The Calcium Controversy: Does it Inhibit Iron Absorption or Not?

If you’ve been reading this blog for a while then chances are that you’ve seen a mention or two about iron absorption inhibitors, including calcium. This is a bit of a controversial topic since some say that calcium greatly impacts iron absorption and others say it doesn’t. It can get a little confusing when you’re getting conflicting information, so I thought it would be worth discussing further.

There is some evidence to support the impact of calcium on iron absorption, albeit from short-term studies focused on this interaction with single meals. On the other hand, long-term studies have found that calcium and milk products don’t have any adverse effect on iron absorption.


What’s the Verdict?

Unfortunately this isn’t a simple case of yes or no – hence the controversy! The actual mechanism of the interaction of calcium and iron absorption is not well understood.

The general consensus is that calcium can interfere with iron absorption on a short term basis. According to the Dietary Reference Intakes, while the interaction of calcium and iron is significantly evident in single meals, little effect has been detected in serum ferritin (circulating iron in your blood) concentrations over the long term. In addition, some studies investigating the interaction of iron and dairy products found no detrimental effect on iron absorption.


What Can You Do?

Calcium and dairy products are integral dietary components for both adults and children (and so is iron). While I’ve noted that studies have found calcium to not have a significant inhibiting effect in the long run, if you or your child is dependent on absorbing as much iron as possible, then I recommend avoiding (or at least limiting) taking iron supplements or eating iron-rich meals with calcium, just to be safe. If you’re taking an iron supplement and a calcium supplement, talk to your doctor or pharmacist about possible interactions, dosing, and the best times to take your pills.


If you still have concerns and would like to do all that you can to get the most iron from your diet and supplement, then check out my guide on How to Get the Most out of Your Iron Supplement!

Content and advice provided on The Iron Maiden is for information purposes only and should not serve as a substitute for a licensed health care provider, who is knowledgeable about an individual’s unique health care needs

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5 thoughts on “The Calcium Controversy: Does it Inhibit Iron Absorption or Not?

  1. Fierce Ninja says:

    Hi there, thank you for this sensible article. I have a quic question. I have a protein bar that has shows Calcium as 12% and Iron as 8%. It has Whey Protein Isolate, Organic Almond butter, Organic Walnuts, Organic Clover Honey, Cinnamon, Chicory Root, Prebiotic fiber. Should I not be taking that bar from a short-term perspective if calcium inhibits iron absorption in short term? Or is the quantity not enough to raise a concern?

    • The Iron Maiden says:

      Hi Fierce Ninja,

      My advice regarding the protein bar is to have the protein bar for the protein alone and not a source of calcium or iron (it’s content is negligible). If necessary supplement with separate iron (preferably polysaccharide iron complex or heme polypeptide as they are better absorbed) and calcium (I prefer calcium citrate or calcium citrate, calcium phosphate combination for better absorption) with Vitamin D. It is recommended that there be a minimum of 2-4 hours between Calcium and Iron supplements.

      Hope that helps!


  2. Bill says:

    I am undergoing a few different investigations with one current diagnoses. my one diagnoses is hyperparathyriodism and during the investigation an iron panel and pituitary hormone screening were completed. So my puitary screen is abnormal and my iron panel revealed hyperferritinemia…
    so hyperparathyroidism is increased PTH and as a direct result hypercalcemia. So question is… can the increase of serum calcium from the hyperparathyroidism affect the results of the iron panel if calcium does effect iron absorption? Ferritin was not crazy high at 440… but binding affect and serum iron were normal. So I am not a large red meat eater but I do have some and have enough iron rich foods from the veggie family which I cut back on… but is there a chance my high level of serum calcium can be causing false or misleading problems?

    • The Iron Maiden says:

      Hi Bill,

      I am truly sorry you are struggling with health issues and having to endure the long process of figuring out what is causing your symptoms. While issues related to parathyroidism are beyond my scope of practice, I can tell you that while ferritin levels are NEVER falsely low (indicating an iron deficiency in its early stages), it can be falsely elevated. If a ferritin level comes back elevated practitioners review other lab values referred to as an “iron panel” (TIBC, Serum Iron, %Transferrin Saturation ). If these are normal range we know that the ferritin level is falsely elevated. Ferritin Levels can be falsely elevated for several reasons including infection, inflammation, chronic illness etc.

      I hope your state of health and wellbeing returns to normal soon.


      • Bill says:

        Thank you for the reply Leona. More deeper looking into things since.. it looks hyperferrentenemia as a redult from inflammation regarding ankylosing spondylitis which i have the HBL7 gene and a working diagnosis and/or early stages of thyroid complications referring back to the hyperparathyroidism and getting closer to a MEN1 diagnosis. Great roll of the dice.. mother has Ankylosing spondylitis and father Neuroendocrine cancer. But it sounds like atleast for now.. liver should be safe.
        Looks like still a long road, but getting currently a good team going.
        Again, thanks for the reply and info. Much appreciated Leona.

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