Taking This Vitamin for Years Could Lower Your Risk for a Dangerous Heart Problem

Atrial fibrillation—often just called “AFib” or AF—is a common heart rhythm disorder that causes an irregular and very fast heart rate. Having AFib can make your heart beat more than 400 beats per minute. For comparison, a normal resting heart rate ranges from 60 to 100 beats per minute.

Over time, having AFib raises your risk for health problems like blood clots, stroke, heart failure, and other heart-related complications. There are a few things that you can do to lower your risk of AFib, and a new study has just found another possibility: a higher dose of a vitamin you might already be taking.

“The 5-year high-dose vitamin D supplementation reduced the incidence of atrial fibrillation (AF) compared to the placebo group,” Jyrki Virtanen, PhD, the study’s lead author and associate professor of nutrition and public health at the University of Eastern Finland Institute of Public Health and Clinical Nutrition, told Verywell. “As AF is very common, especially among the elderly, it is important to find ways to prevent it.”

Here’s what experts say about the study, the benefits and risks of taking high doses of vitamin D, and other ways that you can reduce your risk of AFib.

High-Dose Vitamin D and AFib

The recent study included 2,495 healthy older adults who were considered “vitamin D sufficient”—meaning that they did not have a deficiency in the vitamin. The average age of the participants was 68.2 years and 43% of them were women.

The participants were randomly put into three groups: one placebo group and two groups that received vitamin D3 supplementation.

One of the groups took a supplement of 40 micrograms (1,600 IU) per day, and the other group took a supplement of 80 micrograms (3,200 IU) per day. The participants were also allowed to keep taking a personal vitamin D supplement (up to 20 micrograms (800 IU) per day).

During the 5-year study, the researchers noted that 190 participants were diagnosed with AFib: 76 in the placebo group, 59 in the 40 micrograms group, and 55 in the 80 micrograms group.

The study also showed that compared to the placebo group, the risk of AFib was 27% lower in the 40 micrograms group, and 32% lower in the 80 micrograms group.

Why Would Taking Vitamin D Help Your Heart?

It’s not yet known why vitamin D would reduce a person’s risk for AFib, but Crystal Scott, RD, LD, a certified registered dietitian at Top Nutrition Coaching, told Verywell that it could be because the nutrient is involved in many processes in your body that affect your heart.

According to Scott, vitamin D plays a role in regulating blood pressure, inflammation in the body, and the renin-angiotensin-aldosterone system—all of which are key factors in heart health. By reducing inflammation and improving blood vessel function, Scott said that vitamin D “may help decrease the risk of AFib.”

Amber Core, RD, a registered dietitian at The Ohio State University Wexner Medical Center, told Verywell that vitamin D also helps with the absorption of calcium—a nutrient that’s not just needed for healthy bones but also for heart muscle function.

“Low levels of calcium in the body can lead to an irregular heartbeat, such as AFib,” Core said. “In this way, low vitamin D can indirectly be linked to irregular heartbeats. By taking a vitamin D supplement, we can mitigate some of these concerns around AFib.”

Abhijeet Singh, MD, a clinical cardiac electrophysiologist at the Stony Brook Heart Institute, told Verywell that low vitamin D levels could also lead to scarring (fibrosis) in the left atrium of the heart, which can contribute to the risk for arrhythmias like AFib.

According to Singh, “low vitamin D has been associated with developing hypertension, which is a risk factor for developing AFib.”

How Much Vitamin D Should You Take?

Virtanen said that more research is needed to confirm the study’s findings and determine if doses of vitamin D that are above the current guidelines could be recommended for preventing AFib.

“The greatest reduction in AF incidence was seen in the 80-microgram group, but the risk was also reduced in the 40-microgram group, so it is difficult to say the exact dose from a study like this that would be needed for AF prevention,” he said.

According to Scott, these recommendations are based on maintaining bone health and ensuring adequate vitamin D levels for most individuals.

“However, it’s essential to understand that individual vitamin D needs may vary based on factors such as sun exposure, dietary intake, age, sex, skin color, geographic location, and overall health,” she added.

What Are the Risks of Taking Too Much Vitamin D?

According to Core, most people can get vitamin D from their food and sunlight exposure. In cases where people are not able to meet their daily requirements through these methods, supplements can be helpful.

“It would be nearly impossible to get too much vitamin D from natural resources alone, such as fortified dairy milk or fatty fish like salmon. Since most foods do not contain enough vitamin D and many people do not get adequate sunlight, taking a supplement can prevent deficiency,” said Core.

However, since vitamin D is a fat-soluble vitamin (meaning that it dissolves in fats and oils), Singh said that it has the potential to cause side effects if it’s taken at high doses.

“There are certainly downsides to taking higher than required doses of vitamin D as it can increase calcium levels in blood and urine. Increased calcium in the blood can lead to dehydration, loss of appetite, and vomiting,” said Singh.

Scott said that excessive intake of vitamin D can lead to toxicity (hypervitaminosis D). Extremely high levels can also cause kidney failure, irregular heartbeat, and even death.

According to Scott, these risks are why you have to talk to your healthcare provider before you start upping your vitamin D supplementation—especially if you have a heart condition or other health concerns.

Core said that it’s also important to know that some medications can interact with vitamin D, such as medications for cholesterol or blood pressure. You should always ask your provider before starting a supplement and may want to have your provider check your vitamin D levels to see if you actually need to supplement.

How Can You Lower Your AFib Risk?

One of the most important things you can do to reduce your risk of AFib is to live a heart-healthy lifestyle. Here are some expert-recommend tips:

• Eating a nutritious diet that is low in salt, saturated fats, trans fats, and cholesterol. 
• Engage in regular physical activity for at least 150 minutes a week. 
• Limit how much alcohol and caffeine you have (substances that can increase blood pressure and heart rate).
• Get to and maintain a weight that supports your health.
• Quit smoking. 
• Keep your cholesterol and blood pressure levels in check.
• Manage other medical health conditions such as high blood pressure (hypertension) and diabetes. 

“The risk of AF increases with age, but unfortunately, we cannot stop that,” Virtanen said. “Other known risk factors for AF are low physical activity, obesity, diabetes, and high blood pressure, so keeping those under control could also help reduce AF.”