What is behind the miraculous vitality of Japanese people? The very low incidence of cardiovascular diseases and the high bone hardness, even in the older generation, are attributed to the traditional national dish Natto. This soybeans superfood frequently eaten by the local population is prepared by steaming or cooking and then fermented by the action of the bacterium Bacillus subtilis natto.
This Japanese national delicacy, commonly eaten at breakfast, gains its popularity due to its nutritional value and health benefits, but also for easy digestion (proteins in the soybean are broken down due to fermentation process).
But why is it related to the prevention of heart, blood vessels and bone diseases? Because it is the richest source of vitamin K2 available and in addition to up to 90% contains the most biologically usable form K2 MK-7.
A 100-gram serving contains approximately 108 micrograms of vitamin K2, more than twice the recommended intake. It is the largest and can be said to be perhaps the only guaranteed source of vitamin K2, in addition to up to 90% in the most biologically usable form of MK-7. It is stated that 100g natto contains up to 1000µg of vitamin K2 (the recommended daily dose for K2 has not yet been precisely determined, but the daily intake is stated to be between 80 - 200µg).
Nattó has a typical sticky-stringy texture and strong pungent smell. So you will love it or hate it.
There are also other dietary sources of K2 like organ meats, dairy products or eggs yolks and a small amount of K2 MK7 is also in fermented foods like pickles or sauerkraut.
Are we dependent on a food intake?
The human body is a perfect and very powerful chemical factory and can produce many substances necessary for life. Like animals, for example, it can transform vitamin K2 from plant forms of K1. Vitamin K1 is stored in the membranes of plant chloroplasts and can be found in many sources (mainly green ones) - broccoli, arugula, parsley, spinach, cabbage , but also in kiwi. Unfortunately, this synthesis is not perfect in our body and the amount produced is not enough to cover daily needs.
A small amount of vitamin K2 is also produced by bacterias in our gut. However, even here it is still not clear whether our microbiome can produce a sufficient amount. In addition, our intestinal bacteria are destroyed by antibiotics, improper diet and other factors. This fundamentally changes their diversity, and these variations may be related not only to the manifestation of various diseases, but also to the fact that bacteria do not work sufficiently.
Animal products are important source, but .. breeding matters
As already mentioned, fermented foods like nattó or sauerkraut are great sources of vitamin K2. But vitamin K2 also comes from animal origin. We find it in eggs (32µg per yolk), butter (15µg), milk, some cheeses (gouda - about 50µg) and meat (about 5µg - depending on the type of meat). All these sources contain mainly the form MK-4.
Animals have the ability to transform vitamin K2 in the gut from vitamin K1 but only if they were pasture raised. If they are fed by genetically modified corn and soy, vitamin K2 cannot be derived by gut bacteria. So if you really want to take at least a small amount of vitamin K2, choose animal products from farmers and organic farms (meat and other dairy products from farming according to ancient and traditional principles have many other benefits, including an ecological factor and you can tell the difference in taste).
Can we cover the daily recommended intake by diet?
Vitamin K2 is a very important nutrient but also incredibly low in the modern diet. Typical Western diet makes it more difficult to take this nutrient in adequate amounts. If you are not nattó lover and if you do not consume eggs, meat, milk and cheeses from grass fed animals, you are probably low in vitamin K2.
To obtain a recommended daily amount means to get approximately 3 egg yolks a day and 2 lumps of butter, which not everyone normally consumes. Fortunately, there is no known toxicity to vitamin K2, so we can safely reach for a quality dietary supplement. And especially if you increase your vitamin D3 intake. These 2 nutrients act synergistically and one without the other does not fulfill its function sufficiently.