Crazy about Calcium!
You may hear calcium and immediately think of bone health, but do you ever think about the other important roles in the body? Did you even know it had any other jobs to perform?
Calcium is an abundant mineral throughout the world, our bodies and is responsible for the deep orange colour when used in fireworks. It has cause for celebration in the bones too, while other vital roles of calcium are dependent on where it is found within the body.
Where can you find calcium in the body?
You weren’t wrong to think of bones first.
A whopping 99% of the calcium in our body is found in our bones and teeth, keeping them strong and providing structure to the skeleton. Without calcium, our bones would be soft and weak.
For example, a disease called Rickets is the softening and weakening of bones in growing children, usually because of an extreme and prolonged calcium or Vitamin D deficiency (which we know promotes absorption of calcium from the digestive tract).
Once calcium reaches our bones the story doesn’t end. We constantly remove small amounts of calcium from our bones – this is called bone resorption. However, it is replaced during a process known as bone modelling, with the help of Vitamin K2. Our bones can become weaker if we remove more calcium than we replace, which is why calcium is important throughout our life span. Osteoporosis is an example of brittle bones that commonly affects the ageing population.
The remaining 1% of calcium is found in the bloodstream, influencing nerves and muscles.
Calcium exists in the body as a calcium ion, which means it carries an electrical charge and is an electrolyte. The nervous system uses calcium (and other minerals) to transmit impulses through the body.
For example, nerve endings release a calcium ion, which binds to proteins which activate the process of muscle contraction and relaxation – i.e. muscle movement.
The ions are also involved in cell signalling, hormone production, coagulation and the contraction and expansion of blood vessels.
When calcium accumulates in other places beyond the bones, it’s known as calcification.
Calcification can occur in soft tissues, such as renal tissues, in joints, tendons and on blood vessel walls.
Evidence is limited, but calcium dietary intake doesn't appear to increase the risk of calcification or high levels in the bloodstream. Cause is commonly linked to injury, infection and auto-immune conditions.
How does our calcium know where to go?
To keep that 99% of calcium from building up in our blood and remaining in the bone, a few key players are at work.
- Osteoclasts (cells in bone) break down old bone tissue allowing osteoblasts to replace it with new material. Together, they facilitate bone mending and bone growth.
- Osteoblasts secrete osteocalcin, a protein that binds to calcium, aiding in bone-building and mineralization. Osteocalcin is dependent on Vitamin K2 to help keep calcium in the bones.
- The thyroid produces calcitonin, which lowers calcium levels in the blood by inhibiting osteoclast activity, keeping calcium in the bones and promoting blood calcium excretion through the kidneys.
- Alternately, parathyroid hormone can increase calcium loss from the bones and into the blood. It is involved in bone resorption by enhancing the release of calcium from the bones and by indirectly activating osteoclast activity.