A new, comprehensive review of existing, often conflicting, research on the benefits of vitamin D supplementation extracts a fresh view of its value in maintaining cardiometabolic health.
The researchers from China and the United States examined the details of 99 randomized, controlled trials (RCTs) published until March 26, 2024. The trials involved 17,656 participants and were conducted among widely varying populations in various global locations.
A key component of the meta-study was a cataloging of differences between the RCTs that might explain their varying conclusions. Once those differences were understood, the authors of the meta-study could re-analyze and compare the RTCs’ data in a more balanced, apples-to-apples manner.
The resulting findings were less hampered by conflicts, and a few special cases relating to specific populations emerged.
Simin Liu, MD, ScD, professor of epidemiology, surgery, and medicine at Brown University, Providence, RI, and corresponding author of the meta-study, described some ways in which the RCTs differed from each other that caused them to arrive at different conclusions.
“Several main sources of heterogeneity in earlier studies that led to conflicting findings relating supplementation to cardiometabolic risk factors included ethnocultural background, age, body weight, and study participants’ circulating 25[OH]D levels at enrollment.
Jayne Morgan, MD, cardiologist and the Executive Director of Health and Community Education at the Piedmont Healthcare Corporation in Atlanta, GA, who was not involved in the meta-study, noted another reason the medical community is not as confident regarding vitamin D as one might hope.
The study is published in the journal Engineering. Non-Westerners have relatively lower circulating vitamin D levels, and thus have a higher likelihood of benefiting from vitamin D supplementation.
The same is true of people whose BMI is less than 30 kg· Similarly, serum vitamin D levels tend to decrease with age, which may explain the more significant cardiometabolic improving effect observed with vitamin D supplementation in people aged 50 and older. Meaning, those without low levels of vitamin D to start, and who only enhanced their levels, had less of an effect and moved the needle less than those who ‘covered more ground’ in raising their [vitamin D] blood levels because they started so low.
Further, there are benefits on bone health, muscle function, and reduced inflammation. It’s possible positive effects on both hypertension, diabetes, and lipids are worth watching as well.
Achieving optimal levels of vitamin D for cardiometabolic health would require careful assessment of each person’s ethnocultural background and biological features to implement personalized intervention strategies.
He noted that, according to the meta-study’s findings, people with obesity and low 25[OH]D levels would likely need higher vitamin D doses and for longer durations.
