Vitamin K occurs naturally in the forms of vitamin K1 (phylloquinone) and vitamin K2 (menaquinone). Phylloquinone is mainly found in plants, while menaquinone, which appears to exhibit higher bioactivity, can be produced by gut bacteria. Some fermented foods, such as sauerkraut or natto, are also rich sources of vitamin K2.
Vitamin K2 activates a series of special proteins which play a role in important metabolic processes, including blood clotting as well as calcium transportation and utilisation. Most organisations do not consider vitamin K1 and K2 separately and, as such, there is limited information on the benefits of vitamin K2 specifically.
According to the European Food Safety Authority (EFSA), vitamin K contributes to:
- Normal blood clotting
- The maintenance of normal bones
Vitamin K2 and Vitamin D
Vitamin D and vitamin K2 both play key roles in calcium metabolism. Together, they regulate the cells which form and break down bones as well as the important transport molecules which ensure the correct utilisation of calcium.