“It’s about the body wanting to maintain homeostasis (aka a certain, balanced amount) in calcium levels,” explains registered dietitian and mbg Collective member Jessica Cording, M.S., R.D., CDN.
“This means that 24/7 your body is trying to return to its baseline,” adds dietitian Gabrielle Tafur, M.S., R.D., LDN. Vitamin D comes into play by ramping up calcium absorption as needed to maintain the levels needed in the blood, in a relatively tight range.*
Throughout the last few decades, researchers have come to understand that vitamin D makes this happen in three ways.
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 affect the barrier function of the intestinal wall, and more.*
As mbg’s vice president of scientific affairs Ashley Jordan Ferira, Ph.D., RDN, 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.”*