Vitamin D is a fat-soluble sterol. Contrary to its name, vitamin D is not actually a vitamin but a prohormone which is a precursor to a hormone. A few foods will naturally contain low levels of vitamin D. Some foods are fortified with vitamin D which means someone has artificially added it to that food. Most of our natural vitamin D is produced in our skin by the action sunlight, specifically ultraviolet-B (UVB). A popular misconception is that adequate sunlight exposure should equate to adequate vitamin D levels. We have found this to not be true. Vitamin D levels are affected by multiple factors including adequate nutrition, adequate exercise, adequate sleep, and it is a good indicator of the overall health of our patients.
People with darker skin also tend to have lower vitamin D levels because the melanin within the skin acts as a natural sunblock for UVB. Vitamin D’s role is to help with the intestinal absorption of calcium, magnesium, phosphate, and zinc. Vitamin D is necessary for bone health, but it does have other functions. It has been found to be a potent mediator of immunity, a regulator of insulin and blood sugar balance, supports lung function, benefits the cardiovascular system, promotes optimal hormone levels, and influences the expression of genes involved in cancer prevention.
Vitamin D has anti-inflammatory properties. Many organs in our body contain receptors for vitamin D. This tells us that vitamin D may have many more effects than what we have discovered to date. Ongoing studies have shown that vitamin D deficiency worsens outcome in influenza and Novel 2019 Coronavirus (COVID-19). In the United States, vitamin D deficiency is extremely widespread. In our practice alone, we find that over 75% of our patients are what we would consider to be vitamin D deficient. Vitamin D can be broken up into ergocalciferol also known as D2 and cholecalciferol also known as D3. Vitamin D is metabolized in the liver to form 25–hydroxy vitamin D. It is also further metabolized in the kidney by the action of parathyroid hormone to produce 1,25–hydroxyvitamin D. Most blood tests report a reference range on vitamin D that is inadequate for the maintenance of good health.
At Hybrid Medical Solution, we use what we consider to be an optimal range. Most labs report 25-hydroxyvitamin D (the sum of both vitamin D3 and D2) from a blood sample. As a general rule, we also use the 25-hydroxyvitamin blood test to determine the adequacy of our patient’s vitamin D levels. We believe an optimal range on this to be between 60 and 80 ng/mL. Although there are many positive effects of vitamin D, vitamin D is also toxic at higher levels.
We believe that all patients taking vitamin D should have their blood levels monitored regularly to make sure they stay within the optimal range. Our preferred form of vitamin D supplementation is vitamin D3 preferably with the addition of another vitamin known as Vitamin K2 (also known as menaquinone). K2 (not to be confused with vitamin K1) helps with the metabolism of calcium. Vitamin K2 has been shown to inhibit arterial calcification and arterial stiffening. To further confuse the issue, K2 comes in a variety of forms as well. We believe the most active isoform is MK-4 although MK-7 is more readily available.