Vitamin K2 and artery calcium: what the 2026 trials show

Vitamin K2 is one of the most common add-ons in longevity and "heart and bone" supplement stacks, usually as menaquinone-7 (MK-7) paired with vitamin D3. The pitch rests on a real piece of biology: vitamin K is needed to activate matrix Gla protein, which helps limit how much calcium is laid down in artery walls. In 2026 two randomized trials reported slower buildup of calcium in the heart's arteries, one with K2 alone and one with K2 plus vitamin D3, after earlier K2 trials had mostly found no effect on CT calcium.

Short answer: these two trials are the best evidence yet that the supplements used can change a coronary calcium scan, and the effect was modest. VitaK-CAC used K2 alone. DANCODE used K2 plus vitamin D3, so that result cannot be credited to K2 by itself. Neither trial was designed to show fewer heart attacks, strokes or deaths. DANCODE listed cardiac events as a secondary outcome, but the published report does not give heart attack, stroke or death counts. An earlier trial using the same dose found no effect on calcium in the aortic valve or arteries. K2 looks safe for most people, but it is not a proven way to protect the heart, and anyone taking warfarin should not start it without medical advice.

What a coronary calcium score measures

A coronary artery calcium (CAC) score comes from a CT scan of the heart and is reported in Agatston units. It reflects how much calcified plaque sits in the coronary arteries. The DANCODE investigators describe progression of the score as a strong predictor of cardiovascular events. A slower rise in the score is still a surrogate result: it shows the scan changed, not that people had fewer events.

The 2026 trials

• VitaK-CAC (Netherlands, JAMA Cardiology, August 2026). 180 adults with symptomatic coronary artery disease and a CAC score between 50 and 400 were randomized to 360 mcg of MK-7 a day or placebo for two years; 85 and 82 were analyzed. The median score rose from 145 to 214 on placebo and from 135 to 184 on MK-7, a significant difference (P = .02). Calcium mass showed a similar result. The authors concluded that MK-7 may slow calcification in non-calcified plaques and that the clinical significance remains to be determined. One author reported grants from Gnosis by Lesaffre, a vitamin K2 supplier, and shares in Coagulation Profile, both outside the submitted work.
• DANCODE (Denmark, Circulation, published online August 28, 2026). 400 people with severe calcification, a CAC score of 400 or more, were randomized to 720 mcg of K2 plus 25 mcg (1,000 IU) of vitamin D3 a day or placebo for 24 months; 398 were analyzed. Their median age was 71 and 30% were women. The mean score rose by 196 units on the supplement and 248 on placebo, a difference of 52 units (95% CI 24 to 79). In a subgroup of 143 people with a score below 1,000 who had CT angiography, total plaque volume rose similarly in both groups, non-calcified plaque volume did not differ between the groups, and calcified plaque grew less on the supplement. The published conflict statement is none. The registry protocol says the tablets were expected from Kappa Bioscience and Orkla Care, with no role in the design or analysis.

The 2022 trial did not slow calcium

The same Danish group ran AVADEC, published in 2022. It randomized 365 men with calcification of the aortic valve, mean age 71, to the same 720 mcg of MK-7 plus 25 mcg of vitamin D or placebo for two years. Aortic valve calcium rose by 275 units on the supplement and 292 on placebo, a difference that was not significant. Progression of aortic and coronary calcium was not significantly different either, and cardiovascular events were 10 in each group. The supplement did lower dp-ucMGP, a blood marker of poor vitamin K status, showing that the vitamin was absorbed and active. Unrestricted grants came from the Danish Heart Foundation, the Region of Southern Denmark Research Council and the Novo Nordisk Foundation. Kappa Bioscience and Orkla Care supplied the tablets and had no role in the analysis. The lead investigator had served on a panel that reviewed MK-7 for use in food.

A 2026 review in the Clinical Kidney Journal summed up the field before DANCODE was published: K1 and K2 both reliably improve markers of vitamin K status, K2 had not produced reproducible benefits on CT-measured vascular or valve calcification, and neither form had reduced major cardiovascular events or deaths. Where trials collected events, they were too small to tell. DANCODE adds one positive coronary result to that picture. It does not change the absence of outcome data.

What is still coming

InterVitaminK, a Danish trial of 450 adults aged 52 to 82 with detectable coronary calcium but no previous heart attack, stroke or coronary procedure, is testing 333 mcg of MK-7 a day against placebo for three years, with calcium progression as the main outcome. Its participants are closer to the people buying K2 for prevention than those in the 2026 trials. ClinicalTrials.gov lists its estimated primary completion as January 2027. Kappa Bioscience, a K2 manufacturer, gave the trial funds and the tablets. The protocol also lists grants from the Danish Cardiovascular Academy, funded by the Novo Nordisk Foundation and the Danish Heart Foundation, the Capital Region of Denmark, the study hospital and other foundations. One investigator has applied for a patent on vitamin K and lung function.

Safety and medicines

No tolerable upper intake level has been set for vitamin K, because no adverse effects from vitamin K in food or supplements have been reported, according to the NIH Office of Dietary Supplements. VitaK-CAC reported no significant adverse effects. AVADEC described MK-7 plus vitamin D as generally well tolerated, with adverse events in 16 men on the supplement and 19 on placebo (P = 0.61). The DANCODE paper does not report a side-effect comparison. The important exception is warfarin and similar anticoagulants such as acenocoumarol and phenprocoumon. These drugs work by blocking vitamin K, so a sudden change in vitamin K intake can weaken or strengthen their effect. Anyone taking warfarin, acenocoumarol or phenprocoumon should check with their prescriber before starting a vitamin K supplement.

Our view

• The evidence has moved. Two 2026 randomized trials, in different patients and at different doses, found less coronary calcium progression: VitaK-CAC with K2 alone, and DANCODE with K2 plus vitamin D3. That is more than the earlier record of mostly null K2 imaging trials.
• It has not moved far. Both trials were in people who already had coronary calcium: symptomatic coronary artery disease in VitaK-CAC and severe calcification in DANCODE. The differences were modest, the outcome was a scan, and an earlier trial at the same dose did not slow aortic valve or coronary calcium. Marketing that says K2 "keeps calcium out of your arteries" or protects the heart goes beyond the data.
• If you have a raised calcium score, K2 is not a substitute for the treatments with outcome evidence: blood pressure and cholesterol control, not smoking, and the medicines your doctor recommends. These trials do not show that K2 treats coronary disease or prevents a heart attack. A cardiologist can say whether the scan results change anything in your own care.
• If you take K2 with vitamin D3, the D3 dose matters too. DANCODE used 25 mcg (1,000 IU) a day; check the D3 amount on any combination product against that.
• Wait for InterVitaminK before treating K2 as a prevention supplement for people without heart disease. Its results are expected after January 2027.

US advice

The National Academies set adequate intakes of 120 mcg a day for men and 90 mcg for women, and NIH data show most people in the US get enough from food. FDA has not authorized a health claim for vitamin K. Vitamin K is also sold on its own or with other nutrients, and some of those products contain much higher doses than multivitamins, up to 4,050 mcg. People taking warfarin need to keep their vitamin K intake from food and supplements consistent, so check with the prescriber or anticoagulation clinic before adding or stopping K2.

FAQ

Does vitamin K2 prevent heart attacks?

That has not been shown. The 2026 trials' main results are calcium on CT scans. They were not designed to show an effect on heart attacks, strokes or deaths, and a 2026 review of the earlier trials found no trial in which vitamin K reduced major cardiovascular events.

What dose was used in the trials?

VitaK-CAC used 360 mcg of MK-7 a day. DANCODE and AVADEC used 720 mcg of K2 with 25 mcg (1,000 IU) of vitamin D3. InterVitaminK uses 333 mcg of MK-7. These K2 doses are far above the amounts needed from the diet.

Is K2 better than K1?

MK-7 stays in the blood longer than vitamin K1, according to the NIH Office of Dietary Supplements. A 2026 review found that vitamin K1 had produced the more consistent, though still inconclusive, imaging results, particularly in some high-risk groups and in people on dialysis. There is no head-to-head outcome trial.

Can I take K2 with warfarin?

Not without medical advice. Vitamin K directly counteracts warfarin, and a change in intake can change how well it works. Talk to your anticoagulation clinic or prescriber first.