When it comes to supplementing our diet with calcium, the most common sources have traditionally been rock-based, which come from marble, limestone, and chalk. These forms of calcium, while widely used, come with a set of limitations that can impact their effectiveness and overall benefit to our health. Research has shown rock-based calcium supplements only aid in slowing down bone loss, but they don't actively help repair bones or keep them healthy. Without the right mix of minerals and vitamins, taking too much calcium from these supplements can lead to issues like coronary calcification, which is bad for your heart health.

Firstly, the absorption rate of rock-based calcium is a significant concern. Our bodies often struggle to fully absorb this type of calcium, leading to less-than-optimal increases in our calcium levels. The poor absorption is primarily because these forms of calcium are not in a natural state that our bodies can easily recognize and utilize. Additionally, rock-based calcium supplements typically offer only calcium itself. They lack a broad spectrum of essential minerals and vitamins that can aid in calcium's absorption and contribute to increased bone density (3). 

Furthermore, the consumption of rock-based calcium can lead to digestive issues for many individuals. Common side effects include constipation, bloating, and general digestive discomfort. This is partly due to the unnatural form of the calcium and its interaction with the digestive system.