Softgel capsules, a common form for vitamin D3 and K2 supplements, from Wikimedia Commons
Globallystoners
Illustrative. Generic softgel capsules, not the trial's K2 and D3 supplements.
A Two Year Danish Trial Found Vitamin K2 Plus D3 Slowed Artery Calcification by 21 Percent
Vitamin K2 and D3 is one of the most popular supplement pairings on the market, and until now almost none of the evidence behind it came from watching an actual artery over time. A new two year trial out of Denmark changes that. It did not just measure a blood marker moving in the right direction. It scanned people's hearts, twice, two years apart, and it found a real, measurable slowdown in how fast their arteries kept calcifying.
- A 398 person, randomized, double blind, placebo controlled trial from three Danish hospitals, called DANCODE, tested 720 micrograms of vitamin K2 as MK7 plus 25 micrograms of vitamin D3, daily for two years, in people who already had severe coronary artery calcification.
- Calcification still progressed in both groups, but about 21 percent more slowly with the supplement: calcification scores rose 196 Agatston units in the treatment group versus 248 in placebo.
- The treatment group also ended the trial with lower inactive matrix Gla protein, a marker of vitamin K status, and higher vitamin D levels, with no increase in soft, noncalcified plaque.
- This is a surrogate imaging marker, not a hard outcome. It has not been shown to reduce heart attacks, strokes, or deaths, and it is one trial, not yet independently repeated.
The trial and what it found
Researchers at three Danish hospitals enrolled 398 adults who already had a coronary artery calcification score of 400 Agatston units or higher, meaning meaningful plaque calcification was already present. Half took 720 micrograms of vitamin K2 as MK7 plus 25 micrograms of vitamin D3 every day. Half took a placebo. Neither the participants nor the researchers knew who was in which group. Everyone got a repeat heart scan after two years.
Calcification progressed in both groups, which is expected at this stage of the disease. But it progressed more slowly in the supplement group: scores rose by 196 Agatston units on average, versus 248 in the placebo group, a difference of about 21 percent. The supplement group also had lower levels of inactive matrix Gla protein, a blood marker of vitamin K status, and higher vitamin D levels by the end of the trial. Just as important, the slower calcification was not offset by more soft, noncalcified plaque building up instead, which had been a theoretical worry with vitamin K2 supplementation.
Why this trial is different from the K2 studies you have seen before
Most of the evidence behind vitamin K2 and D3 for heart health has come from blood markers or smaller, shorter studies. This is the largest trial so far to test the combination against a real cardiovascular imaging endpoint, in people who already have documented disease, over a full two years, peer reviewed in the journal Circulation. That combination, real imaging, a meaningful sample size, a real time span, is what makes this result worth paying attention to even before you get to what it does and does not prove.
Honest caveat
Coronary artery calcification is a surrogate marker, not a hard outcome. This trial did not, and at 398 people over two years could not, show fewer heart attacks, strokes, or deaths. It is a single trial, not yet independently repeated. The specific branded ingredient tested, K2VITAL DELTA, is made by Kappa Bioscience, a Balchem company, which is now actively marketing this result. The trial itself appears independently funded by a Danish research foundation and was peer reviewed in a respected journal, but the landmark and largest trial ever framing now circulating is coming from the ingredient maker, not a neutral party. Keep the enthusiasm calibrated to what a surrogate endpoint trial can actually support.
What this means for you
If you already take, or are considering, a vitamin K2 and D3 supplement, this is real, evidence backed reassurance, with real numbers attached, rather than proof that the combination prevents heart attacks or extends life. It also gives you something concrete to check on a label: this trial used 720 micrograms of K2 as MK7 and 25 micrograms of D3 daily, and many shelf products are dosed well below the K2 amount used here. A product with a fraction of that dose has not been shown to do what this trial's dose did.
Primary sources
- Hasific S, Ovrehus KA, Mejldal A, et al. Vitamin K2 and D3 Supplementation in Patients With Severe Coronary Artery Calcification: The DANCODE Trial. Circulation, online August 28, 2026.
- NutraIngredients: "Balchem's vitamin K2 linked to 21% slower CAC progression," September 25, 2026
- Balchem and Kappa Bioscience: "Landmark Circulation Publication Validates K2VITAL DELTA" (ingredient maker's own release, cited here only to confirm the branded ingredient link)
Common questions
Does slowing artery calcification mean fewer heart attacks?
Not necessarily. This trial measured coronary artery calcification, a surrogate imaging marker, not heart attacks, strokes, or deaths. A 398 person trial over two years is not large enough or long enough to prove an effect on those harder outcomes, so treat the finding as slowing a marker, not as heart attack prevention.
What dose of vitamin K2 and D3 did this trial actually use?
Participants took 720 micrograms of vitamin K2 as MK7 and 25 micrograms of vitamin D3 every day for two years. Many shelf supplements are dosed well below the K2 amount used here, so it is worth checking a label against this number rather than assuming any K2 plus D3 product matches what was studied.
Is this result independent, or is a supplement company behind it?
The trial itself was run at three Danish hospitals and appears independently funded by a Danish research foundation, and it was peer reviewed in the journal Circulation. The specific branded ingredient tested, K2VITAL DELTA, is made by Kappa Bioscience, a Balchem company, which is now actively marketing the result. The trial's design and publication look sound, but keep that commercial interest in mind when you read words like landmark or largest trial ever.
Stay Curious.
Better health isn't found in a single article. It's built through curiosity, evidence, and small discoveries over time. Join thousands exploring longevity, gut health, recovery, nutrition, and the tools that truly make a difference.