Ferrous Ascorbate vs. Ferrous Bisglycinate: Which Is Better for You?

Iron deficiency is the most common nutritional deficiency worldwide, affecting an estimated 2 billion people globally. When oral supplementation is necessary, selecting the right form is crucial, with ferrous ascorbate and ferrous bisglycinate being two highly regarded options with distinct advantages and drawbacks.

Quick Summary

This article compares ferrous ascorbate and ferrous bisglycinate, evaluating their absorption rates, gastrointestinal side effects, and overall suitability for treating iron deficiency based on scientific evidence and user tolerance.

Key Points

• Tolerability: Ferrous bisglycinate is significantly gentler on the stomach and causes fewer gastrointestinal side effects than ferrous ascorbate.

• Bioavailability: Both forms offer good bioavailability, but bisglycinate's chelated structure provides superior absorption, especially in the presence of dietary inhibitors.

• Pregnancy: A meta-analysis found ferrous bisglycinate to be more effective at increasing hemoglobin and causing fewer side effects in pregnant women.

• Cost: Ferrous ascorbate is generally more affordable than the chelated ferrous bisglycinate.

• Decision-Making: For those with sensitive stomachs or in special populations like pregnancy, ferrous bisglycinate is often the better, though pricier, choice.

Understanding Ferrous Ascorbate

Ferrous ascorbate is a compound that combines ferrous iron (Fe$^{2+}$) with ascorbic acid (vitamin C). The vitamin C component is key to its mechanism, as it aids in maintaining the iron in its more absorbable ferrous state and prevents its oxidation. This combination has been shown to offer significant clinical advantages over less bioavailable forms like ferrous sulfate. In fact, some studies have noted a rapid increase in hemoglobin levels in patients using ferrous ascorbate, with improvements seen in as little as 15 days.

Benefits of Ferrous Ascorbate

• Enhanced Absorption: The presence of ascorbic acid prevents oxidation, improving the uptake of iron from the gastrointestinal tract.
• Effective Treatment: It is widely used and proven to be effective for treating iron deficiency anemia, including during pregnancy.
• Rapid Response: Studies have shown a quick increase in hemoglobin levels following supplementation.

Disadvantages and Side Effects

• GI Issues: While generally better tolerated than ferrous sulfate, it can still cause side effects such as constipation, nausea, vomiting, and stomach upset in some individuals.
• Drug Interactions: It can interfere with the absorption of certain medications, including some antibiotics and thyroid hormones.

Understanding Ferrous Bisglycinate

Ferrous bisglycinate is an iron amino acid chelate, meaning the iron ion is bound to two molecules of the amino acid glycine. This chelated structure protects the iron from dietary inhibitors and stomach acid, allowing it to remain intact as it passes through the digestive system. This results in a higher bioavailability and less gastrointestinal irritation compared to unchelated iron salts.

Benefits of Ferrous Bisglycinate

• Superior Bioavailability: The chelated form is highly bioavailable, allowing the body to absorb it more efficiently.
• High Tolerability: It causes significantly fewer gastrointestinal side effects, such as constipation and nausea, making it ideal for individuals with sensitive stomachs or chronic digestive issues.
• Reduced Interference: It is less likely to be affected by dietary inhibitors like phytates, tannins, and oxalates.
• Effective for Pregnancy: A meta-analysis confirmed its superiority in increasing hemoglobin levels and reducing adverse events in pregnant women compared to other iron salts.

Potential Drawback

• Higher Cost: Due to its advanced chelated form, ferrous bisglycinate can sometimes be more expensive than ferrous ascorbate or traditional iron salts.

Ferrous Ascorbate vs. Ferrous Bisglycinate: A Head-to-Head Comparison

Feature	Ferrous Ascorbate	Ferrous Bisglycinate
Chemical Structure	Ferrous iron combined with ascorbic acid (vitamin C).	Chelated iron bound to two glycine molecules.
Bioavailability	Good, enhanced by vitamin C. May be affected by food.	Very high, protected from dietary inhibitors by its chelated form.
Tolerability	Generally better than ferrous sulfate, but can still cause GI side effects.	Excellent, with significantly fewer gastrointestinal side effects reported.
Cost	Typically more affordable than bisglycinate.	Often more expensive due to advanced chelation process.
Impact on Other Nutrients	Can interfere with certain medication absorption.	Less interference with other nutrients and medications.

Bioavailability and Absorption

While a study in water found no significant difference in absorption between the two forms, ferrous bisglycinate's chelated structure theoretically provides an advantage, protecting it from dietary inhibitors present in food that can hinder absorption. This suggests bisglycinate may be a more reliable option when taken with meals, though iron supplements are often recommended on an empty stomach for maximum absorption.

Gastrointestinal Side Effects

This is arguably the most significant differentiating factor. Clinical trials have consistently demonstrated ferrous bisglycinate's superior tolerability profile. A meta-analysis highlighted a 64% lower rate of gastrointestinal adverse events in pregnant women taking bisglycinate compared to other iron salts, a significant finding for long-term adherence. Ferrous ascorbate, while generally better tolerated than the older ferrous sulfate, still carries a higher risk of GI upset than its bisglycinate counterpart.

Special Populations: Pregnancy

For pregnant women, who require increased iron intake, tolerability is critical for compliance. A meta-analysis provided compelling evidence favoring ferrous bisglycinate in this group, showing a significant increase in hemoglobin and a reduction in GI side effects. This makes bisglycinate a preferable choice for many expectant mothers.

How to Choose the Right Iron Supplement for You

• Consult a Professional: Always consult a healthcare provider to determine if you need an iron supplement and to get the correct dosage.
• Assess Tolerability: If you have a history of GI issues with iron supplements, ferrous bisglycinate is likely the better choice due to its gentle nature.
• Consider Cost: If budget is a major concern, and you tolerate standard iron supplements well, ferrous ascorbate could be a more economical option.
• Evaluate Specific Needs: For pregnant women or those with inflammatory bowel conditions, the superior tolerability and absorption of ferrous bisglycinate make it highly recommended.
• Look for Enhancers: Some products combine iron with vitamin C or folic acid, which can improve efficacy. Ensure you check the elemental iron content on the label.

Conclusion: Which is Better for Your Needs?

The choice between ferrous ascorbate and ferrous bisglycinate depends largely on individual needs and tolerance. While ferrous ascorbate provides effective iron supplementation with the added benefit of vitamin C for absorption, it is more prone to causing gastrointestinal side effects than its chelated counterpart. Ferrous bisglycinate, with its superior chelated structure, stands out for its high bioavailability and exceptional tolerability, making it a preferable choice for those with sensitive stomachs, chronic digestive issues, or during pregnancy. Ultimately, for those prioritizing comfort and maximum absorption with minimal side effects, ferrous bisglycinate often holds the advantage, assuming the cost is manageable. For more information on iron and other minerals, consult the NIH Office of Dietary Supplements.

Frequently Asked Questions

Can I take ferrous bisglycinate or ferrous ascorbate on an empty stomach?

Both are typically better absorbed on an empty stomach. However, if you experience stomach upset, taking it with a light meal may help, though it could slightly decrease absorption.

Which iron supplement is best for pregnancy?

Ferrous bisglycinate is often recommended for pregnant women due to its high tolerability and proven efficacy in raising hemoglobin levels with fewer GI side effects.

Do these iron supplements cause constipation?

While all oral iron can potentially cause constipation, ferrous bisglycinate is significantly less likely to do so compared to ferrous ascorbate or other iron salts.

What is the main difference between chelated iron and non-chelated iron?

Chelated iron, like ferrous bisglycinate, is bound to an amino acid to enhance absorption and reduce digestive upset. Non-chelated iron, like ferrous ascorbate, relies on other components (like vitamin C) to aid absorption.

Will these supplements cause black or tarry stools?

Yes, black or tarry stools are a normal and harmless side effect of taking oral iron supplements, including these two forms.

Is one form more effective at treating iron deficiency?

While both are effective, ferrous bisglycinate's superior absorption and tolerability can lead to better patient compliance and potentially more consistent results over time, particularly for sensitive individuals.

What is the benefit of ferrous ascorbate containing vitamin C?

The vitamin C in ferrous ascorbate enhances the absorption of the iron by keeping it in the ferrous (Fe$^{2+}$) state, which is more readily absorbed by the body.