Many researchers from many countries have found many reasons why natto is good for your health. It is an extremely nutrient-dense food, full of enzymes, prebiotics, and probiotics; it has anti-bacterial properties, and it is also a uniquely rich source of vitamins that are difficult to find in other foods. For now we’ll focus on one of those vitamins: K2.
Vitamin K was discovered in 1929 by a Danish scientist named Henrik Dam; he isolated a nutrient that was particularly effective at helping chicken (and human) blood coagulate, and named it “K,” after the German Koagulationsvitamin. Since 1929, however, others have differentiated between two distinct types of “K” that occur naturally — K1 and K2 — as well as three types that are synthetically produced: K3, K4, and K5. K1 is available directly to humans through a variety of plant sources; it is important, but easy to get, and so studied with far less rigor than K2.
K2 has been studied extensively, so that it is now recognized to have many distinct sub-types, each named after the chemical designation for K2, menaquinone; hence, each type, 1-9, is commonly known as MK1, MK4, MK7, etc. This is important to understand because the different types of K2 come from different sources and have different effects on your health; when someone refers to vitamin K2 it is important to clarify which version of K2 they are actually talking about.
So, one final technical detail: MK4 and MK7 have both repeatedly been shown to help prevent and treat a wide variety of afflictions that plague Americans: osteoporosis, high blood pressure, heart disease, strokes, and arthritis. Our bodies can synthesize MK4 from K1, which is easy to get from many plants; MK7, however, is more difficult to come by, and far more effective at battling the aforementioned afflictions.
MK7 appears to be available from two major sources: either you eat animal livers, or, perhaps more appetizingly, you eat the beneficial bacteria of fermented foods such as natto. Amongst the wide spectrum of fermented foods available, natto has consistently proven to have the highest concentration of MK7-type K2 available.
Japanese scientists have been studying natto for some time now; as “Western” food gains in popularity, and good health consequently declines (what a surprise), the national government has funded a number of studies to analyze traditional dietary habits and understand exactly why they worked so well for so long. The general idea is to codify ancestral wisdom into specific medical recommendations that will allow their population (and curious foreigners) to stay healthy.
Unfortunately for us, who are probably in need of this information even more urgently than the Japanese, the results of these studies are not always translated into English, and even when they are, their importance is not often recognized widely in this country. But there are a few European and American experts who have turned their attention toward traditional Japanese foods, and the importance of natto is now beginning to be understood outside of Japan.
So, back to MK7-type K2. How does it work? Essentially, your body has a difficult time knowing how to process all the calcium it receives. American medical professionals have long recognized the fact that we need vitamin D to absorb the calcium we consume — which is why it’s added to milk — but are just beginning to recognize what the Japanese have known for some time now: we need vitamin K2, and MK4 or MK7 specifically, to tell our bodies how to use all that calcium we absorb with the benefit of vitamin D.
What happens to all that calcium if it isn’t absorbed properly? Instead of going to our bones, it accumulates in arteries and tissues — leading to high blood pressure, heart attacks, strokes, and arthritis.
This explains why Americans have long been long been plagued by an apparent “calcium paradox,” in that we, as a society, consume far more calcium than most other populations, but suffer from far more osteoporosis. The fact that our diets are often very low in MK7-type K2 suggests that this isn’t a paradox at all. Rather, the fact that we consume lots of calcium, suffer from osteoporosis, and simultaneously suffer from high blood pressure, heart disease, strokes, and arthritis, can all be linked to deficiencies in Vitamin K2. Of course this isn’t the only reason for our national health crisis, but it does appear to be an extremely important element in the equation.
Probably the best-known study to confirm these theories was the so-called Rotterdam Study, which tracked almost 5,000 subjects over the course of 7-10 years, to analyze the importance of adequate K2 in good coronary health. The full study, published in the journal of the American Society for Nutritional Sciences, is available here: http://jn.nutrition.org/content/134/11/3100.full. Further, The Benefits of Vitamin K2, by Dr. Anthony Payne, provides a good technical overview of how K2 works in our bodies and why we need it.
In response to all this information, quite a few people have gone out to buy MK7 pills to take with their meals. As with most vitamins, however, there isn’t much evidence to suggest that our bodies can actually absorb the K2 that has been synthetically crafted, or isolated in pill-form. We can get much more MK7 when we eat it in it’s whole, natural state, in food such as natto.
This is true not only because we can absorb the MK7 more readily, but also because natto has a wide spectrum of other benefits. For example, natto has a unique enzyme — nattokinase — which helps reduce blood-clotting, thereby countering the coagulating effects of the vitamin K family, and further reducing the risk of heart disease and strokes. We’ll get into that more fully in another post. For now, though, I’ll just say that Dr. Hiroyuki Sumi is a good source for information about the nuances of nattokinase in the English language.