Most absorbable forms of vitamin K2 (menaquinone)
Foods that provide the most absorbable forms of vitamin K2 (menaquinone) are chiefly fermented animal foods and natto, a fermented soybean dish. Natto supplies abundant, long-lasting MK-7, while cheese, egg yolks and butter contain smaller amounts of shorter-lived MK-4. Because vitamin K is fat-soluble, eating it with fat improves absorption.
Bioavailability depends on the food matrix, dietary fat, gut health and medication, not merely a food’s reputation. In Australia, much vitamin K comes from leafy greens as K1 rather than K2, so K2-rich foods deserve specific attention.
How the body uses K2
Vitamin K2 is a group of menaquinones, with numbers indicating how many carbon atoms they contain. MK-4 is common in animal foods and has a shorter biological half-life; MK-7 is especially abundant in natto and generally remains active longer in the body.
It helps activate proteins involved in blood clotting and bone mineral metabolism. Adequate intake matters, but foods or supplements cannot be assumed to prevent fractures or cardiovascular disease. For a wider explanation of nutrient roles and deficiency, see vitamin and deficiency guidance.
The strongest food sources
Natto is the most concentrated common food source of K2, usually delivering MK-7, although amounts vary between brands and preparations. A 30-gram serve may contain roughly 700–2,000 micrograms, making it much richer than standard servings of dairy or eggs.
Cheese is the strongest conventional dietary source for many people. Aged hard varieties such as cheddar, Gouda, Edam and Swiss-style cheese generally contain more MK-4 than soft cheese, while egg yolks and butter offer smaller amounts. Liver is very concentrated, but its high vitamin A content makes routine consumption unsuitable, particularly during pregnancy.
What makes K2 absorbable
Vitamin K is fat-soluble, so the fat surrounding it in cheese, eggs and butter helps its uptake. A meal containing some fat is usually more useful than adding a K2-rich food to an otherwise fat-free diet. The food matrix still influences absorption, and individual responses vary.
Full-fat cheese with a boiled egg on wholegrain toast is an easy example. Lower-fat products still provide K2, but they contain less fat to support absorption. Direct food-to-food bioavailability studies are limited, so claims that one dish is universally best should be viewed cautiously.
K2 foods in the Australian diet
Australian supermarkets make K2 accessible even though K2 is rarely discussed on labels. Coles and Woolworths commonly stock aged cheddar, Edam, Gouda, butter and eggs, while full-fat Greek yoghurt and hard cheeses fit familiar Australian meals such as a cheese toastie or a savoury brekkie.
Natto is less usual in the mainstream grocery aisle and is more often found at specialist Asian stores or online. Sydney and Melbourne shoppers can find it in many neighbourhood Asian grocers, with sodium levels varying by brand. Because Australian cheese and yoghurt labels often omit menaquinone amounts, ingredient and serving information matter more than assuming every product is equivalent.
Fermented foods and gut health
Fermentation can produce K2, but the word fermented is not a guarantee of a high content. Natto is a clear example; many commercial yoghurts and cultured butters contain much less or variable amounts. The bacteria used in cheese-making, rather than bacteria already living in the shopper’s gut, account for much of its K2.
Colonic microbes can convert some vitamin K1 into menaquinones, but this process is unpredictable and should not be relied upon as a dosing strategy. Regular fermented foods can still support gut diversity, yet they are best chosen for taste, tolerance and nutritional value rather than assumed K2 content.
Comparing common K2 foods
No single food wins every comparison. Natto leads in dose and MK-7 exposure; aged cheese is convenient and rich in MK-4; eggs and butter contribute smaller amounts alongside fat and protein. Product age, fat content and serving size can change the totals.
Approximate figures below reflect common composition data rather than a promise for every Australian product. Brands can differ substantially, especially for natto and fermented cheese.
| Food | Main form | K2 per typical serve | Practical note |
|---|---|---|---|
| Natto, 30 g | MK-7 | About 700–2,000 µg | Very high; often high in sodium |
| Aged hard cheese, 30 g | MK-4 | About 10–30 µg | Useful fat and protein; full-fat aids uptake |
| Egg yolk, one large | MK-4 | About 10–20 µg | Easy addition to savoury meals |
| Butter, 20 g | MK-4 | About 2–8 µg | Small contribution; easy to overconsume |
Building K2 into everyday meals
For many adults, a practical food-first approach is simple: include a serve of aged cheese and an egg, use butter modestly, or add natto to rice and vegetables. Broader everyday nutrition habits should still centre on variety, since no food supplies every vitamin K benefit.
People taking warfarin should not suddenly increase or reduce K2 from food or supplements. They need a stable, individually adjusted intake and should discuss changes with their prescribing clinician or anticoagulation clinic. K2 can support normal clotting and bone-related protein activity, but it does not replace prescribed anticoagulant treatment.