For good health and a long life, it is not enough that you eat a healthy diet, exercise regularly and see a doctor often. You also need to get enough sun exposure to maintain your serum 25(OH)D level at 30 ng/mL or higher.
Why Sun Exposure?
Humans evolved in the sun, and depend on a certain amount of sun exposure for good health. Photons from the sun interact with your body to produce a variety of biomolecules, each of which is essential for the proper functioning of your complex body chemistry. These biomolecules include vitamin D, nitric oxide, melatonin, serotonin, beta-endorphins, dopamine and others described on this website.
Every one of the 37 trillion cells in your body has a receptor for one or more of these biomolecules. A shortage of these biomolecules manifests over time in higher risk for almost every known disease and adverse health condition including a shortened life expectancy.
What is Serum 25(OH)D?
Serum 25(OH)D is a precursor to vitamin D formed when photons from sun convert 7-dehydrocholesterol located in the lower layers of the skin into vitamin D3, which is then metabolized in the liver to form 25(OH)D (also known as 25-hydroxyvitamin D). The level of 25(OH)D in the blood (serum 25(OH)D) is used to determine a person’s vitamin D status. 25(OH)D is subsequently metabolized in the kidneys into 1-25-dihydroxyvitamin D, the active form of vitamin D.
Since 70%-90% of 25(OH)D is produced by sun exposure, the level of 25(OH)D in your blood is at the same time a measure of your vitamin D status and a biomarker for sun exposure. It is the best metric currently available for the amount of your sun exposure and thus for the adequacy of the other biomolecules produced in your body by sun exposure.
Why 30 ng/mL?
Scientists have correlated risks for various diseases and adverse health conditions with levels of serum 25(OH)D as a biomarker for sun exposure. In hundreds of scientific studies, they have found that significant increased risks of various diseases and adverse health conditions including premature death are correlated with 25(OH)D levels of less than 30 ng/mL It is possible that even higher levels might be beneficial, since the few humans still living the outdoor lifestyle of 500 years ago have serum 25(OH)D levels of 46 ng/mL. 70% of Americans have less than 30 ng/mL. Insufficient sun exposure has silently become the nation’s #2 public health problem.