Researchers studied nearly 275,000 people to understand if low vitamin D levels increase the risk of atrial fibrillation, a condition where the heart beats irregularly. They found that people with very low vitamin D were about 1.8 times more likely to develop this heart rhythm problem compared to those with healthy vitamin D levels. The risk was even higher in people with the most severe vitamin D deficiency. This suggests that maintaining good vitamin D levels might be one way to protect your heart health, though more research is needed to confirm this connection.

The Quick Take

  • What they studied: Whether people with low vitamin D levels are more likely to develop atrial fibrillation (irregular heartbeat) compared to people with normal vitamin D levels
  • Who participated: 137,407 people in each group (matched for fairness), all age 40 and older, tracked between 2010 and 2023. One group had very low vitamin D (below 20 ng/mL), and the comparison group had healthy levels (30 ng/mL or higher)
  • Key finding: People with low vitamin D were 83% more likely to develop atrial fibrillation within 3 years. Those with the most severe deficiency had even higher risk (94% increase). This relationship held true even when researchers looked at people 3-6 years later
  • What it means for you: Getting enough vitamin D may help protect your heart rhythm. If you have low vitamin D, talking to your doctor about checking your levels and possibly increasing vitamin D intake could be worthwhile. However, this study shows a connection, not proof that vitamin D supplements will prevent heart problems—more research is needed

The Research Details

This was a longitudinal cohort study, which means researchers followed the same group of people over time to see what happened to them. They used a large database called TriNetX that includes health records from many hospitals and clinics across the United States. Researchers identified people who had their vitamin D levels measured at least twice between 2010 and 2023. They then compared two groups: people with sustained low vitamin D (below 20 ng/mL) and people with healthy vitamin D levels (30 ng/mL or higher). To make the comparison fair, they used a statistical technique called propensity score matching, which is like pairing up people who are similar in other ways (age, health conditions, medications) so the only major difference between groups was their vitamin D level. They then tracked both groups for up to 6 years to see who developed atrial fibrillation.

This research approach is stronger than previous studies because it followed real people over time rather than just taking a snapshot at one moment. By matching people carefully and using such a large number of participants (over 274,000), the researchers could be more confident that low vitamin D itself—not other differences between people—was connected to heart rhythm problems. The long follow-up period also showed the connection lasted over years, not just weeks or months

This study has several strengths: it’s very large (nearly 275,000 people), it followed people over many years, and it carefully matched groups to make fair comparisons. However, it’s still an observational study, meaning researchers watched what happened naturally rather than randomly assigning some people to take vitamin D and others not to. This means we can see a connection between low vitamin D and heart problems, but we can’t be completely certain that low vitamin D causes the problems. The study also relied on medical records, so some information might be incomplete

What the Results Show

The main finding was clear: people with low vitamin D had significantly higher rates of developing atrial fibrillation. Specifically, those with vitamin D below 20 ng/mL were 83% more likely to develop this heart rhythm problem within 3 years compared to people with healthy vitamin D levels. The risk increased with severity—people with the most severe deficiency (below 10 ng/mL) had a 90% increased risk, while those with moderate deficiency (10-20 ng/mL) had a 94% increased risk. Even people with mild vitamin D insufficiency (20-30 ng/mL) had a 60% increased risk. This dose-response pattern (where more severe deficiency meant higher risk) is important because it suggests a real biological connection rather than just a coincidence. The association remained strong even when researchers looked at people 3 to 6 years after the initial measurement, showing this wasn’t just a short-term effect.

Beyond heart rhythm problems, the study found that low vitamin D was also associated with increased risk of ischemic stroke (a type of stroke caused by blood clots) and pneumonia (a lung infection). These findings suggest that vitamin D may play a broader role in protecting overall health, not just heart rhythm. The researchers also discovered that the connection between low vitamin D and heart problems was stronger in people who also had dyslipidemia (abnormal cholesterol levels). In people with both low vitamin D and high cholesterol, the risk of heart rhythm problems was even higher than in people with just low vitamin D alone

Previous research on this topic had shown mixed results, with some studies suggesting a link between low vitamin D and heart rhythm problems while others found no connection. This new study is larger and more rigorous than most previous work, making it one of the strongest pieces of evidence so far that low vitamin D may increase heart rhythm risk. The findings align with what scientists know about vitamin D’s role in heart health—vitamin D helps regulate inflammation and affects how heart cells function. However, because earlier studies disagreed, this research adds important new information but doesn’t completely settle the question

While this study is large and well-designed, it has some limitations. First, it’s observational, meaning researchers couldn’t randomly assign people to have low or high vitamin D to prove cause-and-effect. Second, the study relied on medical records, which might not capture all relevant information about people’s health or lifestyle. Third, the study couldn’t determine why low vitamin D increases heart risk—it just showed the connection exists. Fourth, most participants were likely from the United States, so results might not apply equally to people in other parts of the world with different sun exposure or dietary patterns. Finally, the study couldn’t account for all possible factors that might affect both vitamin D levels and heart health

The Bottom Line

Based on this research, maintaining adequate vitamin D levels appears important for heart health. Current recommendations suggest vitamin D levels should be at least 20 ng/mL, with 30 ng/mL or higher considered optimal. You can increase vitamin D through sun exposure (10-30 minutes several times per week), eating vitamin D-rich foods (fatty fish, egg yolks, fortified milk), or supplements if recommended by your doctor. However, this study shows an association, not proof that vitamin D supplements will prevent heart problems. Before starting supplements, talk to your healthcare provider about whether your vitamin D level should be checked and what’s right for you personally. Confidence level: Moderate—this is strong evidence of a connection, but more research is needed to prove vitamin D supplements prevent heart rhythm problems

This research is most relevant to people age 40 and older, especially those with risk factors for heart disease, high cholesterol, or a family history of heart rhythm problems. If you have atrial fibrillation or are at risk for it, discussing vitamin D status with your doctor makes sense. People living in northern climates with less sun exposure, those who spend most time indoors, or those with certain medical conditions that affect vitamin D absorption should be particularly attentive to vitamin D levels. However, this doesn’t mean everyone needs vitamin D supplements—your doctor can help determine if testing and supplementation are right for you. This research shouldn’t replace other proven heart disease prevention strategies like exercise, healthy eating, and managing blood pressure

If you start optimizing your vitamin D level, don’t expect immediate changes. The study followed people for 3-6 years, suggesting that vitamin D’s protective effects develop over months to years, not weeks. If you’re deficient and start supplementing, it typically takes 2-3 months to significantly raise vitamin D levels. Any protective effect on heart rhythm would likely take even longer to become apparent. This is a long-term health strategy, not a quick fix

Want to Apply This Research?

  • Track your vitamin D intake sources weekly: record sun exposure time (in 10-minute increments), vitamin D-rich foods consumed, and any supplements taken. Note the date of your last vitamin D blood test and set a reminder to recheck levels annually or as recommended by your doctor
  • Set a weekly goal to get 2-3 sessions of moderate sun exposure (10-30 minutes) and include one vitamin D-rich food daily (such as salmon, fortified milk, or egg yolks). If supplementing, set a daily reminder to take your vitamin D supplement at the same time each day. Log these activities in your app to build consistency
  • Create a long-term tracking dashboard showing: (1) vitamin D blood test results over time with target range highlighted, (2) weekly vitamin D intake sources, (3) heart health markers if available (like heart rate regularity), and (4) overall cardiovascular risk factors. Review quarterly to ensure you’re maintaining adequate vitamin D and discuss results with your healthcare provider at annual checkups

This research shows an association between low vitamin D and increased heart rhythm problems, but does not prove that vitamin D deficiency causes atrial fibrillation. This information is for educational purposes and should not replace professional medical advice. If you have concerns about your vitamin D levels, heart rhythm, or any symptoms like irregular heartbeat, chest pain, or shortness of breath, consult your healthcare provider immediately. Do not start, stop, or change any medications or supplements without talking to your doctor first. Individual responses to vitamin D supplementation vary, and your doctor can determine the appropriate vitamin D level and supplementation strategy for your specific health situation.