The Ups and Downs of the Sun Hormone

Vitamin D is often considered the sunshine vitamin, but it's actually a hormone with several important jobs
BY Ashley Turner TIMEFebruary 20, 2022 PRINT

There has been a lot of discussion about vitamin D circulating among natural health enthusiasts recently. As a certified functional medicine practitioner, vitamin D status is something that I monitor very closely.

Vitamin D is actually a hormone, specifically a prohormone that the body converts into a steroid hormone. It’s synthesized in the skin from sun exposure and activated in the liver and kidneys.

Lately, vitamin D has been a hotly discussed nutrient for its role in supporting the immune system. While vitamin D is a powerful modulator of the immune system, that’s far from its only role in human health.

Functions of Vitamin D

Vitamin D performs many functions throughout the body, many of them critical to core physiological processes. When we don’t have adequate vitamin D levels, it affects every aspect of our physiology because it’s intimately involved with cellular function and genetic expression. The hormone known as vitamin D:

  • Regulates serum calcium and phosphorus
  • Works synergistically with vitamin A and K2
  • Reduces cellular growth
  • Promotes apoptosis (proper cell death)
  • Improves cellular differentiation
  • Controls genetic expression

Vitamin D deficiency is rampant. In fact, 70 percent of American children aren’t getting enough vitamin D. We’ve run tests on thousands of vitamin D over the years at The Restorative Wellness Center and it’s rare to see someone with an optimal, functional level unless they are serious about optimizing their vitamin D status. We’ve had hundreds of patients who live in Florida, California, and other southern states that are well below optimal vitamin D, and magnesium for that matter. Magnesium is critical to getting good physiological mileage out of vitamin D.

Symptoms of Vitamin D Deficiency

Low levels of vitamin D increase the risk of cancer, autoimmune disease, diabetes, high blood pressure, cardiovascular problems, and osteoporosis. Being aware of signs of deficiency can prompt you to address that. Those symptoms include:

  • Fatigue
  • Migraines
  • Muscle pain/weakness
  • Depression
  • Low/improper immune function
  • Hormone dysfunction
  • Increased inflammation
  • Allergies

How to Optimize Vitamin D

From my perspective, there is unsurpassed value in consuming a nutrient-dense diet. I have studied the work of Dr. Weston A. Price, a dentist-turned-nutrition researcher, for close to 15 years now. His work clearly demonstrates the importance of not just consuming vitamin D alone, but also in conjunction with vitamin A and vitamin K2, which Price calls the X factor. These fat-soluble vitamins—A, D, and K—work synergistically, and K2 actually activates proper vitamin D metabolism.

In fact, research indicates that vitamin D is less likely to reach toxic levels when consumed with vitamin A and K2.

Food Sources of Bioavailable Vitamins A, D, and K2

  • Pasture-raised egg yolks
  • Grass-fed red meat
  • Organ meats such as liver
  • Grass-fed raw dairy products such as ghee, butter, cream, milk, kefir, and cheese (if tolerated)
  • Cod liver oil
  • Wild-caught fish such as salmon, herring, sardines
  • Pasture-raised lard, duck, and chicken fat

It’s much more difficult to have toxic levels of these nutrients when they are consumed together. Price observed traditional people groups that consumed nutrient-dense diets high in these fat-soluble vitamins and found they experienced exemplary dental health and overall wellness; chronic illness and disease was virtually nonexistent within these groups. Often, nutritional intervention isn’t enough, especially among chronically sick individuals. A skilled clinician will take vitamin A, vitamin D, vitamin K2, and magnesium status into account when recommending supplementation and be guided by evidence on labs.

Vitamin D From the Sun

Nothing can replace the health benefits of exposure to vibrant, natural sunlight. Our skin is ultimately responsible for producing vitamin D. During exposure to sunlight, ultraviolet radiation penetrates into the epidermis (skin) and photolyzes provitamin D3 to previtamin D3 to be used by the body.

It’s estimated that 80 to 100 percent of the vitamin D we need is a result of sun exposure. The sun exposure that tans the skin (called 1 minimum erythemal dose) produces the equivalent of 10,000 to 25,000 international units (IU) of vitamin D in our bodies. Sadly, aging, sunscreens, and increased melanin have decreased the skin’s ability to produce previtamin D3.

You may ask, “why don’t I just avoid the sun and take vitamin D instead?” Well, even if you could get all the vitamin D you need through supplementation, and it was as perfectly designed and absorbed by your body as the stuff you make from your own skin, you would still miss the other benefits of sunlight, including enhanced mitochondrial ATP production, cell signaling, and growth factor synthesis, and an attenuation of oxidative stress. So the best way to get vitamin D is through the skin. I recommend working up to 20 to 30 minutes of direct, unrestricted sun exposure a day between 10 a.m. and 3 p.m. Those with fair skin may need to work their way up to this to avoid burning. Those with darker skin will need longer periods of sun exposure.

Still concerned about burning?

Evidence shows that optimal levels of other fat-soluble vitamins, vitamin C, magnesium, and essential fatty acids go a long way in protecting the skin from burning. Conventional wisdom asserts that the sun is to be feared and that we must slather hormone-disrupting, cancer-causing chemicals on our bodies to protect us from disease. I would suggest that the literature reveals just the opposite. Sunlight protects against many chronic illnesses and symptoms. In fact, a 2016 study following 29,518 subjects for 20 years found that individuals avoiding sun exposure were twice as likely to die from all causes.

Should I Supplement?

When a clinician recommends vitamin D supplementation, they must consider a wide range of factors that could go into how the body metabolizes that supplement. Those factors include the patient’s levels of vitamin A, vitamin K, calcium, magnesium, and parathyroid hormone status along with how they assimilate food. From my perspective, vitamin D3 is the only form that should be supplemented and it should be used in conjunction with vitamin K2. Everyone supplementing with vitamin D should be closely monitored to ensure that they are not going outside of the optimal range.

Scrutiny over vitamin D supplementation has arisen because vitamin D is a hormone. Not everyone needs to supplement with it. However, there is a time and place for supplementation when used in the correct ratios with other nutrients. Many clinicians consider blood levels of 25(OH)D (vitamin D metabolites in the blood) under 30 ng/mL to be problematic. You’ll be hard-pressed to heal from chronic illness or put autoimmune disease into remission without optimal levels of this important vitamin, and others.

Can You Get Too Much Vitamin D?

Absolutely! Just as low levels of vitamin D are cause for concern, so are levels in excess. Ideal vitamin D levels, like many things, fall onto a bell-shaped curve. When blood levels of 25(OH)D levels close to 100 ng/mL and beyond, it’s considered toxic. With many people promoting vitamin D supplementation, often in high doses, it’s wise to know that this vitamin can increase to toxic levels within the body because it is fat-soluble. This means they are stored in the liver, adipose tissue, and skeletal muscle and are more likely to become toxic than water-soluble vitamins that are relatively quickly excreted from the body.

There are cases, often with over-supplementation, that can cause significant problems. These include:

  • Heart attack
  • Stroke
  • Kidney stones
  • Headache
  • Nausea
  • Vomiting
  • Diarrhea
  • Anorexia
  • Weight loss
  • Low bone density

Vitamin D can be a life-changing nutrient. It’s important to understand its importance in human health and be armed with safe, appropriate strategies to optimize levels within the body.

Ashley Turner
Dr. Ashley Turner is a traditionally trained naturopath and board-certified doctor of holistic health for Restorative Wellness Center. As an expert in functional medicine, Dr. Ashley is the author of the gut-healing guide “Restorative Kitchen” and “Restorative Traditions,” a cookbook comprised of non-inflammatory holiday recipes.
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