Dietary Sources of Vitamin K2
Vitamin K2 (menaquinones) is primarily obtained from fermented foods and certain animal products, with fermented cheeses, fermented soybeans (especially natto/douchi), and to a lesser extent meat and dairy being the main dietary sources. 1
Primary Food Sources
Fermented Foods
- Fermented cheeses are a major source of vitamin K2, as bacterial cultures used in fermentation synthesize menaquinones 1
- Fermented soybean products contain substantial vitamin K2, particularly:
- Douchi (fermented black soybeans) contains the highest levels (437.55 μg/100 g on average), with bacterial-type douchi containing more than mold-fermented varieties 2
- Dry douchi contains significantly more vitamin K2 (1,517.45 μg/100 g) compared to water-type douchi (297.58 μg/100 g) 2
- Other fermented soy products like sufu and soybean paste contain lower amounts (7.48 and 2.47 μg/100 g respectively) 2
Animal Products
- Meat products, particularly organ meats, contain vitamin K2 3
- Dairy products contain vitamin K2, especially full-fat varieties and fermented dairy 1
- Eggs provide modest amounts of vitamin K2 3
Important Distinctions
Vitamin K2 vs. K1
- Vitamin K1 (phylloquinone) is found in green leafy vegetables, cruciferous vegetables, asparagus, prunes, peas, and parsley 1
- Vitamin K2 has distinct sources and is not abundant in typical Western diets due to lower consumption of fermented foods 4
- The two forms have different kinetics: vitamin K2 has a longer half-life and greater extrahepatic activity compared to K1's shorter half-life 5
Clinical Considerations
Fermentation as Key Factor
- The production of vitamin K2 depends heavily on bacterial fermentation processes 1
- Fermented dairy products (yogurt, cheese) may provide cardiometabolic benefits partly through their vitamin K2 content, which may improve insulin sensitivity 1
- The type of fermentation microorganism and processing technology significantly affects vitamin K2 content 2
Geographic and Dietary Patterns
- Vitamin K2 intake varies substantially based on cultural dietary patterns, with populations consuming more fermented foods having higher intakes 6
- Current dietary guidelines often lack specific recommendations for vitamin K2, focusing only on total vitamin K (primarily K1) 1
Note: While vitamin K1 and K2 are not associated with toxicity, patients on warfarin therapy should maintain consistent vitamin K intake, as variations can affect anticoagulation control 1