Vitamin D Supplements

Updated April 23, 2025

Main Points:

Vitamin D is made from cholesterol when getting UV-B light exposure from sunlight
UV light provides many health benefits independent of vitamin D including lower cholesterol, improved cardiovascular function, and improved immune function
Taking vitamin D supplements block the full benefits of UV light
Vitamin D made from sunlight is biochemically different than vitamin D found in supplements
Research seems to show that low vitamin D is not really a vitamin D deficit but a reflection of a UV light deficit
Sunlight is overall safe, though some people cannot tolerate sunlight due to underlying health problems

Vitamin D supplementation has become very popular in recent years. Doctors frequently recommend it due to the widespread occurrence of low serum vitamin D levels. Many people take it either to prevent illness or to manage a health condition. On the surface, taking vitamin D makes logical sense, as nearly all chronic health conditions are associated with low serum vitamin D.

However, chronic disease continues to rise, and those taking vitamin D supplements often report little to no improvement—even though their blood levels appear normal. On top of this, people are told they can get vitamin D from sunlight, yet are simultaneously warned that sun exposure is dangerous. Why the contradiction? And what’s the real answer?

Let’s dive into some research to help clarify this issue.

The Studies

A 2019 study titled “Skin Exposure to Narrow Band Ultraviolet (UVB) Light Modulates the Human Intestinal Microbiome,” published in Frontiers in Microbiology, divided healthy subjects into two groups: those who had taken vitamin D supplements during the prior winter, and those who had not. Both groups received three ultraviolet B (UV-B) light exposures in one week. As expected, serum vitamin D levels increased in all participants. However, only the group that had not taken supplements experienced an improvement in gut microbiome diversity.

A similar result was found in a 2018 mouse study titled “Ultraviolet Irradiation of Skin Alters the Faecal Microbiome Independently of Vitamin D in Mice,” published in Nutrients.

Takeaway? You cannot replace sunlight with a supplement.

UV-B light is the wavelength in sunlight that humans require to convert cholesterol (yes, cholesterol!) into vitamin D3. If you have low cholesterol or insufficient UV exposure, your body can't produce vitamin D. Furthermore, UV-B has other health effects independent of vitamin D—hence why supplementation doesn't deliver the same benefits.

And these aren’t the only studies showing this difference.

More Evidence

A 2024 review titled “Sunlight: Time for a Rethink?” published in the Journal of Investigative Dermatology notes:

“Vitamin D synthesis is dependent on UVB exposure,” and
“Sunlight has health benefits through vitamin D-independent pathways, such as photomobilization of nitric oxide from cutaneous stores with reduction in cardiovascular morbidity.”

Of major note, the abstract begins with:

“No studies link sun exposure to increased all-cause mortality.”

A 2010 study titled “UV radiation suppresses experimental autoimmune encephalomyelitis independent of vitamin D production” found that UV radiation suppressed a multiple sclerosis (MS)-like condition in mice. The authors stated:

“Vitamin D supplementation alone may not replace the ability of sunlight to reduce MS susceptibility.”

Finally, a 2017 randomized controlled trial titled “Randomized Control Trial Assessing Impact of Increased Sunlight Exposure versus Vitamin D Supplementation on Lipid Profile in Indian Vitamin D Deficient Men” found striking differences. Men exposed to increased sunlight showed lowered total cholesterol, LDL, and HDL. Meanwhile, those who took vitamin D3 (cholecalciferol) supplements had higher total and HDL cholesterol.

So What Does This Mean?

With reading the above, it should now be clear: the vitamin D our bodies produce from sunlight is not the same as the vitamin D found in a pill. In addition, they are biochemically different. Supplemental vitamin D is fat-soluble. When sunlight hits the skin it first sulfates cholesterol, so the vitamin D that's produced is sulfated, which is water-soluble—a distinction that alters how it functions in the body. Understanding this, it appears low vitamin D is not a vitamin D deficit but instead a UV light deficit.

Are there times that supplemental vitamin D is appropriate? Yes, there are exceptions. However, determining when it’s truly necessary requires deep knowledge of human physiology and physics. Unfortunately, few physicians today are trained to understand light and its biological influence. Medicine, as it stands, is largely taught through the narrow view of biochemistry, often ignoring the powerful effects of natural forces like light. This limited perspective leads to protocols that often fail to deliver real healing.

In Summary

The best way to support your health with vitamin D is through sunlight, as it appears it is a UV light deficit, not a vitamin deficit. Sunlight is safe though some people cannot tolerate sun well due to underlying health problems—but that’s a topic for another day. In the meantime, remember: nature heals.

References:

1. https://pmc.ncbi.nlm.nih.gov/articles/PMC6821880/

2. https://pubmed.ncbi.nlm.nih.gov/30103486/

3. https://pubmed.ncbi.nlm.nih.gov/38661623/

4. https://pubmed.ncbi.nlm.nih.gov/20308557/

5. https://pubmed.ncbi.nlm.nih.gov/32668607/

6. https://pmc.ncbi.nlm.nih.gov/articles/PMC5434721/