Many people know that vitamin K1 is important for blood clotting. There is another K vitamin, however, that is often overlooked. It’s found in such small quantities in the modern diet that until recently, many nutrition experts did not think it played an important role in the body.
We now know that is not the case.
K2 may actually be one of the most important vitamins for preventing osteoporosis and calcification of the arteries. And a widespread K2 deficiency may be the contributing factor to the rise of these diseases in modern society.
How it works
You know that calcium is important for building strong bones, and you know that vitamin D is important for helping your body absorb the calcium you eat. But after that calcium is absorbed, it just floats around in your bloodstream. It requires a specific protein, called osteocalcin, to carry that calcium into your bones.
What activates osteocalcin? Vitamin K2.
Without activated osteocalcin, the calcium doesn’t get the direction of where to go and stores itself in your arteries, leading to arterial calcification and heart disease. And since bones aren’t getting the calcium they need, osteoporosis can develop.
In the Rotterdam study, a very large and well-known study, it was shown that people who consumed the most amounts of K2 had a reduced risk of having heart disease. Vitamin K1 did not show any correlation with a reduced risk. (1)
Another observation study of over 16,000 women showed an inverse correlation with K2 consumption and heart disease risk. (2)
Vitamin K2 may also help prevent or reverse varicose veins, as it is believed they may be caused by calcification of the arteries.
Different Forms of K2
There are 4 different forms of K2 including:MK4, MK7, MK8, and MK9. The MK stands for menaquinones and the numbers refer to the number of carbon side chains.
The most frequently studied are MK-4 and MK-7. MK-4 is the main dietary source of K2 in Western populations, while the Japanese eat much more MK-7.
The two different forms appear to have slightly different properties in the body, though research hasn’t fully elucidated their distinctive roles. We do know that MK-7 is absorbed better than MK-4 and stays in the body longer. (3)
It takes up to 500 mcg of MK-4 for fully carboxylate (activate) osteocalcin, whereas only 45-90 mcg of MK-7 is needed, indicating better bioavailability and effectiveness of MK-7.(4)
Where to get K2
Vitamin K1 is found mainly in dark leafy greens, and body can convert some K1 to K2, but it’s not very efficient at it. The bacteria in our guts are responsible for this conversion, but as many people face digestive dysbiosis due to antibiotics, poor diet and stress, the conversion ability becomes further compromised. Also, many folks don’t eat dark greens on a regular basis.
The dietary main sources of K2 are certain soft cheeses and egg yolks. Butter from pasture-raised cattle contains K2, and if the cows were eating rapidly growing green grass, the K2 content is higher. Dairy sources such as these contain mostly MK-4. Liver is also ricc in K2.
One of the absolute best sources of K2 in the form of MK-7, is natto. Natto is a fermented soybean dish frequently eaten by the Japanese. However, it has a slimy, stringy textures and smells like old gym socks, (according to some).
Most call it an “acquired taste” but it’s highly unlikely it will ever become a staple health food in America. It’s also really hard to find; some Asian markets may have it but it’s not common in most grocery stores. Another issue with natto is whether its made from GMO soybeans.
Regardless, the Japanese eat a lot of the stuff, and appear to reap the benefits. One study found that women who ate the most natto had lower incidence of hip fractures. (5)
A very recent study on a MK-7 supplement revealed amazing benefits for protecting against heart disease in postmenopausal women. The women were given 180 mcg of MK-7 (Mena-Q brand) for three years, or a placebo. When they compared the stiffness index of the arteries between the two groups at the end of the study, they found that the group that got the MK-7 actually reversed the stiffness of their arteries, while the placebo groups had an increase in stiffness. (6)
They also found that it decreased bone loss in the women compared to the placebo group. (7)
Another study using MK-4 found that 15 mg given three times a day for 36 months led to significant decreases in bone loss in postmenopausal women, compared to the placebo group. (8)
How to Choose a K2 Supplement
Some studies suggest that just about everyone is not getting enough K2. Since the modern Western diet is not very rich in K2, many people may want to supplement. Certainly anyone taking supplemental calcium and vitamin D, and anyone at risk for osteoporosis and heart disease should consider supplementing.
Both MK-7 and MK-4 forms of K2 have been studied in humans, and both have shown to beneficial in slowing bone loss. Only MK-7 has so far been shown to reversing arterial stiffness. For that reason, I’d recommend find a product that contains MK-7, or a product that contains both MK-4 and MK-7. MK-7 also lasts longer in the body, so you may not need to supplement with it daily.
You don’t necessarily need to consume both MK-7 and Mk-4, as it appears the body can convert MK-7 to MK-4. (9)
The studied dose for MK-7 is 180 mcg, while the studied dose for MK-4 is 45 mg (which is A LOT). However, other research has shown that as little as 45 mcg of MK-7 and 500 mcg of MK-4 can fully activate osteocalcin, so doses higher than those may not be needed in every one.
If you’re a post menopausal women, or taking large doses of vitamin D, 180 mcg of MK-7 is probably your best bet. Look for the brand used in the study: Mena-Q.