It used to be thought that virtually everyone got enough vitamin K, since it’s synthesized to some extent by microbes in the gut, but it was later realized that much of this is not absorbed. It turns out that vitamin K has very important effects on health, and how much you ingest via diet can mean the difference between life and death, since vitamin K2 prevents heart disease and cancer.
Vitamin K comes in two basic forms, phylloquinones or vitamin K1, which are found in plants, and menaquinones or vitamin K2, found in animal foods. (These can be further subdivided, but for our purposes, that’s all we need to know.)
A study undertaken in The Netherlands found huge differences in heart disease mortality, all-cause mortality, and aortic calcification among subsets of people grouped by vitamin K2 intake: Dietary Intake of Menaquinone Is Associated with a Reduced Risk of Coronary Heart Disease: The Rotterdam Study (The Journal of Nutrition).
The relative risk of death from coronary artery disease in the highest tertile (third) of vitamin K2 intake was 0.42; in other words, those with an intake of vitamin K2 in the highest third, compared to those in the lowest third, had nearly a 60% reduction in risk of death from heart disease.
Risk of all-cause mortality was 0.74, or ~25% less, and the risk of aortic calcification was only about half that of the lowest intake group.
Another study found that each 10 μg/d intake of vitamin K2 was associated with ~10% lower risk of coronary artery disease. (Atherosclerosis). The highest quartile of vitamin K2 intake in another study had about a 20% lower risk of coronary artery calcification, in line with the other study’s 25% lower rate of aortic calcification. (Atherosclerosis.)
Worthy of note, none of these studies found that phylloquinones, the vitamin K from plants, had any effect; it was all vitamin K2.
One reason that this is noteworthy is that it seems to rule out the healthy user effect seen in so many studies. The healthy user effect is what happens when people who are already healthy enthusiastically follow health recommendations and their subsequent health is misattributed to the recommendation. For example, many studies have found health benefits for low-fat eating, but the people most likely to eat that way are those who are smart, conscientious, and likely to have kept abreast of health recommendations over the past few decades. They’re healthier, but not because of their diets. In contrast, those who consumed lots of meat have been more likely to smoke, be overweight, and not exercise.
So, healthy users will have been more likely to eat lost of plant foods, high in vitamin K1, but these were shown to have no effect on mortality. It’s the unhealthy users that will have been likely to eat more vitamin K2, and this did show an effect.
Other studies have found lower cancer rates with vitamin K2 consumption. (AJCN) This was a “trend”, i.e. not considered significant, at a 28% lower rate of cancer mortality.
The inverse association between vitamin K2 consumption and lower rates of heart disease makes complete sense, since one of the functions of vitamin K2 is in calcium metabolism. Calcification of the arteries is a cause of coronary heart disease. Essentially, vitamin K2 gets calcium into the right places, bones instead of arteries.
How do you get more vitamin K2? It’s found mainly in cheese, butter, and eggs, much more so if these come from grass-fed animals. The thing is, this also depends on the season of the year, where the animals are fed and what exactly they eat. So it’s somewhat undependable.
Therefore, naturally, I take a vitamin K2 supplement, Carlson.
Two things about this supplement: it’s a bit on the expensive side, and one capsule provides over 6000% of daily value, a bit much. So I solve this problem in one step, by opening up the capsule and putting about one fifth of it into my whey shake, or even my coffee on a day I’m not taking the whey.
Given the huge health benefits of K2, as well as the fact that my family has a rather poor record when it comes to coronary artery disease, I think it’s well worthwhile.