Effect of calcium on iron absorption - GulfToday

Effect of calcium on iron absorption

Abeer Majed Al Kusayer

Clinical Nutrition and Dietetics, Al Qassimi Hospital – Ministry of Health and Prevention

Clinical Nutrition and Dietetics, Al Qassimi Hospital – Ministry of Health and Prevention


The photo has been used for illustrative purposes.

Iron is a mineral, and its main purpose is to carry oxygen in the haemoglobin of red blood cells throughout the body so cells can produce energy. Iron also helps remove carbon dioxide.

When the body’s iron stores become so low that not enough normal red blood cells can be made to carry oxygen efficiently, a condition known as iron deficiency anaemia develops.

Recommended Dietary Allowances (RDAs) for iron:

Gender/Age    Iron RDA    
Children 1-3    7 mg
Children 4-8    10 mg
Children 9-13    8 mg
Males/14-18    11 mg
Females/14-18    15 mg
Males/19+    8 mg
Females/19-50    18 mg
Females/51+    8 mg

Iron in food exists as two types, heme and non-heme. Animal foods such as meat, seafood and poultry provide both types and are better absorbed by the body. Non-heme iron is found in plant foods, such as spinach and beans, grains that are enriched, like rice and bread, and some fortified breakfast cereals.

To increase the absorption of iron from plant sources, it’s recommended to eat them with meat, seafood, or poultry or a good source of vitamin C, such as citrus fruits, kiwi, strawberries or bell peppers. A good way to improve your iron intake is by eating a balanced, healthy diet that includes a variety of foods.

Effect of calcium on iron absorption

Calcium is perhaps the most essential nutrient when it comes to bone health. Calcium is found in foods such as milk, yoghurt, cheese, sardines, canned salmon, tofu, broccoli, almonds, and figs.

Some studies say that it is the only know substance to inhibit absorption of both non-heme and heme iron. While 50 milligrams or less of calcium has little effect on iron absorption, calcium in amounts of 300-600 milligrams inhibits the absorption of heme iron as well as non-heme iron.

One cup of skimmed milk contains about 300 milligrams of calcium. When calcium is recommended by a healthcare provider, as is often the case for women trying to prevent bone loss, supplements can be taken at bedtime. Calcium supplements are best taken with vitamin D and in a citrate rather than carbonate form.

However other studies tend to show no effect of increased calcium intake on iron absorption. In addition, experimental studies of calcium and iron status measures such as serum ferritin show no long-term effect of calcium supplementation on iron status.

Prevention and treatment of iron deficiency should emphasise adequate consumption of iron- rich foods and, when indicated, the use of iron supplements. Recommended calcium intakes are important for skeletal health and do not appear to increase the risk for iron deficiency in healthy people.


Many researchers report substantial reductions in iron availability when dairy products are consumed with solutions of iron. Yet other studies indicate that dairy products have little effect on iron availability when added to complex meals. More work is needed to identify the factors that influence iron-calcium interactions. The nutritional benefits provided by dairy products outweigh the slight inhibitory effect they may have on iron availability.

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