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Overview:
Vitamin K was discovered in 1929 as an essential nutrient for blood coagulation, the scientific term for blood clotting. The initial discovery was reported in a German scientific journal, where it was called “Koagulationsvitamin.” That’s where the K in vitamin K comes from.
- Vitamin K1 (phylloquinone): found in plant foods like leafy greens
- Vitamin K2 (menaquinone): found in animal foods and fermented foods, also produced by gut bacteria
How do Vitamin K1 and K2 Work?
Some scientists have suggested that the roles of vitamins K1 and K2 are quite different, and many feel that they should be classified as separate nutrients altogether.
However, more human studies are needed before the functional differences between vitamins K1 and K2 can be fully understood.
Vitamin K1 and K2 Supports…
Bone Health and Osteoporosis
Osteoporosis — which translates to “porous bones” — is common, especially among older adults. It strongly increases the risk of fractures.
As mentioned above, vitamin K2 plays a central role in calcium metabolism, the main mineral found in your bones and teeth.
Vitamin K2 activates the calcium-binding actions of two proteins — matrix GLA protein and osteocalcin, which help to build and maintain bones.
Interestingly, there is also substantial evidence from controlled studies that K2 may provide major benefits for bone health.
A 2022 meta-analysis of 16 studies in 6,425 postmenopausal women found that those taking vitamin K2 supplements had a positive effect on bone mineralization and increased bone strength.
Dental Health
A 2023 review of 4,965 elderly individuals concluded that regular vitamin K supplementation coupled with moderate fiber intake was effective at helping to prevent tooth loss from periodontal disease, particularly in males.
This effectiveness was not as evident for Black test subjects as other populations, so more studies are needed. Based on animal studies and the role vitamin K2 plays in bone metabolism, it’s reasonable to assume that this nutrient affects dental health as well.
One of the main proteins regulating dental health is osteocalcin — the same protein that is critical to bone metabolism and is activated by vitamin K2. Osteocalcin triggers a mechanism that stimulates the growth of new bone and new dentin, which is the calcified tissue underneath the enamel of your teeth.
Vitamins A and Vitamin D are also believed to play an important role here, working synergistically with vitamin K2.
Tumor Prevention
Several studies have been done on vitamin K2 and certain types of cancer.
Cell and animal studies suggest that K2 may inhibit the growth of liver cancer cells. Still, larger, well-controlled, long-term studies are needed to show the benefit of reduced liver cancer recurrence rates and improved survival.
Some studies have linked a high intake of MK with an increased risk of breast cancer. More high quality studies are needed before any strong claims can be made.
Vitamin K Intake
Several widely available foods are rich sources of vitamin K1, but vitamin K2 is less common. Your body can partly convert vitamin K1 to K2. This is useful because the amount of vitamin K1 in a typical diet is nine times that of vitamin K2.
However, only 10-15% of ingested vitamin K1 is absorbed in the digestive tract, so absorbed K1 makes up about 50% of all vitamin K in the diet.
Current evidence indicates that the conversion process is inefficient. As a result, you may benefit much more from eating vitamin K2 directly. Gut bacteria in your large intestine also produce vitamin K2. Some evidence suggests that broad-spectrum antibiotics contribute to K2 deficiency.
Still, the average intake of this important nutrient is incredibly low in the modern diet
Vitamin K2 is mainly found in certain animal and fermented foods. Rich animal sources include high fat dairy products from cows and egg yolks, as well as liver and other organ meats.
Vitamin K is fat-soluble vitamin, which means low fat and lean animal products don’t contain much of it. Animal foods contain the MK-4 subtype, while fermented foods like sauerkraut, natto, and miso pack more of the longer subtypes, MK-5 to MK-14.
Taking supplements can be a helpful alternative if these foods are inaccessible. Talk with a healthcare professional before adding extra vitamin K2 to your diet.
The benefits of supplementing with K2 may be enhanced even further when combined with a vitamin D supplement. These two vitamins have synergistic effects, which means they may work together.