Iron Bisglycinate Bioavailability & Efficacy

About Iron Deficiency 

Iron deficiency anemia (IDA) is defined as having a haemoglobin level of less than the 5th percentile for the age category. (1) Approximately 30% of total worldwide population, and 43% of all children, suffer from IDA. (1) Children under two are at the highest risk for IDA, because of high demand due to rapid growth, however, the early stages of IDA are often missed by parents due to the relatively subtle warning signs. (1) 


Besides anemia, iron deficiency can lead to increased fatigue, poor concentration, and poor memory, all of which may effect cognitive and social function. (1) Iron deficiency may also cause pica; cravings for non-food substances such as soap and dirt, and pasophagia; cravings for rice.(1)


About Iron Supplementation

Two of the most common forms of iron supplementation are iron polymaltose, and ferrous sulphate. Both of these options, however, have unpleasant or inefficient characteristics. (1) Ferrous sulphate has been shown to raise haemoglobin levels much more rapidly than polymaltose, but common side effects include vomiting, nausea, abdominal pain, constipation, diarrhea, and stained teeth. (1) Iron polymaltose typically causes less gastrointestinal side effects, however, is less efficient at restoring iron stores. (2) 


More recently, iron bisglycinate has been recognised as a potentially superior treatment option for iron deficiency than iron polymaltose and ferrous sulphate. 


Iron Bisglycinate Bioavailability & Efficacy

The differing structural and absorption characteristics of iron bisglycinate and iron polymaltose may contribute to the contrast in their bioavailability and efficacy. Iron bisglycinate has a stable structure, with a molecular weight of approximately 204 daltons. In contrast, iron polymaltoses are complexes with molecular weights between 50,000 and 452,000 daltons. (2) This higher molecular weight of iron polymaltose has been shown to decrease absorption capabilities. (2)


Iron bisglycinate has a higher bioavailability than both ferrous sulphate and iron polymaltose; 90.9% compared to around 26.7% for ferrous sulphate and iron polymaltose. (1, 2) This higher bioavailability can be explained by the fact that iron bisglycinate doesn’t form insoluble compounds with iron absorption inhibitors like phytates, oxalates, and tannins, found in high quantities in cereals and cereal-based products. (1) 


Several studies support the efficacy of iron bisglycinate as a treatment for IDA or low ferritin levels. (2, 3, 4) One randomised controlled pilot trial of 20 children with IDA compared the effect of supplementation with iron bisglycinate to polymaltose iron. (2) After 45 days, both groups showed improvement in haemoglobin levels, Mean Corpuscular Volume (MCV) and cell distribution width, but only those in the bisglycinate group displayed a significant increase in ferritin and Mean Corpuscular Haemoglobin (MCH) levels. (2) Considering the low dosage (3-6mg/kg of elemental iron/day), and the relatively short treatment period (45 days), these results support the efficacy of iron bisglycinate supplementation. (2) These results have also been reinforced by a study on iron-deficient infants (6-36 months), who were assigned either ferrous sulphate, or iron bisglycinate. (4) Although haemoglobin levels increased significantly in both the ferrous sulphate and the iron bisglycinate group, plasma ferritin, which represents iron stores in the body, increased significantly only in the iron bisglycinate group. (4)


Another study of 200 children (5 -13 yrs of age) with low ferritin levels also found that iron bisglycinate supplementation for 12 weeks elicited a significant increase in the MCH levels, whereas iron polymaltose supplementation did not. (3) MCH changes can only be detected after several weeks, sometimes months, of iron storage by the body, therefore these results further indicate the efficacy of iron bisglycinate for restoring bodily iron stores compared to iron polymaltose. (3) 


This same study also highlighted a more sustained ferritin increase in the iron bisglycinate group, compared to ferrous sulphate supplementation. Although ferritin levels increased in both groups after the 12 weeks of supplementation, when measured again 6 months later, the increase was significantly higher in the iron bisglycinate group. (3)


Iron Regulation

An additional significant benefit of iron bisglycinate, as opposed to iron polymaltose, is its ability to regulate its absorption rate according to the needs of the person taking it. (2, 5) An inverse correlation between initial haemoglobin levels and the increase in iron reserves provided by iron bisglycinate supplementation demonstrates a regulatory capability. (2) Adaptive absorption can help avoid iron overload, which can result in metal-induced oxidative damage and diabetes, osteoporosis, joint pain, and neurodegeneration. (2) This characteristic also suggests that iron bisglycinate is a safer way to treat iron deficiencies with long-term supplementation, even after the normalisation of haemoglobin levels. In contrast, iron absorption via FeP supplementation is not regulated, leading to a greater risk of iron overload. (2)



Iron bisglycinate exhibits good tolerability, with low incidence of adverse effects. (1.2) A number of studies have shown that iron bisglycinate is much better tolerated than ferrous sulphate, with less of the gastrointestinal side effects commonly reported after ferrous sulphate supplementation. (1, 2)








  1. Perveen A, Raja NF, Khan IM, Shaheen H, Imran M, Ahmad RS. Comparison of Conventional and Newer Iron Preparations for the Treatment of Iron Deficiency Anaemia in Children. Journal of Rawalpindi Medical College. 2020 Jun 26;24(2):112-6.
  2. Vasconcelos AR, Valzachi Rocha Maluf MC. Iron Bisglycinate Chelate and Polymaltose Iron for the Treatment of Iron Deficiency Anemia: A Pilot Randomized Trial. Current pediatric reviews. 2018 Nov 1;14(4):261-8.
  3. Duque X, Martinez H, Vilchis-Gil J, Mendoza E, Flores-Hernández S, Morán S, Navarro F, Roque-Evangelista V, Serrano A, Mera RM. Effect of supplementation with ferrous sulfate or iron bis-glycinate chelate on ferritin concentration in Mexican schoolchildren: a randomized controlled trial. Nutrition journal. 2014 Dec;13(1):1-0.
  4. Pineda O, Ashmead HD. Effectiveness of treatment of iron-deficiency anemia in infants and young children with ferrous bis-glycinate chelate. Nutrition. 2001 May 1;17(5):381-4.
  5. Bovell-Benjamin AC, Viteri FE, Allen LH. Iron absorption from ferrous bisglycinate and ferric trisglycinate in whole maize is regulated by iron status. The American journal of clinical nutrition. 2000 Jun 1;71(6):1563-9.



Brittany Darling
Tags: Iron