You Might Not Be Getting All The Benefits Of Vitamin D If You're Low In Magnesium

Vitamin D has been making headlines for its relationship to the pandemic, and a recent study found that in one cohort of patients hospitalized with COVID-19, 80% were deficient in the micronutrient.

The human body uses nutrients systematically, and proper absorption and metabolism of one nutrient often depend on the availability of another. Vitamin D and magnesium are a prime example. "The pathways in the body that result in activation of vitamin D involve a number of enzymes, and most or all of them require magnesium as a cofactor," explains double board-certified surgeon and author Kent Sasse, M.D. 

That may pose a problem for some people: While magnesium is plentiful in foods like nuts and seeds, leafy greens, whole grains, and legumes, it's estimated that less than half of the U.S. population3 get the required daily amount.

Vitamin D deficiency is another issue affecting more than half the population. This deficiency boils down to a limited number of foods with naturally occurring vitamin D and minimal exposure to the sun. "There are very few foods that contain significant amounts of vitamin D," says Zara Patel, M.D., a researcher and associate professor at Stanford, "and much of what we produce in our bodies comes from sunlight and UV rays hitting our skin and producing the precursor molecules needed to make this vitamin." That means for those of us religiously using sunscreen and not eating stacks of fish—a great source of vitamin D!—we may need to supplement.

To correct vitamin D deficiency in adults, the U.S. Endocrine Society recommends 6,000 IU of vitamin D daily7 for 8 weeks (which would require a supplement), followed by a maintenance dose of at least 1,500 to 2,000 IU per day after that. Healthcare practitioners can test vitamin D status with a straightforward blood test.