Calcium

Overview

Calcium is the most abundant and one of the most important minerals in the body. It is essential for cell signaling and the proper functioning of muscles, nerves, and the heart. Calcium is needed for blood clotting and is crucial for the formation, density, and maintenance of bones.

Calcium levels are tightly controlled; if there is too little absorbed or ingested, or if there is excess loss through the kidney or gut, calcium is taken from bone to maintain blood concentrations. Roughly half of the calcium in the blood is ‘free’ and is metabolically active. The remaining half is ‘bound’ to albumin.

Some calcium is lost from the body every day, filtered from the blood by the kidneys and excreted into the urine. Measurement of the amount of calcium in the blood is used to determine how much calcium the kidneys are eliminating.

Why you should keep track of your calcium level

A total calcium level is often measured as part of a routine health screening. When an abnormal total calcium result is obtained, it is viewed as an indicator of an underlying problem.

Parathyroid hormone (PTH) and vitamin D are responsible for maintaining calcium concentrations in the blood within a narrow range of values. If the calcium is abnormal, measuring calcium and PTH together can help determine whether the parathyroid glands are functioning normally.

Measuring calcium can help determine whether the kidneys are excreting the proper amount of calcium, and testing for vitamin D, phosphorus, and/or magnesium can help determine whether other deficiencies or excesses exist. Frequently, the balance among these different substances (and the changes in them) is just as important as the concentrations.

Calcium can be used as a diagnostic test if a person has symptoms that suggest:

• Kidney stones
• Bone disease
• Neurologic disorders

Large fluctuations in calcium can cause the heart to slow down or to beat too rapidly, can cause muscles to go into spasm (tetany), and can cause confusion or even coma. In those who are critically ill, it can be extremely important to monitor the ionized calcium level in order to be able to treat and prevent serious complications.

How to prevent it

Your body needs calcium to help muscles and blood vessels contract and expand, to secrete hormones and enzymes and to send messages through the nervous system.

It is important to get plenty of calcium in the foods you eat. Foods rich in calcium include:

• Dairy products such as milk, cheese, and yogurt
• Leafy, green vegetables
• Fish with soft bones that you eat, such as canned sardines and salmon
• Calcium-enriched foods such as breakfast cereals, fruit juices, soy and rice drinks, and tofu.

The exact amount of calcium you need depends on your age and other factors. Growing children and teenagers need more calcium than young adults. Older women need plenty of calcium to prevent osteoporosis. People who do not eat enough high-calcium foods should take a calcium supplement.