Vitamin K is a fat-soluble vitamin which is used in the body to produce a protein that plays an important role in blood clotting. It is also essential in building strong bones, helping to prevent heart disease and there is some evidence that vitamin K can help improve memory in older people. Recent evidence suggests vitamin K and vitamin D together play an important role in bone health and may help slow the progression of arterial calcification. Good dietary sources of vitamin K include leafy green vegetables, dairy products and eggs.