Vitamin D, Heart Attacks and Arterial Plaque: What the Evidence Actually Shows

Vitamin D is essential for bone health, but it has also attracted considerable interest as a possible way to protect the heart. Some observational studies associate low vitamin D levels with cardiovascular disease, and laboratory research suggests several plausible biological mechanisms.

But an association is not proof of cause and effect. Does raising vitamin D actually prevent heart attacks? Does reaching 50 ng/mL offer more protection than reaching 30 ng/mL? And can vitamin D slow the progression of arterial plaque?

The evidence is more complicated than many online claims suggest.

1. Does Vitamin D Supplementation Prevent Heart Attacks?

The largest randomized trials have produced mostly null results for cardiovascular prevention, although one major trial found a potentially important signal.

The VITAL trial: More than 25,000 US adults were randomized to take 2,000 IU of vitamin D3 daily or a placebo. Supplementation did not significantly reduce major cardiovascular events. Among participants whose vitamin D levels were measured at baseline, the average was 30.8 ng/mL; only 12.7% had levels below 20 ng/mL. The trial therefore tells us much more about supplementation in a largely vitamin-D-replete population than about treating severe deficiency.

A 2019 meta-analysis: An analysis of 21 randomized trials involving more than 83,000 participants found no significant reduction in major cardiovascular events, heart attacks, strokes, or cardiovascular death from vitamin D supplementation.

The D-Health trial: Published in The BMJ in 2023, this Australian trial included 21,302 adults aged 60–84 in its analysis. Participants received 60,000 IU of vitamin D3 monthly or a placebo for a median of five years.

Major cardiovascular events occurred in 6.0% of the vitamin D group and 6.6% of the placebo group. The hazard ratio was 0.91 (95% confidence interval 0.81–1.01). The primary result was not statistically significant.

Heart attacks, a secondary outcome, were less frequent in the vitamin D group: hazard ratio 0.81 (95% CI 0.67–0.98). However, the investigators examined numerous outcomes, and the heart-attack result was not adjusted for multiple comparisons. It should therefore be treated as a promising signal, not definitive proof.

The trial also found a potentially stronger result among participants taking statins or other cardiovascular medications. But the subgroup interaction tests were not statistically significant, meaning the apparent difference could have occurred by chance.

TARGET-D: A New Study Raises Hope for Preventing Repeat Heart Attacks

The TARGET-D trial, published in the European Heart Journal in September 2026, studied 630 people who had recently experienced a heart attack. Researchers adjusted vitamin D supplementation to target blood levels of 40–80 ng/mL, rather than giving everyone the same dose.

• Heart attacks: Occurred in 3.8% of the targeted vitamin D group versus 7.9% of the usual-care group.
• Primary combined outcome: Death, heart attack, hospitalization for heart failure, or stroke occurred in 15.7% versus 18.4%. This difference was not statistically significant (HR 0.85, 95% CI 0.58–1.24; P=0.40).

The heart-attack result was a secondary outcome. It is encouraging but not conclusive: the trial's primary outcome was not statistically significant, and further research is needed to establish whether targeted vitamin D treatment reduces repeat heart attacks.

These participants had recently suffered a heart attack. The study does not establish that the same target benefits healthy people or everyone with coronary artery disease. It did not directly compare a vitamin D level of 30 ng/mL with 50 ng/mL, nor prove that a particular level prevents heart attacks. The 40–80 ng/mL range was a study target—not a proven universal treatment target.

TARGET-D concerns cardiovascular events, not direct measurements of plaque progression or coronary artery calcium. Its findings do not show that vitamin D stops plaque or slows coronary calcification.

Taken together, D-Health and TARGET-D leave open the possibility of cardiovascular benefit in selected groups, including fewer repeat heart attacks after a recent heart attack. But neither trial's primary outcome was statistically significant. These findings support further research, not treating vitamin D as proven heart-attack prevention.

2. What About Plaque Formation and Progression?

Vitamin D influences inflammation, calcium metabolism, and other biological processes relevant to blood vessels. Those mechanisms make a protective effect plausible—but biological plausibility does not establish a clinical benefit.

A 2024 Scientific Reports Mendelian randomization study examined genetically predicted vitamin D status and several measures of atherosclerosis. It found no statistically significant association with carotid artery plaque (odds ratio 0.99, P=0.91), coronary artery calcium, or carotid intima-media thickness.

Mendelian randomization uses genetic differences to investigate possible causal relationships. It has limitations, and it is not a substitute for a supplementation trial, but these findings do not support the idea that higher vitamin D status automatically protects against plaque.

There is an important nuance: a separate nonlinear Mendelian randomization analysis found an L-shaped relationship between vitamin D and cardiovascular risk. Risk declined as predicted vitamin D levels rose from low values, then largely flattened around 50 nmol/L—equivalent to 20 ng/mL. This supports investigating and correcting deficiency, not pushing levels progressively higher. Genetic analyses also cannot prove that supplements will reproduce the same effects.

The key distinction: Evidence suggesting that severe deficiency may be harmful does not demonstrate that raising an already adequate level from 30 to 50 ng/mL prevents additional plaque.

3. What Does the Research Say About Coronary Calcium?

Coronary artery calcium (CAC) is a marker of calcified plaque burden. It is useful for assessing cardiovascular risk, but it does not measure every component of plaque or directly reveal how vulnerable a particular plaque is.

A 2010 Women's Health Initiative substudy followed 754 women who had been randomized to 1,000 mg of calcium plus 400 IU of vitamin D3 daily or placebo. After an average of about seven years, CAC scores did not differ significantly between the groups. The results among women with more than 50% adherence were also similar. Because the vitamin D dose was relatively low and calcium was given at the same time, this study cannot isolate vitamin D's effect or settle what higher doses might do.

The DANCODE trial: an important new finding, with limits

A trial published in Circulation in August 2026 offers new evidence worth watching.

DANCODE randomized 398 participants with severe coronary calcification—CAC scores of at least 400—to receive either vitamin K2 (720 micrograms daily) plus vitamin D3 (1,000 IU daily), or placebo, for 24 months. Participants had a median age of 71, a median starting CAC score of 903, and 44% had CAC scores of at least 1,000.

The main results were:

• CAC progression: The average increase was 196 Agatston units with vitamin K2 plus D3, compared with 248 units with placebo.
• Difference between groups: −52 Agatston units (95% CI −79 to −24).
• CT angiography subgroup: Among 143 participants, progression of calcified plaque volume was lower by 8 mm³ (95% CI −13 to −2).
• Other plaque measures: Total plaque volume increased similarly in both groups, and there was no difference in noncalcified plaque volume.

These are measurable differences in calcification progression. But the study does not establish that the combination prevents heart attacks, reduces total plaque burden, or makes existing plaque disappear. Most importantly, because the trial combined vitamin K2 with vitamin D3, we cannot tell how much—if any—of the effect came from vitamin D alone.

Earlier trials of vitamin K and D combinations have produced mixed findings. A 2023 randomized trial found no statistically significant reduction in overall CAC progression, although a subgroup with CAC scores of at least 400 had less progression. A 2023 systematic review found a possible benefit from vitamin K supplementation but emphasized the need for better-designed trials.

DANCODE strengthens the case for further research. It does not establish a new vitamin D blood-level target or justify recommending this supplement combination as proven cardiovascular treatment.

Safety note: Vitamin K2 can interact seriously with warfarin and similar vitamin K-antagonist anticoagulants. Anyone taking these medicines should not start K2 supplements without discussing it with their prescribing clinician.

4. Why Can Calcium Increase During Statin Treatment?

This is particularly relevant to people with high CAC scores.

Statins reduce LDL cholesterol and can reduce lipid-rich plaque and promote changes associated with more stable plaque composition. Imaging studies have found that statin treatment can be associated with greater plaque calcification or calcium density even as other aspects of plaque improve.

That does not mean a rising CAC score is harmless. CAC remains a marker of atherosclerotic burden and cardiovascular risk. Nor can a higher score alone tell us whether an individual plaque has become more or less dangerous.

The important point is that CAC progression and plaque vulnerability are not the same thing. Statins have strong evidence for reducing cardiovascular events; vitamin D does not have comparable evidence as a plaque-stabilizing or heart-attack-prevention treatment.

5. Is a Vitamin D Level of 50 Better Than 30?

There is no established evidence that a blood level of 50 ng/mL provides better heart protection than 30 ng/mL.

The 2024 Endocrine Society guideline concluded that clinical trials have not established specific vitamin D blood-level targets for preventing disease in generally healthy adults. The US National Institutes of Health notes that 20 ng/mL or higher is sufficient for most people for bone and overall health, while levels above 50 ng/mL can be associated with adverse effects. These are general reference points, not universal treatment targets for every medical condition.

Some people may have a clinical reason to aim for a different level. Deficiency, certain bone disorders, malabsorption, kidney problems, and other individual circumstances can change what is appropriate.

The honest conclusion is narrower: research has not shown that raising an already adequate level from 30 to 50 ng/mL prevents heart attacks or slows coronary plaque progression. The nonlinear genetic evidence suggests that correcting low levels may matter more than raising adequate levels further, but it does not prove a particular supplement dose will prevent cardiovascular events.

6. What Should People With Coronary Artery Disease Do?

For people with established coronary artery disease or high CAC scores, the priorities remain interventions with strong evidence for reducing cardiovascular risk:

• Manage LDL cholesterol and other atherogenic lipoproteins with an individualized treatment plan.
• Control blood pressure and diabetes when present.
• Avoid tobacco, remain physically active within appropriate limits, and follow a sustainable heart-healthy diet.
• Correct vitamin D deficiency when clinically indicated, but do not treat a higher vitamin D number as a substitute for proven cardiovascular prevention.

If you have a high CAC score, DANCODE is an interesting development to follow—but it is not yet a reason to start high-dose vitamin D or vitamin K2 specifically to slow coronary calcification. Discuss supplements and target levels with your healthcare professional, especially if you take anticoagulants or have conditions affecting calcium or kidney function.

What the new evidence changes: TARGET-D raises the possibility that targeted vitamin D treatment could reduce repeat heart attacks in selected patients who recently had a heart attack. The heart-attack finding was secondary, however, and the primary combined outcome was not statistically significant. Further research is needed. This is separate from the evidence on plaque progression and coronary artery calcium: TARGET-D does not show that vitamin D stops plaque, establish that 50 ng/mL is better than 30 ng/mL, or make 40–80 ng/mL a proven universal target.

Evidence label: MIXED — strong evidence against a proven 30-versus-50 ng/mL cardiovascular target; limited evidence for cardiovascular event prevention, including TARGET-D's encouraging secondary heart-attack finding despite a primary outcome that was not statistically significant; emerging evidence for slower CAC progression with combined K2 and D3 in people with severe calcification. Further research is needed before targeted vitamin D treatment can be considered proven prevention for repeat heart attacks.