Combining Vitamin D3 with Magnesium and Calcium: The Health Trio Explained When it comes to building a strong foundation for lifelong health, three nutrients stand out: Vitamin D3, magnesium, and calcium. These three work synergistically to support bone density, muscular function, nerve health, and even immune performance. While many people focus on calcium for bones, the truth is, that it needs both D3 and magnesium to be properly absorbed and utilized by the body....