MK-4, also known as Menaquinone-4, is a form of vitamin K2 that plays a crucial role in bone health and cardiovascular function. It helps in the regulation of calcium in the body, ensuring that calcium is deposited in bones and teeth rather than in soft tissues, which can lead to health issues. This vitamin is found in certain foods, particularly in animal products like egg yolks and dairy, as well as fermented foods such as natto. MK-4 is also available as a dietary supplement, often recommended for individuals looking to support their bone density and overall health.