Landmark Trial Finds Vitamin K2 and D3 Slow Coronary Artery Calcification by 21%

For vitamin K2 to successfully keep calcium out of coronary arteries, the body first has to produce a specific protein called matrix Gla protein (MGP) for the vitamin to activate. That biological dependency means taking K2 alone often falls short. In a new landmark clinical trial, researchers met that constraint by pairing high-dose vitamin K2 with vitamin D3—which stimulates MGP production—and proved the combination can slow the hardening of arteries by 21% in patients with severe heart disease.[1][5]

The findings, published in August 2026 in Circulation, the journal of the American Heart Association, offer the clearest evidence to date that an over-the-counter supplement can physically alter the progression of cardiovascular disease. The multicenter Danish Coronary Decalcification (DANCODE) study enrolled 398 men and women with a median age of 71.[1][5]

Crucially, this was not a preventative study on healthy adults. Every participant already had severe coronary artery calcification (CAC), defined as a baseline Agatston score of at least 400 units, with the median score sitting at 903. CAC is a strong imaging predictor of future cardiovascular events, reflecting the cumulative burden of atherosclerosis.[3][5]

Researchers at Odense University Hospital and other Danish centers randomly assigned participants to receive either a daily placebo or a combination of 720 micrograms of vitamin K2 (as MK-7) and 25 micrograms (1,000 IU) of vitamin D3. The trial utilized Balchem's K2Vital Delta ingredient and tracked the patients for 24 months.[1][2]

After two years, CT scans revealed that calcification had advanced in both groups, which cardiologists expect given the progressive nature of the disease. However, the rate of that progression diverged significantly. The placebo group saw their mean calcium score increase by 248 units, while the supplement group's score rose by only 196 units.[1][5]

That 52-point difference represents a 21% relative reduction in the progression of arterial calcification. The protective effect remained consistent across both men and women, and held true regardless of whether participants started with moderate or extremely high baseline calcification.[1][5]

The mechanism behind the result lies in how the two vitamins interact with calcium in the bloodstream. "Vitamin K2 MK-7 in its all-trans form activates matrix Gla protein, which helps direct calcium to where it is needed in the body," explained Axel Diederichsen, lead author and professor at Odense University Hospital.[1]

Diederichsen noted that the blood tests confirmed the biological pathway was working as intended. "In this study, the reduction in calcification progression was accompanied by a marked fall in the inactive form of matrix Gla protein, which tells us the supplementation reached the pathway it was aiming for," he said.[1]

While the results are highly encouraging for patients looking to manage their calcium scores, the clinical translation requires careful framing. The trial demonstrated a reduction in calcified plaque progression, but detailed artery scans showed no significant difference in the volume of non-calcified, or "soft," plaque.[3][5]

Soft plaque is the volatile component of atherosclerosis that is most prone to rupturing and causing acute heart attacks. Because the DANCODE trial did not reduce this non-calcified burden, it remains unknown whether the 21% slower calcification rate will actually result in fewer heart attacks or improved overall survival over the next decade.[4][5]

Furthermore, high-dose vitamin K supplementation is not universally safe. Vitamin K directly interacts with blood-thinning medications like warfarin, which function by inhibiting vitamin K-dependent clotting factors. Patients on these anticoagulants must consult their cardiologists before adding K2 to their regimen.[4]

For the broader population of older adults with known arterial calcification, the DANCODE trial establishes a practical, evidence-based intervention. By confirming that the K2 and D3 pairing successfully activates the body's calcium-regulating proteins, the research provides a low-risk tool to help slow a disease process that has historically been difficult to modify.[2][3]