Synergy-D provides a clinically useful dose of vitamin D3 along with vitamin K as both K1 and the MK-7 form of K2.
Vitamin D3, supplied by the sun and contained in various foods including varying amount founds in fish, milk, eggs and mushrooms is an essential fat soluable vitamin. Deficiency of vitamin D has been implicated in many health concerns including cancer, weakened immune system, heart health, osteoporosis, dementia and depression just to name a few. For many people, eating fish, eggs or drinking milk can be problematic.
As well, many people do not live in locations that get year round sun in the intensity needed in order to produce enough of a consistent dosage of vitamin D (plus just being in the sun doesn't mean you'd get D, skin pigment, duration of exposure along with the sun needing to actually contact bare skin are more things to consider. In other words, we all can't spend time at a beach or sun bathing).
Vitamin D is essential in another way in that it helps with the absorption of calcium from the foods you eat. When you have a deficiency in D, other than some of the cited diseases above, the body pulls calcium from your bones in order to attempt to create the homeostasis or "balance" needed for proper function. Unfortunately, Vitamin D wasn't intended to be isolated. It doesn't direct where the absorbed calcium goes to inside the body. Of course, we want it to go to such places as our bones, our teeth but not places like our kidneys, or into our vascular system.
This is where Vitamin K1 and MK-7 K2 comes into play.
K1 is found mostly in leafy greens and other vegetables though roughly only 10% of this form is absorbed from these veggie sources. K2 on the other hand is more readily absorbed yet found in fermented products such as Natto and certain animal products. K activates certain proteins (osteocalcin and matrix GLA protein) that together serve to direct calcium to where it is needed along with inhibiting calcification in the vascular system and other areas where it shouldn't be such as the kidneys.
Together Vitamins D3, K1, MK-7 K2 work in a synergistic manner to supply the body with valuable nutrients needed for proper maintenance, repair and ultimately, continued health.