Vitamin D is a fat-soluble essential vitamin synthesized by the skin when it is exposed to direct sunlight. Vitamin D plays a key role in numerous bodily processes including mood, immune system health, and bone health. While those who get plenty of sun likely do not need to supplement Vitamin D those who work indoors or dont spend much time outside are likely to be deficient and can benefit from supplementing. Vitamin K is another of the essential fat-soluble vitamins and supports proper cardiovascular and bone health. K2 should always be supplemented with Vitamin D3 as high-dose supplementation of D3 alone can cause short-term hypercalcemia in some people. Our Vitamin D3 + K2 supplement includes the all-trans version of K2 (K2 Vital), which is much more effective than the cheaper cis-K2 variety and uses an MCT oil base providing plenty of fat for proper absorption so it is not necessary to take this product with food.