Acute Consumption of Prebiotic Galacto-Oligosaccharides Increases Iron Absorption from Ferrous Fumarate, but not from Ferrous Sulfate and Ferric Pyrophosphate: Stable Iron Isotope Studies in Iron-Depleted Young Women

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.

Iron Absorption from an Iron-Fortified Follow-Up Formula with and without the Addition of a Synbiotic or a Human-Identical Milk Oligosaccharide: A Randomized Crossover Stable Isotope Study in Young Thai Children

BACKGROUND

Previous studies showed that pre- and probiotics may enhance iron absorption. Probiotics combined with prebiotics (synbiotics), including human-identical milk oligosaccharides (HiMOs), are commonly added to infant and follow-up formula (FUF). Whether these additions enhance iron absorption from iron-fortified commercial milk formula is uncertain.

OBJECTIVES

We determined the effect of adding 1) a synbiotic [galacto-oligosaccharide [GOS] + Limosilactobacillus reuteri (L. reuteri)] or 2) the HiMO 2'-fucosyllactose (2'FL) to iron-fortified FUF on iron absorption in young Thai children.

METHODS

In a randomized, controlled, single-blinded (participants) crossover study, 82 Thai children aged 8-14 mo were enrolled to consume single servings (235 mL) of FUF with isotopically labeled ferrous sulfate (2.2 mg iron) with 1) the synbiotic (400 mg/100 mL GOS and L. reuteri DSM 17938), 2) the HiMO 2'FL (100 mg/100 mL), and 3) without synbiotic and 2'FL (control) in random order and a 3-d washout period between administrations. Fractional iron absorption [FIA (%)] was assessed by measuring erythrocyte incorporation of isotopic labels 14 d (n = 26) and 28 d (n = 76) after consumption of the last test FUF.

RESULTS

Median (IQR) FIA from iron-fortified FUF with the synbiotic [8.2 (5.2, 12.9)%] and with 2'FL [8.4 (5.5, 14.1)%] did not differ from the control FUF [8.1 (4.8,14.7)%] (synbiotic compared with control, P = 0.24; 2'FL compared with control, P = 0.95). FIA from all FUF did not differ when measured after 14 and 28 d of erythrocyte incorporation (Time, P = 0.368; FUF, P = 0.435; Time × FUF, P = 0.937). Fecal pH and hemoglobin were negatively associated with FIA.

CONCLUSIONS

In young Thai children, the addition of a synbiotic (GOS + L. reuteri) or 2'FL to iron-fortified FUF did not impact FIA from a single serving. The study was registered at clinicaltrials.gov as NCT04774016.

Iron deficiency anemia: a critical review on iron absorption, supplementation and its influence on gut microbiota

Iron deficiency anemia (IDA) caused by micronutrient iron deficiency has attracted global attention due to its adverse health effects. The regulation of iron uptake and metabolism is finely controlled by various transporters and hormones in the body. Dietary iron intake and regulation are essential in maintaining human health and iron requirements. The review aims to investigate literature concerning dietary iron intake and systemic regulation. Besides, recent IDA treatment and dietary iron supplementation are discussed. Considering the importance of the gut microbiome, the interaction between bacteria and micronutrient iron in the gut is also a focus of this review. The iron absorption efficiency varies considerably according to iron type and dietary factors. Iron fortification remains the cost-effective strategy, although challenges exist in developing suitable iron fortificants and food vehicles regarding bioavailability and acceptability. Iron deficiency may alter the microbiome structure and promote the growth of pathogenic bacteria in the gut, affecting immune balance and human health.

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.

The effects of 2'-fucosyllactose and lacto-N-neotetraose, galacto-oligosaccharides, and maternal human milk oligosaccharide profile on iron absorption in Kenyan infants

BACKGROUND

Whether prebiotic human milk oligosaccharides (HMO), such as 2'-fucosyllactose (2'-FL) and lacto-N-neotetraose (LNnT), enhance iron absorption in infants is unknown. Moreover, whether maternal HMO profile affects absorption of iron fortificants or the effects of prebiotic galacto-oligosaccharides (GOS) and/or HMO on iron absorption is uncertain.

OBJECTIVES

The aim of this study was to test whether consumption of 3.0 g GOS or HMO enhances iron absorption from iron-fortified maize porridge in partially breastfed Kenyan infants and whether maternal HMO profile modulates these effects.

METHODS

In a randomized, prospective crossover study, 55 infants (aged 8-12 mo) were fed test meals fortified with 1 of the following: 1) 5.0 mg iron as ⁵⁴Fe-labeled ferrous fumarate (FeFum); 2) 5.0 mg iron as ⁵⁸FeFum and 3.0 g GOS (FeFum+GOS); and 3) 5.0 mg iron as ⁵⁷FeFum and 2.0 g 2'-FL and 1.0 g LNnT (FeFum+HMO). Fractional iron absorption (FIA) was assessed by erythrocyte incorporation of iron isotopes. HMO profiles were determined by capillary gel electrophoresis with laser-induced florescence detection. Data were analyzed with mixed-effect models, and iron dialyzability was measured in vitro.

RESULTS

Of the 55 infants included, 49 were fed as instructed. FIA from the FeFum+GOS group [median (IQR) 22.2% (16.5%-25.9%)] was higher than that from the FeFum group [12.5% (9.5%-20.9%)] (P = 0.005). FIA from the FeFum+HMO group was 13.3% (7.1%-24.4%) and did not differ from the FeFum group (P = 0.923). Maternal HMO profile did not predict FIA or modulate the effects of GOS or HMO on FIA. Iron dialyzability ratios at pH 2 of FeFum+GOS to FeFum and FeFum+HMO to FeFum were 2.1 and 0.9 (P = 0.001 and P = 0.322), respectively.

CONCLUSIONS

In Kenyan infants consuming FeFum-fortified maize porridge, co-provision of 3.0 g GOS increased FIA by 78%, whereas co-provision of 3.0 g HMO did not affect FIA. Variations in maternal HMO profile, including secretor and Lewis phenotype, did not predict FIA. These data argue against a physiologic role for 2'-FL and LNnT in facilitating iron absorption in infancy. The study was registered at clinicaltrials.gov as NCT04163406 (https://clinicaltrials.gov/ct2/show/NCT04163406).

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.

Prebiotics, Probiotics, and Postbiotics in the Prevention and Treatment of Anemia

Iron deficiency anemia (IDA) is very common and affects approximately 1/3 of the world’s human population. There are strong research data that some probiotics, such as Lactobacillus acidophilus and Bifidobacterium longum improve iron absorption and influence the course of anemia. Furthermore, prebiotics, including galactooligosaccharides (GOS) and fructooligosaccharides (FOS), increase iron bioavailability and decrease its destructive effect on the intestinal microbiota. In addition, multiple postbiotics, which are probiotic metabolites, including vitamins, short-chain fatty acids (SCFA), and tryptophan, are involved in the regulation of intestinal absorption and may influence iron status in humans. This review presents the actual data from research studies on the influence of probiotics, prebiotics, and postbiotics on the prevention and therapy of IDA and the latest findings regarding their mechanisms of action. A comparison of the latest research data and theories regarding the role of pre-, post-, and probiotics and the mechanism of their action in anemias is also presented and discussed.

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.

Prebiotic Galacto-oligosaccharides and Fructo-oligosaccharides, but not Acacia Gum, Increase Iron Absorption from a Single High-dose Ferrous Fumarate Supplement in Iron-depleted Women

BACKGROUND

Prebiotic galacto-oligosaccharides (GOS) increase iron absorption from fortification-level iron doses given as ferrous fumarate (FeFum) in women and children. Whether GOS or other fibers, such as prebiotic fructo-oligosaccharides (FOS) and acacia gum, increase iron absorption from higher supplemental doses of FeFum is unclear.

OBJECTIVES

In iron-depleted [serum ferritin (SF)< 25μg/L] women,  we tested if oral co-administration of 15g of GOS, FOS or acacia gum increases iron absorption from a 100mg iron supplement given as FeFum.

METHODS

In a randomized, single-blind cross-over study, 30 women (median age 26.2 years, median SF 12.9μg/L) consumed a 100mg iron tablet labelled with 4mg of 57Fe or 58Fe, given with either: a) 15g GOS; b) 15g FOS; c) 15g acacia gum; or d) 6.1g lactose and 1.5g sucrose (control; matching the amounts of sucrose and lactose present in the GOS powder providing 15 g GOS), dissolved in water. The primary outcome, fractional iron absorption (FIA), was assessed by erythrocyte isotopic incorporation 14 days after administration. Data were analysed using a linear mixed-effect model. We also tested, in vitro, iron solubility at different pH and dialyzability from the different supplement combinations administered in vivo.

RESULTS

FIA from FeFum given with GOS and FOS was significantly higher (+45% and 51%, respectively; P < 0.001 for both) compared with control; total iron absorption [median (IQR)] was 34.6 (28.4; 49.1); 36.1 (29.0; 46.2) and 23.9 (20.5; 34.0) mg, respectively. Acacia gum did not significantly affect FIA from FeFum (P = 0.688). In vitro, iron dialyzability of FeFum + GOS was 46% higher than of FeFum alone (P = 0.003).

CONCLUSIONS

In iron-depleted women, both GOS and FOS co-administration with FeFum increase iron absorption by ∼50% from a 100mg oral iron dose, resulting in an additional 10-12mg of absorbed iron. Thus, GOS and FOS may be promising new enhancers of supplemental iron absorption.The study was registered at clinicaltrials.gov as NCT04194255 (https://clinicaltrials.gov/ct2/show/NCT04194255).

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

BACKGROUND

Prebiotic galacto-oligosaccharides (GOS) are novel enhancers of iron absorption from ferrous fumarate (FeFum). However, the mechanism(s) of this effect, and whether it occurs in the proximal or distal gut, are uncertain.

OBJECTIVES

We studied: 1) in vitro, the effect of GOS on iron solubility and dialyzability from FeFum; 2) in volunteers, the absorption kinetics of FeFum given with and without GOS using stable isotope appearance curves (SIAC).

METHODS

We measured iron solubility at various pH and dialyzability from FeFum with and without GOS. In crossover design, iron-depleted women [n = 11; median serum ferritin (SF) 15.2; IQR: 12.6-21.2 µg/L] received 2 14-mg iron doses as labeled (57Fe,58Fe) FeFum 14 d apart with and without 15 g GOS in randomly assigned order. Multiple blood samples were collected over a time period of 24 h and 14 d later to determine SIAC and fractional iron absorption (FIA), respectively. SIAC data were fitted using nonlinear mixed effects modeling to a 1-compartment model with first-order absorption, and AUC and time of peak serum isotope concentration (tmax) were calculated.

RESULTS

Iron dialyzability was 75% higher with GOS (P < 0.001) and iron solubility was more than doubled at pH 4 and 6 with GOS [both P < 0.001]. Mean ± SD AUC (5830.9 ± 4717.3 μg/min with GOS, 4454.0 ± 3260.7 μg/min for control), and median (IQR) FIA (20.3% (8.6%-38.7%) with GOS, and 15.6% (10.6%-24.8% f)or control) were not different with compared to without GOS (P = 0.064; P = 0.080). Mean ±SD tmax was not altered with GOS (3.08 ± 0.47 h with GOS; 2.80 ±0.50 h for control; P = 0.096). Iron bioavailability significantly increased with decreasing SF and this effect was significantly enhanced by GOS (P = 0.037, interaction of GOS with SF).

CONCLUSIONS

GOS increases iron solubility from FeFum at physiological pH characteristic of the proximal duodenum. The absorption kinetics in vivo are consistent with effects on iron absorption in the proximal, rather than distal, parts of the gut. There was no overall effect of GOS on FIA in vivo, but the interaction of GOS and SF on FIA might benefit iron-deficient women, an effect potentially mediated by the higher solubility shown in vitro. This study was registered at clinicaltrials.gov as NCT03996421.

Iron

Iron deficiency anemia affects approximately one-third of the world's population, and about half the cases are due to iron deficiency. The latest research on iron metabolism published in original articles and systematic reviews is described, and references to recent reviews provided. The topics include dietary sources and bioavailability, iron homeostasis, functions of iron in the body, and biomarkers of status. The consequences of iron deficiency and excess are discussed, with particular focus on vulnerable populations such as pregnant women, infants and the elderly. The newest dietary recommendations, including dietary reference values and food based dietary guidelines, are briefly summarized, followed by the latest developments in food fortification and iron supplementation.