Are you low in vitamin D or do you just have a magnesium deficiency?
For years I was low in vitamin D and couldn’t figure out why since I have always spent a lot of time in the sun over the summer. There are a few reasons this can happen such as constantly wearing sunscreen, hats, etc. What I learned though is that the real reason that I wasn’t making vitamin D was because I was low in magnesium.
Magnesium plays a crucial biochemical role in vitamin D metabolism, and a deficiency in magnesium can impair the body's ability to properly utilize vitamin D. Double whammy!
Magnesium and Vitamin D Synthesis
Vitamin D is synthesized in the skin (via sunlight) The body must convert it into its active form (calcitriol or 1,25-dihydroxyvitamin D) to be useful (also why we should be testing the active form, not the storage form). This activation occurs through two enzymatic steps in the liver and kidneys, both of which require magnesium as a cofactor.
Getting Active Vitamin D into Cells
Vitamin D also needs specific binding proteins to be transported in the bloodstream.
Magnesium helps regulate these proteins, ensuring vitamin D can circulate and reach target tissues.
The active form of vitamin D (calcitriol) binds to vitamin D receptors (VDRs) in various cells to exert its effects (e.g., regulating calcium absorption). Magnesium plays a role in maintaining VDR function.
Important Note: If magnesium is low, parathyroid hormone (PTH) and vitamin D can't work efficiently, leading to potential bone problems. If you have osteopenia or osteoporosis then you absolutely need to be taking a magnesium supplement.
Why Vitamin D Supplements Don't Work
Even if you take vitamin D supplements, a magnesium deficiency can prevent your body from properly activating and using vitamin D.
This can lead to low vitamin D levels in blood tests despite supplementation.
Testing Magnesium Levels
Most people are deficient in magnesium. Unfortunately, our soil is depleted of this important mineral and we burn through magnesium easily. Stress, alcohol, prescription medications, and exercise all deplete magnesium. Caffeine and gut issues can affect magnesium absorption.
I recommend asking your doctor for a red blood cell (RBC) magnesium test in order to get an accurate assessment of your magnesium status. The optimal range is 6.0-6.5 mg/dL.
For more information on magnesium supplements and which ones I recommend read my Magnesium - The Miracle Mineral post.