What inhibits iron absorption
Pro Research Analysisby 
Searched over 200M research papers
Factors Inhibiting Iron Absorption
Iron absorption is a critical process for maintaining adequate iron levels in the body. However, several dietary components can inhibit this process, leading to potential iron deficiency. This article explores the various inhibitors of iron absorption, supported by multiple research studies.
Calcium and Iron Absorption
Calcium is known to inhibit iron absorption. Studies have shown that the addition of calcium to meals can reduce iron absorption by 18-27%, depending on the amount of calcium added 1. This inhibitory effect can be counteracted by ascorbic acid (vitamin C), which enhances iron absorption significantly 1.
Phytates and Iron Absorption
Phytates, found in many plant-based foods, are potent inhibitors of iron absorption. Research indicates that even small amounts of phytates can significantly reduce iron absorption. For instance, 2 mg of phytate can inhibit iron absorption by 18%, while 250 mg can reduce it by 82% 3. The presence of ascorbic acid can mitigate this inhibitory effect to some extent 3.
Polyphenols and Tannins
Polyphenols and tannins, present in foods and beverages like tea, coffee, and certain vegetables, also inhibit iron absorption. The inhibition is dose-dependent, with higher amounts leading to greater reductions in iron absorption. For example, tannic acid, a type of tannin, can inhibit iron absorption by up to 88% at higher doses 5. Similarly, coffee can reduce iron absorption by up to 64% when consumed with meals 4.
Proteins from Soy, Milk, and Eggs
Proteins from soybeans, milk, and eggs have been identified as inhibitors of iron absorption. These proteins can form complexes with iron, making it less available for absorption in the gastrointestinal tract 2.
Competitive Inhibition by Other Minerals
Manganese and zinc can competitively inhibit iron absorption due to their similar physicochemical properties and shared absorptive pathways. Manganese, in particular, has been shown to significantly reduce iron absorption when present in higher amounts 6. Zinc can also inhibit iron absorption, but this effect is more pronounced in solution rather than in mixed meals 6.
Tea and Iron Absorption
Tea is a well-documented inhibitor of iron absorption due to its high tannin content. Studies have shown that tea can reduce iron absorption by 41-95%, depending on the type and amount of tea consumed 910. The inhibitory effect of tea is significant enough to contribute to iron deficiency, especially in diets that rely heavily on plant-based foods 10.
Conclusion
Understanding the factors that inhibit iron absorption is crucial for managing and preventing iron deficiency. Calcium, phytates, polyphenols, tannins, certain proteins, and competitive minerals like manganese and zinc all play a role in reducing iron absorption. Strategies to mitigate these effects include increasing the intake of ascorbic acid and heme iron sources, and adjusting the timing of consumption of inhibitory foods and beverages.
Sources and full results
Most relevant research papers on this topic