Natural Food Sources of Vitamin K
Vitamin K is a fat-soluble vitamin with two main dietary forms: K1 (phylloquinone), found primarily in plant foods, and K2 (menaquinones), found mainly in fermented foods and some animal products. Both forms play roles in blood coagulation and bone health, though they differ in absorption, tissue distribution, and biological activity. Understanding which foods are richest in vitamin K helps you build a diet that supports these functions naturally.
Top Food Sources of Vitamin K
Vitamin K1 Sources (Plant Foods)
Vitamin K1 is the predominant form in the diet for most people eating a Western-style diet:
- Kale and other leafy brassicas: among the most concentrated plant sources of K1
- Spinach: high K1 content per serving, widely available year-round
- Swiss chard and collard greens: similarly rich, though less commonly consumed in Estonia
- Broccoli: a reliable everyday source with good K1 content
- Brussels sprouts: high density of K1 relative to serving size
- Lettuce and green salad leaves: a lower but consistent contributor when eaten regularly
- Green herbs (parsley, chives, coriander): small amounts used as garnish can add up
Vitamin K2 Sources (Fermented and Animal Foods)
K2 menaquinones are less abundant in typical diets but may have distinct benefits for bone and cardiovascular tissue:
- Natto (fermented soybeans): by far the richest dietary source of K2, specifically the long-chain MK-7 form
- Hard cheeses (e.g., Gouda, Edam): provide meaningful K2, particularly MK-4 and longer-chain menaquinones
- Soft cheeses and cottage cheese: lower amounts than hard cheeses
- Fermented dairy (certain types of kefir, some yoghurts): modest K2 contribution
- Chicken liver and dark meat: contain moderate K2
- Egg yolks: provide small amounts of K2
Bioavailability: Food vs. Supplement
Vitamin K1 absorption from whole plants is lower than from supplements or oils, largely because K1 is tightly bound to plant cell membranes (Schurgers & Vermeer, 2000). Cooking breaks down these membranes and improves absorption. Eating K1-rich vegetables with dietary fat further enhances uptake because, like all fat-soluble vitamins, K1 requires fat for absorption.
K2 from fermented foods — especially natto — is better absorbed and has a longer half-life in the body than K1. The MK-7 form from natto remains active in the bloodstream significantly longer than MK-4 or K1 (Schurgers & Vermeer, 2000). This is one reason K2 supplements often use MK-7 as the active form.
Daily Targets from Diet
Adequate intake values for vitamin K have been established by various health bodies, expressed in micrograms per day. A diet that includes one to two servings of dark leafy greens daily is generally considered sufficient for K1 intake for most healthy adults. K2 intake is harder to ensure without natto or a K2-rich cheese habit.
Cooking and Storage Effects
Vitamin K1 is relatively stable to heat and moderate light exposure. Cooking vegetables such as spinach and kale typically does not dramatically reduce K1 content, and — as noted — may actually improve bioavailability. Prolonged boiling in large amounts of water can result in some leaching of K1 into the cooking liquid.
Storage at room temperature and exposure to UV light can degrade vitamin K over time. Fresh or frozen dark leafy greens are preferable to stored produce that has been kept in warm, light conditions.
When Food Isn't Enough
Most adults eating a moderate amount of green vegetables will meet K1 requirements. However, K2 is harder to obtain without specific fermented foods, and several groups may have insufficient vitamin K status overall:
- People taking anticoagulant medications (e.g., warfarin): vitamin K intake directly affects how these drugs work; these individuals need medical guidance — not supplementation without oversight
- Those with fat malabsorption: biliary disease, celiac disease, or other conditions affecting fat absorption reduce K absorption
- Long-term users of antibiotics: gut bacteria contribute to some menaquinone production; antibiotic courses can temporarily reduce this
- People with very low dietary fat intake: fat-free or very low-fat diets impair absorption of all fat-soluble vitamins including K
For supplementation, vitamin K2 (MK-7) combined with vitamin D3 is a popular format because D3 and K2 interact in bone mineralisation pathways. At maxfit.ee, the vitamin K category includes products such as NOW Vitamin K-2 (MK7) 100mcg 60 veg. caps., OstroVit Vitamin D3 + K2 90 tabs, and OstroVit Vitamin K2 200 Natto MK-7 90tabs — all providing MK-7 in clearly labelled doses.
FAQ
Which food has the most vitamin K2?
Natto (fermented soybeans) is by far the richest food source of K2, particularly the MK-7 menaquinone form. Hard cheeses, especially varieties like Gouda and Edam, are the next most significant sources in diets not including natto. Natto is not commonly eaten in Estonia, which is one reason many people here have low K2 intake.
Can I get enough vitamin K from eating salad every day?
A daily salad provides K1 (phylloquinone) and can contribute meaningfully to K1 intake. However, salad greens typically contain far less K1 than cooked dark leafy greens like kale or spinach. K2 intake from salad is negligible. If you rely on salad as your main green vegetable, you may under-consume K1 relative to individuals who eat cooked greens regularly.
Does vitamin K interact with any medications?
Yes — vitamin K has a well-known interaction with warfarin (and related anticoagulants). Warfarin works by inhibiting vitamin K-dependent clotting factors, so significant changes in vitamin K intake can alter how the drug works. Anyone on warfarin should keep their vitamin K intake stable day-to-day and discuss any planned supplement use with their healthcare provider.
References
Schurgers, L. J., & Vermeer, C. (2000). Determination of phylloquinone and menaquinones in food: effect of food matrix on circulating vitamin K concentrations. Haemostasis, 30(6), 298-307. https://pubmed.ncbi.nlm.nih.gov/11356998/
Geleijnse, J. M., Vermeer, C., Grobbee, D. E., Schurgers, L. J., Knapen, M. H., van der Meer, I. M., ... & Witteman, J. C. (2004). Dietary intake of menaquinone is associated with a reduced risk of coronary heart disease: the Rotterdam Study. Journal of Nutrition, 134(11), 3100-3105. https://pubmed.ncbi.nlm.nih.gov/15514282/
Vermeer, C. (2012). Vitamin K: the effect on health beyond coagulation. Food & Nutrition Research, 56, 5329. https://pubmed.ncbi.nlm.nih.gov/22489224/
