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Your Body and Calcium

The content of this page has been reproduced, with permission, from Cancer Help UK (www.cancerhelp.org.uk) – the patient information website of Cancer Research UK.


Why our body needs calcium

Calcium is a mineral that is stored in the bones. Nearly all the calcium in the body is stored in bone tissue. But a small amount (around 1%) circulates in the blood and other body fluids, or is inside our cells. This is necessary for

  • Keeping bones and teeth healthy
  • Blood clotting
  • Normal functioning of brain and spinal cord(central nervous system)
  • Keeping our muscles working properly

If your blood calcium level gets too high or too low it can be dangerous. Having too much calcium in the blood is called hypercalcaemia (pronounced hyper-kal-seem-ia). Not having enough is called hypocalcaemia (hypo-kal-seem-ia). Hypercalcaemia in cancer can be a serious problem for some people.


Where does the body get its calcium?

Our diet provides us with calcium. The foods highest in calcium include

  • Dairy products such as eggs, milk, butter and cheese – this is where most of our calcium comes from
  • Green vegetables such as broccoli, spinach and beans
  • Nuts
  • Wholegrain products such as bread, rice and cereals

Our bodies absorb calcium from the food we eat through the lining of the bowel. The calcium is broken down before it is stored in the bones. The body controls the amount of calcium in the bloodstream very carefully. When blood levels of calcium fall too low, the bones release calcium into the blood. The amount of calcium absorbed from food in the bowel also increases. And the kidneys get rid of less calcium through the urine. If blood levels of calcium get too high, the opposite happens.

There are 3 hormones in the body that play an important role in this complicated control system. These are

  • Parathyroid hormone (PTH)
  • Vitamin D and
  • Calcitonin

These hormones help to keep the correct balance of calcium in the blood.

If this balance is upset, the amount of calcium in our blood can become too high (hypercalcaemia) and cause serious problems.

The main causes of hypercalcaemia are

  • Taking in too much calcium from the foods we eat
  • Your kidneys not being able to get rid of excess calcium
  • Too much calcium leaking out of the bones into the blood

Click on these links for more information about hypercalcaemia in cancer and managing hypercalcaemia at CancerHelp UK.

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