Many people know vitamin D as the “sunshine vitamin” because our bodies make it when our skin is exposed to sunlight.
Vitamin D is well known for helping build and keep strong bones, but it also supports the immune system, muscles, and many other parts of the body.
Over the past several years, scientists have also become interested in the possible role of vitamin D in protecting the heart and blood vessels.
People with low vitamin D levels have often been found to have a greater chance of developing heart disease, suffering a heart attack, or having a stroke.
However, studies testing vitamin D supplements have produced mixed results, leaving doctors uncertain about how much vitamin D people really need.
Now, researchers from Intermountain Health in Salt Lake City believe one important reason for these mixed findings may be that many studies simply used doses that were too low.
Their new research suggests that current vitamin D recommendations may not be enough for many people, especially those with heart disease or a high risk of future heart problems.
In the United States, adults are generally advised to get between 600 and 800 International Units (IU) of vitamin D each day. These recommendations were mainly designed to keep bones healthy and prevent vitamin D deficiency. The new studies suggest that the amount needed to support heart health may be different for some people.
The research team was led by epidemiologist Dr. Heidi May. According to Dr. May, many earlier clinical trials may not have raised participants’ vitamin D levels high enough to produce measurable heart benefits. If blood vitamin D levels remain too low, even after taking supplements, researchers may wrongly conclude that vitamin D does not help protect the heart.
The scientists found that many patients needed much larger daily doses than current guidelines recommend. Some participants required more than 10,000 IU a day before their blood vitamin D levels reached what the researchers considered a healthy target.
This does not mean everyone should take very high doses on their own. Too much vitamin D can also be harmful, so any high-dose treatment should only be done under medical supervision with regular blood tests.
Another member of the research team, Viet T. Le, explained that every person responds differently to vitamin D supplements. Age, body weight, existing health conditions, genetics, diet, medications, and even how much time people spend outdoors can all affect vitamin D levels. Because of these differences, one standard dose may work well for one person but not for another.
One of the main studies carried out by the team was called the Target-D trial. It included patients who had experienced a serious cardiovascular event, such as a heart attack, within the previous 30 days. Instead of giving every participant the same amount of vitamin D, the researchers adjusted each person’s supplement dose until their blood vitamin D level reached more than 40 nanograms per milliliter (ng/mL), which the team believed was the best target for heart health.
The results surprised the researchers. Nearly 90 percent of the participants needed vitamin D supplements to reach this goal. Many patients required three to six months, or even longer, before their vitamin D levels reached the target. Quite a few people needed doses much higher than current recommendations before their blood levels improved.
These findings suggest that future studies should focus on reaching healthy blood vitamin D levels rather than simply giving everyone the same dose. This approach fits with the growing idea of personalized medicine, where treatments are adjusted to meet each person’s individual needs instead of relying on one standard plan for everyone.
The researchers believe that future clinical trials using personalized vitamin D dosing may provide a clearer answer about whether improving vitamin D levels can reduce heart attacks, strokes, and other cardiovascular problems. If future studies confirm these findings, doctors may eventually reconsider current vitamin D recommendations for patients who have heart disease or who face a high risk of developing it.
For now, experts still advise people not to start taking very large vitamin D supplements without medical advice. Blood testing can help doctors determine whether someone is deficient and whether a higher dose is appropriate. The research highlights the importance of treating patients as individuals rather than assuming the same amount of vitamin D will work equally well for everyone.
The findings from these studies were presented by researchers from Intermountain Health, including Dr. Heidi May and colleagues, and included results from the Target-D trial. The work adds new evidence to the ongoing discussion about vitamin D and heart health and may help guide larger clinical studies in the future.
If you care about heart health, please read studies about the best time to take vitamins to prevent heart disease, and scientists find how COVID-19 damages the heart.
For more health information, please see recent studies about Aspirin linked to higher risk of heart failure, and results showing Blackcurrants could improve artery functions, blood pressure in older people.
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