What decreases iron absorption
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Factors That Decrease Iron Absorption
Iron absorption is a critical process for maintaining adequate iron levels in the body. However, several factors can inhibit this process, leading to reduced iron uptake. This article explores various elements that decrease iron absorption, including physical activity, dietary components, and physiological conditions.
Strenuous Physical Activity and Iron Absorption
Impact of Strenuous Exercise
Strenuous physical activity has been shown to decrease iron absorption significantly. This effect is primarily due to the increase in the iron regulatory hormone hepcidin, which is stimulated by inflammation and muscle glycogen depletion during intense exercise. Hepcidin inhibits iron absorption by binding to ferroportin, the only known cellular iron exporter, leading to its internalization and degradation . Studies involving military personnel and athletes have demonstrated that periods of intense physical activity result in elevated hepcidin levels and reduced iron absorption compared to rest periods .
Energy Deficit and Iron Absorption
An energy deficit, often accompanying strenuous physical activity, exacerbates the decline in iron absorption. When the body's energy intake does not meet its expenditure, the increase in hepcidin is more pronounced, further reducing iron absorption. This suggests that maintaining energy balance during periods of intense physical activity may help mitigate the negative impact on iron absorption.
Dietary Factors Affecting Iron Absorption
Inhibitory Compounds in Food
Several dietary components are known to inhibit iron absorption. These include:
- Phytic Acid/Phytates: Found in grains and legumes, phytic acid binds iron and reduces its bioavailability.
- Polyphenols/Tannins: Present in tea, coffee, and some fruits and vegetables, these compounds form complexes with iron, hindering its absorption .
- Calcium: High calcium intake from dairy products can interfere with iron absorption.
- Proteins from Soy, Milk, and Eggs: These proteins can also inhibit iron uptake.
Effect of Beverages
Consuming certain beverages with meals can significantly reduce iron absorption. For instance, coffee and tea are potent inhibitors of iron absorption due to their high polyphenol content. Studies have shown that coffee can reduce iron absorption by up to 39%, and tea by 64%, when consumed with meals. The timing of beverage consumption also matters; drinking coffee an hour before or after a meal can still inhibit iron absorption, though to a lesser extent than simultaneous consumption.
Iron Supplementation Practices
The frequency and timing of iron supplementation can influence iron absorption. Daily or twice-daily iron supplementation increases serum hepcidin levels, which in turn decreases iron absorption from subsequent doses. Alternate-day supplementation has been found to optimize iron absorption by allowing hepcidin levels to normalize between doses .
Physiological Conditions
Obesity and Iron Absorption
Obesity is associated with chronic low-grade inflammation, which increases hepcidin levels and reduces iron absorption. Studies have shown that overweight and obese individuals have lower iron absorption rates compared to normal-weight individuals. Additionally, the enhancing effect of ascorbic acid on iron absorption is less pronounced in obese individuals.
Genetic Conditions
In conditions like genetic haemochromatosis, where hepcidin expression is decreased, dietary modifications can help manage iron levels. Avoiding foods and beverages that promote iron absorption and focusing on those that inhibit it can be beneficial for individuals with this condition.
Conclusion
Iron absorption is influenced by a variety of factors, including physical activity, dietary components, and physiological conditions. Strenuous exercise and energy deficits increase hepcidin levels, reducing iron absorption. Certain foods and beverages, particularly those high in phytic acid, polyphenols, and calcium, also inhibit iron uptake. Understanding these factors can help in managing iron levels more effectively, particularly in individuals with specific health conditions or dietary needs.
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