The Claim
Calcium intake inhibits both heme and nonheme iron absorption in humans, with 500 mg of calcium reducing iron absorption from a single meal from 10.2% to 4.8% in premenopausal women, and 100–200 mg reducing absorption by 18–27% in children; however, long-term calcium supplementation does not appear to affect overall iron status, potentially due to adaptive mechanisms.
What the research says
Roughly balanced
Support and challenge are close. The picture may shift as more studies come in.
These are independent scores, not a percentage. Higher-grade studies count more, so a single strong opposing study can outweigh several weaker ones.
Calcium can make it harder for your body to absorb iron from food, especially in women and kids, but taking calcium supplements over time might not actually lead to low iron because your body could adjust.
See the scientific wording
Calcium inhibits both heme and nonheme iron absorption, with 500 mg of calcium reducing iron absorption from a single meal from 10.2% to 4.8% in premenopausal women, and 100–200 mg reducing absorption by 18–27% in children, though long-term calcium supplementation does not appear to affect overall iron status, possibly due to adaptive mechanisms.
What the research says
1 studyStudy: Iron Absorption: Factors, Limitations, and Improvement Methods
The study says calcium can reduce how much iron your body absorbs from food, which matches the main idea of the claim.
Score breakdown, mechanism chain, raw evidence, ideal studies needed & 1 supporting studies
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.