You need both iron and calcium for good health. Your body doesn't absorb iron well, especially non-heme iron found in plants. Calcium and other iron inhibitors may have less of an absorption effect on heme iron in meat. While calcium blocks iron absorption in theory, in practice it may or may not have much of an effect. Yogurt serves as a rich source of calcium but you may want to eat it separately from meals high in iron.
Normal Iron Absorption
You normally absorb around 15 percent of the iron you ingest, but the amount varies with the type of iron. You absorb between 15 and 35 percent of heme iron, an amount not affected by other dietary factors such as calcium intake, according to the Office of Dietary Supplements, although some studies disagree. Calcium, on the other hand, may have an effect on non-heme iron absorption, which normally ranges from 2 to 15 percent, ODS reports.
Calcium and Iron Absorption
Yogurt contains around 300 mg of calcium per cup, the same as 1 cup of milk. In a clinical study conducted by the Swedish University of Göteborg and reported in the January 1991 issue of "The American Journal of Clinical Nutrition," giving 165 mg of calcium in dairy form reduced non-heme iron absorption in wheat rolls by 50 to 60 percent. A significant drop in heme iron also occurred when people ingested 165 mg of calcium-rich foods.
Studies That Showed No Effect
Not all studies have shown an effect on the amount of iron absorbed when people ate dairy along with iron-rich foods. A study reported in the April 1992 "Nutrition Research Letter" found that adding yogurt to a meal containing meat, which increases non-heme iron absorption when consumed at the same time, did not decrease non-heme iron absorption in the meal.
Considerations
Ingesting vitamin C and heme iron in the same meal as non-heme iron enhances non-heme iron absorption. Adding vitamin C to a meal containing non-heme iron can increase iron absorption up to six-fold, registered dietitian Reed Mangels, Ph.D., of the Vegetarian Resource Group reports. If you're eating a meal containing yogurt and iron-rich foods, adding foods high in vitamin C and heme iron may help overcome any effect that calcium in yogurt has on your non-heme iron uptake.
References
- Office of Dietary Supplements: Iron
- Vegetarian Resource Group; Iron in the Vegan Diet; Reed Mangels, Ph.D.
- "The American Journal of Clinical Nutrition"; Calcium: Effect of Different Amounts on Nonheme- and Heme-Iron Absorption in Humans; L. Hallberg, et al.; January 1991
- "Nutrition Research Newsletter"; Effects of Dairy Products on Iron Absorption; April 1992
- The Calcium Information Resource: Food Sources: Best Sources of Calcium
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