Vitamin D: Daily supplements can improve heart health

• According to a new meta-study, an average supplemental dose of 3,320 IU of vitamin D per day is associated with reduced blood pressure, total cholesterol, hemoglobin A1C, and rapid blood insulin and glucose levels.
• The findings come from a new study of 99 randomized controlled trials from around the world investigating the benefits of vitamin D for heart health.
• A meta-study attempts to explain and debunk the sometimes conflicting findings about vitamin D.

A new, comprehensive review of the available, often conflicting, research on the benefits of vitamin D supplementation sheds new light on its importance in maintaining heart health.

The authors of the meta-study found that taking a median dose of 3,320 International Units (IU) of vitamin D per day, or about 83 micrograms, was associated with several important cardiometabolic benefits.

These benefits included reductions in systolic and diastolic blood pressure, total cholesterol, hemoglobin A1C—a marker of type 2 diabetes—and fasting blood glucose and insulin.

Researchers from China and the United States reviewed data from 99 randomized controlled trials (RCTs) published through March 26, 2024. The trials involved 17,656 participants and done among very different people in different parts of the world.

An important part of the meta-study was the list of differences between the RCTs that could explain their different conclusions. Once those differences were understood, the authors of the meta-study could re-examine and compare the data of RTCs in a balanced, apples-to-apples fashion.

The resulting investigations were not marred by controversy, and a few special cases involving specific individuals emerged.

Researchers found vitamin D supplementation provided the greatest benefit in non-Western people, people with low levels of circulating vitamin D in their blood, people with a BMI of less than 30, and people 50 years and older.

Simin Liu, MD, ScD, professor of epidemiology, surgery and medicine at Brown University, Providence, RI, and co-author of the meta-study, described some of the ways in which RCTs differ that led to their findings. in different places. decisions.

“Several main sources of variation in previous studies that have led to conflicting findings related to the contribution of cardiovascular risk factors include the cultural background, age, weight and circulation of study participants 25.[OH]D in terms of registration,” he said.

Jayne Morgan, MD, a cardiologist and Senior Director of Health and Community Education at Piedmont Healthcare Corporation in Atlanta, GA, who was not involved in the meta-study, noted another reason doctors lack confidence. in relation to vitamin D alone. I hope.

“Although there are many studies that show a link between vitamin D intake and a lower risk of heart disease, there is still a lack of direct cause and effect. Furthermore, although low serum vitamin D levels are associated with increased cardiovascular risk, it remains unclear whether this is a cause or a contributor to cardiovascular disease, or rather a consequence of heart attack.
— Jayne Morgan, MD

However, “Here is where the data depends but [there is] nothing is clear about the ends of the heart. So while there are no evidence-based data standards here, it really comes down to an evidence-based knowledge metric,” Morgan said.

In addition, there are benefits for bone health, muscle function and reduced inflammation. There may be positive effects on blood pressure, diabetes and lipids are also important to watch,” he added.

“Non-Western people have lower levels of circulating vitamin D, and therefore have a greater chance of benefiting from vitamin D supplementation,” said Liu. The same goes for people whose BMI is less than 30 kg·^m−2.

“Similarly, serum vitamin D levels tend to decrease with age, which may explain the significant cardiometabolic improvement effect observed with vitamin D supplementation in people 50 years and older, ” he added.

Morgan said all this “seems to show that ‘catching’ can be an important part of the game.”

“Meaning, those who didn’t have low vitamin D to begin with, and those who only improved their levels, had less of an effect and lowered the needle than those who had ‘covered a lot’ of raising the level. they see. [vitamin D] blood levels because they started very low,” he explained.

Liu said that even with the positive associations seen for 3,320 IU of vitamin D per day for most people, the racial differences observed in the meta-study suggest that, “There is certainly a in the saying, ‘one size does not fit all.’

“Achieving optimal levels of vitamin D for cardiovascular health will require careful analysis of individual cultural background and biological factors to implement individualized strategies,” said Liu.

He noted that, according to the findings of the meta-study, people who are obese and under 25.[OH]D levels may require higher doses of vitamin D and longer durations.

“We may need to test for higher levels of vitamin D with a longer intervention period to see if the effects on heart health in different populations differ with the selected variables. in our study: cultural background, age, weight, and circulation of study participants 25[OH]D in enrollment status,” said Liu.