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  • Writer's pictureDr. 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)

The impact of vitamin D pathway genetic variation and circulating 25-hydroxyvitamin D on cancer outcome: systematic review and meta-analysis


"Higher 25OHD concentration is associated with better cancer outcome, and the observed association of functional variants in vitamin D pathway genes with outcome supports a causal link. This analysis provides powerful background rationale to instigate clinical trials to investigate the potential beneficial effect of vitamin D in the context of stratification by genotype."

The immunological functions of the vitamin D endocrine system

Vitamin D: modulator of the immune system

"However 1,25(OH)(2)D(3) also has a physiological role beyond its well-known role in skeletal homeostasis. Here, we describe 1,25(OH)(2)D(3) as an immunomodulator targeting various immune cells, including monocytes, macrophages, dendritic cells (DCs), as well as T-lymphocytes and B-lymphocytes, hence modulating both innate and adaptive immune responses. Besides being targets, immune cells express vitamin D-activating enzymes, allowing local conversion of inactive vitamin D into 1,25(OH)(2)D(3) within the immune system. Taken together, these data indicate that 1,25(OH)(2)D(3) plays a role in maintenance of immune homeostasis. Several epidemiological studies have linked inadequate vitamin D levels to a higher susceptibility of immune-mediated disorders, including chronic infections and autoimmune diseases."

Vitamin D for infections

Control of autoimmune diseases by the vitamin D endocrine system

"It regulates the growth and differentiation of multiple cell types, and displays immunoregulatory and anti-inflammatory properties. Cells involved in innate and adaptive immune responses--including macrophages, dendritic cells, T cells and B cells--express the vitamin D receptor (VDR), and can both produce and respond to 1,25(OH)(2)D(3). The net effect of the vitamin D system on the immune response is an enhancement of innate immunity coupled with multifaceted regulation of adaptive immunity. Epidemiological evidence indicates a significant association between vitamin D deficiency and an increased incidence of several autoimmune diseases, and clarification of the physiological role of endogenous VDR agonists in the regulation of autoimmune responses will guide the development of pharmacological VDR agonists for use in the clinic. The antiproliferative, prodifferentiative, antibacterial, immunomodulatory and anti-inflammatory properties of synthetic VDR agonists could be exploited to treat a variety of autoimmune diseases, from rheumatoid arthritis to systemic lupus erythematosus, and possibly also multiple sclerosis, type 1 diabetes, inflammatory bowel diseases, and autoimmune prostatitis."

Vitamin D endocrine system and the immune response in rheumatic diseases


"Epidemiological evidence indicates a significant association between vitamin D deficiency and an increased incidence of autoimmune diseases. The presence of vitamin D receptors (VDRs) in the cells of the immune system and the fact that several of these cells produce the vitamin D hormone suggested that vitamin D could have immunoregulatory properties, and now potent immunomodulatory activities on dendritic cells, Th1 and Th17 cells, as well as B cells have been confirmed. Serum levels of vitamin D have been found to be significantly lower in patients with systemic lupus erythematosus, undifferentiated connective tissue disease, and type-1 diabetes mellitus than in the healthy population. In addition, it was also found that lower levels of vitamin D were associated with higher disease activity in rheumatoid arthritis. Promising clinical results together with evidence for the regulation of multiple immunomodulatory mechanisms by VDR agonists represent a sound basis for further exploration of their potential in the treatment of rheumatic autoimmune disorders."

Vitamin D deficiency and connective tissue disease

Vitamin D controls T cell antigen receptor signaling and activation of human T cells

Vitamin D and inflammatory bowel disease


"Crohn's disease (CD) and ulcerative colitis (UC) are the main forms of inflammatory bowel disease (IBD), chronic relapsing-remitting inflammatory conditions of uncertain origin affecting the gastrointestinal tract. Much effort has recently been made both in defining the mechanisms underlying the development of IBD, and in broadening the spectrum of effective treatment. Substantial progress has been made in characterising immune-cell populations and inflammatory mediators in IBD. 1,25-Dihydroxyvitamin D(3) [1,25(OH)(2)D(3)], the bioactive form of Vitamin D(3), besides having well-known control findings of calcium and phosphorus metabolism, bone formation and mineralization, also has a role in the maintenance of immune- omeostasis. The immune-regulatory role of vitamin D affects both the innate and adaptive immune system contributing to the immune-tolerance of self-structures. Impaired vitamin D supply/regulation, amongst other factors, leads to the development of autoimmune processes in animal models of various autoimmune diseases, including IBD. The administration of vitamin D in these animals leads to improvement of immune-mediated symptoms. Future studies now need to focus on the potential of vitamin D and its derivatives as therapeutic adjuncts in the treatment of IBD."

Vitamin D and its role in immunology: multiple sclerosis, and inflammatory bowel disease

Vitamin D deficiency is independently associated with mortality among critically ill patients. Clinics (Sao Paulo). 2015;70(5):326-32.

A study in 2015 entailing 135 ICU patients revealed a 32.2% risk of mortality when vitamin D levels were below 12 ng/mL.....compared to a 13.2% risk of mortality if levels were greater. This finding shows that vitamin D deficient patients die at a 2.4-fold greater rate. (1)

Scientific documentation of the relationship of vitamin D deficiency and the development of cancer. J Environ Pathol Toxicol Oncol. 2009;28(2):133-41.

Anti-inflammatory effect of 1alpha,25-dihydroxyvitamin D(3) in human coronary arterial endothelial cells: Implication for the treatment of Kawasaki disease. J Steroid Biochem Mol Biol. 2009;113(1-2):134-8.

For kiddos

Dermatoendocrinol. 2016 Oct 14;8(1):e1248324. eCollection 2016 Jan-Dec.

Estimated economic benefit of increasing 25-hydroxyvitamin D concentrations of Canadians to or above 100 nmol/L.


  • "The diseases affected by 25(OH)D concentration included cancer, cardiovascular disease, dementia, diabetes mellitus, multiple sclerosis, respiratory infections, and musculoskeletal disorders. We used 25(OH)D concentration-health outcome relations for breast cancer and cardiovascular disease and results of clinical trials with vitamin D for respiratory infections and musculoskeletal disorders to estimate the reductions in disease burden for increased 25(OH)D concentrations. If all Canadians attained 25(OH)D concentrations>100 nmol/L, the calculated reduction in annual economic burden of disease was $12.5 ± 6 billion on the basis of economic burdens for 2016 and a reduction in annual premature deaths by 23,000 (11,000-34,000) on the basis of rates for 2011. "

  • Important to note: You MUST address all other essentials of health to remain healthy!! "However, the effects on disease incidence, economic burden, and mortality rate would be phased in gradually over several years primarily because once a chronic disease is established, vitamin D affects its progression only modestly."

Dr. Mark Hyman

When we don’t get enough vitamin D, it impacts every area of our biology, because it affects the way our cells and genes function.

Your body makes vitamin D when it’s exposed to sunlight. In fact, 80 to 100 percent of the vitamin D we need comes from the sun. The sun exposure that makes our skin a bit red (called 1 minimum erythemal dose) produces the equivalent of 10,000 to 25,000 international units (IU) of vitamin D in our bodies.

The problem is that most of us aren’t exposed to enough sunlight.

Overuse of sunscreen is one reason. While these products help protect against skin cancer, they also block a whopping 97 percent of your body’s vitamin D production.

If you live in a northern climate, you’re not getting enough sun (and therefore vitamin D), especially during winter. And you’re probably not eating enough of the few natural dietary sources of vitamin D: fatty wild fish like mackerel, herring, and cod liver oil.

Plus, aging skin produces less vitamin D—the average 70 year-old person creates only 25 percent of the vitamin D that a 20 year-old does. Skin color makes a difference, too. People with dark skin also produce less vitamin D. And I’ve seen very severe deficiencies in Orthodox Jews and Muslims who keep themselves covered all the time.

With all these causes of vitamin D deficiency, and how hard it is to get from diet alone, supplementing is so important. The right amount differs from person to person. From my own clinical experience and taking into account the latest research on vitamin D, I’ve seen that people generally do well with blood levels of 25(OH)D between 30-100 ng/mL, but that the optimal range falls between 40-70 ng/mL.

Overview of Vitamin D

"bile acids initiate the emulsification of lipids, pancreatic lipase hydrolyzes the triglycerides into monoglycerides and free fatty acids, and bile acids support the formation of lipid-containing micelles, which diffuse into enterocytes". Lipids, lipoproteins, cholesterol and vitamin D are all transported through the lymphatic system via chylomicrons. It's quickly taken up by tissues that can break down these transport vessicles with lipase, particularly in adipose (fat) tissue and skeletal muscle.

"when calcitriol is required due to a lack of calcium (or lack of phosphate), 25OHD is 1α-hydroxylated in the kidney to form calcitriol, the active form, by the 1α-hydroxylase enzyme"

"This metabolic step is very tightly regulated by blood calcium and phosphate levels through PTH and the phosphaturic hormone, FGF23, and constitutes the basis of the vitamin D endocrine system that is central to maintaining calcium and phosphate homeostasis"

"all naturally occurring vitamin D compounds interact with DBP. Calcitriol and vitamin D have significantly lower affinity for this protein than does 25OHD. Whereas vitamin D has an average lifetime in the body of approximately 2 months, 25OHD has a lifetime of 15 days, and calcitriol has a lifetime measured in hours"

"Adipose tissue stores of vitamin D probably represent “non-specific” stores sequestered because of the hydrophobic nature of vitamin D, but the extent to which the processes of accumulation or mobilization are regulated by normal physiological mechanisms remains unknown at this time. "

Age and weight: "Work by Liel et al. (1988) suggested that there was enhanced uptake and clearance of vitamin D by adipose tissue in obese subjects compared with those of normal weights. Similarly, Wortsman et al. (2000) concluded that in obese subjects, vitamin D was stored in adipose tissue and not released when needed. Finally, Blum et al. (2008) found that, in elderly subjects supplemented with 700 IU of vitamin D per day, for every additional 15 kg of weight above “normal” at baseline, the mean adjusted change in 25OHD level was approximately 10 nmol/L lower after 1 year of supplementation. The authors estimated that in order for subjects with body mass indexes (BMIs) above the normal range to obtain an increase in serum 25OHD level similar to that of subjects with weight in the normal range, an additional 17 percent increase in vitamin D above the administered dose of 700 IU/day would be needed for every 10 kg increase in body weight above baseline in their study population.'

Steenbock H, Black A. Fat-soluble vitamins. Journal of Biological Chemistry. 1924;61(2):405–22.

Vitamin D picture


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