Most supplement users are vaguely familiar with vitamin K, a nutrient found in green leafy vegetables that has been synthesized as an ingredient in supplements. Discovered by Danish scientists in 1929, vitamin K plays a vital role in the coagulation of blood. In fact, its name comes from the Danish word koagulation.
Vitamin K2 has a somewhat different chemical structure from vitamin K1, along with a reputation for impacting both bone and arterial health. K2 serves as a critical partner in the body’s construction of healthy bones. The body uses a protein called osteocalcin to carry calcium from the blood and knit it into the bone matrix. Without enough K2, the calcium becomes deposited in arterial walls, where it doesn’t belong. This is likely why studies have shown that vitamin K2 can help prevent bone loss.
Food Sources of Vitamin K2
Beneficial bacteria in our intestines are able to produce a limited amount of K2 from vitamin K. Another source is food. The richest concentration of K2 is found in natto, a Japanese fermented soybean dish. And it’s interesting to note that in Tokyo, where natto is very popular, there is a low incidence of osteoporosis compared to areas of Japan were natto is less popular. However, before you rush out to an Asian grocer to stock up on natto, you should be forewarned that its taste is not considered pleasant. Most Westerners are turned off by it unless they apply some creative, palatable spicing.
Most cheeses contain what is considered a protective amount of K2, though hardly as much as what’s found in natto. Each 100 g (about 4 oz.) of natto contains 1,000 mcg of K2 compared to 30–60 mcg in an equal amount of cheese.
Supplements offer another option for obtaining vitamin K2. Two K2 subtypes are available today in health food stores. A synthetic form called MK-4 has been used commercially for about 20 years. More recently, MK-7, derived from natto, has been shown to have significant effects in the body.
If you’re looking for K2 benefits in supplements, you can find products formulated with either MK-4 or MK-7. Research suggests that an effective daily dosage of MK-4 is around 45 mg, while MK-7 shows effectiveness at a much lower level, about 150 mcg.
Individuals taking anticoagulant medications, such as Coumadin (warfarin), should consult their doctors before using any vitamin K supplements, which may interfere with the drug.