Why care about getting enough vitamin K from our diets? Vitamin K is actually a group of fat-soluble vitamins with a similar molecular structure, existing as K1, multiple isoforms of K2, and the synthetic form K3. This nutrient plays a vital role in coagulation, due to serving as a cofactor for proteins needed for blood clotting; it’s also essential for bone metabolism, cellular function, and the prevention of soft tissue calcification. Getting enough vitamin K2 can help protect against cardiovascular disease, may improve bone mineral density and skeletal health, and may even support endocrine function and brain health; there’s also some limited evidence it has anti-cancer and anti-inflammatory properties.
Vitamin K is actually a group of fat-soluble vitamins with a similar structure, existing in the forms of K1 (phylloquinone), multiple isoforms of K2 (menaquinones—which range from MK-2 to MK-14, numbered based on the repeats of 5-carbon units in their molecular side chain), and the less common synthetic form K3 (menadione). Whereas most vitamins were named in alphabetical order, the “K” in vitamin K actually comes from the Danish word for blood clotting, koagulation, due to its important role in blood clot formation (AKA coagulation!). In fact, vitamin K was first discovered by accident during cholesterol experiments in 1929, when scientists found that feeding chickens fat-free diets led to excessive bleeding—leading them to deduce that a “coagulation vitamin” existed and had been removed along with the dietary fat.
All forms of vitamin K are critical for making important proteins in the body that are involved in blood clotting and metabolism, and are also central to maintaining bone and cardiovascular health.
The richest food sources of vitamin K1 are high-chlorophyll plant foods such as green leafy vegetables (especially kale, chard, collard greens, and spinach), broccoli, and Brussels sprouts. Vitamin K2 is found in natto (a fermented soybean product), organ meats (especially liver), egg yolks, some hard cheeses, butter, pork, and dark chicken meat. High-quality olive oil also contains vitamin K.
This article explains the biological roles of vitamin K, the difference between vitamin K1 and vitamin K2, the interactions between dietary vitamin K and our risk of four major health conditions, symptoms and signs that we’re getting too little vitamin K, how much vitamin K we need by demographic, and shares the top 25 best common whole food sources of vitamin K. Paid subscribers also can download a printer-friendly PDF version of this information below!
The Biological Roles of Vitamin K
Vitamin K serves as the essential cofactor for vitamin K-dependent proteins needed for blood coagulation, regulating cellular function, bone metabolism, and preventing
