Vitamin K-2 is a nutrient required for bone health and blood clotting. Although all forms of vitamin K may be useful for treating and preventing the same conditions, research has shown that vitamin K-2 may have special properties that make it useful in preventing coronary heart disease and prostate cancer, as well as improving bone health.
Background and Dietary Sources
Vitamin K is a fat-soluble vitamin that is stored in the liver. Its primary purpose is to aid in coagulation, or blood clotting. Vitamin K-1 is the only over-the-counter form of vitamin K available in the United States, though vitamin K-2 may be obtained through prescriptions. The body, however, is able to convert vitamin K-1 into K-2. Vitamin K deficiency is rare because the body is able to produce it. Dietary sources that are rich in vitamin K-2 include ground beef, salami, butter, egg yolks, hard cheese, natto and chicken breast. No recommended upper limit has been set for vitamin K intake.
Vitamin K comes in different forms, including K-1 (phylloquinone), K-2 (menaquinone) and K-3 (synthetic menadione). The Linus Pauling Institute notes that while vitamins K-1 and K-2 are nontoxic, vitamin K-3 can be toxic, which is why it is no longer used to treat vitamin K deficiency. MedlinePlus notes that K-1 is usually the most preferred form of vitamin K because it's stronger, works faster and is less toxic than other forms of vitamin K. Vitamin K-2, however, may have benefits of its own not available in vitamin K-1.
Preventative Health Properties of Vitamin K-2
A 2004 study published in the "Journal of Nutrition" found that the risk of coronary heart disease mortality was reduced as vitamin K-2 consumption increased. The study concluded that vitamin K-2 may be useful in the prevention of coronary heart disease. These benefits were not seen with vitamin K-1. A 2013 study published in "Osteoporosis International" found that vitamin K-2 supplements could help postmenopausal women prevent bone loss caused by osteoporosis. A 2008 study published in the "American Journal of Clinical Nutrition" found that increased vitamin K-2 consumption was associated with a lower risk of prostate cancer. This relationship was not, however, seen with vitamin K-1.
Bones and Teeth
Vitamin K, in all forms, is important in maintaining bone health, as it helps bind calcium to bones. Vitamin K-2 may be particularly important because it is used preferentially by the body to deposit calcium in the teeth and bones, while K-1 is primarily used for blood clotting. The University of Maryland Medical Center notes that low vitamin K levels have been found in individuals with osteoporosis. Studies also suggest that Vitamin K in athletes can aid in bone health.