“A review published in The Journal of the American Osteopathic Association found Vitamin D can’t be metabolized without sufficient magnesium levels, meaning Vitamin D remains stored and inactive for as many as 50 percent of Americans.”
Read more here.
Anne Marie Uwitonze, Mohammed S. Razzaque. Role of Magnesium in Vitamin D Activation and Function. The Journal of the American Osteopathic Association, 2018; 118 (3): 181