation and production, and the essential measures to be implemented.

Influence of different nano/micro-carriers on the bioavailability of iron: Focus on in vitro-in vivo studies

Anemia resulting from iron (Fe) deficiency is a global public health problem. The deficiency of Fe is usually due to insufficient dietary intake of iron, interaction of Fe with other food components, and thus low bioaccessibility/bioavailability. Fe encapsulation has the potential to tackle some major challenges in iron fortification of foods. Various nano/micro-carriers have been developed for encapsulation of Fe, including emulsions, liposomes, hydrogels, and spray-dried microcapsules. They could reduce the interactions of Fe with food components, increase iron tolerance and intestinal uptake, and decrease adverse effects. This article review covers the factors affecting the bioavailability of Fe along with emerging carriers that can be used as a solution of this issue. The application of Fe-loaded carriers in food supplements and products is also described. The advantages and limitations associated with the delivery efficiency of each carrier for Fe are highlighted.

The Effect of Prebiotics on Human Iron Absorption: A Review

Iron deficiency remains the most common nutritional deficiency. Oral iron supplementation is the recommended first-line treatment and used as a preventive measure as well. Enhancers of iron absorption are highly sought after to improve supplementation outcomes. Evidence from animal and human studies exists that prebiotics can enhance iron absorption. The purpose of this present narrative review of the literature is to summarize the existing evidence on the effects of prebiotics on human iron absorption. Relevant articles were identified from PUBMED, Scopus, and Web of Science from inception to November 2021. Only human trials investigating the effect of prebiotics on iron absorption were included. Eleven articles were identified and included for review. There are promising findings supporting an enhancing effect of certain prebiotics, but inconsistencies between the studies and results exist. The most convincing evidence exists for the prebiotics galacto-oligosaccharides and fructo-oligosaccharides combined with the commonly used iron compound ferrous fumarate, from studies in adult women with low iron stores and in anemic infants. Many factors seem to play a role in the enhancing effect of prebiotics on iron absorption such as type of prebiotic, dose, acute (single-dose) or chronic (long-term) prebiotic consumption, iron compound, iron status, inflammatory status, and age of the population studied. More research investigating the optimal combination of prebiotic, iron compound, and dose as well as the effect of long-term application on iron status outcomes is needed.

Effects of dietary fiber on intestinal iron absorption, and physiological status: a systematic review of in vivo and clinical studies

The benefits of dietary fiber on intestinal health have been well established. However, there is no consensus on the dietary fiber effects on mineral absorption. The objective of this systematic review is to discuss the evidence on the dietary fiber effects on iron absorption and iron status-related biomarkers. A comprehensive search of 3 databases: PubMed, Scopus and Web of Science was carried out. We followed the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines, and a total of 32 studies were included with 9 of them clinical studies and 23 in vivo. The studies included assessment of dietary fiber in the form of fructo-oligosaccharides, galacto-oligosaccharides, inulin, pectin, guar gum, oligofructose, xylo-oligosaccharides, and mannan-oligosaccharide. Hemoglobin (n = 21) and fractional iron absorption (n = 6) were the most frequently reported outcomes. The results showed no significant correlations between consumption of dietary fiber to iron absorption/status-related biomarkers. However, the current evidence may not be substantial to invalidate the recommendation of dietary fiber as an agent to improve dietary iron bioavailability, and absorption. In conclusion, there is a need to conduct further clinical trials with long dietary fiber intervention focusing on population at high risk for iron deficiency.