What is one thing that everyone can do free to improve his or her health? Increasing proper sunlight exposure! In this post, we are going to cover endogenous vitamin D production from sunlight and how it can change your life. Most people do not get enough sun exposure, and we have a medical epidemic of reduced vitamin D levels in our modern world. We consume a diet lacking in retinol (vitamin A), vitamin K, and magnesium which we need to utilize vitamin D. We also are dealing with certain conditions that deplete our vitamin D reserves including gut dysbiosis, autoimmunity (chronic infections), improper diet, and liver and kidney disease.

Vitamin D the Hormone That Will Change Your Life

Vitamin D is a fat-soluble steroid that can be produced endogenously (within our body) from proper sunlight exposure (UV-B), or obtained from supplementation or in smaller quantities from our diet. There are different forms of vitamin D that our body recognizes. The first form is ergocalciferol, which is vitamin D that is produced by fungi. It has a poor conversion to calcidiol (a storage form of vitamin D3), so I do not recommend it. 25-hydroxy vitamin D, also known as calcidiol, is the inactivated form or storage form of vitamin D3. Calcidiol is the form of vitamin D3 that we get when we take supplements and the form that our body produces from sunlight exposure. ^{1 2 3 4 5}

Calcitriol is the active form of vitamin D our body uses to provide homeostasis, support our innate immune system, and help improve our overall health. Most of the time your doctor tests only your 25-hydroxy (storage form) but not 1-25 hydroxy (active form). It is necessary for your 1-25 hydroxy levels also to be checked so you know if your vitamin D is being converted correctly to improve your health. ^{6 7 8 9 10}

Our kidneys and liver convert 25-hydroxy to 1-25 hydroxy, or calcitriol, when needed which is the active form of vitamin D3. The pathway for vitamin D conversion occurs from the skin (vitamin D) to the liver (25-hydroxy), to the kidneys (1-25 hydroxy), and then to specific VDR targets, where needed by the body. Recent studies into vitamin D conversion have confirmed that many localized tissues throughout the body can convert vitamin D when needed instead of only the kidneys converting it. ^{11 12 13 14 15}

If your vitamin D is not being correctly converted into the active form, you may not be getting much benefit from having normal 25-hydroxy levels. Also, if your 1-25 hydroxy levels are too high and not enough vitamin D is being stored (low 25-hydroxy), immune dysregulation may occur. ^{16 17 18 19 20}

Endogenous production of vitamin D creates 25-hydroxy, but studies have shown that the body can regulate the production and conversion of endogenously produced 25-hydroxy to the active form 1-25 hydroxy better; therefore, there are a lot fewer issues associated with vitamin D toxicity if the body primarily produces vitamin D. The body even has a negative feedback loop with endogenous produced 1-25 hydroxy, which inactivates the conversion of vitamin D to 25, then to 1-25 hydroxy. The body excretes the inactivated excess, and it helps prevent against vitamin D hypervitaminosis. There are few if any known causes of endogenous vitamin D toxicity. Most toxicity occurs from vitamin D over supplementation. The chance of developing vitamin D toxicity might also be reduced if you ingest enough retinol (vitamin A) in your diet. Sources of retinol in our diet include animal liver, cod liver oil, tuna, butter, milk, and eggs. Symptoms of vitamin D toxicity (hypervitaminosis D) include dehydration, vomiting, decreased appetite, increased serum calcium, soft tissue calcification, fatigue, constipation, muscle weakness, and irritability.

Blood levels of 25-hydroxy and 1-25 hydroxy for proper health differ between each person and the season. For most people if you are endogenously producing vitamin D in the summer you want your 25-hydroxy level to be between 60–100 ng/ml and you want your 1-25 hydroxy level to be within normal range. In the winter, you want your 25-hydroxy level to be between 40–70 ng/ml and you want your 1-25 hydroxy level to be within normal range. Depending on where you live in the world and your genetics, your vitamin D levels should be lower in the winter to match the waning of endogenous vitamin D production that occurs from the lack of UV-B. If you only supplement with vitamin D, your levels should be between 50–70 ng/ml year-round. Check to make sure that 25-hydroxy is converting properly to 1-25 hydroxy by getting blood tests of both every few months. ^{21 22 23 24 25}

How Does Vitamin D Improve Our Health?

Vitamin D does a lot to improve our overall health: ^{26 27 28 29 30}

• It helps with absorption of dietary phosphorus, magnesium, iron, manganese, zinc, and calcium. Proper calcium absorption and metabolism are important because you want it to be concentrated in your bones, not the arteries. Magnesium should also be taken when one is trying to increase their vitamin D level; it helps with conversion of 25-hydroxy to 1-25-hydroxy and prevents arterial calcification from regulating calcium homeostasis. Vitamin D also helps to regulate phosphorus use and excretion by the body.
• Plays a role in proper insulin secretion and may help prevent or improve diabetes type 1 and 2.
• It prevents osteoporosis and may help prevents its effects if you already have the condition.
• It possibly decreases the risk of some types of cancer by reducing cell proliferation (rapidly dividing cells). The body needs cell proliferation for wound healing and growth, but cancer may develop if too much occurs unchecked. It may also help treatment of some types of cancer when vitamin D levels (25 and 1-25 hydroxy) are balanced. ³¹
• It normalizes blood pressure by inhibiting renin, an enzyme our kidney produces to regulate blood pressure through the renin-angiotensin system. Elevated renin may lead to high blood pressure.
• Vitamin D helps to regulate the immune system properly and helps to prevent leaky gut by regulating T cells to protect the GALT. Helps reduce Th1 (inflammation) and Th2 (histamine) dominance.
• Endogenous Vitamin D production reduces the production of the inflammatory cytokines, TNF-alpha, and IL-6 (supplemental vitamin D may increase some cytokines [anti and inflammatory] in people who are deficient). ^{32 33} Vitamin D reduces pathogen load by activating the immune system to produce cathelicidin an antimicrobial peptide.
• It reduces your chances of developing or eliminates psoriasis, an inflammatory skin condition if your vitamin D production mainly comes from sunlight exposure. Endogenous vitamin D production might be why in studies psoriasis improves when exposed to proper light therapy.

How Does One Appropriately Increase Their Endogenous Vitamin D Production?

For most people, the best way to increase your vitamin D levels is proper sunlight exposure. Sunlight is free. The only cost to you is your time, and we all need to be outdoors more often in this modern word. To make vitamin D from the sun, you have to be exposed to UV-B rays from the sun. UV-B does not penetrate the skin as deep as UV-A, so less photodamage will occur to the skin when used correctly. There are many different factors that influence how much vitamin D we can produce from UV-B exposure, those include: ^{34 35 36 37 38 39 40}

• UV-B radiation exposure mainly occurs from 10 AM to 5 PM, but the period can be shorter depending on how far away you are from the equator. The farther you live from the equator, live in a smoggy, polluted environment, or reside in a climate that is cloudy and rainy, the harder it may be to get proper sunlight and produce vitamin D endogenously depending on the time of year.
• Your age also affects how much vitamin D your body will produce. The older you are, the less vitamin D will be endogenously produced.
• The higher the UV index, the more vitamin D will be produced, but it also increases the likelihood of you acquiring a sunburn.
• The higher your altitude, the more vitamin D you will produce from intense exposure to UV-B radiation.
• Do not sit behind glass and let the sunlight hit your skin; glass blocks most of the UV-B radiation. Therefore, you would not produce any vitamin D.
• The darker your skin, the longer sunlight exposure is needed to produce vitamin D endogenously. The more melanin in one’s skin (the pigment that gives our skin color) the harder it is for one to get a sunburn, but it does make it harder to produce endogenous vitamin D.
• People with chronic kidney disease or kidney failure might have a harder time producing vitamin D endogenously.
• Obesity can also be a factor. The more fat mass you have, the harder it is for vitamin D to be bioavailable.
• Magnesium deficiency can also make it harder to increase endogenous vitamin D production from the sun. Make sure you are supplementing with magnesium, when you are trying to increase your vitamin d levels.
• Genetic variations in VDR, CYP2R1, CYP27A1, and DBP (vitamin D-binding protein) can make it difficult to produce or convert endogenous vitamin D. People of African descent have a greater chance of DBP mutations, making it more difficult to produce endogenous vitamin D.

Endogenous vitamin D production may be difficult depending on where you live in the world, but there are ways to maximize your endogenous vitamin D production. First, I suggest the app Dminder on your phone to help with this. If you input where you live, it can tell you when you can produce vitamin D from the sun and can track how much you are producing depending on your skin type and the amount of clothing covering your body. It even has a light sensor that can help determine how much vitamin D is being produced even if it is cloudy day outside. It can also keep track and graph the amount of vitamin D you are producing from sunlight exposure over time. It is best to start out with 10 – 20 minutes of proper sunlight exposure to prevent from burning if you have fairer skin. Proper ingestion or supplementation of omega 3 fatty acids might further help to avoid sunburn, excessive inflammation from the sun, and photoaging of the skin. Endogenous vitamin D production from the sun is very safe. If you are concerned about skin cancer, just do not overdo your sunlight exposure long enough to get a sunburn. Ingest enough omega 3 fatty acids (seafood) and healthy saturated fats (extra virgin coconut oil, butter, pastured meats) in your diet to protect yourself from photo-oxidation (sunlight damage). Some people swear by the supplement astaxanthin to protect their skin from sunlight damage. ^{41 42 43 44 45 46 47}

What should you do, if you are unable to produce enough Vitamin D from sun exposure? ⁴⁸

• The proper use of a UV-B low-pressure tanning bed may help you in producing endogenous vitamin D. Wear UV eye protection while you are in the tanning bed to protect them from photo-oxidation.
• Rayminder Model 2, which is a vitamin D producing lamp, would also help increase endogenous vitamin D production and is FDA approved. Wear UV eye protection while you are using a lamp to protect them from photo-oxidation. I would also shine the lamp behind my head at a short distance, if possible. I would put the lamp about a foot away from my body, and use it only for a couple of minutes when starting out, it can be very potent. Be careful with the bulb it does contain mercury.
• Finally, you can use special UVB producing bulbs in your fixtures, but they have to be away from your body when in use, preferably hung shining down towards your back. In addition, these bulbs may not fit a standard light socket and may need to be modified to work properly in your house. I would consult an electrician first before use, and use with caution. You also need to wear UV eye protection while using UVB producing bulbs to protect your eyes from photo-oxidation damage. Some examples of bulbs would be, Osram Vitalux and Exo Terra (be careful with the bulb because it does contain mercury).

So How Does Gut Health and Genetics Play Into Developing Healthy Vitamin D Levels?

Some people, depending on their lifestyle or genetics (VDR, DBP, CYP2R1, and CYP27A1), are not able to produce or convert supplemental vitamin D very well and in those people, more UV-B exposure to help convert or produce 1-25 hydroxy may be needed. If vitamin D supplementation is required it is still important to get sunlight (UV-B mainly) within reason whenever possible to try to help with the endogenous conversion of 25-hydroxy to 1-25 hydroxy. If you are supplementing with vitamin D, blood serum tests of 25-hydroxy and 1-25 hydroxy need to be performed more often by your doctor to prevent vitamin D toxicity and to make sure proper conversion is taking place. ^{49 50 51 52}

Microbial overgrowth and increased inflammation from gut issues can change the body’s need for vitamin D. In someone that is having chronic infections; it is not odd to see their blood test results show that they have high 1-25 hydroxy and low 25-hydroxy. Elevated 1-25 hydroxy is one way the body tries to fight the overgrowth through chronic immune activation and to activate VDR receptors to enhance the immune system. Their VDR receptors become changed epigenetically, possibly from your chronic infections or environment. 1-25 vitamin D increases CD14 gene expression, which helps the immune system recognize endotoxins and eliminate them. Finally, the less active your VDR receptors are in the gut, the more vulnerable you are to endotoxins and leaky gut. ^{53 54 55 56}

“Autoimmune” conditions that improve once vitamin D is normalized in the body and gut health is restored include: ^{57 58 59 60 61 62 63}

• Alzheimer’s
• Diabetes (type 1 and 2)
• Inflammatory bowel disease
• Multiple Sclerosis
• Parkinson’s disease
• Psoriasis
• Rheumatoid arthritis
• Systemic lupus erythematosus

A recent study has come out that shows that proper sunlight exposure modulates our microbiome separately from endogenous vitamin D production. Some of the mice were exposed to UV radiation, and other mice were not. Some mice were fed vitamin D in their feed where other mice were not fed any vitamin D supplemental feed. There were microbiome changes in the mice that were exposed to UV independently from them being fed or not being fed vitamin D supplemental feed. There was a dramatic shift from Bacteroidetes to Firmicutes in the mice that were exposed to UV radiation. Clostridium was also increased, it appeared that it would be the more probiotic forms that produce butyrate, but it is unknown if it might also increase the pathogenic bacteria Clostridioides difficile. Desulfovibrio also increased, which may cause issues for people with hydrogen sulfide dysbiosis. If you are suffering from a Clostridioides difficile or Desulfovibrio dysbiosis you might want to limit sunlight exposure to a few minutes daily until you resolve the dysbiosis. Finally, Helicobacter was also shown to increase in the group that was exposed to UV, but Lactobacillus does as well which may compete with H. pylori and help to overcome it. ⁶⁴

Butyrate (short-chain fatty acid) production was also noted to possibly increase which would reduce dysbiosis and inflammation in the gut. The mice that were properly exposed to UV radiation had reduced inflammation markers in the gut, especially the mice that supposedly had sufficient vitamin D levels (significantly reduced IL-17 which is an inflammatory cytokine that is increased in IBD).⁶⁵

“Mice deriving vitamin D through exposure to UVR (D−UVR+) had greater CYP27B1 gene expression in the proximal colon than was measured in vitamin D-sufficient mice not exposed to UVR (D+UVR−). This suggested that UVR may have stimulated increased 1,25(OH)2D3 synthesis in the colon and may explain local effects on luminal microbiota. To our knowledge, prior studies have not examined colonic gene expression of CYP27B1 after UV irradiation of shaved skin. In a previous study, greater CYP27B1 expression was measured in the distal rather than the proximal colon, but treatment with DSS induced greater expression of the enzyme in the proximal rather than the distal colon. While not specific to UVR exposure, these previous findings support the concept of differential CYP27B1 expression in the proximal compared to the distal colon with different environmental exposures. Increased CYP27B1 expression is expected to cause higher 1,25(OH)2D3 levels and activation of downstream pathways to promote the intracellular killing of bacteria, attenuation of dendritic cell capacity for antigen presentation, promotion of IL-10, and inhibition of IL-12 expression. Recent data support a fundamental role for IL-1β in Th17 modulation, with IL-1β able to induce the expression of transcription factors necessary for Th17 development. Thus, the reduced proximal colon expression of IL-1β in UV-irradiated mice is consistent with the lower levels of circulating IL-17 also measured in the UV-irradiated mice.”⁶⁶

Proper Sunlight exposure is paramount for most people to improve their gut health!

The best way to help correct this imbalance is to Fix Your Gut, reduce the chronic infection, fix your circadian rhythm, reduce Th1/Th2 dominance, and maintain proper sunlight exposure. Over time, the VDR receptors should change epigenetically and facilitate proper vitamin D metabolism, returning your markers to normal.

Proper sunlight exposure is something that most people can do for free to improve their overall health. Not enough people in today’s modern world get enough sunlight, and most people are vitamin D deficient. Endogenous vitamin D is very important for proper health and can be obtained easily from the sun in most cases. Get your daily sun!