Vitamins · 7 min read
Vitamin D: The essential hormone most people are deficient in
Why 42% of adults are insufficient, the optimal serum range, and how D3 + K2 work together.
Why vitamin D is technically a hormone
Vitamin D is unusual among nutrients: your skin synthesizes it from cholesterol when exposed to UVB sunlight, and it then circulates as a pro-hormone that regulates over a thousand genes involved in immunity, bone metabolism, and cellular growth.
Because modern indoor lifestyles and northern latitudes block adequate UVB exposure for most of the year, the CDC estimates roughly 42% of US adults are insufficient (<20 ng/mL) and another 24% are sub-optimal (<30 ng/mL).
The optimal serum range
Most longevity-focused clinicians target a serum 25-hydroxyvitamin D level between 40 and 60 ng/mL — well above the deficiency threshold but below the supraphysiological range where calcification risk begins to rise.
Reaching that range typically requires 2,000–5,000 IU per day of supplemental D3 in winter for adults living above 35° latitude, alongside 5–15 minutes of midday sun in summer.
Why D3 + K2 belong together
Vitamin D upregulates calcium absorption from the gut. Vitamin K2 (specifically the MK-7 form) then directs that calcium into bone matrix and away from soft tissue and arterial walls. Without K2, high-dose D can shift calcium into the wrong compartments.
ZYVORA Vitamin D3 + K2 pairs 5,000 IU of cholecalciferol with 100 mcg of all-trans MK-7 in a single softgel suspended in MCT oil for fat-soluble absorption.
What the research shows
Meta-analyses in The BMJ and JAMA link sufficient vitamin D status to reduced acute respiratory infection risk, lower all-cause mortality, and improved bone mineral density in adults over 50.
Citations available on request. ZYVORA articles reference peer-reviewed clinical research published in journals including JAMA, The Lancet, Nutrients, and the American Journal of Clinical Nutrition.
Citations
References available on request. ZYVORA articles cite peer-reviewed research from journals including JAMA, The Lancet, Nutrients, and the American Journal of Clinical Nutrition.
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