What is the role of calcium in the body?

Calcium accounts for nearly 2% of the body weight of an adult male, or almost half of the body's mineral content. Most calcium is concentrated in bones and teeth, where it combines with phosphorus. This calcium phosphate provides the body with a strong skeletal framework. However, although the body's skeleton is hard and strong, it is not a permanent structure. Calcium is taken into the skeleton and then returned to the body. For example, in adults, about one-fifth of the calcium in their bones is returned to other parts of the body within a year. This is why the need for calcium in food is not limited to growing children but also includes adults. However, in teeth, calcium phosphate is not easily eliminated and is not released to other parts of the body.

Calcium is also present in the blood, other fluids, and other cells of the body in small amounts. Calcium is essential for blood clotting, for the absorption of B vitamins, and for the transmission of nerve impulses throughout the body. Calcium helps regulate cell permeability, allowing nutrients and other substances to enter and exit cells, enabling cells to release unwanted substances and to capture others.

Calcium plays a part in the process of muscle contraction and relaxation. This is crucial for people to be able to move and perform tasks both inside and outside the body, and for the heart to beat and lungs to function normally.

The amount of calcium absorbed into the body through the digestive tract varies greatly and depends on several factors. Infants typically absorb 50-70% of the calcium in breast milk, while adults with a mixed diet absorb less. Calcium absorption varies from person to person and depends on different conditions. Calcium absorption is related to the presence of phosphorus, vitamin D, lactose, hydrochloric acid in gastric juices, vitamin C, and certain amino acids in the small intestine. Vitamin D is not only essential for calcium absorption into the bloodstream but also for its utilization in the body. Oxalic acid, found in some fruits and vegetables, and phytic acid, found in wheat bran, form insoluble compounds with calcium, thus reducing calcium absorption when consumed together.

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