November 12, 2025, 4:14 pm | Read time: 7 minutes
Is vitamin D important for a healthy heart? This very question is the focus of research. With less than 40 percent of adults adequately supplied with the vitamin, it’s crucial to understand the consequences of a deficiency.1 Especially considering heart diseases, which are the leading cause of death in Germany.2
The “sunshine vitamin” vitamin D is increasingly being recognized as an all-around nutrient, not only important for bone health but potentially significant for the body and organs overall. For instance, one study found that adequate vitamin D supply reduces the risk of colon cancer, while another study highlighted the negative impact of vitamin D deficiency on brain function and health.
Also intriguing are the findings of a 2023 study published in the journal “Nutrients.” It concluded that vitamin D might also be important for the heart. Like a study in 2021, the 2023 study found that a vitamin D deficiency can increase the risk of heart disease. Whether eliminating a vitamin D deficiency could have positive effects on the heart was examined in a recent 2025 study. FITBOOK provides an overview of the research on vitamin D deficiency and heart health.
2023 Study: Is There a Connection Between Vitamin D Levels and Heart Disease?
This question was explored by a study from Switzerland. Researchers investigated the potential link between vitamin D levels and heart disease. They measured and monitored the vitamin D levels in the blood of 5,684 participants with an average age of 53, of whom 53 percent were female.
The vitamin D levels were categorized as:
- normal (≥75 nmol/L or 30 ng/mL)
- insufficient (50-74 nmol/L or 21-29 ng/mL)
- deficient (<50 nmol/L or 20 ng/mL)
The vitamin D measurements were then related to the occurrence of heart disease, deaths due to heart disease, and overall mortality. The follow-up period averaged 14 years.3
The Impact of Vitamin D Levels
During the 14-year follow-up, there were 568 cardiovascular events among the participants. There were 114 deaths related to heart disease and 679 deaths from other causes.
Statistical analysis showed that an increase in vitamin D levels (by 10 nmol/L) was associated with a lower risk of heart disease. Regarding mortality—both from heart disease and other health causes—vitamin D levels did not seem to play a significant role. No notable differences were observed among participants in the different vitamin D level groups.
Vitamin D Could Reduce Disease Risk, but Not Mortality Risk
According to the Swiss study, a vitamin D deficiency is associated with the risk of developing heart disease. Therefore, supplementation could help eliminate the deficiency and reduce the risk.
However, participants who developed heart disease could not significantly reduce the risk of dying from the disease with additional vitamin intake. A recent 2025 study has since provided new and different insights. More on that later.
The findings of the 2023 study expanded the understanding of vitamin D deficiency and heart disease. They supported, for example, an Australian study published in 2021.
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2021 Study: Vitamin D Deficiency Increases Risk of Heart Disease
Using a novel analytical approach, researchers at the University of South Australia identified vitamin D deficiency as an additional factor that can increase the likelihood of heart disease. They discovered this in a study involving 295,788 participants from the UK Biobank, aged 37 to 73, over three years. These participants not only completed questionnaires providing comprehensive health and lifestyle information at the start of the study, but also provided blood samples for biomarkers and genetic tests. Of all participants, 44,519 had cardiovascular disease. The researchers aimed to determine whether the diagnosis might also be related to low vitamin D levels.4
Vitamin D Levels Compared with Occurrence of Heart Disease
The research team then conducted a genetic test for each participant with complete information on 25(OH)D concentrations. The 25(OH)D level in blood serum is the established marker for vitamin D status. It was found that:
- 11.4 percent (32,868) of participants had concentrations below 25 nmol/L, indicating a deficiency.
- 41.3 percent (119,243) of participants had concentrations between 25 and 49.9 nmol/L, indicating a mild deficiency.
Less than half of the individuals were optimally supplied with vitamin D. It is estimated that one-third of Germans suffer from mild to severe vitamin deficiency.
Vitamin D Deficiency Increased Heart Disease Risk by 11 Percent
The researchers compared the results with a control group without heart disease. After thorough calculations, the scientists found that a vitamin D deficiency of 25 nmol/L or less increased the risk of heart disease by 11 percent. In individuals with 50 nmol/L or more, no increased risk was observed. “In our study population, we estimate that 4.4 percent of all disease cases could have been prevented by raising people with vitamin D deficiency to at least 50 nmol/L,” explained lead researcher Prof. Elina Hyppönen in a university statement.5 Interestingly, levels above 50 nmol/L had no significant impact. An oversupply of vitamin D in the sense of “more is better” apparently offers no advantage for heart health.
Cardiovascular Diseases Still the Leading Cause of Death
Cardiovascular diseases are estimated to be responsible for 17 million deaths worldwide each year.6 Vitamin D deficiency is also a widespread phenomenon. While many factors, such as family history and lifestyle, play a role in heart health, according to Hyppönen, “a population-wide approach to eliminating vitamin D deficiency could reduce the global burden of cardiovascular diseases.” Unfortunately, foods like fatty fish, eggs, and mushrooms are not enough to provide sufficient vitamin D. The body can only meet its daily needs with the help of sunlight—or in winter with a high-quality supplement. Therefore, it is all the more important for people beyond the equator to have their vitamin D levels checked regularly.
2025 Study: Eliminating Vitamin D Deficiency Reduced Heart Attack Risk
A new study presented at the “2025 American Heart Association Scientific Sessions” further expanded the understanding of the interplay between vitamin D and heart health. It examined whether eliminating a vitamin D deficiency could have a heart-protective effect.7
One limitation: It has not yet been independently peer-reviewed. This does not rule out that a review could uncover flaws in design and findings, but it does not necessarily mean this will happen.
In the new study, 630 individuals were examined, with an average age of 63. Seventy-eight percent were men, and 48 percent were women. All had already suffered a heart attack. Eighty-five percent of the participants had a vitamin D level below 40 ng/mL at the start of the study. The heart patients were randomly divided into two groups. One group received vitamin D in individualized dosages—so that each person reached a vitamin D level of at least 40 ng/mL but not over 80 ng/mL. The second group received no vitamin supplement. The observation period was four years. Every three months, researchers tested the participants’ vitamin D levels and adjusted the vitamin D intake dosage as needed to maintain the desired level.
Risk of Second Heart Attack Halved
The result is indeed impressive: Participants whose vitamin D levels were adjusted to between 40 ng/mL and 80 ng/mL had—compared to the control group—a 50 percent reduced risk of suffering a second heart attack.
It is not known whether the researchers sufficiently excluded other factors to ensure that vitamin D had the most significant influence. Moreover, it is still only an observation that the higher vitamin D level was associated with a lower incidence of heart attacks. A causal relationship has not yet been proven.