Does iron supplementation interact with milk consumption?

From the Guidelines

The concurrent administration of iron supplements with milk may decrease iron absorption due to the inhibitory effects of calcium on iron bioavailability 1.

Key Considerations

• Iron supplements such as ferrous sulfate, ferrous fumarate, and ferrous gluconate may have reduced absorption when taken with milk due to the presence of calcium, which can inhibit iron absorption 1, 2.
• To minimize this interaction, it is recommended to take iron supplements 1-2 hours apart from milk consumption 2.
• Alternative iron formulations such as ferrous fumarate may be less affected by milk intake, but more research is needed to confirm this 2.
• Vitamin C can enhance iron absorption, and taking iron supplements with citrus fruits or drinks may aid absorption 2, 3.
• Tea and coffee should be avoided within an hour after taking iron supplements, as they can inhibit iron absorption 3.

Recommendations

• Take iron supplements 1-2 hours apart from milk consumption to minimize the inhibitory effects of calcium on iron absorption.
• Consider alternative iron formulations such as ferrous fumarate.
• Take iron supplements with vitamin C to enhance absorption.
• Avoid consuming tea and coffee within an hour after taking iron supplements.

From the Research

Interaction between Iron Supplementation and Milk Consumption

• The effect of milk consumption on iron supplementation has been studied in various research papers 4, 5, 6, 7, 8.
• A study published in 1975 found that milk does not significantly inhibit the absorption of iron from ferrous ion, ferric-NTA, or ferric fructose in mice and chicks 4.
• Another study published in 1992 reported that dairy products may have a slight inhibitory effect on iron availability, but the nutritional benefits of dairy products outweigh this effect 5.
• A randomized trial published in 2019 found that iron absorption from an iron-casein complex was not significantly different from that of ferrous sulfate in healthy young women 6.
• A study published in 2004 found that calcium from milk or calcium-fortified foods does not inhibit nonheme-iron absorption from a whole diet consumed over a 4-day period 7.
• A study published in 2012 found that the addition of zinc up to 20 mg/L does not significantly inhibit iron absorption from milk fortified with 10 mg/L of iron 8.

Factors Influencing Iron Absorption

• The absorption of iron from milk can be influenced by various factors, including the type of iron compound, the presence of other nutrients, and the overall diet composition 4, 5, 7.
• Human milk has been found to have superior bioavailability of iron compared to cow's milk, possibly due to differences in casein, phosphate, and calcium content 5.
• The iron-casein complex has been found to have iron bioavailability comparable to that of ferrous sulfate in healthy young women 6.

Implications for Iron Supplementation

• The findings of these studies suggest that milk consumption does not significantly inhibit iron absorption from iron supplements 4, 6, 7, 8.
• Iron supplementation can be effectively delivered through milk or milk-based products, especially in populations with high rates of iron deficiency 4, 5, 6.