Your body and calcium

Calcium is an important mineral that our bodies need to keep us healthy. Having cancer can affect the amount of calcium in the body.

Why do we need calcium?

Nearly all the calcium in the body is stored in bone tissue. A small amount circulates in our blood and other body fluids. There is also some inside our cells.

We need calcium to:

• build and keep our bones and teeth healthy
• help our blood clot
• regulate some of the normal functioning of the brain and spinal cord (central nervous system)
• keeping our muscles working properly

Where we get calcium from

We need to get calcium from our diet. Foods which contain calcium include:

• dairy products such as eggs, milk, butter and cheese – this is where most of our calcium comes from
• green leafy vegetables such as broccoli, kale and spring greens
• soya beans
• tinned oily fish such as sardines with bones
• calcium fortified cereals and drinks

Normal calcium levels

The level of calcium in the blood is normally between 2.1 mmol per litre and 2.6 mmol per litre. But remember that blood levels can vary a little from person to person.

You might need treatment if your calcium level goes above or below these levels.

What happens to calcium in the body?

Our bodies absorb calcium from the food we eat through the lining of the bowel. The calcium is stored in our 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 the bowel absorbs from food increases and the kidneys get rid of less calcium through the urine.

The opposite happens if blood levels of calcium get too high.

There are 3 hormones in the body that play an important role in keeping the correct balance of calcium in the blood. These are:

• parathyroid hormone (PTH) – made by the parathyroid glands in the neck
• calcitonin
• vitamin D

Blood calcium levels that are too high or too low can cause serious problems. 

Having too much calcium in the blood is called hypercalcaemia. This is pronounced hyper-kal-seem-ia. Not having enough calcium is called hypocalcaemia. This is pronounced hypo-kal-seem-ia.

The main causes of hypercalcaemia include:

• too much parathyroid hormone in the blood
• some types of cancer
• your kidneys not being able to get rid of excess calcium
• endocrine diseases
• some medicines

A low calcium level is rare in people with cancer. The main causes of having a low level of calcium in the blood include:

• removal of your parathyroid glands or damage to them when having surgery to the head and neck area
• some medicines
• vitamin D deficiency