Vitamin D is essential for your mental and physical health. Virtually every cell in the body has a vitamin D receptor, which, when bound to vitamin D, can influence the expression of more than 200 genes . Vitamin D promotes calcium absorption in the intestine and maintains calcium and phosphate levels in the blood, protecting against osteoporosis, rickets, and bone fracture . It also regulates immune function, cell growth, and neuromuscular function . Vitamin D deficiency has been found to increase the risk of heart attack, cancer, diabetes, asthma, and autoimmune disease and can also contribute to depression. Our modern indoor lifestyle limits our sun exposure, and we can only get a small amount of vitamin D from diet . According to the lower boundary of the U.S. lab range of 30 ng/mL, as many as 70 percent of Americans are considered deficient .
However, it’s important to note that, like many nutrients, vitamin D follows a U-shaped curve, meaning that both low levels and very high levels are associated with potential problems.
Vitamin D status is measured by 25(OH)D in blood- the precursor to active vitamin D and the U.S. laboratory reference range for adequate 25(OH)D is 30 to 74 ng/mL however there is little evidence showing benefit to 25(OH)D levels above 50 ng/mL, and increasing evidence to suggest that levels of this magnitude may cause harm. Consequences of vitamin D toxicity include heart attack, stroke, kidney stones, headache, nausea, vomiting, diarrhea, anorexia, weight loss, and low bone density .
Interestingly , some research on Israeli lifeguards suggests that, contrary to popular belief, vitamin D toxicity from sunlight alone (in the absence of supplementation) is possible . That said, it is much more difficult to achieve toxic levels through sun exposure alone. Sunlight is the optimal source of vitamin D, and has numerous benefits above and beyond improving vitamin D status.
Vitamin D is really just the tip of the iceberg when it comes to the benefits of sunlight. A recent 20-year study following 29,518 subjects found that those individuals avoiding sun exposure were twice as likely to die from all causes . While this study did not assess vitamin D levels, findings from other epidemiological studies suggest that this cannot be accounted for by the increase in vitamin D production alone. Indeed, humans make several important peptide and hormone “photoproducts” when our skin is exposed to the UVB wavelength of sunlight . These include:
β-Endorphin: a natural opiate that induces relaxation and increases pain tolerance
Calcitonin Gene-Related Peptide: a vasodilator that protects against hypertension, vascular inflammation, and oxidative stress
Substance P: a neuropeptide that promotes blood flow and regulates the immune system in response to acute stressors
Adrenocorticotropic Hormone: a polypeptide hormone that controls cortisol release by the adrenal glands, thus regulating the immune system and inflammation
Melanocyte-Stimulating Hormone: a polypeptide hormone that reduces appetite, increases libido, and is also responsible for increased skin pigmentation
Exposure to the UVA wavelength of sunlight has also been shown to have benefits, including increasing the release of nitric oxide from storage . Nitric oxide is a potent cellular signaling molecule that dilates the blood vessels and thus reduces blood pressure .
In addition to the production of photoproducts and release of nitric oxide, sunlight also entrains circadian rhythms. Exposure to bright light during the day activates neurons in the suprachiasmatic nucleus of the hypothalamus, which sends signals to the pineal gland that regulate melatonin production. Disruption of circadian rhythm has been associated with mood disorders, cognitive deficits, and metabolic syndrome .
Vitamin D Optimal Levels
Ethnicity is one major consideration. For example, blacks have lower 25(OH)D than whites in the U.S., yet they typically have much higher bone mineral density. Furthermore, non-Caucasians have lower 25(OH)D levels than Caucasians, even at their ancestral latitudes (32). From these and other studies, it has been suggested that people with non-white ancestry may be adapted to a lower optimal 25(OH)D level than people with white ancestry.
Another factor that influences toxicity is nutritional status. The fat-soluble vitamins A, D, and K work synergistically, and adequate vitamin A and K may protect against toxic effects of excess vitamin D . Sufficient levels of potassium and magnesium have also been suggested to protect against vitamin D toxicity . Unfortunately, most people are deficient in these micronutrients in the developed world, making them more susceptible to vitamin D toxicity.
For optimum health , consider checking your vitamin D status every spring .
If your 25(OH)D level is:
less than 35 ng/mL: you likely need some combination of UV exposure, and a vitamin D supplement. Our Trinity Wellness recommended product is found here. The delivery system makes it very easy to absorb and very potent. One capsule a day recommended.
35 to 50 ng/mL: continue your current diet and lifestyle for maintaining adequate vitamin D
greater than 50 ng/mL: try reducing your vitamin D supplements, and make sure you are getting adequate amounts of the other fat-soluble vitamins to protect against toxicity
Check your levels after three to four months to see if you have achieved or maintained adequate levels of vitamin D. If not, adjust your diet, lifestyle, or supplements accordingly and check again in another three to four months.
Get sunlight or UV exposure as your primary form of vitamin D.
Reap the many benefits of sunlight beyond just subcutaneous production of vitamin D, and reduce your chance of achieving toxic levels. Spend about 15 to 30 minutes, or about half the time it takes your skin to turn pink, in direct sunlight.
Spring is here, go get some sun and boost your vitamin D!