Foods containing vitamin K2 include high-fat dairy products, egg yolks and fermented foods such as sauerkraut, natto and miso. Cattle are able to synthesize K2 from the vitamin K1 contained in grass, therefore dairy and organ meat from grass-fed cows may be higher in K2 than from grain-fed cows.
In combination, vitamins K1 and K2 help with the coagulation of blood. A Dutch study also found that increased consumption of K2 in particular may lower the risk of coronary heart disease in women.
Humans and animals are able to convert some vitamin K1 into vitamin K2 in the body, therefore K2 levels are also affected by the consumption of foods high in vitamin K1. K1 is readily available in more food sources than K2. For example, K1 is found in high amounts in dark leafy greens such as kale, spinach and Swiss chard. Vitamin K2 is fat-soluble, meaning it is generally found in higher concentrations in high-fat foods such as liver and hard cheeses. K2 is also found in other meat such as chicken, bacon and ham. Lean proteins and low-fat dairy products do not contain significant amounts of K2.
Fermented foods, including soy products such as miso and natto, are good vegetarian sources of K2. In natto, a strain of bacteria used in the fermentation process also synthesizes K2.