Vitamin K2 – have you heard of it? You’re probably familiar with vitamin K as a vitamin but you hear less about vitamin K2 a specific type of vitamin K. Vitamin K comes in two chemical forms: vitamin K1 (a phylloquinone) and vitamin K2 (a menaquinone). Each form has a different function in your body.
The “standard form of vitamin K is vitamin K1. You get it by eating leafy greens, such as Swiss chard, spinach, collard greens, kale, and mustard greens but, as you’ll see, these foods aren’t a reliable source of vitamin K2, though they supply your body with copious amounts of vitamin K1.
Why do you need vitamin K1? Vitamin K1 is essential for blood clotting since it converts clotting factors in the bloodstream into a mature form your body can use to form clots. That’s important should you get a laceration or injury. Without enough vitamin K1 to form a clot, you would risk bleeding to death with just a scrape or puncture wound.
Fortunately, your body can convert a certain portion of the vitamin K1 you take in from sources like greens to vitamin K2. However, this conversion isn’t very efficient, and many experts believe humans can benefit from getting more K2 in its direct form.
What Health Benefits Does Vitamin K2 Have?
It’s clear that you need vitamin K1, but what about vitamin K2? The research looking at vitamin K2 is still in its early stages. However, vitamin K2 seems to play two important roles in the human body. One pertains to the health of your bones. Early studies show vitamin K2 is essential for bone health and is of special importance to women at high risk of osteoporosis.
When you consume calcium, you want most of it to go to your bones where cells can use it to form new bone tissue. When you consume food or a supplement with vitamin K2, it stimulates the release of osteocalcin, a hormone that directs calcium to the bone where osteoblasts, cells that build bone, can use it. This also keeps vitamin K2 away from the inner walls of blood vessels where you don’t want it.
Is there science to support vitamin K2s role in bone health? A study of postmenopausal women found those who supplemented with 45 milligrams of vitamin K2 each day experienced improvements in hip bone density. Plus, some studies show that people who consume more dietary vitamin K2 have a lower risk of developing bone fractures. Another analysis of 13 separate studies found that 7 of the studies where participants supplemented with vitamin K2 had reduced rates of hip and vertebral fractures relative to those who didn’t take supplemental vitamin K2.
Secondly, vitamin K2 matters for heart and blood vessel health. As mentioned, preliminary studies show vitamin K2 directs calcium away from the inner walls of arteries where it could build up plaque and cause cardiovascular disease. So, vitamin K2 is a vitamin that points calcium to where it should be—your bones—and away from where it shouldn’t be—your arteries.
How much data is there to support the heart and blood vessel benefits of vitamin K2? One study found that people who consumed more vitamin K2 had a lower risk of cardiovascular disease. The study also found that consuming more vitamin K1 alone does not seem to lower the risk of cardiovascular disease. So, it’s better to get vitamin K2 directly as opposed to depending on a diet rich in vitamin K1 with the hope your body will convert enough of it to vitamin K2.
Food Sources of Vitamin K2
Since you can’t count on getting enough vitamin K2 from sources of vitamin K1, like leafy greens, how can you add more vitamin K2 to your diet? One of the best sources of vitamin K2 is a fermented soy food called natto. It’s popular in Asian countries but harder to find in Western countries, although Japanese food markets sell it.
Unfortunately, natto has a disagreeable aroma and a sticky texture that some find offensive, but it’s possible to develop a taste for this unique source of vitamin K2, and some people eat it with gusto once they overcome its texture and odor. Other sources of vitamin K2 are meat and dairy from grass-fed animals and organ meat. Since most people don’t eat a lot of these foods, the average person doesn’t get a lot of vitamin K2. However, people in Japan consume more vitamin K2 since they eat natto.
Vitamin K2 Comes in Supplement Form Too
If the idea of eating natto or grass-fed meat and dairy doesn’t appeal to you, vitamin K2 supplements are also available. Vitamin K2 as a supplement comes in several forms – MK-4, MK-7, MK-8, and MK-9. The form found in natto is MK-7, and that’s the one many experts recommend. The other form that you often find in supplements is MK-4, the type found in grass-fed meat and dairy.
Always talk to your doctor before taking a vitamin K2 supplement. You shouldn’t take supplemental vitamin K in any form if you’re taking a blood thinner, and you should limit the amount of vitamin K you get through diet too. Vitamin K can make some blood thinners less effective. Talk to your physician about what you should eat or not eat and what supplements you should avoid if you’re taking a blood thinner.
The Bottom Line
Vitamin K2 doesn’t get the attention it deserves. For most people, getting more vitamin K2 through diet is safe and may have positive health benefits for bone and cardiovascular health and most people get little vitamin K in the K2 form. So, get to know this vitamin you don’t hear enough about and make sure you’re getting it from dietary sources or, in some cases, a supplement. Talk to your healthcare provider first though.
References:
- Curr Pharm Des. 2004;10(21):2557-76.
- National Institutes of Health. “Vitamin K
- J Nutr. 2004 Nov;134(11):3100-5.
- 2009 Apr;203(2):489-93.
- Osteoporos Int. 2007 July; 18(7): 963-972.
- Arteriosclerosis, Thrombosis, and Vascular Biology. 2011; 31: 2169-2171.
- org. “Calcium and bones”
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