Calcium is a major mineral needed by the human body to build and maintain healthy bones and teeth, as well as regulate blood pressure. Iron, a trace mineral, carries oxygenated red blood cells throughout the body and supports the immune system. Certain segments of the population, such as teenagers, young adults and women require more of these important minerals. Consuming foods rich in both calcium and iron, such as fortified cereals, grains, dairy products and legumes, is particularly important for these individuals.
Significance
Teenagers, young adults and women, especially pregnant women, generally require more of these nutrients. Teenagers are growing and building bone up until the age of 25, on average, and, along with vitamin D, phosphorus and magnesium, taking in enough calcium is essential for this process. All women of childbearing age need significantly more iron than men due to blood loss through menstruation. Pregnant women require more iron, in particular, to nourish a developing fetus.
Recommended Intake
According to the Institute of Medicine Dietary Reference Intake Tables, both males and females ages 9 to 18 years, require the most calcium. The Recommended Adequate Intake, or AI, level for adolescents and teens is 1,300 mg per day. During adulthood the AI for calcium drops to 1,000 mg until the age of 50, when it increases to 1,200 mg daily. Women, 19 to 50 years require 18 mg daily, 10 mg more than their male counterparts. Pregnant women need the most iron of any population segment, 27 mg daily.
Absorption
It was once thought that iron and calcium "compete" for absorption by the human body but, according to several research studies, including one published by the British Journal of Nutrition in 1993, this effect is not significant. However, these minerals do not enhance the absorption of each other. On its own, neither calcium nor iron is well absorbed by the human body. However, if your body requires more calcium or iron, such as during growth and pregnancy, it absorbs more from the foods you eat. For example, calcium absorption, when stores are low, may go from absorbing 25 percent to 60 percent.
Enhancing Absorption
According to dietary supplement fact sheets published by the National Institutes of Health, consuming calcium with vitamin D enhances absorption. Though green vegetables, such as kale and mustard greens, are calcium-rich, they contain a binding substance called oxalic acid, which prevents some calcium from being absorbed. Iron is best absorbed from animal sources and, in this form is called heme iron. It is absorbed twice as readily as non-heme iron, which comes from plant foods. Like calcium, oxalic acid binds iron absorption. You can absorb more of the non-heme iron from the foods you eat by pairing them with vitamin C rich foods or foods rich in heme iron.
Best Food Sources
The best food sources of both calcium and iron are Atlantic sardines or anchovies, with bones, canned in oil, drained; cooked clams; whole, dried eggs or powdered eggs; and goat cheese.
Since foods richest in both calcium and iron are not the most popular foods in general, other good food sources of both minerals include fortified ready-to-eat breakfast cereals, tofu and soy products, seeds, such as sesame, sunflower and pumpkin seeds; nuts, such as almonds, cashews and hazelnuts; beans, such as white and kidney beans; spinach, enriched breads and grits and fortified oatmeal.
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