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Iron (Ferrous Bisglycinate)

MINERALS · Evidence Monograph

Iron (Ferrous Bisglycinate) is an evidence-graded minerals monograph evaluated across 27 peer-reviewed PubMed studies (1 meta-analyses, 0 systematic reviews, and 7 randomized controlled trials, encompassing n = 2,363 cumulative participants). Current clinical evidence is rated GRADE High (4.0 / 4.0) for electrolyte balance, neuromuscular signaling, and enzymatic cofactor activity.

Evidence Grade (GRADE) High (4.0 / 4.0)
Indexed PubMed Studies 27 Studies
Meta-Analyses · Reviews 1 Meta · 0 Systematic Reviews
Randomized Trials (RCT) 7 RCTs (5 Double-Blind)
Cumulative Participants n = 2,363
Reported Trial Dosages 18 mg · 60 mg · 0 mg
Trial Duration Range 4 weeks · 56 days · 19 weeks
Reading Time ~14 min
RECOMMENDED FOR Clinical Indication

Evidence Supports Supplementation When:

  1. 01 Individuals seeking evidence-backed support for electrolyte balance, neuromuscular signaling, and enzymatic cofactor activity (supported by 27 indexed PubMed studies, GRADE High).
  2. 02 Adults matching clinical trial dosing protocols (18 mg · 60 mg · 0 mg) over a structured 4 weeks evaluation window.
  3. 03 Users who have verified compatibility with their gastrointestinal tolerance and current prescription regimen.
FORMULATION SPECIFICATION · Preferred Form Amino-Acid Chelate (Bisglycinate) or Organic Citrate Salt
Avoid low-bioavailability inorganic oxides or carbonates if you have a sensitive stomach; organic chelates minimize GI irritation and transporter competition.
CLINICAL RESPONSE · Body Signal Check
Expected Response: Smooth gastrointestinal tolerance without bloating, cramps, or osmotic loose stools.
Dose Adjustment Signal: If loose stools or abdominal cramping occur, reduce the elemental dose by 50% or switch to a bisglycinate chelate.
CHRONOBIOLOGY · Optimal Dosing Window PM 19:00
With Dinner or 4 Hours Apart from Thyroid/Antibiotic Rx
Divalent cations bind to levothyroxine and fluoroquinolone/tetracycline antibiotics in the GI tract; maintain a strict 4-hour separation window.
Primary Clinical Endpoints & Physiological Biomarkers Studied Based on Indexed PubMed Trials
alopecia (PubMed clinical endpoint)
hair (PubMed clinical endpoint)
inflammation (PubMed clinical endpoint)
gut (PubMed clinical endpoint)
01

What Is Iron (Ferrous Bisglycinate) & Why Does Form Matter?

Iron (Ferrous Bisglycinate) is classified under MINERALS and has been investigated across 27 peer-reviewed PubMed publications for its role in electrolyte balance, neuromuscular signaling, and enzymatic cofactor activity.

In clinical nutrition, physiological efficacy depends heavily on the specific chemical salt, chelate, or standardized extract used, as well as adherence to trial-validated dosing (18 mg, 60 mg, 0 mg).

02

Who Benefits Most & Common Depletion Factors

Suboptimal status or increased physiological demand for Iron (Ferrous Bisglycinate) frequently arises from restrictive dietary patterns, age-related declines in gastrointestinal absorption, chronic metabolic stress, or medication-induced nutrient depletion.

Before initiating supplementation, identify whether your primary goal aligns with the endpoints evaluated in human randomized controlled trials (7 RCTs indexed) rather than generalized marketing claims.

03

Physiological Mechanism of Action

Within human physiology, Iron (Ferrous Bisglycinate) acts on pathways governing electrolyte balance, neuromuscular signaling, and enzymatic cofactor activity. Bioavailability is determined by dissolution kinetics in the stomach, active or passive transport across enterocytes, and hepatic first-pass metabolism.

Avoid low-bioavailability inorganic oxides or carbonates if you have a sensitive stomach; organic chelates minimize GI irritation and transporter competition.

04

PubMed Clinical Evidence & GRADE Evaluation

NICEVIVA assigns Iron (Ferrous Bisglycinate) an overall evidence rating of GRADE High (4.0 / 4.0) based on 27 PubMed studies: 1 meta-analyses, 0 systematic reviews, and 7 randomized controlled trials (5 double-blind, n = 2,363 total participants).

Representative peer-reviewed findings include: • PMID:36728680 (2023) — "The effects of oral ferrous bisglycinate supplementation on hemoglobin and ferritin concentrations in adults and children: a systematic review and meta-analysis of randomized controlled trials." (CONCLUSION: Ferrous bisglycinate shows some benefit over other iron supplements in increasing hemoglobin concentration and reducing GI adverse events among pregnant women.) • PMID:41082982 (2025) — "Iron Supplementation with Ferrous Sulfate or Ferrous Bisglycinate for 12 Weeks Does Not Influence Group B Streptococcus Colonization in Cambodian Women: A Secondary Analysis of a Randomized Controlled Trial." (CONCLUSIONS: Oral iron supplementation for 12 wk did not increase cfb expression in this population of predominantly iron-replete Cambodian women, compared with placebo.) • PMID:40819648 (2025) — "Ferritin-guided iron supplementation as an alternative or complement to prolonged blood donation intervals (FORTE): a double-blind, randomised, controlled trial." (Compared with daily placebo, all iron supplementation groups exhibited similar significantly lower odds of iron deficiency at 56 days, with odds ratios (ORs) of 0·62 (95% CI 0·56-0·68) for 30 mg daily, 0·63 (0)

05

Formulation Selection, Dosing & Chronobiology

Recommended Formulation: Amino-Acid Chelate (Bisglycinate) or Organic Citrate Salt. Avoid low-bioavailability inorganic oxides or carbonates if you have a sensitive stomach; organic chelates minimize GI irritation and transporter competition.

Clinical Trial Dosing & Timing: Published studies most commonly utilize 18 mg · 60 mg · 0 mg · 30 mg over 4 weeks · 56 days · 19 weeks · 12 weeks. Optimal timing window: PM 19:00 · With Dinner or 4 Hours Apart from Thyroid/Antibiotic Rx (Divalent cations bind to levothyroxine and fluoroquinolone/tetracycline antibiotics in the GI tract; maintain a strict 4-hour separation window.).

06

Body Response Monitoring & Dose Adjustment

Expected Positive Response: Smooth gastrointestinal tolerance without bloating, cramps, or osmotic loose stools.

Adjustment & Discontinuation Signals: If loose stools or abdominal cramping occur, reduce the elemental dose by 50% or switch to a bisglycinate chelate.

07

Prescription Drug Interactions & Contraindications

• [MODERATE] Levothyroxine: Pharmacokinetic or pharmacodynamic interaction reported in clinical literature (PMID:11131757). Consult your prescribing physician or pharmacist to separate dosing windows or monitor clinical labs.

08

4 Essential Safety Rules Before & After Dosing

01 · Stop Immediately If:
  • Discontinue use immediately if acute hives, facial/airway swelling, severe abdominal pain, unexplained jaundice, or abnormal bruising/bleeding occurs.
  • Stop 7–14 days prior to scheduled surgery, dental extraction, or invasive endoscopic procedures.
02 · Best Practices for Bioavailability:
  • Follow the optimal chronobiology window (PM 19:00 · With Dinner or 4 Hours Apart from Thyroid/Antibiotic Rx) with a full glass of water.
  • Stay within clinically studied daily dosages (18 mg · 60 mg · 0 mg) and re-evaluate efficacy after 4 weeks.
03 · Habits to Avoid:
  • Avoid stacking multiple multi-ingredient supplements that contain overlapping active compounds.
  • Do not wash capsules down with high-tannin coffee, strong tea, or alcohol, which can chelate minerals and irritate gastric mucosa.
04 · Consult Physician / Pharmacist Before Use If:
  • Consult your physician or pharmacist before use if taking Levothyroxine.
  • Seek professional medical guidance if you are pregnant, breastfeeding, or managing chronic kidney or liver disease.
09 · PUBMED CLINICAL STUDIES

Indexed PubMed Clinical Studies & Abstracts (27 Studies) · 8 Quantitative Analyses

01
META-ANALYSIS Nutrition reviews (2023) PMID: 36728680 ↗
The effects of oral ferrous bisglycinate supplementation on hemoglobin and ferritin concentrations in adults and children: a systematic review and meta-analysis of randomized controlled trials.
Clinical Trial Synthesis 2023 Meta-Analysis published in Nutrition reviews; statistical significance reported at p = 0.01 (RR 0.36). Key conclusion: CONCLUSION: Ferrous bisglycinate shows some benefit over other iron supplements in increasing hemoglobin concentration and reducing GI adverse events among pregnant women.
View Original PubMed Abstract ↓

CONTEXT: Iron deficiency and anemia have serious consequences, especially for children and pregnant women. Iron salts are commonly provided as oral supplements to prevent and treat iron deficiency, despite poor bioavailability and frequently reported adverse side effects. Ferrous bisglycinate is a novel amino acid iron chelate that is thought to be more bioavailable and associated with fewer gastrointestinal (GI) adverse events as compared with iron salts. OBJECTIVE: A systematic review and meta-analysis of randomized controlled trials (RCTs) was conducted to evaluate the effects of ferrous bisglycinate supplementation compared with other iron supplements on hemoglobin and ferritin concentrations and GI adverse events. DATA SOURCES: A systematic search of electronic databases and grey literature was performed up to July 17, 2020, yielding 17 RCTs that reported hemoglobin or ferritin concentrations following at least 4 weeks' supplementation of ferrous bisglycinate compared with other iron supplements in any dose or frequency. DATA EXTRACTION: Random-effects meta-analyses were conducted among trials of pregnant women (n = 9) and children (n = 4); pooled estimates were expressed as standardized mean differences (SMDs). Incidence rate ratios (IRRs) were estimated for GI adverse events, using Poisson generalized linear mixed-effects models. The remaining trials in other populations (n = 4; men and nonpregnant women) were qualitatively evaluated. DATA ANALYSIS: Compared with other iron supplements, supplementation with ferrous bisglycinate for 4-20 weeks resulted in higher hemoglobin concentrations in pregnant women (SMD, 0.54 g/dL; 95% confidence interval [CI], 0.15-0.94; P < 0.01) and fewer reported GI adverse events (IRR, 0.36; 95%CI, 0.17-0.76; P < 0.01). We observed a non-significant trend for higher ferritin concentrations in pregnant women supplemented with ferrous bisglycinate. No significant differences in hemoglobin or ferritin concentrations were detected among children. CONCLUSION: Ferrous bisglycinate shows some benefit over other iron supplements in increasing hemoglobin concentration and reducing GI adverse events among pregnant women. More trials are

02
RANDOMIZED TRIAL (RCT) The Journal of nutrition (2025) PMID: 41082982 ↗
Iron Supplementation with Ferrous Sulfate or Ferrous Bisglycinate for 12 Weeks Does Not Influence Group B Streptococcus Colonization in Cambodian Women: A Secondary Analysis of a Randomized Controlled Trial.
Clinical Trial Synthesis 2025 Randomized Controlled Trial (RCT) published in The Journal of nutrition. Key conclusion: CONCLUSIONS: Oral iron supplementation for 12 wk did not increase cfb expression in this population of predominantly iron-replete Cambodian women, compared with placebo.
View Original PubMed Abstract ↓

BACKGROUND: Iron deficiency in women of reproductive age can have severe adverse perinatal consequences. Although iron supplementation can be effective at treating iron deficiency, excess unabsorbed iron in the gut may also promote colonization by enteropathogens such as Group B Streptococcus (GBS), increasing the potential risk of maternal and neonatal infection. OBJECTIVES: We examined whether 12 wk of supplementation with 18 mg elemental iron as ferrous bisglycinate, 60 mg as ferrous sulfate, or a placebo differentially influences GBS colonization in Cambodian women of reproductive age. METHODS: This study is a secondary analysis of a randomized controlled trial conducted in 25 villages in 3 districts of Kampong Thom province, Cambodia, including 144 nonpregnant women (18‒45 y) who received 18 mg of elemental iron as ferrous bisglycinate, 60 mg ferrous sulfate, or placebo for 12 wk. GBS colonization was assessed by real-time quantitative polymerase chain reaction targeting the cfb gene (which encodes the Christie-Atkins-Munch-Peterson [CAMP] factor, an indicator of GBS colonization) from stool collected at baseline and 12 wk. Cycle threshold values were compared within and across groups using Kruskal-Wallis and Wilcoxon signed-rank tests. RESULTS: No changes in cfb expression were detected between baseline and endline within any treatment arm, nor were there differences across groups at 12 wk. However, regional differences in cfb expression were detected, with participants from the Srayov district exhibiting lower baseline and endline expression, than those from Prey Kuy and Tboung Krapeu. CONCLUSIONS: Oral iron supplementation for 12 wk did not increase cfb expression in this population of predominantly iron-replete Cambodian women, compared with placebo. However, the observed geographic variation in cfb expression across districts suggests that environmental or behavioral factors may contribute to GBS colonization risk. These findings highlight the need to further investigate region-specific risk factors and provide a foundation for future research into GBS screening in Cambodia. This trial was registered at clinicaltrials.gov as NCT04017598.

03
RANDOMIZED TRIAL (RCT) The Lancet. Haematology (2025) PMID: 40819648 ↗
Ferritin-guided iron supplementation as an alternative or complement to prolonged blood donation intervals (FORTE): a double-blind, randomised, controlled trial.
Clinical Trial Synthesis 2025 Randomized Controlled Trial (RCT) published in The Lancet. Haematology involving n = 108 participants. Key conclusion: Compared with daily placebo, all iron supplementation groups exhibited similar significantly lower odds of iron deficiency at 56 days, with odds ratios (ORs) of 0·62 (95% CI 0·56-0·68) for 30 mg daily, 0·63 (0
View Original PubMed Abstract ↓

BACKGROUND: Regular blood donation is associated with an increased risk of iron deficiency and anaemia. Oral iron supplementation is known to shorten post-donation iron recovery time and could serve as an alternative to extended donation intervals. We aimed to evaluate the effect of different iron supplementation protocols on ferritin and haemoglobin levels, gastrointestinal side-effects, iron deficiency-related symptoms, and donor return compared with placebo supplementation. METHODS: In this double-blind, randomised, placebo-controlled trial conducted at seven of Sanquin's blood donation centres in The Netherlands, donors aged 18-80 years with ferritin levels equal to or less than 30 μg/L were randomly allocated to one of six study groups, using block randomisation in equal numbers by sex and age. Donors were instructed to adhere to a ferrous bisglycinate supplementation protocol for 56 days, taking capsules containing 0 mg (placebo), 30 mg, or 60 mg of elemental iron, either daily or on alternate days. The primary outcomes were presence of iron deficiency (<15 μg/L), low ferritin (15-30 μg/L), and low haemoglobin (≤135 g/L for male donors and ≤125 g/L for female donors) at 56 days' follow-up. Analyses were conducted using an intention-to-treat approach. This trial is registered in the Dutch trial registry (NL7328.018.20) and is complete. FINDINGS: Between Aug 1, 2021, and Jan 15, 2023, 830 donors (464 [56%] female donors and 366 [44%] male donors; 789 [95%] of Dutch origin and 26 [3%] of non-Dutch origin) had low ferritin and were included in the trial. At 56 days, 55 (51%) of 108 participants in the placebo daily group, 58 (49%) of 119 participants in the placebo alternate day group, 11 (10%) of 107 participants in the 30 mg daily group, eight (7%) of 112 participants in the 30 mg alternate day group, one (1%) of 114 participants in the 60 mg daily group, and four (4%) of 110 participants in the 60 mg alternate day group presented with iron deficiency. Compared with daily placebo, all iron supplementation groups exhibited similar significantly lower odds of iron deficiency at 56 days, with odds ratios (ORs) of 0·62 (95% CI 0·56-0·68) for 30 mg daily, 0·63 (0

04
RANDOMIZED TRIAL (RCT) Journal of pregnancy (2024) PMID: 39582678 ↗
Low-Dose Prophylactic Oral Iron Supplementation (Ferrous Fumarate, Ferrous Bisglycinate, and Ferrous Sulphate) in Pregnancy Is Not Associated With Clinically Significant Gastrointestinal Complaints: Results From Two Randomized Studies.
Clinical Trial Synthesis 2024 Randomized Controlled Trial (RCT) published in Journal of pregnancy involving n = 482 participants. Key conclusion: Conclusion: Low-dose iron supplementation appears to have no clinically significant GI side effects, as none of the included women p
View Original PubMed Abstract ↓

Background: Many pregnant women are reluctant to follow the recommendation concerning oral iron prophylaxis due to concerns about gastrointestinal (GI) side effects. Objective: To assess the frequency of GI complaints during low-dose oral iron prophylaxis and compare three iron formulas in equipotent doses: ferrous fumarate versus ferrous bisglycinate versus ferrous sulphate, in healthy women with an uncomplicated single pregnancy. Methods: Results from two randomized, double-blind studies are reported: the Gentofte study comprising 404 women allocated into four groups taking 20, 40, 60, and 80 mg of elemental iron as ferrous fumarate/day and the Naestved study comprising 78 women allocated into two groups: 25 mg of elemental iron as ferrous bisglycinate/day and 50 mg of elemental iron as ferrous sulphate/day between meals from 15 to 19 weeks of gestation to delivery. GI complaints (nausea, vomiting, epigastric pain/pyrosis, belching, meteorism, borborygmi, intestinal colic, flatulence, loose stools, constipation, and use of laxatives), as well as black stools, were recorded by interview at the time of inclusion and at regular intervals during gestation. Results: At inclusion, the frequency of total combined GI complaints in all women (n = 482) was 21%. The Gentofte study showed that in the groups taking 20-60 mg iron/day as fumarate, there was no association between the iron dose and the frequency of GI side effects. An iron dose of 80 mg as fumarate was associated with significantly higher frequencies of constipation and the use of laxatives. Comparing the three equipotent doses of iron formulas, which can prevent iron deficiency, ferrous bisglycinate 25 mg iron had the most favourable GI side effect profile, while ferrous fumarate 40 mg iron and ferrous sulphate 50 mg iron had higher but similar GI side effect profiles. The frequency of black stools increased with the iron dose. Ferrous bisglycinate 25 mg iron had a lower frequency of black stools (8%) than ferrous fumarate 40 mg iron (22%) and ferrous sulphate 50 mg iron (31%). Conclusion: Low-dose iron supplementation appears to have no clinically significant GI side effects, as none of the included women p

05
RANDOMIZED TRIAL (RCT) The Journal of nutrition (2023) PMID: 37271416 ↗
Is a Lower Dose of More Bioavailable Iron (18-mg Ferrous Bisglycinate) Noninferior to 60-mg Ferrous Sulfate in Increasing Ferritin Concentrations While Reducing Gut Inflammation and Enteropathogen Detection in Cambodian Women? A Randomized Controlled Noninferiority Trial.
Clinical Trial Synthesis 2023 Randomized Controlled Trial (RCT) published in The Journal of nutrition involving n = 480 participants; statistical significance reported at p = 0.001. Key conclusion: CONCLUSIONS: Ferrous bisglycinate (18-mg) was not as effective as ferrous sulfate (60-mg) in increasing ferritin concentrations and did not differentially influence biomarkers of gut health in this predominantly iron-replete population of Cambodian women.
View Original PubMed Abstract ↓

BACKGROUND: Global guidelines recommend untargeted iron supplementation for women in regions of anemia prevalence ≥40%, such as Cambodia. However, the potential harms of untargeted iron on the gut have not been rigorously studied in women and likely vary depending on iron dose and form. OBJECTIVES: We investigated if a lower dose of a highly bioavailable iron amino acid chelate was as effective as the standard dose of iron salts in increasing ferritin concentrations and whether any differences were observed in gut inflammation or enteropathogen detection. METHODS: A double-blind, randomized placebo-controlled noninferiority trial was conducted in Cambodia. Nonpregnant women (n = 480, 18-45 y) were randomly assigned to 60-mg ferrous sulfate, 18-mg ferrous bisglycinate, or placebo for 12 wk. Nonfasting blood and stool specimens were collected at baseline and 12 wk. Ferritin and fecal calprotectin were measured with an ELISA. A molecular assay was used to detect 11 enteropathogens in a random subset of n = 100 women. Generalized linear mixed-effects models were used to estimate the adjusted mean difference in ferritin concentrations at 12 wk (primary outcome), as compared with our 'a priori' noninferiority margin of 20 μg/L. RESULTS: Baseline anemia and iron deficiency prevalence was low (17% and 6%, respectively). The adjusted mean difference in ferritin concentrations between the iron groups was 14.6 (95% confidence interval [CI]: 7.6, 21.6) μg/L. Mean ferritin concentration at 12 wk was higher in the ferrous sulfate (99 [95% CI: 95, 103] μg/L, P < 0.001) than in ferrous bisglycinate (84 [95% CI: 80, 88] μg/L) and placebo groups (78 [95% CI: 74, 82] μg/L). No differences in fecal calprotectin concentrations or enteropathogen detection were observed across groups at 12 wk. CONCLUSIONS: Ferrous bisglycinate (18-mg) was not as effective as ferrous sulfate (60-mg) in increasing ferritin concentrations and did not differentially influence biomarkers of gut health in this predominantly iron-replete population of Cambodian women. This trial was registered at clinicaltrials.gov registry as NCT04017598.

06
RANDOMIZED TRIAL (RCT) Microbiology spectrum (2023) PMID: 37199608 ↗
The Effect of Oral Iron Supplementation on Gut Microbial Composition: a Secondary Analysis of a Double-Blind, Randomized Controlled Trial among Cambodian Women of Reproductive Age.
Clinical Trial Synthesis 2023 Randomized Controlled Trial (RCT) published in Microbiology spectrum involving n = 172 participants. Key conclusion: Our study found that iron supplementation with ferrous bisglycinate increases the relative abundance of Enterobacteriaceae, which is a family of bacteria that includes many Gram-negative enteric pathogens like Salmonella, Shigella, and Escherichia
View Original PubMed Abstract ↓

The World Health Organization recommends untargeted iron supplementation for women of reproductive age (WRA) in countries where anemia prevalence is greater than 40%, such as Cambodia. Iron supplements, however, often have poor bioavailability, so the majority remains unabsorbed in the colon. The gut houses many iron-dependent bacterial enteropathogens; thus, providing iron to individuals may be more harmful than helpful. We examined the effects of two oral iron supplements with differing bioavailability on the gut microbiomes in Cambodian WRA. This study is a secondary analysis of a double-blind, randomized controlled trial of oral iron supplementation in Cambodian WRA. For 12 weeks, participants received ferrous sulfate, ferrous bisglycinate, or placebo. Participants provided stool samples at baseline and 12 weeks. A subset of stool samples (n = 172), representing the three groups, were randomly selected for gut microbial analysis by 16S rRNA gene sequencing and targeted real-time PCR (qPCR). At baseline, 1% of women had iron-deficiency anemia. The most abundant gut phyla were Bacteroidota (45.7%) and Firmicutes (42.1%). Iron supplementation did not alter gut microbial diversity. Ferrous bisglycinate increased the relative abundance of Enterobacteriaceae, and there was a trend towards an increase in the relative abundance of Escherichia-Shigella. qPCR detected an increase in the enteropathogenic Escherichia coli (EPEC) virulence gene, bfpA, in the group that received ferrous sulfate. Thus, iron supplementation did not affect overall gut bacterial diversity in predominantly iron-replete Cambodian WRA, however, evidence does suggest an increase in relative abundance within the broad family Enterobacteriaceae associated with ferrous bisglycinate use. IMPORTANCE To the best of our knowledge, this is the first published study to characterize the effects of oral iron supplementation on the gut microbiomes of Cambodian WRA. Our study found that iron supplementation with ferrous bisglycinate increases the relative abundance of Enterobacteriaceae, which is a family of bacteria that includes many Gram-negative enteric pathogens like Salmonella, Shigella, and Escherichia

07
RANDOMIZED TRIAL (RCT) Nutrients (2022) PMID: 35276810 ↗
Efficacy and Safety of Ferrous Bisglycinate and Folinic Acid in the Control of Iron Deficiency in Pregnant Women: A Randomized, Controlled Trial.
Clinical Trial Synthesis 2022 Randomized Controlled Trial (RCT) published in Nutrients involving n = 120 participants; statistical significance reported at p = 0.001. Key conclusion: In conclusion, ferrous bisglycinate with folinic acid as a multivitamin nutraceutical format is comparable to standard ferrous fumarate for the clinical management of iron deficiency during pregnancy, with comparatively better absorption, tolerability, and efficacy and with a low
View Original PubMed Abstract ↓

Iron deficiency in pregnancy is a major public health problem that causes maternal complications. The objective of this randomized, controlled trial was to examine the bioavailability, efficacy, and safety of oral ferrous bisglycinate plus folinic acid supplementation in pregnant women with iron deficiency. Subjects (12−16 weeks of gestation, n = 120) were randomly allocated to receive oral iron as ferrous bisglycinate (equiv. iron 24 mg) in supplement form with folinic acid and multivitamins (test group, n = 60) or as ferrous fumarate (equiv. iron 66 mg iron, control group, n = 60) after breakfast daily. Iron absorption was assessed by measuring fasted serum iron levels at 1 and 2 h immediately after supplementation. Hematological biomarkers and iron status were assessed before intervention, and at 3 and 6 months. Side effects were monitored throughout the intervention. A significant increase in serum iron was seen in both groups (p < 0.001) during the bioavailability assessment; however, the test group increases were comparatively higher than the control values at each timepoint (p < 0.001). Similarly, both test and control groups demonstrated a statistically significant increases in hemoglobin (Hb) (p < 0.001), erythrocytes (p < 0.001), reticulocytes (p < 0.001), mean corpuscular volume (MCV) (p < 0.001), mean corpuscular hemoglobin (MCH) (p < 0.001), mean corpuscular hemoglobin concentration (MCHC) (p < 0.001), % transferrin saturation (p < 0.001), and ferritin (p < 0.001) at 3 and 6 months after supplementation. However, in all cases, the test group increases were numerically larger than the control group increases at each timepoint. The test intervention was also associated with significantly fewer reports of nausea, abdominal pain, bloating, constipation, or metallic taste (p < 0.001). In conclusion, ferrous bisglycinate with folinic acid as a multivitamin nutraceutical format is comparable to standard ferrous fumarate for the clinical management of iron deficiency during pregnancy, with comparatively better absorption, tolerability, and efficacy and with a lower elemental iron dosage.

08
CLINICAL STUDY The Journal of nutrition (2022) PMID: 34958374 ↗
Iron Bioavailability from Infant Cereals Containing Whole Grains and Pulses: A Stable Isotope Study in Malawian Children.
Clinical Trial Synthesis 2022 Randomized Controlled Trial (RCT) published in The Journal of nutrition involving n = 30 participants; statistical significance reported at p = 0.02. Key conclusion: CONCLUSION: In Malawian children, when given with ascorbic acid at a molar ratio of 2:1, iron bioavailability from Fefum-fortified infant cereals containing WG wheat and pulses is ≈13-15%, whereas that from FeBG- and Fefum-fortified infant cereals based on WG oats is ≈7-9%.
View Original PubMed Abstract ↓

BACKGROUND: Compared with infant cereals based on refined grains, an infant cereal containing whole grains (WGs) and pulses with adequate amounts of ascorbic acid to protect against absorption inhibitors could be a healthier source of well-absorbed iron. However, iron absorption from such cereals is uncertain. OBJECTIVE: We measured iron bioavailability from ferrous fumarate (Fefum) added to commercial infant cereals containing 1) refined wheat flour (reference meal), 2) WG wheat and lentil flour (WG-wheat-lentil), 3) WG wheat and chickpea flour (WG-wheat-chickpeas), and 4) WG oat flour (WG-oat) and from ferrous bisglycinate (FeBG) added to the same oat-based cereal (WG-oat-FeBG). METHODS: In a prospective, single-blinded randomized crossover study, 6- to 14-mo-old Malawian children (n = 30) consumed 25-g servings of all 5 test meals containing 2.25 mg stable isotope-labeled iron and 13.5 mg ascorbic acid. Fractional iron absorption (FIA) was assessed by erythrocyte incorporation of isotopes after 14 d. Comparisons were made using linear mixed models. RESULTS: Seventy percent of the children were anemic and 67% were iron deficient. Geometric mean FIA percentages (-SD, +SD) from the cereals were as follows: 1) refined wheat, 12.1 (4.8, 30.6); 2) WG-wheat-lentil, 15.8 (6.6, 37.6); 3) WG-wheat-chickpeas, 12.8 (5.5, 29.8); and 4) WG-oat, 9.2 (3.9, 21.5) and 7.4 (2.9, 18.9) from WG-oat-FeBG. Meal predicted FIA (P ≤ 0.001), whereas in pairwise comparisons, only WG-oat-FeBG was significantly different compared with the refined wheat meal (P = 0.02). In addition, FIAs from WG-wheat-lentil and WG-wheat-chickpeas were significantly higher than from WG-oat (P = 0.002 and P = 0.04, respectively) and WG-oat-FeBG (P < 0.001 and P = 0.004, respectively). CONCLUSION: In Malawian children, when given with ascorbic acid at a molar ratio of 2:1, iron bioavailability from Fefum-fortified infant cereals containing WG wheat and pulses is ≈13-15%, whereas that from FeBG- and Fefum-fortified infant cereals based on WG oats is ≈7-9%. © The Author(s) 2021. Published by Oxford University Press on behalf of the American Society for Nutrition.

09
CLINICAL STUDY International journal for vitamin and nutrition research. Internationale Zeitschrift fur Vitamin- und Ernahrungsforschung. Journal international de vitaminologie et de nutrition (2004) PMID: 15743016 ↗
Enhancing the absorption of fortification iron. A SUSTAIN Task Force report.
Clinical Trial Synthesis 2004 Clinical Study published in International journal for vitamin and nutrition research. Internationale Zeitschrift fur Vitamin- und Ernahrungsforschung. Journal international de vitaminologie et de nutrition. Key conclusion: Research relevant to each of these strategies for enhancing the bioavailability or utility of iron food fortificants is reviewe
View Original PubMed Abstract ↓

Iron deficiency remains a major global health problem affecting an estimated 2 billion people. The World Health Organization ranked it as the seventh most important preventable risk for disease, disability, and death in 2002. Since an important factor in its causation is the poor bioavailability of iron in the cereal-based diets of many developing countries, SUSTAIN set up a Task Force, consisting of nutritional, medical, industry, and government experts to consider strategies for enhancing the absorption of fortification iron. This paper summarizes the findings of this Task Force. Detailed reviews of each strategy follow this overview. Highly soluble compounds of iron like ferrous sulfate are desirable food fortificants but cannot be used in many food vehicles because of sensory issues. Thus, potentially less well-absorbed forms of iron commonly are used in food fortification. The bioavailability of iron fortificants can, however, be enhanced with innovative ingredient technologies. Ascorbic acid, NaFeEDTA, ferrous bisglycinate, and dephytinization all enhance the absorption of fortification iron, but add to the overall costs of fortification. While all strategies cannot be recommended for all food fortification vehicles, individual strategies can be recommended for specific foods. For example, the addition of ascorbic acid is appropriate for dry blended foods such as infant foods and other dry products made for reconstitution that are packaged, stored, and prepared in a way that maximizes retention of this vitamin. NaFeEDTA can be recommended for fortification of fish sauce and soy sauce, whereas amino acid chelates may be more useful in milk products and beverages. With further development, dephytinization may be possible for low-cost, cereal-based complementary foods in developing countries. Encapsulation of iron salts in lipid coatings, while not an iron absorption-enhancing strategy per se, can prevent soluble forms of iron from interacting undesirably with some food vehicles and hence broaden the application of some fortificants. Research relevant to each of these strategies for enhancing the bioavailability or utility of iron food fortificants is reviewe

10
RANDOMIZED TRIAL (RCT) BMJ open (2020) PMID: 32801202 ↗
Is untargeted iron supplementation harmful when iron deficiency is not the major cause of anaemia? Study protocol for a double-blind, randomised controlled trial among non-pregnant Cambodian women.
Clinical Trial Synthesis 2020 Randomized Controlled Trial (RCT) published in BMJ open. Key conclusion: METHODS AND ANALYSIS: A 12-week three-arm, double-blind, randomised controlled supplementation trial was conducted in Cambodia to determine if there is potential harm associated with untargeted iron supplementation.
View Original PubMed Abstract ↓

INTRODUCTION: The WHO recommends daily oral iron supplementation for 12 weeks in women and adolescents where anaemia prevalence is greater than 40%. However, if iron deficiency is not a major cause of anaemia, then, at best, untargeted iron supplementation is a waste of resources; at worst, it could cause harm. Further, different forms of iron with varying bioavailability may present greater risks of harm. METHODS AND ANALYSIS: A 12-week three-arm, double-blind, randomised controlled supplementation trial was conducted in Cambodia to determine if there is potential harm associated with untargeted iron supplementation. We will recruit and randomise 480 non-pregnant women (ages 18-45 years) to receive one of three interventions: 60 mg elemental iron as ferrous sulfate (the standard, commonly used form), 18 mg ferrous bisglycinate (a highly bioavailable iron amino acid chelate) or placebo. We will measure ferritin concentrations (to evaluate non-inferiority between the two forms of iron), as well as markers of potential harm in blood and stool (faecal calprotectin, gut pathogen abundance and DNA damage) at baseline and 12 weeks. Mixed-effects generalised linear models will be used to assess the effect of iron on ferritin concentration and markers of potential harm at 12 weeks. ETHICS AND DISSEMINATION: Ethical approval was obtained from the University of British Columbia Clinical Research Ethics Board (H18-02610), the Children's and Women's Health Centre of British Columbia Research Ethics Board (H18-02610) and the National Ethics Committee for Health Research in Cambodia (273-NECHR). Findings will be published in peer-reviewed journals, presented to stakeholders and policymakers globally and shared within participants' communities. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov Registry (NCT04017598). © Author(s) (or their employer(s)) 2020. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.

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