Study: High Doses of Vitamin D Do Not Improve Heart, Circulatory Health

Vitamin D may strengthen bones, boost immune function, and support heart health; however, high doses of the vitamin do not improve heart and circulatory health for most adults any more than modest doses do, according to a study funded by the National Institutes of Health.

“It takes only small-to-moderate amounts of vitamin D to have optimal cardiovascular function,” said study author JoAnn E. Manson MD, DrPH, chief of the division of preventive medicine at Brigham and Women’s Hospital and Harvard Medical School, in a press release. “More is not better.”

Ongoing research has found that adults who take either moderate- or high-dose daily vitamin D supplements of approximately 1000 IU do not have a lower risk for heart attack, stroke, or cardiovascular-related death compared to adults administered a placebo without vitamin D.

Additionally, the new data found that vitamin D supplements do not offer support prevention of a number of health issues as is commonly believed. For example, higher vitamin D intake has not been found to prevent cancer, bone fractures, or falls, and have not alleviated knee pain, cognitive decline, or atrial fibrillation, among other conditions.

The National Academy of Medicine recommends a daily intake of 600 IU vitamin D for people between 1 to 70 years of age, and 800 IU for adults 71 years of age and older. However, Manson added it was reasonable for adults who were concerned about not getting enough vitamin D to take a daily supplement of 1000-2000 IU during the COVID-19 pandemic.

With all of this information, the best way to consume vitamin D is to get incidental sun exposure, which includes being physically active outdoors, eating vitamin-D rich foods, and reading nutrition labels to make sure the right amount is obtained.

To assess heart health, the researchers conducted randomized, controlled trials, including the VITAL trial. Between 2011 and 2013, more than 25,000 adults were enrolled in VITAL, which found that high-dose vitamin D supplements did not prevent cardiovascular events.

After an extensive review of 21 randomized trials, Manson found that both vitamin D and cardiovascular disease, “did not show clear benefits of vitamin D supplements in preventing heart disease or stroke.”

Elements such as exercise, diet, and levels of inflammation were all targeted as reasons that adults with higher vitamin D levels have been less likely to have cardiovascular disease in observational studies.

Researchers are now focusing on how high-dose vitamin D supplements may support immune function in people with autoimmune conditions, including rheumatoid arthritis, lupus, and psoriasis. Other types of research around this topic include whether vitamin D can reduce the severity of COVID-19 infections, shorten recovery, and lower the risk of long COVID-19.

Further, vitamin D is being studied to see whether higher intake may slow its progression and reduce cancer-related deaths.

“There may be subgroups of patients who are at higher risk for adverse cardiovascular outcomes who may benefit from vitamin D supplementation,” said Alvin A. Chandra, MD, VITAL researcher and assistant professor in the division of cardiology at the University of Texas Southwestern Medical Center, in a press release.

Other areas of study that are being evaluated are:

• Skin color and its relation to vitamin D and sun exposure
• Aging
• Allergies
• Underlying conditions, such as Crohn disease and celiac disease
• How vitamin D interacts with other nutrients
• Genetic links to vitamin D in terms of how the vitamin is metabolized and binds to receptors

REFERENCE

Vitamin D for heart health: where the benefits begin and end. NIH. September 27, 2022. Accessed October 10, 2022. https://www.nhlbi.nih.gov/news/2022/vitamin-d-heart-health-where-benefits-begin-and-end