Iron absorption and dairy products
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Iron Absorption and Dairy Products: Overview
Iron absorption from the diet is influenced by many factors, including the presence of dairy products. Dairy foods are a common part of many diets, so understanding their effect on iron absorption is important for nutritional planning and preventing iron deficiency.
Dairy Products and Iron Absorption in Mixed Meals
Studies show that adding dairy products like milk or yogurt to typical meals has little to no significant effect on total iron absorption. For example, when a glass of milk or yogurt was added to a standard meal, non-heme iron absorption changed only slightly (from 2.2% to 2.0–2.1%), and total iron absorption remained nearly the same (9.7% to 9.4–9.5%) . This suggests that, under real-life eating conditions, increasing dairy intake does not meaningfully reduce iron absorption from meals that already contain dairy .
Dairy Proteins and Iron Bioavailability
Research indicates that certain proteins in cow’s milk, specifically casein and whey, can reduce iron absorption when compared to other protein sources like egg white. Meals containing casein or whey had lower dialyzable (absorbable) iron fractions and lower iron absorption percentages than those with egg white protein . However, when these milk proteins are broken down (hydrolyzed), their inhibitory effect on iron absorption is reduced .
Calcium in Dairy and Its Effect on Iron Absorption
Calcium, a major component of dairy products, can inhibit both heme and non-heme iron absorption, especially when calcium and iron are consumed together in the same meal. However, the overall effect of calcium from dairy on iron status is generally small, especially in people with adequate iron intake. Most studies show that calcium supplements or increased dairy consumption have only a minor impact on iron absorption, unless calcium intake is habitually very low or iron intake is marginal . The small negative effect of dairy on iron absorption could be more important during pregnancy or in populations at risk of iron deficiency if iron supplements are not used .
Iron Absorption from Human Milk vs. Cow’s Milk
Iron is absorbed much better from human milk than from cow’s milk or infant formulas. Human milk contains less casein, phosphate, and calcium—components that are thought to inhibit iron absorption. Even though human milk has less iron than cow’s milk formulas, infants absorb a higher percentage of it, making it a better source of bioavailable iron for infants 25.
Iron Fortification of Dairy Products
Fortifying dairy products like milk and yogurt with iron can improve their contribution to dietary iron intake. The type of iron compound used for fortification matters: ferrous sulfate and iron-casein complexes in yogurt, for example, have been shown to enhance iron absorption more effectively than some other iron compounds . In fortified milk drinks, iron absorption from ferrous ammonium phosphate and ferrous sulfate is higher than from ferric pyrophosphate, especially in children . Adding ascorbic acid (vitamin C) to fortified milk also significantly increases iron absorption .
Milk Components That May Enhance Iron Absorption
Some peptides produced during milk digestion, as well as specific milk proteins like osteopontin, may actually enhance iron uptake in intestinal cells. These components can bind iron and help deliver it in a form that is more easily absorbed, even in the presence of inhibitors like phytic acid 69. However, the nutritional significance of these effects in real diets still needs further study 69.
Conclusion
Dairy products can have a small inhibitory effect on iron absorption, mainly due to their calcium and protein content, but this effect is generally minor in the context of a balanced diet. Human milk remains superior to cow’s milk for infant iron absorption. Fortification of dairy products with appropriate iron compounds and the addition of enhancers like vitamin C can help improve iron bioavailability. Some milk-derived peptides and proteins may even support iron absorption, suggesting that the relationship between dairy and iron is complex and influenced by many factors. Overall, the nutritional benefits of dairy products outweigh their slight inhibitory effect on iron absorption for most people 12345678+2 MORE.
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