Why You Should NOT Be Taking Calcium and Iron Together

Calcium and iron are both essential minerals that play vital roles in the human body. Calcium is responsible for building and maintaining strong bones, while iron helps transport oxygen in the blood. Though both minerals are crucial, there is a common recommendation to avoid taking iron and calcium supplements together. Here's why:

1.  Competitive Absorption: Calcium and iron have a competitive relationship when it comes to absorption. When consumed together, calcium can inhibit the absorption of iron. This is particularly concerning for those at risk of iron-deficiency anemia.¹ Both calcium and non-heme iron (the type of iron found in plant-based foods and supplements) use divalent metal transporters for absorption in the intestines. When both minerals are present in high concentrations, they compete for these transporters. As a result, the absorption of one or both can be reduced.²

2.  Digestive Issues: High doses of calcium, especially when taken with iron supplements, can cause digestive issues like constipation. On the other hand, some iron supplements can cause stomach cramps, nausea, or diarrhea.³ The stomach's acidic environment is essential for iron absorption. Calcium carbonate, a common form of calcium supplement, can act as an antacid, raising the pH in the stomach. This change can potentially decrease the solubility and absorption of non-heme iron.⁴

3.  Optimal Absorption: To get the most out of your supplements, it's essential to optimize absorption. By separating the intake of calcium and iron supplements, one can ensure that the body maximally absorbs both minerals.⁵ In the intestines, calcium can bind with iron, forming insoluble complexes. These complexes are not absorbable. Thus, even if there's a large quantity of iron in the digestive system, it might not be absorbed efficiently if there's also a high concentration of calcium.⁶

4.  Special Populations: Pregnant women, vegetarians, weight loss surgery patients, and others at a higher risk of iron deficiency might be particularly affected by the competitive absorption between calcium and iron.⁷

5.  Meal Considerations: When planning meals, especially for those who rely on fortified foods for their iron intake, it might be beneficial to separate foods high in calcium from those rich in iron. For example, having dairy products at a different time from iron-fortified cereals can help optimize the absorption of both minerals.⁸

6.  Heme vs. Non-Heme Iron: It's worth noting that heme iron (found in animal-based foods) is absorbed differently than non-heme iron. While calcium can affect non-heme iron absorption, its impact on heme iron absorption is less significant. This differentiation can be attributed to the distinct pathways these two types of iron take during absorption.⁹

7.  Regulation of Iron Homeostasis: The body has a sophisticated system to regulate iron levels. When iron stores are low, the intestines increase iron absorption. When iron levels are adequate or high, absorption decreases. The presence of other minerals, including calcium, can further influence this regulatory system.¹⁰

While both iron and calcium intake are vital for our health, it's important to be strategic about their intake. By understanding and considering their interactions, one can make informed decisions about diet and supplementation to ensure optimal absorption and health benefits. Understanding these mechanisms highlights the importance of mindful consumption of calcium and iron. When planning a diet or supplement routine, it might be beneficial to separate the intake of calcium-rich foods or supplements from iron-rich ones to ensure optimal absorption.

RESOURCES

1-  Hallberg L, Brune M, Rossander L. Effect of ascorbic acid on iron absorption from different types of meals. Human Nutrition. Applied Nutrition. 1986;40(2):97-113.

2-  Gunshin H, Mackenzie B, Berger UV, Gunshin Y, Romero MF, Boron WF, Nussberger S, Gollan JL, Hediger MA. Cloning and characterization of a mammalian proton-coupled metal-ion transporter. Nature. 1997;388(6641):482-488.

3-  Fine KD, Santa Ana CA, Porter JL, Fordtran JS. Intestinal absorption of magnesium from food and supplements. Journal of Clinical Investigation. 1991;88(2):396-402.

4-  Diaz M, Rosado JL, Allen LH, Abrams S, Garcia OP. The efficacy of a local ascorbic acid-rich food in improving iron absorption from Mexican diets: a field study using stable isotopes. American Journal of Clinical Nutrition. 2003;78(3):436-440.

5-  Cook JD, Monsen ER. Vitamin C, the common cold, and iron absorption. American Journal of Clinical Nutrition. 1977;30(2):235-241.

6-  Hallberg L, Rossander-Hulten L. Calcium and iron absorption: mechanism of action and nutritional importance. European Journal of Clinical Nutrition. 1991;45(5):225-233.

7-  Milman N, Byg KE, Bergholt T, Eriksen L. Iron status and iron balance during pregnancy. A critical reappraisal of iron supplementation. Acta Obstetricia et Gynecologica Scandinavica. 1999;78(9):749-757.

8-  Lynch SR. Interaction of iron with other nutrients. Nutrition Reviews. 1997;55(4):102-110.

9-  Hallberg L, Hulthen L. Prediction of dietary iron absorption: an algorithm for calculating absorption and bioavailability of dietary iron. American Journal of Clinical Nutrition. 2000;71(5):1147-1160.

10-  McKie AT, Barrow D, Latunde-Dada GO, Rolfs A, Sager G, Mudaly E, Mudaly M, Richardson C, Barlow D, Bomford A, Peters TJ, Raja KB, Shirali S, Hediger MA, Farzaneh F, Simpson RJ. An iron-regulated ferric reductase associated with the absorption of dietary iron. Science. 2001;291(5509):1755-1759.