Calcium and Iron Absorption: Is There an Interaction?
Evidence suggests that calcium does not have any significant long-term effect on iron absorption. In addition, milk and milk products have not been found to affect iron absorption.
As the bioavailability of nutrients can sometimes be affected due to interactions, concerns have been raised about the potential for calcium to influence iron absorption. While short-term studies suggest that calcium may interfere with iron absorption, long-term calcium and milk product intake has not been linked to any adverse effect on iron status.
Most short-term studies which have indicated that calcium may be detrimental to iron absorption have focused on single meals.1-3 Studies conducted over the long term to investigate composite and varied complete diets have found that calcium does not have a significant effect on iron absorption.4-6
Additionally, the validity of certain methods used to investigate the potential interaction between calcium and iron has been questioned. The magnitude of the effect observed in certain studies appears to be dependent on the study design, including the method used to measure absorption and the timing of the measurement.7
Furthermore, some studies have investigated whether milk product consumption may impact iron absorption. In a randomized crossover trial over 4 days, the consumption of a glass of milk with 3 main meals, or the consumption of calcium-fortified foods providing an equivalent amount of calcium, did not inhibit nonheme-iron absorption.8 In another study, it was found that the addition of milk or yogurt to a plant-based diet did not affect iron bioavailability.9
In conclusion, evidence suggests that calcium does not interfere with iron absorption in the long term. Moreover, the consumption of milk products does not appear detrimental to iron absorption and bioavailability.
References
- Dawson-Hughes B et al. Effects of calcium carbonate and hydroxyapatite on zinc and iron retention in postmenopausal women. Am J Clin Nutr 1986;44(1):83-8.
- Hallberg L et al. Calcium: effect of different amounts of nonheme- and heme-iron absorption in humans. Am J Clin Nutr 1991;53(1):112-9.
- Benkhedda K et al. Effect of calcium on iron absorption in women with marginal iron status. Br J Nutr 2010;103(5):742-8.
- Minihane AM and Fairweather-Tait SJ. Effect of calcium supplementation on daily nonheme-iron absorption and long-term iron status. Am J Clin Nutr 1998;68(1):96-102.
- Cook JD et al. Assessment of the role of nonheme-iron availability on iron balance. Am J Clin Nutr 1991;54(4):717-22.
- Reddy MB and Cook JD. Effect of calcium intake on non-heme iron absorption from a complete diet. Am J Clin Nutr 1997;65(6):1820-5.
- Lönnerdal B. Calcium and iron absorption--mechanisms and public health relevance. Int J Vitam Nutr Res 2010;80(4-5):293-9.
- Grinder-Pedersen L et al. Calcium from milk or calcium-fortified foods does not inhibit nonheme-iron absorption from a whole diet consumed over a 4-d period. Am J Clin Nutr 2004;80(2):404-9.
- Rosado JL et al. The addition of milk or yogurt to a plant-based diet increases zinc bioavailability but does not affect iron bioavailability in women. J Nutr 2005;135(3):465-8.
Keywords: bioavailability , calcium
