„Role of Magnesium in Vitamin D Activation and Function.“
The Journal of the American Osteopathic Association, March 2018

Abstract
Nutrients usually act in a coordinated manner in the body. Intestinal absorption and subsequent metabolism of a particular nutrient, to a certain extent, is dependent on the availability of other nutrients. Magnesium and vitamin D are 2 essential nutrients that are necessary for the physiologic functions of various organs. Magnesium assists in the activation of vitamin D, which helps regulate calcium and phosphate homeostasis to influence the growth and maintenance of bones. All of the enzymes that metabolize vitamin D seem to require magnesium, which acts as a cofactor in the enzymatic reactions in the liver and kidneys. Deficiency in either of these nutrients is reported to be associated with various disorders, such as skeletal deformities, cardiovascular diseases, and metabolic syndrome. It is therefore essential to ensure that the recommended amount of magnesium is consumed to obtain the optimal benefits of vitamin D.

„...Conclusion
Magnesium homeostasis is maintained by the delicate interactions of the intestine, bone, and kidneys. Magnesium is an essential cofactor for vitamin D synthesis and activation and, in turn, can increase intestinal absorption of magnesium and establish a feed-forward loop to maintain its homeostasis. Dysregulation in either of these nutrients can be associated with various disorders, including skeletal deformities, cardiovascular disorders, and metabolic syndrome.91 A core principle of osteopathic medicine lies in promoting the body's innate ability to heal itself. A better understanding of how magnesium supplementation might reduce complications related to vitamin D deficiency would help improve patient care...“

Full paper: http://jaoa.org/article.aspx?articleid=2673882