September 2025 letter - vitamin K2
This month we briefly talk about vitamin K2 - one of the most important vitamins for blood clotting, heart health, and bone health. One of its most important functions is to regulate calcium deposition. In other words, it promotes the calcification of bones and prevents the calcification of blood vessels and kidneys. As you know, calcium buildup in the arteries around your heart is a huge risk factor for heart disease.
Vitamin K2 improves bone and heart health. A higher intake of vitamin K2 is strongly associated with a reduced risk of heart disease.
Vitamin K1 is generally found in plant foods like leafy greens and K2 in animal based foods such as mature cheese and also in fermented foods.
In addition to preventing heart disease, vitamin K2 also effectively prevents osteoporosis. It plays a central role in the metabolism of calcium, the main mineral found in your bones and teeth by activating the calcium-binding actions of two proteins — matrix GLA protein and osteocalcin, which help to build and maintain bones. K2 deficiency can lead to osteoporosis (and heart disease) as calcium is deposited in the arteries, instead of bones.
K2 is also important for our brain health and it prevents strokes.
It is also worth mentioning that several studies have been done on vitamin K2 and certain types of cancer, some of which suggest that vitamin K2 reduces the recurrence of liver cancer and increases survival times.
How the to get enough vitamin K2? As always, it is important to look after your gut microbiome. Gut bacteria produce vitamin K2 and some evidence suggests that broad-spectrum antibiotics contribute to K2 deficiency.
In addition to include fermented foods (saucer kraut, kimchi, natto and miso for example) into your diet, make sure you eat food from animal sources which include high fat dairy products such as mature cheese and egg yolks, as well as butter, meat and especially liver and other organ meats.
Weston A. Price, a well known dentist who in his time was studying dental decay and physical degeneration in his practice, found higher levels of vitamin K2 especially in the milk of cows eating green grass. He also found that the content of vitamin K2 varied with the species of the cows, the time of year and the quality of what the cows ate. It is very important to eat grass fed meat and dairy products to ensure K2 and prevent deficiency. These foods are particularly important for growing children.
There are many reasons for the modern, widespread deficiency of vitamin K2: our aversion to eating offal, animals raised eating anything other than grass, factory farms, high antibiotic use in animal feeds and in humans, animals fed GMO corn and soy, soil depletion, glyphosate, processed foods and dysfunction of the gut. In addition, certain medication such as statins or blood thinners, can create a deficiency in vitamin K2.
How can you tell if you are deficient in vitamin K2? Vitamin K2 is very important for calcium homeostasis, so if you have osteoporosis, cardiovascular or coronary disease, kidney disorders, diabetes or cancer, it may be due to a deficiency of this nutrient. Tooth decay is another sign of vitamin K2 deficiency. As Weston A Price found in his research, children brought up on diets lacking in K2, starting in the womb, tend to have narrow faces and crowded and crooked teeth.
There are many forms of vitamin K, and they are very different in origin and function. The main forms usually studied are K2 MK-4 and K2 MK-7. There are some differences in their source, bioavailability, and half-life. MK-7 is generally thought to be superior to have a longer half-life and better bioavailability, meaning it stays in the body longer and is more effectively used. MK-4 is typically found in animal products, while MK-7 comes from fermented foods.
I good source of vitamin K2 MK-4 is also through to be from K1, which we get from green leafy vegetables. However, our bodies only absorb very small amounts— less than 10 percent—of K1 from plant foods, and our MK-4 needs are greater than anything we could convert from vitamin K1. Unlike many other animals, humans have a digestive system adapted to having our vitamin K2 MK-4 needs met predominantly from eating grass-fed or pastured animals and products made from them.
Natto, a fermented soy product, is the only food with high amounts of vitamin K2 MK-7. It originates from the eastern part of Japan but has not been in most of the world’s diet except in trace amounts. And the Japanese traditionally eat egg yolks, a source of MK-4, with natto.
The following observations by The Weston A. Price Foundation were very interesting:
In 1988, a Japanese study done by Dr. Hidekazu Hiraike divided pregnant women into two groups. Group A was asked to eat a normal diet and Group B was asked to eat a diet high in natto. Vitamins K1, K2 MK-4, MK-6 and MK-7 were found in the placentas and mothers’ blood plasma. Samples were taken of the placentas and umbilical cord plasma right after delivery.
Only K1 and MK-4 were found in the umbilical cord plasma, even though there were high concentrations of MK-7 available. It appeared that the placental tissues effectively blocked the passage of MK-7 while allowing MK-4 into the unborn child. High concentrations of vitamin K2 MK-4 were found in the placenta.
MK-7 scientists say that MK-7 is more bioavailable or has a longer half-life because it remains in the blood plasma longer than MK-4. However, the Japanese natto study provides a living account of nature’s selection for the type of vitamin K2 needed for the development of the child—that is, the animal form MK-4. Could MK-7 remain in the blood longer because the body has no use for it?
Some studies indicate that MK-7 from food and synthetics induces more complete carboxylation of osteocalcin, a vitamin K-dependent protein involved in bone homeostasis. One study involving menopausal women taking MK-7 as natto over one year showed reduced serum levels of uncarboxylated osteocalcin (ucOC), but the treatment had no effect on bone loss rates. Could MK-7 increase the carboxylation of calcium and yet lack the ability to move it into the tissues? Could this increase in carboxylation increase the calcification of the placenta or form excess osteocalcin, which does cross into the placenta, causing a decrease in the blood supply (thus less oxygen) and explain the findings of small for gestational age and other defects in the natto study?
In 1992, Dr. Hideaki Iioka found that vitamin K2 MK-4 is transported into the placenta by a carrier protein via an existing transport carrier system in the brush border membrane of the human placenta. Vitamins A, D and E are also carried in the blood by a carrier protein. Could this be the reason that vitamin K2 MK-4 is often not detected in the blood, because it is attached to a carrier protein? Little to no research has been done to answer these questions.
What we do know is that the traditional sacred foods for preconception and pregnancy were foods rich in MK-4, and that traditional weaning foods for babies were poultry liver and egg yolk, also great sources of vitamin K2 MK-4.
We most likely need vitamin K2 as MK-4 from food sources. It is already in the form that the body needs. And finally, MK-4 is more efficient than other forms, appearing in food with other synergists and activators that work together to maintain therapeutic aspects.
The type of vitamin K2 that we get in supplements is MK-7, not the type we get in food. The best way to get vitamin K2 is from food. This is true for most vitamins.
Stuffed peppers
3 organic peppers
400g minced beef
150g feta cheese
200g mushrooms cut into small cubes
1 onion, chopped
Salt
Black pepper
100ml chicken or beef stock
For garnish and sauce:
Fresh herbs: mint, rosemary, thyme, parsley, etc.
Sauce:
Greek yogurt
½ lemon juice
Salt
Black pepper
A handful of chopped fresh herbs (see above)
This is a good and quick everyday dish. Heat a splash of olive oil in a pan. Add the onion and cook for a few mins to soften. Add the beef, and cook until the meat is browned. Add the mushroom and cook for a few more minutes. Crumble the feta cheese and mix with the beef mixture. Add salt and black pepper. Halve the bell peppers and fill the halves with the mixture.
Grease a baking dish with butter and/or olive oil. Place the stuffed bell peppers in a baking dish and pour chicken or meat stock into the bottom of the dish. If you like, you can sprinkle the peppers with grated cheese.
Cook the peppers at 200 degrees (fan 180 degrees) for at least half an hour. Enjoy with a yogurt sauce seasoned with herbs.