One of the main known disease that caused by the lack of calcium is Osteoporosis.
Our bones were the places where our body keep calciums for emergency use. The level of calciums stored in our bones will decrease as we tend to continue to apply less calcium intake in our daily diet. In order to support our daily bodily needs, our body always destroy and rebuild our bone. Automatically this will lessen the calcium level in our bone. If the body continue to use the stored calciums without them getting replaced, this will result in weaker and brittle bone. This will lead to thinner, brittle and easily broken bone quality. Whenever we fall down or meeting an accident, the risk of having broken bone will be higher.
One silent threat to all people in this world that related to the lack of calcium level is the bone thinning. This progressive disease is known as Osteoporosis. Usually this disease will not be detected until the patient had small accident that damaged the bone or repeated bone aches. That's why calcium intake in our daily diet can reduce the risk of getting Osteoporosis.