Best Sources of Vitamin K2: Which Foods Contain It?
Articles
The people of Japan can boast of remarkable vitality. Their very low rate of cardiovascular disease and strong bones, even in older generations, are attributed to a traditional national dish called natto, which the local population eats in large amounts. It is prepared from soybeans left to ferment with the bacterium Bacillus subtilis natto, and it is the richest source of vitamin K2. We also wrote more about vitamin K2 in our article Vitamin K2: A Vital but Little-Known Nutrient.
What will you learn from this article?
- Why is natto considered the best source of vitamin K2?
- Do we depend only on dietary intake?
- Is vitamin K2 also found in animal products?
- How to ensure an adequate daily intake of vitamin K2?
- Key takeaways
Why is natto considered the best source of vitamin K2?
Besides being an incredibly nutritious Japanese delicacy packed with nutrients, natto is also very easy to digest thanks to its fermented protein. But why is it linked specifically to the prevention of heart, blood vessel and bone disease? It is the largest, and arguably the only reliably guaranteed, source of vitamin K2, and up to 90% of it is in the most biologically usable form, MK-7. It is said that 100 g of natto contains up to 1000 µg of vitamin K2 (the recommended daily intake for K2 has not yet been precisely established, but a daily intake of 80–200 µg is cited).
A smaller amount, in the less usable MK-4 form, is also found in other fermented foods, such as pickles or sauerkraut.
Do we depend only on dietary intake?
The human body is a highly capable "chemical factory" that can make many substances essential for life on its own. Like animals, it can convert vitamin K1 into vitamin K2. K1 is found in many green foods: it is stored in the chloroplast membranes of plants, so it occurs in foods such as broccoli, rocket, parsley, spinach, kale or kiwi. However, this conversion is not efficient enough to cover our need for vitamin K2.
K2 should also be partly produced by bacteria that live in our digestive tract. Even here, though, it is still unclear whether our microbiome can produce an adequate amount. On top of that, our gut bacteria are harmed by antibiotics, an unsuitable diet and other factors. You can also read our article Why Do We Need Vitamin K2?
Is vitamin K2 also found in animal products?
Besides the fermented foods already mentioned, K2 also comes from animal sources. All of these sources, however, mainly contain the MK-4 form. You can find it in:
- eggs (32 µg per yolk)
- butter (15 µg), milk
- some cheeses (gouda: about 50 µg)
- meat (around 5 µg, depending on the type of meat)
Under natural conditions, animals convert vitamin K1 into vitamin K2 in their bodies, that is, from the green plants they graze on. They lose this ability once they stop grazing on grass and are fed genetically modified corn and soy. So if you really want to take in even a small amount of vitamin K2, choose animal products from farmers and organic farms.
How to ensure an adequate daily intake of vitamin K2?
If you want to make sure you get enough vitamin K2, it is good to know that it is one of the vitamins that is fairly difficult to get enough of from a typical modern diet.
Its natural sources are mainly fermented foods and animal products:
- natto (fermented soy),
- well-fermented sauerkraut,
- quality eggs, meat, milk and cheeses from pasture-raised animals.
Key takeaways
Vitamin K2 is important for proper calcium metabolism: it supports the deposition of calcium in bones and teeth, while helping to limit its unwanted buildup in blood vessels and soft tissues.
Natto is the richest natural source of vitamin K2: this traditional Japanese fermented soy food contains a high amount of vitamin K2, mainly in the MK-7 form, which has very good usability.
K2 is hard to get enough of from a modern diet: if you do not regularly eat natto, fermented foods or quality animal products from pasture-raised animals, your vitamin K2 intake may be low.
The quality of animal foods matters: eggs, butter, dairy products or meat can contain vitamin K2, but the amount depends mainly on how the animals are raised and whether they graze naturally.
Vitamin K2 and D3 work together: with a higher intake of vitamin D3, it is also worth making sure you get enough vitamin K2, as the two nutrients complement each other in how the body handles calcium.
What next?: If natto is not a regular part of your diet, a quality food supplement with vitamin K2 in the MK-7 form can be a practical solution.
Sources:
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