Calcium is one of the most important minerals in the body. It is essential for the proper functioning of muscles, nerves and the heart and is necessary for blood clotting and bone formation. About 99% of calcium is found in the bones, while the remaining 1% circulates in the blood. Approximately half of the calcium in the blood is “free” and is metabolically active. The other half is “bound” to albumin and other compounds and is metabolically inactive.
Calcium is supplied by the food we consume or by taking calcium supplements. Vitamin D and parathyroid hormone help regulate the level of calcium that is absorbed and how much it is eliminated by the kidneys. Healthy kidneys convert vitamin D into an active hormone (calcitriol), which helps increase the absorption of calcium from the gut into the blood. A balanced, healthy diet provides 1000 milligrams of calcium per day.
Hypercalcemia is a condition in which the level of calcium in the blood is way above normal. Too much calcium in the blood can weaken the bone system, form kidney stones and interfere the normal function of the heart and brain. Hypercalcaemia is usually the result of overactivity of the parathyroid glands (located in the neck, close to the thyroid gland). Other causes of hypercalcemia include certain cancer types, health problems, certain medications, and taking too many calcium and vitamin D supplements.
According to the guidelines for clinical practice of the National Kidney Foundation, the total calcium intake for people with kidney disease should not exceed 2000 mg per day. This includes the intake of total calcium from the diet plan, calcium supplements and phosphorus binders based on calcium.