Excess, calcium

An abnormally high level of calcium in the blood (hypercalcemia). Overly high intake of calcium can result in levels of calcium that are too high in the blood. This may cause muscle weakness and constipation, affect the conduction of electrical impulses in the heart (heart block), lead to calcium stones in the urinary tract (nephrocalcinosis), impair kidney function, and interfere with the absorption of iron, predisposing to iron deficiency. In the body calcium is found mainly in the hard part of bones which serve as a storage area for calcium. Normal levels of calcium are not just essential for healthy bones. They are also important for muscle contraction, heart action, nervous system maintenance, vitamin B-12 absorption and normal blood clotting. Food sources of calcium include dairy foods, some leafy green vegetables such as broccoli and collards, canned salmon, clams, oysters, calcium-fortified foods, and tofu. Milk packs a fairly high dose of calcium: 300 milligrams in an eight-ounce glass. When children consume calcium, they absorb 75% of it into their bones. By the age of 20, this absorption drops to 30 to 50% and calcium is no longer used to build but to maintain bone density, to replace the calcium lost as the bones constantly remodel themselves. According to the National Academy of Sciences, adequate intake of calcium is 1,200 milligrams a day (four glasses of milk) for men and women 51 and older, 1,000 milligrams a day for adults 19 through 50, and 1,300 milligrams a day for children 9 through 18. The upper limit for calcium intake is 2.5 grams daily.