There is something comforting about a slice of mature farmhouse cheese at the end of a long day. Cheesemakers across Scotland and beyond have been ageing and fermenting food for centuries, long before anyone knew what was happening inside the wheel.
What they could not have known is that those slow, patient fermentations produce a nutrient that scientists are now studying closely. It is called vitamin K2, and in 2026 it has been in the headlines more than ever.
In this guide we look at what vitamin K2 is, why researchers are interested in vitamin K2 heart health, what the newest studies actually found, and what we can say with confidence today.
What is vitamin K2, and how is it different from K1?
Vitamin K is not one single vitamin but a small family. Vitamin K1, also called phylloquinone, is the main form in our diet and comes mostly from green leafy vegetables such as spinach and broccoli1.
Vitamin K2 is a group of compounds called menaquinones. The best studied are MK4 and MK7, and it is MK7 that most supplements and research trials use1.
Where K1 comes from leaves, K2 comes largely from bacteria. That is why it turns up in fermented foods, with natto, a Japanese dish of fermented soybeans, by far the richest source. Cheese, eggs, meat and dairy contain smaller and more variable amounts1.
Why are scientists interested in vitamin K2 and calcium?
Our bodies make a protein called matrix Gla protein, found in the walls of blood vessels as well as in bone and cartilage, and it needs vitamin K to work properly1.
Researchers believe this protein may help stop calcium settling where it should not. The idea, based largely on animal studies, is that low vitamin K could leave the protein less active, which might allow more calcium to build up in artery walls over time1.
It is an elegant theory, and it is the reason so many studies have looked at vitamin K2 and calcium in the arteries. But a theory is only the start of the journey.
What did the earlier research on vitamin K2 find?
The first big clue came from the Rotterdam Study in the Netherlands. Researchers followed 4,807 adults for several years and compared how much menaquinone they ate with their later health2.
People in the top third for K2 intake had less severe calcification of the aorta and a lower rate of death from coronary heart disease than those in the bottom third. Interestingly, vitamin K1 intake showed no such link2.
This kind of study shows an association, not cause and effect. People who eat more fermented foods may differ in many other ways, so researchers needed proper trials to test the idea.
What do the latest vitamin K2 studies show?
In a randomised trial, people are given either the supplement or a dummy tablet without knowing which. Several of these trials have now looked at vitamin K2 and coronary artery calcium, measured on a heart scan.
The AVADEC trial in Denmark
AVADEC gave older Danish men a high daily dose of MK7 together with vitamin D, or a placebo, for two years. Overall, the build up of calcium in the heart arteries was not significantly different between the two groups3.
There was a possible difference in men who already had heavy calcification at the start. The researchers described this as something to explore further rather than a firm result3.
The VitaK CAC trial in the Netherlands
Published in JAMA Cardiology in June 2026, VitaK CAC followed 167 adults with mild to moderate coronary calcium. They took 360 micrograms of MK7 or a placebo every day for two years4.
The calcium score rose in both groups, but it rose less in the MK7 group. Over two years, the median score went from 135 to 184 with MK7, compared with 145 to 214 on placebo4.
The authors described the effect as modest. An accompanying editorial called the results intriguing but questioned how much they mean for patients in practice4.
The DANCODE trial in Denmark
Published in Circulation in August 2026, DANCODE included 398 people with severe coronary calcification. Half took MK7 with vitamin D3 and half took a placebo for two years5.
Calcium build up was slower in the supplement group, by roughly a fifth, without an increase in softer, non calcified plaque. The study was funded by a vitamin K2 producer, though the university says the company did not influence the results6.
Why are people talking about vitamin K2 and heart health?
Part of the interest comes from reviews that pull this research together. In 2021, researchers writing in the journal Open Heart described vitamin K2 as "a neglected player in cardiovascular health"7.
Their review sets out the theory in more detail. Matrix Gla protein only works once vitamin K has activated it, and studies have linked higher blood levels of the inactive form with stiffer arteries and more calcification7.
The same review notes that most of this evidence comes from observational studies rather than randomised trials, and that some large studies found no link at all7. The authors called for more research before K2 could be established as an effective supplement, which is why the conversation is lively but the question is still open.
So, is vitamin K2 proven to help the heart?
The short answer is no, not yet. These are encouraging early findings, not proof.
The trials measured calcium on scans, which is a marker researchers watch closely. None of them was designed to show whether taking K2 means fewer heart attacks or strokes, and that is the question that really matters.
The doses also varied, and two of the trials combined K2 with vitamin D, so it is hard to know which did what. Even the DANCODE researchers have said they cannot yet recommend that their patients take these supplements, and that larger, longer studies are needed6.
If heart health is on your mind, the foundations still matter most. Our heart health guide covers diet, movement, sleep and stress, alongside traditional herbs such as hawthorn berry.
What do we know vitamin K does for the body?
While the research above continues, some things about vitamin K are well established. Vitamin K contributes to normal blood clotting and to the maintenance of normal bones8.
The NHS notes that adults need about 1 microgram a day for every kilogram of body weight, and that most people can get this from a varied, balanced diet8.
Why are vitamin D3 and K2 often taken together?
Vitamin D helps the body absorb calcium, and vitamin K plays its own part in normal bone health. Many people like to take the two together, particularly through the darker winter when we make very little vitamin D from sunlight.
Our Napiers Vitamin D3 and K2 Spray is a simple daily spray onto the tongue, the kind of thing you keep by the kettle so you remember it each morning. You can read more about the sunshine vitamin in Vitamin D: everything you need to know, and about keeping bones strong in our guide to strength and bone health.
Is vitamin K2 safe for everyone?
For most people, vitamin K from food is safe. The NHS advises that taking 1mg or less a day from supplements is unlikely to cause harm8.
The important exception is anyone taking warfarin or a similar anticoagulant. These medicines work against vitamin K, so a sudden change in intake can alter how well they work1. Please speak to your GP or pharmacist before taking vitamin K in any form.
If you would like to talk through whether a supplement is right for you, you can book a free 15 minute consultation with one of our herbalists.
Frequently asked questions
Is vitamin K2 good for your heart?
It has not been proven. Recent trials found that K2 may slow calcium build up seen on heart scans, but no study has yet shown that it prevents heart attacks or strokes.
What is the difference between vitamin K1 and K2?
K1 comes mainly from green leafy vegetables, while K2 comes from bacteria and is found in fermented foods, cheese, eggs and meat. They are absorbed and used slightly differently in the body1.
What foods are high in vitamin K2?
Natto, a Japanese fermented soybean dish, is by far the richest source. Aged cheese, eggs, meat and other fermented foods contain smaller amounts that vary a great deal1.
What is MK7?
MK7, or menaquinone 7, is one form of vitamin K2. It stays in the blood longer than some other forms, which is why it is the form used in most supplements and recent trials.
Why do people take vitamin D3 and K2 together?
Vitamin D helps the body absorb calcium and vitamin K contributes to the maintenance of normal bones. Many people find a combined product a convenient way to take both.
Can I take vitamin K2 if I am on warfarin?
Not without medical advice. Vitamin K can change how warfarin and similar medicines work, so always check with your GP or pharmacist first.
Can I get enough vitamin K from my diet?
Most people can. The NHS says a varied, balanced diet should provide all the vitamin K you need8.
References
- National Institutes of Health Office of Dietary Supplements (n.d.). Vitamin K: Fact Sheet for Health Professionals. NIH. ods.od.nih.gov.
- Geleijnse, J.M. et al. (2004). Dietary intake of menaquinone is associated with a reduced risk of coronary heart disease: the Rotterdam Study. Journal of Nutrition. maastrichtuniversity.nl.
- Hasific, S. et al. (2023). Effects of Vitamin K2 and D Supplementation on Coronary Artery Disease in Men: A RCT. JACC: Advances. jacc.org.
- Vossen, L.M. et al. (2026). Two Years of Menaquinone 7 Supplementation and Coronary Artery Calcification: A Randomized Clinical Trial. JAMA Cardiology. acc.org.
- Hasific, S. et al. (2026). Vitamin K2 and D3 Supplementation in Patients With Severe Coronary Artery Calcification: The DANCODE Trial. Circulation. ahajournals.org.
- University of Southern Denmark (2026). Vitamin K and D supplementation may slow the progression of coronary artery calcification. SDU. sdu.dk.
- Hariri, E. et al. (2021). Vitamin K2, a neglected player in cardiovascular health: a narrative review. Open Heart. ncbi.nlm.nih.gov.
- NHS (n.d.). Vitamins and minerals: Vitamin K. NHS. nhs.uk.
