Calcium is an essential mineral in the body that is required for healthy bone development and other vital functions of the body. Some of the health risks associated with calcium deficiency and calcium toxicity are described below.
A calcium deficiency can be caused in three ways which include:
- Inadequate calcium intake via the diet
- Poor calcium absorption due to diseases such as rickets and osteomalacia
- Vitamin D deficiency causing reduced calcium absorption
- Excessive calcium loss
A low calcium intake from the diet reduces the blood concentration of ionized calcium. This stimulates the release of parathyroid hormone (PTH), which acts in several ways to increase and maintain serum calcium levels. For example, PTH increases the production of calcitrol, which in turn, increases calcium absorption in the gut and re-absorption of calcium in the kidneys. PTH also breaks down bone tissue (bone resorption) releasing calcium from the bone and increasing blood calcium levels.
Low blood levels of ionized calcium can also lead to tetany, which causes muscle contractions, spasms, numbness and pain in the hands and feet. Long-term calcium deficiency is also linked to osteoporosis, a condition that causes decreased bone mass and an increased susceptibility to fracture.
A calcium level that is too high is also harmful to the body. Abnormally high blood calcium levels are usually due to certain disease conditions rather than excessive calcium intake. With excessive intake, the intestines are programmed to shut off further absorption, which prevents calcium intoxication.
The causes of high blood calcium levels include:
- Bone cancer
- Overactive thyroid gland or hyperthyroidism
- Overactive parathyroid gland or hyperparathyroidism
Examples of health conditons that can causes a high blood calcium level include kidney stones or nephrolithiasis and milk-alkali syndrome. Calcium can also disrupt the absorption of iron, zinc, magnesium and phosphorous, leading to deficiency of these essential minerals.
Reviewed by Sally Robertson, BSc