Shining Genetic Light on Your Vitamin D Levels

Vitamin D is essential to so many processes in the body! It isn't actually a vitamin at all, but a prohormone that is synthesized in the skin using cholesterol in a chemical reaction with UVB radiation from the sun. Most people think of vitamin D in regards to bone health because it regulates the uptake of calcium in our intestines, but it also acts in the nucleus of cells to regulate the production of hundreds of different enzymes, influencing health in a multitude of ways. Genes play a big role in your body's vitamin D levels.  Read on to learn how to check your 23andMe results for your vitamin D genes and solutions tailored to your specific genetic variants.

Importance of Vitamin D

Connections exist between Vitamin D levels and a variety of chronic conditions, from mood disorders to cancer risk to immunity to bone density. In general, higher vitamin D levels correspond to a lower risk of getting a variety of chronic diseases.vitamin_D_levels_chart While low levels of vitamin D have been associated with a higher risk of a bunch of chronic conditions, supplementing with vitamin D doesn't always give impressive results in placebo-controlled studies. For example, a recent clinical trial found little benefit for postmenopausal women when looking at bone mineral density. On the other hand, the amount of vitamin D used in the trial may have been too small to get a result.[ref] One reason that some of the research studies and clinical trials of vitamin D supplementation showed no positive results is because the doses used may have been too low.  A study came out a couple of years ago claiming there was a statistical error in the calculation for the recommended daily intake of vitamin D.[ref] This error changed the supplemental doses needed by a factor of 10; instead of 600IU, some people may need 6,000IU+ per day. Other recent studies have backed this up, showing also that a person's weight plays a big role in the amount of vitamin D needed for sufficiency. A recent meta-analysis combining the data from 52 different trials found that vitamin D supplementation did not impact overall mortality rates, but it did decrease the risk of death from cancer.

Conversion of vitamin D: from skin production to the active form

Genes involved in converting vitamin D to the active form.
  The form of vitamin D produced in our skin is the biologically inactive form, cholecalciferol or Vitamin D3. It is formed through a reaction between UVB rays from sunlight and cholesterol in our skin. Vitamin D3, cholecalciferol, must then be converted to the active form that our body uses. The first step in the conversion takes place in the liver, where cholecalciferol is hydroxylated in the liver into calcidiol (25(OH)D) using an enzyme that is encoded by the gene CYP27A1. Calcidiol (25(OH)D) can then be converted in the kidneys or macrophages into calcitriol, the biologically active form of vitamin D also known as 1,25(OH)2D.  This conversion takes place using an enzyme coded for by the gene CYP27B1. For Vitamin D to be used in the nucleus of cells, it needs to be transported there by a binding protein that is coded for by the GC gene, and then it needs to bind to the vitamin D receptor, which is coded for by the VDR gene.

Vitamin D Genetic Variants:

Genetics can play a role in vitamin D levels in several ways, which makes sense when looking at the different steps involved in converting it to the active form which then acts on the vitamin D receptors in a cell. Below are genetic variants that have been shown in multiple research studies to impact vitamin D levels.

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