Quick Summary

Iron bisglycinate (ferrous bisglycinate) is a chelated form of iron commonly used in dietary supplements. It is designed to potentially enhance iron absorption while reducing gastrointestinal side effects often associated with traditional iron salts like ferrous sulfate. Iron itself is an essential mineral involved in oxygen transport, energy metabolism, and various enzymatic processes in the body.

What Is It?

Iron bisglycinate, chemically known as ferrous bisglycinate, is iron bound to two glycine molecules forming a chelate complex. This structure is intended to improve the mineral’s stability and bioavailability when taken as a supplement. It differs from more commonly used iron salts such as ferrous sulfate, fumarate, or gluconate.

Main Functions in the Body

  • Component of hemoglobin, the protein in red blood cells responsible for oxygen transport.
  • Constituent of myoglobin, which helps store oxygen in muscle cells.
  • Participates in cellular energy metabolism via cytochrome enzymes involved in electron transport and oxidative phosphorylation.
  • Required as a cofactor for numerous enzymatic reactions critical for DNA synthesis, neurotransmitter production, and immune function.

Recommended Intake and Upper Limit

Recommended intake values for iron vary by age, sex, and life stage. Iron bisglycinate supplements provide elemental iron, contributing toward meeting these requirements. For general guidance, refer to official recommendations such as those from the NIH Office of Dietary Supplements.

The established upper intake level (UL) for iron is based on elemental iron. Exceeding recommended limits may increase the risk of adverse effects, including gastrointestinal irritation and systemic toxicity.

Best Food Sources

  • Heme iron sources: red meat, poultry, fish — generally have higher bioavailability.
  • Non-heme iron sources: legumes, fortified cereals, and many plant-based foods — typically less bioavailable but important dietary contributors.

Deficiency: Causes, Symptoms and Risk Groups

Iron deficiency is the most common nutrient deficiency worldwide. Causes include inadequate dietary intake, increased requirements (e.g., pregnancy), or chronic blood loss.

Risk groups:

  • Infants and young children
  • Women of reproductive age
  • Pregnant women
  • Individuals experiencing chronic blood loss (e.g., gastrointestinal bleeding)

Signs and symptoms of iron deficiency may include:

  • Fatigue and general weakness
  • Paleness (pallor)
  • Shortness of breath on exertion
  • Impaired cognitive and physical performance
  • Reduced immune function

Iron deficiency in at-risk groups may sometimes require supplementation under healthcare guidance.

Supplement Forms

The chelated form (ferrous bisglycinate) is among the forms used to potentially improve absorption and reduce side effects.

Absorption and Bioavailability

Iron bisglycinate is a chelated form intended to improve absorption and gastrointestinal tolerance compared to some conventional iron salts.

Enhancers of absorption include:

Inhibitors of absorption include:

  • Phytates found in some grains and legumes
  • Polyphenols found in tea, coffee, and some plant foods
  • Calcium

Form differences:

  • Ferrous bisglycinate is often better tolerated with fewer gastrointestinal side effects than ferrous sulfate.
  • It may have superior bioavailability compared to some non-chelated iron forms, although evidence is limited and not definitive.

Potential Benefits: What Does the Evidence Say?

Improvement of iron status and anemia:

Moderate-quality human clinical trial evidence indicates that iron bisglycinate supplementation can effectively increase hemoglobin and ferritin levels in individuals with iron deficiency or iron deficiency anemia. It may also cause fewer gastrointestinal side effects compared to traditional iron salts such as ferrous sulfate. However, the number of large-scale, long-term trials is limited, and study designs vary, so conclusions should be considered cautiously.

There is currently no strong evidence supporting benefits of iron bisglycinate supplementation in iron-replete (non-deficient) healthy individuals.

Side Effects and Toxicity

  • Common side effects include constipation, nausea, and gastrointestinal discomfort.
  • Iron bisglycinate is generally associated with fewer and less severe gastrointestinal side effects compared to ferrous sulfate, but mild symptoms may still occur.

Toxicity: Excess intake of iron, especially at doses above the established upper limit for elemental iron, can cause toxicity. Symptoms of iron overdose include gastrointestinal irritation, nausea, vomiting, and in severe cases, systemic effects potentially causing organ damage.

Users should not exceed recommended upper intake levels for iron supplements, and use should be supervised by healthcare professionals especially when taken long-term or in high doses.

Special populations: Individuals with iron overload disorders such as hemochromatosis should avoid iron supplementation without medical supervision to prevent toxicity risks.

Drug and Nutrient Interactions

No specific interactions unique to iron bisglycinate were identified in the available evidence. However, iron supplements generally can interact with certain medications, including some antibiotics and thyroid medications, by reducing their absorption. People on medication should consult a healthcare professional before taking iron supplements.

Who Should Be Careful?

  • People with iron overload disorders (e.g., hemochromatosis) should avoid iron supplements unless advised by a physician.
  • Individuals with kidney disease or thyroid disorders should exercise caution and seek medical guidance before supplement use.
  • Pregnant and breastfeeding women should consult their healthcare provider to determine appropriate iron intake.
  • Anyone with chronic medical conditions or on prescription medications should discuss iron supplementation with their healthcare professional.

Frequently Asked Questions

How is iron bisglycinate different from ferrous sulfate?
Iron bisglycinate is a chelated form where iron is bound to glycine molecules, which may enhance absorption and reduce gastrointestinal side effects compared to ferrous sulfate, a common non-chelated iron salt.
Can iron bisglycinate cause constipation?
Yes, constipation is a possible side effect, but iron bisglycinate is generally considered to cause fewer digestive issues than some other iron forms.
Who needs to take iron supplements?
Individuals diagnosed with iron deficiency or iron deficiency anemia, particularly infants, women of reproductive age, pregnant women, and those with chronic blood loss, may benefit under medical advice.
Is iron bisglycinate suitable for vegetarians or vegans?
Yes, iron bisglycinate supplements do not contain animal-derived heme iron, but dietary sources of iron should be balanced to meet individual needs.
Should I take vitamin C with iron bisglycinate?
Vitamin C can enhance absorption of non-heme iron including iron bisglycinate, so taking them together may improve efficacy.

Evidence Limitations

  • There are no specific EU-authorized health claims for iron bisglycinate at this time.
  • Available clinical trials vary in size and duration; large-scale, long-term randomized controlled trials comparing iron bisglycinate with other iron forms are limited.
  • Safety data regarding long-term supplementation beyond improving iron status are incomplete.
  • Differences among iron supplement forms should not be overgeneralized due to limited direct comparative evidence.

References

Disclaimer: This information is intended for educational purposes and does not constitute medical advice. Individuals who are pregnant, breastfeeding, have medical conditions such as kidney or thyroid disease, iron overload disorders, or who are taking medications should consult a qualified healthcare professional before starting any new supplement.

Last Reviewed

June 2024