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  • Dr. J

Vitamin D: What you need to know

Updated: Jan 6, 2022

First discovered as a necessary 'nutrient' to prevent rickets in the 1920's.

Ever since, the scientific community has continuously unveiled a diverse array of vital physiological actions that vitamin D plays in the body.

Health Functions of Vitamin D

Technically, vitamin D can be considered a 'pro-hormone' rather than a 'vitamin'. This active hormone influences and regulates many functions within the body.

  • Elevation of plasma calcium and phosphate levels: required for bone mineralization, nerve transmission, vasodilation, and hormonal secretion.

  • Gene activation/regulation: Assay studies show that 5% of the genome is influenced by the presence of calcitriol.

  • Immune sytem

  • Cellular immunity

  • Inflammation modulation

  • Aging process

  • Cognitive health

  • Athletic performance

  • Respiratory and Vascular system

  • Sleep quality

  • Mood: Anxiety, depression

  • Cell formation/proliferation/apoptosis (cell death): Important role in cancer control

  • Suppression of autoimmune conditions

Deficiency spans far and wide

Upwards of 1 billion people, including 42-80% of American adults are deficient (depending on the research you're looking at), and 70% of American children 6-11.

Those who are at highest risk:

  • Live in northern hemispheres,

  • Don't get regular exposure to sunlight

  • Dark skin (and don't get regular sunlight exposure)

  • Elderly

  • Obese

  • Pregnant

Upgrade your Immune System RESILIENCE

Vitamin D has long been recognized as an essential component to optimizing immune system function and regulation.

Most of our immune system cells have a high concentration of vitamin D receptors, and adequate vitamin D is needed for proper activation and function. Certain immune cells will release more activated vitamin D to other nearby immune cells!

Improving our cellular immune system:

Particular cells with high concentrations of vitamin D receptors include important cells of the immune system: T-cells, cytotoxic T-cells, antigen presenting cells, macrophages, monocytes. Production of cathelicidin in macrophages and monocytes produces anti-microbial peptides (AMPs). As many as 200 different types of these peptides are produced.

This is our body's first natural line of defense, as they are particularly produced by immune, gut, and skin cells. Those with high levels of AMP product have greater immune resiliency, while those that have low production, tend to get sicker more often.

Role in Cancer Prevention

  • Adequate levels shown to positively affect 16 different types of cancer

Potentially reducing your risk of cancer by 60%

(A separate article will have to be written here.)

Support the Foundations First:




Primary Sources


Yes, we're meant to be exposed to full spectrum sunlight. It's not the devil and not going to cause cancer with regular, moderate exposure (a topic for a different article).

Vitamin D happens to be the only 'vitamin' our body can create... so let's work with nature and produce sufficient amounts of vitamin D the way we were designed.

10-20 minutes of direct sunlight to, ideally, 40% of your skin. Darker complexion may require more sunlight. Sunscreen and blunt this effect as UVB rays are needed to convert 7-dehydrocholesterol into its active form that can be converted into vitamin D3 (cholecalciferol), or calcitriol, in the liver.


Cold-water fatty fish, pasture-raised beef/duck/chicken liver, pasture-raised grass-fed butter/ghee, pasture-raised eggs, mushrooms (exposed to sunlight):

Have limited amounts of D3.

More importantly, providing your body with a wide variety of foods to support all other functions of the body will be essential from an overall perspective of attaining optimal health. Although vitamin D is important, your body also needs adequate amounts of other vitamins, minerals, and phytonutrients to function optimally, as well as convert and utilize vitamin D properly. (more below)


There can be a time and place. It's just not, all the time.

Your best bet is to get your serum 25(OH)D (vitamin D) levels checked. Relatively cheap, and gives you a good baseline of where you're at. This active form circulates for about 15 days, whereas calcitriol only lasts for hours in the body.

What should be really checked if you're looking to be as comprehensive as possible?

Active AND Storage vitamin D levels

Mineral levels: Magnesium/Ionized calcium

If levels are low, it may be necessary to supplement at a higher dosage until levels are back between 60-100 ng/dl.


You will also want to change other lifestyle factors as well.

Your body requires certain enzymes to convert certain precursors to active compounds that serve important biological purposes. There are countless examples in the body; literally every cell in the body is undergoing thousands of these reactions every second.

The same applies for Vitamin D, as Vitamin D needs to be converted from a cholesterol molecule, to it's active form. Along the way, there are conversions happening that are regulated by enzymes.

And all enzymes require cofactors; components to activate function. Many cofactors are minerals.

Make sure you're consuming adequate amounts of magnesium. (68% of Americans don't meet the RDA-- which is pretty low already-- of magnesium)

Magnesium is needed for proper conversion of vitamin D. Low magnesium levels with added vitamin D can cause increased inflammation, as well as possible calcification in your blood vessels and tissues as opposed to your bones. Potassium, vitamin A, and copper can be depleted as well. Making sure you're consuming a variety of foods to help replenish these stores would be beneficial as well.

Having enough copper (as well as other minerals) available is essential in providing your the enzymes in your body with the key components they need to function optimally. Without them, the very enzymes that help convert inactive forms of vitamin D, into their active state (ex. 25 hydroxylase) will not be able to carry out the conversion process.

Those with chronic infections (ex. mold), or high viral loads can also be negatively impacted as certain viruses can benefit from the additional calcium, as well as suppress the immune system in certain cases (contradicting, I know...).

So, you're better off getting your vitamin D from natural sources; preferably creating your own... for FREE!

D2 vs. D3

Ergocalciferol (D2) is the mostly created by plants and fungi.

Cholecalciferol (D3) is greater by the body with the conversion of a special cholesterol in your skin after exposure to UV light.

Best practices:

As far as obtaining optimal amounts of dietary vitamin D (from foods and/or supplements)--Best absorbed with fats, as this triggers the release of bile acids and pancreatic lipase. All of which are required for proper absorption and assimilation. More detailed info under 'resources'.


References and Resources:


Live in a cold climate and struggle to get enough sun exposure?

Sun Lamps / Vitamin D lamps

Vitamin D Protects Against Infections

Prevalence of Vitamin D Deficiency and Associated Risk Factors in the US Population (2011-2012)