Vitamin D provides critical functions for hundreds of genes and nearly all of your tissues, especially your immune system. This “sunshine vitamin” is absolutely essential to your health and physiology just like sunshine provides critical life support for our planet. About one in seven individuals, or over one billion people worldwide, has insufficient or deficient vitamin D. Are you getting enough?

Sun Exposure & Vitamin D

When sunshine hits your skin, ultraviolet B (UVB) radiation converts cholesterol molecules into pre-vitamin D, then vitamin D where it is further metabolized by your liver and kidneys into its biologically active form – vitamin D3. Vitamin D is actually more of a steroid hormone than it is a vitamin because of this process. (Humans do not make vitamin D2.)

To make vitamin D3 from sun exposure, you need to spend 15-20 minutes daily in the sunshine with 40 percent of your skin surface exposed. Less than 40 percent of body surface area exposure leads to lesser amounts of vitamin D3 formed in your body. For many individuals, this can easily represent why your vitamin D3 levels fail to substantially increase with summer sun exposure.

Total body surface area values are as follows. For an average size adult, your entire head is about 10% of total surface area, your front/back of one arm 9%, front/back of one leg 18%, front torso 18%, and back torso 18%. The few minutes or seconds of typical face and hand exposure to sunshine that you get when walking from the car to your office, store, or walking out to your mailbox will fall substantially short of 40 percent surface area for 15-20 minutes per day.

Angle of Sun

The angle of the sun’s rays also determines whether or not UVB radiation reaches your skin to make vitamin D3. Early morning and evening hours decrease the angle of the sun’s rays and result in very little UVB radiation produced in the skin. For those in the northern states, the sun angle from October to April is not strong enough for vitamin D3 production.

Agents that Block UVB Radiation

If you use sunscreen with an SPF of 8, the UVB production is reduced by 95 percent. Sunscreen with SPF of 15 blocks more than 98 percent of UVB. In addition, UVB is blocked by clothing and the windows in your car, home, and office.

Skin Tone 

Skin tone also affects UVB and vitamin D3 production. Skin tone darkens with higher melanin levels. Melanin is a skin pigment that blocks UVB radiation. Melanin is not the same as melatonin the sleep hormone. The darker your natural skin tone, the higher your melanin levels, which makes it harder for you to synthesize vitamin D. In addition, aging reduces natural vitamin D production from your skin.

Vitamin D Levels

Vitamin D insufficiency occurs when 25-hydroxyvitamin D (25OHD) are between 20-29 ng/mL. Levels at or below 20 ng/mL are considered vitamin D deficient. Optimal levels are between 50-80 ng/mL.

Toxicity from high vitamin D is considered rare. It may occur from very high, prolonged intake of vitamin D2 or D3. However, this more commonly reflects an underlying medical issue that should be properly evaluated.

Essential for Your Whole Body

Vitamin D is immensely important for normal physiology and function. Receptor sites for Vitamin D (VDR) are widely found throughout your body. High concentrations are in the kidneys, intestines, parathyroid gland, pituitary gland, skin, and nearly all of the other 400 tissues and cell types in your body. In this article, the focus pertains to vitamin D and its numerous positive effects on immune health.

Vitamin D Critical for Immune Health

Vitamin D targets hundreds of genes including those vital to immune system function. It critically impacts and regulates your innate and adaptive immunity thus immeasurably affects your defense against germs and immune inflammation.

Cell studies show that vitamin D plays a significant role in “respiratory homeostasis” as it helps cells fight against germs and interferes with how viruses replicate, affecting respiratory health. Vitamin D also increases gene expression related to glutathione activity. Glutathione is a master antioxidant system essential to immune function and homeostasis.

Vitamin D affects certain white blood cells and immune compounds like monocytes and T cells and B cells, inflammatory cytokines IL-6 and TNF and NF-kappa B signaling etc. which are essential for inflammation management and protecting your vulnerability to viruses and bacteria. Vitamin D makes immune cells like monocytes more efficient at recognizing a germ invader.

In addition, gene proteins involved with the immune system rely on vitamin D to keep your immune cells from attacking self (autoimmunity). Immune genes impacted by vitamin D affect the flow of blood and coagulation processes. If vitamin D is inadequate, blood doesn’t flow as readily when there is a lot of immune inflammation.

Vitamin D status impacts prenatal and early infancy with lung and immune system development. Healthy vitamin D levels during pregnancy have been shown to aid immune tolerance against dust mites and support lung health in early childhood.

Vitamin D Helps the Immune System in Your Brain

Vitamin D helps your brain’s microglial cells. These cells are your brain’s immune clean-up army that manages stress, infection, free radicals and damage. If microglial cells lack adequate vitamin D, these immune defenders of your brain are much more vulnerable to injury and cell death.

Vitamin D Gene SNPs

Since the completion of the Genome Project, endless discoveries have occurred in understanding how gene SNPs (pronounced snips) or genetic variations affect health. In the case of vitamin D receptor (VDR) SNPs, they readily impact how your body responds to vitamin D. You need properly functioning vitamin D receptors and adequate vitamin D for your body to get the full benefits of vitamin D3. Gene testing is available through your provider or commercial DNA ancestry sites.

Dietary Concerns

The most predominant vitamin D food sources are egg yolk, fatty fish, beef liver, and fortified dairy products. Much smaller amounts may be found in some mushrooms. Plant-based and vegan lifestyles contain very little vitamin D.

If you work indoors, regularly use sunscreen or deliberately avoid sun exposure, are of older age, obese, or darker skinned, you are at higher risk of vitamin D deficiency. If you are vegan or vegetarian, you are more likely to be vitamin D deficient.

Vitamin D Intake

These are the general suggested guidelines by the American Endocrine Society for vitamin D3 intake in individuals with normal vitamin D levels, adequate sunshine exposure, and no other risk factors.

Infants 0-1 yr require at least 400IU/day.

Children 1 yr -18 yr require at least 600 IU/day.

Adults 19-70 yrs require at least 600 IU/day.

Adults 70 yrs and older require at least 800 IU/day

If you are at risk or lack adequate vitamin D, supplemental intake of vitamin D3 may increase to 1000 – 10,000 IU/day. Higher doses may be also needed to reach optimal tissue levels. Vitamin D3 is the preferred supplement form of vitamin D.

Team Player Nutrients and Drugs That Deplete

Vitamin D works together with calcium, phosphorus, magnesium, and vitamin K2. 

Several medications deplete vitamin D. These include anti-inflammatory (inhalant, systemic, and topical corticosteroids), antibiotics (antituberculosis agents), anticonvulsants (barbiturates, hydantoin derivatives), cholesterol lowering (bile acid sequestrants), lubricant laxatives, and antacid and ulcer medications (histamine H2 antagonists). Statin cholesterol lowering medications and their risk of adverse effects are affected by inadequate vitamin D. Check with your pharmacist for more specific information.

If it has been 6 months or longer or you have never had your vitamin D level measured, get it done. This simple blood test can help provide insight into the power or limits of vitamin D in your body.

Sunshine’s effect on our bodies is enormously powerful in so many ways ranging from light, electrical energy and heat, growth of our food supply and of course vitamin D synthesis. It provides essential vitality to our lives.

Unfortunately, many individuals have reached a point in their lives where sun exposure is greatly limited and vitamin D levels are likely inadequate to meet optimal needs. Don’t let low vitamin D levels lead to a decline in health. Make sure your immune system has this essential regulator in place so it can do its job.