Vitamin K2 or menaquinone is one of three types of vitamin K, the other two being vitamin K1 (phylloquinone) and K3 (menadione). K2 is both a tissue and bacterial product (derived from vitamin K1 in both cases) and is usually found in animal products or fermented foods.

Dietary sources of vitamin K-2 include:
Natto, a traditional Japanese dish of fermented soybeans
Sauerkraut
Dairy products, especially hard cheeses
Liver and other organ meats
Beef,pork,egg yolks,chicken,fatty fish, such as salmon

Vitamin K2 has a protective effect on bone mineral density and reduced risk of hip, vertebral and non-vertebral fractures. These effects appear to be accentuated when combined with vitamin D and in the setting of osteoporosis. The possible health benefits suggested for further investigation relate to bone strength and arterial health (reducing calcification or even decalcifying, with a possible reduction in blood pressure).