Have you heard of vitamin K2? Most people haven't, or confuse it with vitamin K1. While both are considered "vitamin K", many experts believe they're different enough to warrant a completely different classification!
Intake of this critical nutrient is incredibly low in the typical diet. It's found in fatty parts of animal products (especially organ meats) and fermented foods.
Let's talk about what vitamin K, how K1 is different from K2, specific vitamin K2 benefits, and how to get more in your diet.
What is Vitamin K?
Vitamin K was discovered by a nobel-prize winning Danish scientist named Henrik Dam in 1929. He cured chicks of a bleeding disorder by feeding them green leaves and hog liver and realized the foods must be rich in something besides A, D, or C that was necessary for blood clotting.
He performed further experiments and named the newly-discovered compound vitamin K for the German spelling, Koagulation. (1)
Around the same time, the famous dentist Weston A. Price traveled the world studying indigenous populations and found that they were high in a mysterious nutrient he called "activator X".
He noticed that compared with those in industrial nations, these populations experienced less chronic disease and tooth decay.
We now know the mystery nutrient to be vitamin K2. (2)
There are two forms of vitamin K, although they are very different: Vitamin K1 (phylloquinone) which comes from plant foods, and K2 (menaquinone) which comes from fermented foods and fatty animal foods.
Within K2, there are many different sub-forms, with the most common ones being MK-4 and MK-7.
Vitamin K1 vs Vitamin K2
Both Vitamin K1 and K2 are in the vitamin K family, as both activate proteins that help blood clot. It was believed that both metabolize calcium and improve heart health, but there's growing evidence to suggest this is only the case for K2.
Vitamin K2 helps regulate calcium deposition, moving it away from soft tissues where it shouldn't be (like the kidney and blood vessels) and into the places it should be, like bones and teeth. (3,4)
Some scientists believe that K1 and K2 should be classified as completely different nutrients.
Studies using vitamin K supplements for bone and heart health improvement have shown that vitamin K2 has a positive impact whereas K1 did not improve outcomes. (5)
K1 also did not reduce arterial calcification in studies on rats like K2 did. (6)
Vitamin K2 Benefits
While both vitamins K1 and K2 help with blood clotting to prevent excessive bleeding and bruising, K2 provides benefits above and beyond those of K1.
Vitamin K2 breaks down calcium in the body to prevent calcification of the soft tissues like artery walls. This allows the arteries to stay flexible which is crucial for healthy circulation, meaning a lower risk of blood clots and heart disease.
The risk of dying from heart disease decreases by 9% for every 10 mcg K2 consumed each day, but this effect has not been shown from K1. (7)
The breakdown of calcium is also important for bone health. When K2 breaks down calcium, it activates a protein that helps calcium bind to bones and teeth. Higher K2 intake is linked to improved bone density and lower risk of fractures. (8)
It can even slow or stop the activity of cancer cells. It's been shown to reduce the rate of cancer recurrence and improve survival rates in certain types of cancer like prostate, lung, and liver, and several other forms. (9)
What Foods Have K2?
Most people consume ten times more K1 than K2. In theory some K1 can be converted to K2, but it's a very inefficient process. It's preferable to consume K2 directly.
K2 can also be produced in the intestine, and there's evidence that antibiotics can contribute to K2 deficiencies. (10)
The richest sources of K2 are:
Animal products, especially organ meats like beef liver. Eel, butter, and some cheeses (like muenster) are also high in K2. Some egg yolks contain K2, but it depends on the diet of the hen as many types of feed are fortified with only plant-based K1. Animal foods tend to be richest in the MK4 form of K2.
Fermented foods, such as natto. This Japanese dish consists of fermented soybeans and can be found at specialty shops. In just one teaspoon there's 150 mcg of K2. Sauerkraut and miso also contain K2.
It's always a good idea to take vitamin K2 in supplement form like the Why Not Natural D3-K2 to make sure you're getting enough, especially if you take it with vitamin D3 to benefit from the synergy of these two vitamins.
(3) Osteocalcin: the vitamin K-dependent Ca2+-binding protein of bone matrix
(4) The role of vitamin K in soft-tissue calcification