https://www.drberg.com/ 

Let’s talk about magnesium and vitamin D. About 75 percent of the population has low vitamin D levels, and 45 percent have low magnesium levels. All of the enzymes involved in converting vitamin D to the active form depend on magnesium. Vitamin D won’t work in the body if you have a magnesium deficiency. Vitamin D is vitally important for the body, and it’s crucial to do what you can to avoid a vitamin D deficiency. Vitamin D also supports the absorption of magnesium. Vitamin D and magnesium work synergistically. Vitamin D and magnesium are also important to support the absorption and regulation of calcium. Magnesium helps prevent calcium from building up in your arteries. The body needs about twice as much calcium as magnesium. But many people are actually getting about three times as much calcium as magnesium. Having excess calcium with a magnesium deficiency can lead to serious side effects, including cancer. Thankfully, the solution is simple. You need to increase magnesium by consuming magnesium-rich foods, like leafy greens. 

https://pubmed.ncbi.nlm.nih.gov/29480918/