The European Prospective Investigation into Cancer and Nutrition (EPIC) cohort.
The most famous findings regarding Vitamin K2 come from the EPIC-Norfolk (a subset of the overall EPIC study) and EPIC-Heidelberg cohorts.
1. EPIC-Norfolk (Cardiovascular Disease)
Study Title/Focus: “A high menaquinone intake reduces the incidence of coronary heart disease.”
Cohort: Approximately 16,000 women aged 49–70 from the Prospect-EPIC cohort (a Dutch subset of EPIC-Norfolk).
Key Findings:
Researchers found an inverse association between the intake of menaquinones (Vitamin K2) and the risk of developing Coronary Heart Disease (CHD).
For every 10 \mu \text{g/day} increase in Vitamin K2 intake, there was an approximately 9\% lower risk of CHD.
This protective association was mainly driven by the longer-chain forms of K2 (MK-7, MK-8, and MK-9), which are common in fermented foods and certain cheeses.
Significantly, the intake of Vitamin K1 (phylloquinone), found in leafy greens, was not significantly related to CHD risk in this study.
Conclusion: The study was one of the first large-scale cohort studies to suggest that higher dietary intake of Vitamin K2, specifically, may protect against cardiovascular disease.
2. EPIC-Heidelberg (Cancer Risk)
Study Title/Focus: “Dietary vitamin K intake in relation to cancer incidence and mortality.”
Cohort: Over 24,000 participants from the EPIC-Heidelberg cohort in Germany.
Key Findings:
Dietary intake of menaquinones (Vitamin K2) was inversely associated with a reduced risk of overall cancer mortality.
The association was particularly pronounced for a reduced risk of prostate cancer and lung cancer, especially in men.
As with the cardiovascular study, Vitamin K1 (phylloquinone) showed no protective association.
Conclusion: This finding supported the hypothesis that Vitamin K2, highly determined by the consumption of foods like cheese, may be associated with a reduced risk of certain cancers.
In summary, the EPIC studies are landmark population-based research that provided strong observational evidence distinguishing the health effects of Vitamin K1 (K1) and Vitamin K2 (menaquinones), suggesting K2 is the more potent form for protecting against chronic diseases like heart disease and cancer.

Sources of K2

Vitamin K2, or menaquinone, is less common in the Western diet than Vitamin K1 (phylloquinone, found in leafy greens). K2 is primarily found in fermented foods and animal products, and its content can vary based on the animal’s diet (e.g., grass-fed vs. grain-fed).
Vitamin K2 exists in various forms (MK-4, MK-7, MK-8, MK-9), and the food sources below are excellent for these forms, with Natto being, by far, the richest source.
Here are the top 10 sources of Vitamin K2:
Nattō (Fermented Soybeans): This traditional Japanese dish is the single richest source of Vitamin K2, specifically the MK-7 form.
Goose/Chicken Liver: Organ meats, particularly chicken liver, are among the best animal sources of the MK-4 form of Vitamin K2.
Hard Cheeses (e.g., Gouda, Edam): The fermentation and aging process in certain cheeses creates high amounts of the longer-chain menaquinones, like MK-8 and MK-9. Gouda is often cited as a top source.
Soft Cheeses (e.g., Brie, Camembert): These cultured cheeses also contain significant levels of K2, though often slightly less than the hard varieties.
Sauerkraut: Like natto, this is a fermented food (cabbage) where bacteria produce K2 (specifically MK-7).
Egg Yolks (especially from pasture-raised/grass-fed chickens): The Vitamin K content is higher when the chickens are fed a diet rich in K1 (grass), which they convert to MK-4 in the yolk.
Grass-Fed Butter and Ghee: Dairy fat from cows that graze on grass (which is high in K1) will contain higher amounts of the MK-4 form of Vitamin K2 compared to dairy from grain-fed animals.
Chicken Meat (e.g., Thigh, Breast): Chicken meat, particularly the dark meat, is a reliable source of MK-4 for those who prefer muscle meat over organ meat.
Salami and Other Cured Meats: The bacterial fermentation and aging processes used to cure sausages can result in the formation of K2 (both MK-4 and MK-7).
Ground Beef/Organ Meats (Beef): While general beef meat contains K2 (MK-4), the amount is generally lower than in chicken or liver, but it still contributes to overall intake.