Vitamin D is an essential nutrient that plays critical roles in several physiological processes. Poor vitamin D status has been implicated in the pathogenesis of many acute and chronic diseases. A 2018 review suggested that magnesium is essential for vitamin D metabolism.

Vitamin D synthesis begins when 7-dehydrocholesterol, which is found primarily in the skin’s epidermal layer, reacts to ultraviolet light and converts to pre-vitamin D. Subsequent processes in the liver and kidneys convert the pre-vitamin to calcitriol, the active form of the vitamin. The enzymes that catalyze these processes require magnesium.

Approximately 42 percent of people living in the United States are vitamin D deficient. The authors of the review pointed out that approximately one-third of otherwise healthy adults are magnesium deficient. Although many people take vitamin D supplements, without sufficient magnesium, the body cannot properly metabolize vitamin D, promoting calcification of blood vessels, a critical factor in the development of atherosclerosis and coronary heart disease. Conversely, people whose magnesium levels are sufficiently high require less vitamin D supplementation to achieve healthy levels.

The recommended dietary allowance for magnesium for adults between the ages of 31 and 50 years is 420 milligrams for men and 320 milligrams for women per day. According to the authors of the study, the typical American diet provides less than half of these amounts. Dietary sources of magnesium include green leafy vegetables, nuts, legumes, and fish.

It’s noteworthy that poor vitamin D status is associated with poor outcomes in COVID-19. Listen to this clip in which Dr. Rhonda Patrick describes how vitamin D might reduce the risk of acute lung injury in COVID-19.

• Link to full study.