Natural Factors Vitamin K & D features vitamin K2 as menaquinone-7 (MK-7), an advanced, fat-soluble form of vitamin K that serves multiple functions in the body including support for health bones.
The K family consists of a trio of vitamins: K1 (phylloquinone), found naturally-occurring in leafy green vegetables and plant oils; K2 (menaquinone) which is present in butter, cows liver, eggs, certain cheeses and natto, a fermented soybean food; and K3, a synthetic form of the vitamin. K3 has been shown to have toxic effects on the liver and K1 doesn't have adequate benefits on calcium metabolism to dramatically improve osteoporosis or atherosclerosis. Only K2 in the form of MK-7 has been shown to offer 24-hour protection from a single daily dose. Other commercially-available subtypes of K2, such as MK-4, only last four to six hours in the body and are required in much larger dosages to be effective.
Vitamin D has long been considered a classic nutrient for bone metabolism. It supports bone development and is needed for calcium absorption. Vitamin K & D uses vitamin D3 (cholecalciferol), a natural form of vitamin D that is safer and more biologically active than D2 (ergocalciferol), a synthetic form of vitamin D. Evidence shows that vitamins K2 and D3 work synergistically to improve bone density. Many of the clinical trials examining the effects of K2 on bone density found a much greater effect when vitamins K2 and D3 were given together as opposed to either nutrient alone.
Vitamin D is required for the absorption of minerals such as calcium while vitamin K is needed to direct the minerals to the right place, preventing an inappropriate calcification of soft tissues. Likewise, cells only produce osteocalcin and the matrix Gla protein (MGP) in the presence of vitamin D, but vitamin K is necessary to activate those proteins to do their jobs. There is even evidence to suggest that the safety of vitamin D is dependent on adequate vitamin K and that vitamin D toxicity (which is extremely rare with the D3 form) is actually an induced deficiency of vitamin K2.