Why Vitamin D is the Unsung Hero for Your Health
Vitamin D is like a superhero for your health, yet vitamin D deficiency is like a global pandemic.
Vitamin D regulates so many aspects of our health, and a deficiency in this nutrient has been linked to numerous autoimmune diseases. Furthermore, I believe the high prevalence of vitamin D deficiency is a symptom of a bigger problem in modern society— people spend way too much time indoors and aren’t exposed to enough sunlight and aren’t getting out in nature enough.
What is vitamin d
Vitamin D is actually a misnomer because it acts more like a hormone or prohormone, especially the inactive form calcidiol. In fact, the molecular structure of vitamin D is very similar to steroid hormones.
There are several forms of vitamin D, all of which have different biological effects and they are:
Vitamin D2 (ergocalciferol)- needs to undergo hydroxylation to be converted into the active form
25-hydroxyvitamin D [25(OH)D], also known as calcidiol, is found in the liver when it’s converted from D2 to the active form.
1,25(OH)₂D or calcitriol: biologically active form in which calcidiol is converted in the kidneys into calcitriol.
Vitamin D3 (cholecalciferol): made in the skin when exposed to UVB rays or from supplements
How it works in our body
VITAMIN D3 SYNTHESIS FROM SUN EXPOSURE AND FOOD. Source: https://rb.gy/qnx6
Vitamin D3 is synthesized most effectively from sun exposure or, alternatively, from consuming animal foods such as liver, fatty fish, fish oil, and egg yolks. Vitamin D2 is found in foods such as fortified milk, cereal, and mushrooms.
UVB rays from the sun at frequencies between 280 and 320 hit the skin where 7-dehydrocholesterol is converted into pre-vitamin D3 and is then isomerized into vitamin D3 (cholecalciferol). Vitamin D-binding protein (DBP) then facilitates vitamin D3’s entrance into the dermal capillary bed of the skin.
On the right of the figure above, ingested vitamin D2 (ergocalciferol) from food or supplements is incorporated into chylomicrons, which enter the lymphatic system and blood.
Once in the bloodstream, both vitamin D2 and vitamin D3 move to the liver where the enzyme cytochrome P450 hydroxylates both forms of the vitamin to 25(OH)D3. Then, the CYP27B1 further hydroxylates 25(OH)D3 (calcidiol) into the active form of the vitamin [1,25(OH)2D3] in the kidneys.
Unlike D2 or other vitamin D metabolites, vitamin D3 is the active form of vitamin D that binds to the vitamin D receptor (VDR). The activated VDR binds to vitamin D responsive elements (VDREs) to form a heterodimer with another nuclear receptor retinoid-X receptor (RXR, retinoid meaning vitamin A receptor), which can regulate directly or indirectly the expression of ~1,000 human genes. Most importantly, nearly all cells have VDRs which illustrates just how vital vitamin D is for our health.
Vitamin D supplementation is NOT the same as sunlight exposure
Another issue that very few are talking about with the exception of Dr. Jack Kruse and a handful of others, is that sun exposure on our skin is key for proper vitamin D synthesis. Sunlight exposure triggers cholesterol sulfate synthesis in the skin.
Sulfate synthesis in the skin cells absorbs the sun’s energy (UV rays) in order to carry out vital functions such as blood vessel health, the body’s electrical supply, and the delivery of key molecules like cholesterol, vitamin D, dopamine, and melatonin.
Sun exposure to our eyes and skin is essential for our health and it cannot be emphasized enough. We have been lied into believing that the sun is toxic for us and it couldn’t be further from the truth. Our bodies rely on sunlight to not only synthesize vitamin D but to also regulate our electromagnetic energies which regulate our mitochondrial function and basically all aspects of our health. This is beyond the scope of this post, but suffice it to say that sunlight is an essential nutrient.
Health benefits of VItamin D
Improves mitochondrial function
Vitamin D3 metabolite 1α,25(OH)2D3 regulates oxygen consumption in the mitochondria and has been shown to increase energy production in the mitochondria (ATP).
Bone health
The inactive form calcitriol can increase calcium absorption in the intestines and promotes calcium reabsorption in the kidneys. Additionally, it promotes bone growth by regulating bone cells (osteoblasts) and parathyroid hormone via VDRs.
Cardiovascular health
In line with the point above about regulating calcium levels, vitamin D deficiency has been linked to vascular calcification and atherothrombosis. VDRs or calcitriol are abundant in cardiomyocytes and vascular and endothelial cells of the cardiovascular system.
Vitamin D has several positive effects on the immune system (see below), and cardiovascular disease, such as atherosclerosis, is largely inflammatory.
Low vitamin D levels have been linked to hypertension.
Cancer prevention
Immune health 1: Prevents autoimmune symptoms
Prevents autoimmune symptoms by increasing the production of T regulatory cells (Tregs) through various pathways, which help the immune system know “self” cells from foreign invaders.
Immune health 2: Anti-microbial properties
It induces antimicrobial peptides like cathelicidin and beta-defensin.
Immune health 3: Anti-inflammatory properties
For a complete list, check out the peer-review article I wrote here, but to summarize: down-regulates pro-inflammatory cytokines, activates dendritic and T cells and macrophages, and decreases B cells and antibody-producing cells IgG and IgM.
Immune health 4: Maternal vitamin D programs the fetal immune system
Maternal serum 25(OH)D3 levels can directly affect infant vitamin D levels and immune programming. Interestingly 1,25(OH)2D3, can cross the placenta and enter the fetal cord blood, and maternal serum 25(OH)D3 levels directly correlate with concentrations in the umbilical cord at birth.
Maternal vitamin D insufficiency and deficiency can also lead to childhood allergies, eczema, asthma, and autoimmune diseases.
Immune health 5: Works with other vitamins to promote immune health
See below about other vitamins.
Gut health
Vitamin D3 interacts directly with the gut microbiota and can improve the gut microbiota composition (ecosystem).
Improves intestinal barrier function by regulating tight junction proteins of the intestinal epithelial cells, which prevents inflammatory responses and promotes overall gut health.
Promotes anti-inflammatory signaling
When vitamin D3 binds to a VDR, it regulates a bunch of immune cells within the gut, many of which promote immune tolerance (i.e. not autoimmune or excessive inflammatory responses) within the gut.
Regulates hormones
Thyroid, glucocorticoids, estrogen, parathyroid hormone
Reduces pain
Although the exact mechanisms are unclear, vitamin D does interact with the central nervous system and can regulate neurotransmitters and the immune system. Researchers have recently discovered a link between fibromyalgia and vitamin D.
Improves mood and cognitive health
Adequate vitamin D levels have been shown to combat depression, ADHD, and autism spectrum disorder symptoms, and may play a role in cognitive function in Alzheimer’s patients.
Vitamin D works with other nutrients
As I’ve said many times, vitamins don’t work in a vacuum. They work synergistically with other nutrients in order to exert their health benefits.
Vitamin A
As mentioned above, vitamin D binds to its receptor VDR inside the nucleus, which then binds to the vitamin A receptor RXR to form what’s called a heterodimer. Inside the nucleus, this heterodimer works to control the expression of genes involved in immune health.
The two types of vitamin A are: beta-carotene (orange and yellow fruits and vegetables) and retinol (from foods like liver and egg yolks). Retinol is the active form and most people have a genetic mutation that makes the conversion from beta-carotene to retinol very inefficient. If you have to supplement for some reason, it’s best to take retinol, but be careful with overdosing as vitamin A toxicity is much more common than taking too much vitamin D.
Vitamin K
The two forms are K1, which you get from eating leafy greens, and K2, which you get from eggs, liver, cheese, and stinky natto. Our gut microbiome also synthesizes K2.
Zinc
Zinc can help vitamin D to work inside your cells and might work with vitamin D to improve bone health.
Magnesium
Magnesium can activate vitamin D and has antioxidant properties. Magnesium deficiency, unfortunately, is another major global health problem.
How to get sufficient vitamin D
Sun exposure:
About 20 min of sun exposure on the arms and face between latitudes 42°N and 42°S is equivalent to 200–400 IU of vitamin D3 ingestion.
An adult exposed to 1 minimal erythemal dose (slight pinkness to the skin 24 h after exposure) is equivalent to an oral intake of about 20,000 IU (500 µg) of vitamin D3, but this depends on your skin color and overall health. Whereas arm and leg exposure of 0.5 erythemal dose is equivalent of an oral intake of 3,000 IU of vitamin D2.
Food:
Generally, the ingestion of 1,000 IU vitamin D2/day increases the 1,25(OH)2D3 levels ~10 ng/mL.
Supplementation (always take D3!)- what I recommend based on the current scientific evidence
Not all supplements are created equally. It’s best to always supplement with vitamin D3, which is the active form. I like liquid vitamin D3 because you can easily adjust the dosage depending on your sun exposure, your serum levels, and if you’re sick. Check the label because the amount of vitamin D3 in each drop can vary anywhere from 200 IU to 2,000 IU of vitamin D3 per drop.
Adults: 5,000 IU/ day
Children: 1,000 IU per 25 lbs (11 kg) of body weight up to 125 lbs (57 kg).
Infants: 1,000 IU/ day (upper limit 2,000 IU/ day) (If formula fed, check label for amount and type of vitamin D (D3 is far superior to D2)
Pregnant women: 4,000- 6,000 IU/ day (upper limit 10,000 IU/ day) (always check with your OBGYN and ideally get your serum levels tested before, during each trimester, and after pregnancy).
Although the Endocrine Society recommends 1,500-2,000 IU/day, the fact is most women are already deficient when entering pregnancy, and a recent study concluded that 4,000 IU/day was enough to ensure the newborn had sufficient vitamin D levels.
Breastfeeding women: 6,000 IU/ day (if not getting any sun exposure that day and exclusively breastfeeding)
Therefore, you do not need to give your baby any supplemental vitamin D3. If you get adequate sun exposure one day, you don’t need to take your vitamin D3 supplement that day, but be careful not to skip your supplements when you do need them because vitamin D gets cleared out of breastmilk quickly. (Always check with your OBGYN and get your serum levels tested regularly).
Optimal levels and testing
According to the Vitamin D Council, which is a major authority in all things related to vitamin D:
Deficient: 0-40 ng/ml (0-100 nmol/l)
Sufficient: 40-80 ng/ml (100-200 nmol/l) (I would argue that sufficient should be at least 50 ng/ ml).
High Normal: 80-100 ng/ml (200-250 nmol/l)
Undesirable: > 100 ng/ml (> 250 nmol/l)
Toxic: > 150 ng/ml (> 375 nmol/l)
If you got your serum vitamin D levels checked, read this post about how to adjust your supplementation to get your level in the optimal range.
Vitamin D deficiency Risk
An estimated 20–80% of Canadians and Europeans are vitamin D deficient, while approximately one-third of the U.S. population is deficient. Unfortunately, there is a surprising lack of research on vitamin D deficiency in African and South American populations. The most common sign of a severe deficiency is rickets, but there are usually few obvious symptoms before having a severe deficiency, so unless you supplement daily or get adequate sunlight on a regular basis, which most people don’t, it’s best to get your serum levels tested annually.
Vitamin D deficiency risk is higher in:
Little to no sun exposure on skin
Pregnant women
Infants and children >5 years old
People with an autoimmune disease
Adults 65 + years old
Dark-skinned people because the skin has more melanin which filters out UVB rays thus making it more difficult to synthesize vitamin D from the sun.
Obese people
People who cover their skin when outside
Living in higher or lower latitudes.
Sources
https://pubmed.ncbi.nlm.nih.gov/33549285/
https://www.hindawi.com/journals/ije/2015/375349/
https://www.vitamindcouncil.org/health-conditions/alzheimers-disease/
https://www.vitamindcouncil.org/about-vitamin-d/vitamin-d-and-other-vitamins-and-minerals/
https://www.vitamindcouncil.org/i-tested-my-vitamin-d-level-what-do-my-results-mean/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7861592/
https://microbiomejournal.biomedcentral.com/articles/10.1186/s40168-022-01298-9
