The first (and central method): By boosting calcium absorption in the intestines (from the food, beverages, and supplements we consume) in order to shuttle the calcium you get from these inputs into the bloodstream. “The principal function of vitamin D in calcium regulation is to increase calcium absorption from the intestine, which is the main site of absorption for most micronutrients,”* explains Tafur.

Basically, “when serum calcium levels are low, vitamin D stimulates an increase in calcium absorption from the intestines so calcium doesn’t get leached from the bones,”* Cording adds. It’s smart like that.

Just how vitamin D does this is also a little more complex than meets the eye, and research suggests that it gets the job done by interacting with intestinal stem cells, regulating cells that impact the barrier function of the intestinal wall, and more.*

In addition to this primary intestinal action, vitamin D can also work to pull calcium from the bones and (along with parathyroid hormone) signal the kidneys to retain calcium.*

As mbg’s director of scientific affairs Ashley Jordan Ferira, Ph.D., R.D.N. summarizes, “The vitamin D-calcium relationship has been simplified to absorption in the gut. In reality, this smart vitamin is proactively multitasking on our behalf to ensure calcium homeostasis through multiple, simultaneous mechanisms in the body.”*

Ferira goes on to say that this vitamin-mineral partnership is critical because calcium is required by cells throughout our entire body. “Calcium is the most abundant mineral in the human body. It’s the cellular gatekeeper for cellular signaling and communication. Pragmatically that looks like strong bones, muscles contracting (including your heart!), nerves sending impulses, and so much more.”*