Vitamin D Deficiency: Why Supplementation Is Only A Band-Aid?

Vitamin D deficiency is quite prevalent, and vitamin D supplements are becoming increasingly popular. However, the majority of vitamin D insufficiency discussions focus on supplementation, which does not address the underlying reasons.

What, then, are the TRUE reasons for vitamin D deficiency?

Let's take a quick look at how vitamin D is processed in the body...

Vitamin D Metabolism: Beginning with Skin Cholesterol + Sunshine

Vitamin D3 (cholecalciferol) is synthesized in the skin from 7-dehydrocholesterol (a precursor to cholesterol) when exposed to sunshine. Without proper sunshine exposure, vitamin D levels will naturally be suboptimal. Although a modest quantity of vitamin D can be obtained from diet, sun exposure is the primary source.

What influences UV-induced vitamin D production?

Sunscreen and clothing prevent vitamin D synthesis; therefore, moderate, unprotected sun exposure is required and healthy. In addition, residents of higher latitudes will experience fewer sunny days and hence produce less vitamin D during the overcast months. Vitamin D, however, is a fat-soluble 'vitamin' (it is actually a hormone, not a vitamin) that can be stored in fat cells. This is why healthy summer sun exposure is so important: The vitamin D produced in the summer can sustain you throughout the winter without supplementation.

Do You Suffer From Vitamin D Deficiency Despite Extensive Sun Exposure?

In naturopathic medical school, we learned that vitamin D levels below 30 ng/mL required supplementation with a specified number of IU for every desired 10 ng/mL increase in serum 25-OH vitamin D.

While supplementation may be beneficial, vitamin D levels do not consistently increase with supplementation and return to suboptimal levels when supplementation is terminated. We've also often questioned how people who lived in sunny climes and were constantly outside could be deficient in vitamin D, given that vitamin D production begins with sun exposure.

Consequently, the sun is required for vitamin D production, and a lack of sun exposure can cause deficient levels. But what about individuals who enjoy a good amount of sun exposure?

The Liver and Kidneys' Role in Vitamin D Metabolism

Vitamin D3 (cholecalciferol) is produced in the skin and subsequently transformed to 25-OH-D3 in the liver (the form that is often measured in the blood). The kidneys are then responsible for converting vitamin D to its active form, 1,25-OH-D3. Vitamin D must be converted to its active form, 1,25-OH-D3, for its positive effects, including calcium control and immunological modulation, to manifest.

Low levels of 25-OH vitamin D may indicate a problem with liver and/or renal function. Despite the fact that a variety of disorders can affect the liver and kidneys, it is also possible to have subclinical liver or kidney function impairment that may not be detectable by standard laboratory indicators.

Take insulin resistance as an example: You can exhibit tendencies toward insulin resistance, blood sugar dysregulation, and metabolic dysfunction before your labs indicate high blood sugar levels, and this can negatively impact the health of your liver and kidneys, as well as your vitamin D metabolism and immune system.