Is Sunlight Really the Source of Vitamin D?

Nourishment and Renewal, Sun and Surf

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Common Misconceptions About Vitamin D and its Sources.

There is considerable misinformation that is provided to the public about the true source of Vitamin D. There are often statements in the media that imply that exposure to sunlight is all that you need to get the necessary amount of vitamin D.

The mistaken implication is that sunlight is your only source of vitamin D.

With this misinformation, you may conclude that with sufficient sunlight exposure, it is not necessary to be concerned with how much vitamin D you ingest with food or supplementation.

Presently there is increasing, legitimate concerns about viral infections and the importance of optimizing your immune system. Because vitamin D plays an important role in supporting your immune system, it is critical that you have a good understanding of this topic.

The Origins of the Misconception

The misconception is understandable. It is true that the effect of sunlight on your skin is critical to the synthesis of vitamin D, but that is not the whole story. 

A major contribution to the misunderstanding is that there are various sources and forms of vitamin D; they are described by different names. In addition, its complex metabolism gives rise to different derivatives of vitamin D that ultimately result in the active form that our bodies can use. These different forms are also described by a variety of names and synonyms.

All this this easily creates misunderstanding.

Let’s “shine” some light on this topic and examine some useful facts.

Sunlight, in and of itself, is not the source of vitamin D.

If sunlight is not the source of vitamin D, then what is its critical role?

A Primer on Vitamin D Metabolism

It is important to know that there are two major sources of vitamin D: one is derived from what we ingest and the second source is synthesized by our body.  Our diet provides us with modest amounts of vitamin D2 (ergocalciferol) as well as vitamin D3 (cholecalciferol). Another external source of vitamin D3 is through supplementation.

The second source of vitamin D is created in our body which first synthesizes a precursor molecule that is present in the skin. As sunlight penetrates the skin, its ultraviolet B component acts upon this precursor molecule, 7-dehydrocholesterol.

The effect is to convert it into vitamin D3 (cholecalciferol).  This molecule is an intermediate, inactive form of vitamin D. It is further metabolized by the liver and then the kidneys where at least one active form of vitamin D is formed.

The role of ultraviolet light B, a component of sunlight, is to act upon the precursor molecule, 7-dehydrocholesterol in order to enable further metabolism.  Our bodies can then create the active forms of vitamin D.

The role of sunlight is not to provide vitamin D, but rather to act upon the precursor form of vitamin D as a necessary step in the synthesis of its active forms.

In order for sunlight to effect its role, there must be sufficient cholecalciferol circulating through the microscopic blood vessels of your skin for ultraviolet light B to be effective.

So Why Do These Facts Matter to Your Health?

In the course of the last 10 to 20 years, careful scientific studies have established that vitamin D has a profound effect our bodies. Far beyond its important role in calcium and bone metabolism, it is known to have a critical role in the proper function of our immune systems. Vitamin D deficiency impairs the ability of our immune system to fight infectious diseases, cancers and the onset of debilitating diseases.

For example, we know that vitamin D deficiency is a risk factor for various cancers such as colon, prostate and breast.  There is recent scientific research that describes an association between vitamin D insufficiency and Alzheimer’s disease, as well as dementia.

We know that for a variety of reasons, approximately two-thirds of the population of the United States is deficient in vitamin D. In addition, our typical diet is insufficient to provide you the necessary nutrients to metabolize and create the active form of vitamin D.

The incorrect belief that only exposure to sunlight suffices to have proper vitamin D levels may create the risk of vitamin D deficiency.  Consequently, if a person's level is low, it may remain that way. It can be increased to normal levels with sufficient vitamin D in your diet and possibly pharmaceutical grade cholecalciferol (D3) supplementation.

This is an important health matter to you and your loved ones. The medical profession is increasingly vigilant in diagnosing vitamin D deficiency by means a simple blood test and treating it.

For those who are deficient, the importance of oral supplementation with high quality, vitamin D3 (cholecalciferol) is increasingly recognized and recommended by medical experts.

Disclaimer: Although I am a board certified plastic surgeon, my comments should not be construed as personal medical advice.

Updated May 28, 2021

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