The study, conducted by researchers at Quest Diagnostics and The Rockefeller University, is published in Circulation, a publication of the American Heart Association.
Lead researcher Manish Ponda, M.D., M.S., assistant professor of Clinical Investigation for The Rockefeller University's Laboratory of Biochemical Genetics and Metabolism, explained:
"Prior studies have associated low vitamin D level with an unhealthy lipid profile, but the effect of therapeutically correcting a vitamin D deficiency by itself on lipids is unclear.
The novel study on a large U.S. population suggests that correcting a vitamin D deficiency may not translate into a clinical benefit on the lipid profile. Patients should follow their physician's advice on whether vitamin D supplements are right for them."
According to a linked editorial in Circulation, the study is found to be of "great importance" for demonstrating that biomarkers like vitamin D, which are linked to risk of disease in certain studies may not be found to cause those risks in other types of research.
Cardiovascular disease is the leading cause of death in the United States, and people with high total cholesterol levels are 50% more likely to develop heart disease than those with optimal cholesterol levels.
Numerous studies show a negative association between heart disease markers, such as total cholesterol and other lipids, and deficient levels of vitamin D.
Researchers plan to conduct studies in order to evaluate whether low levels of vitamin D is a cause or simply a marker of poor cardiovascular health. In addition, they plan to assess the affect of therapy to correct a vitamin D deficiency.
The team conducted two studies on individuals tested for vitamin D and lipids by Quest Diagnostics in the US. In the cross-sectional study, the team examined 107,811 patients in order to compare lipid levels between patients with optimal vitamin D levels with patients deficient in vitamin D.
Optimal levels of vitamin D were defined as 30 ng/ml or higher, while deficient levels were defined as less than 20 ng/ml.
The team found that patients with optimal levels had a statistically significant lower lipid risk profile, including lower LDL (bad) cholesterol and triglycerides, and higher HDL (good) cholesterol.
Harvey W. Kaufman, M.D., senior medical director, Quest Diagnostics, said:
"Increases in vitamin D levels were associated with step-wise improvements in lipids. Although these findings support prior association studies, they do not demonstrate if vitamin D is a causal factor in lipid health or a passive marker for it."
In the longitudinal analysis study, the team examined data for 8,592 patients in order evaluated the affect of therapy to correct vitamin D deficiency on lipid levels.
They found that increasing vitamin D levels had a minimal effect on total and HDL cholesterol, but no significant impact on LDL cholesterol or triglycerides.
Dr. Ponda, explained:
"The seemingly conflicting findings of the cross-sectional analysis and longitudinal analysis suggest that while vitamin D deficiency is associated with an unfavorable lipid profile, correcting a deficiency through therapeutic vitamin D supplementation may have limited value in improving lipids."
Although randomized clinical trials (RCT) are believed to be the gold standard of therapeutic interventions and clinical research, they can take years to complete and require significant financial investment.
In this study, the researchers used sophisticated data mining techniques in order to examine Quest Diagnostics' de-identified dataset to provide insights on the therapeutic impact of correcting vitamin D levels.
According to Drs. Rolf Jorde and Guri Grimnes, the study is: "Of great importance as it underscores that cross-sectional results are not necessarily reproduced in prospective studies, and that cross-sectional data cannot and should never be taken as evidence for causality." In addition, they characterize it as "another approach that with its cost-effectiveness is highly attractive and similar study methods could be used by others with access to large databases with laboratory results."
Jan L. Breslow, M.D., Frederick Henry Leonhardt, Professor and head of The Rockefeller University's Laboratory of Biochemical Genetics and Metabolism, said: "In the absence of RCT, observational studies based on mining large clinical databases can provide important medical insights. Our novel, inexpensive analysis fills a major gap in current medical research on vitamin D. An analogous prospective, randomized, controlled trial would take years to complete and possibly be prohibitively expensive. While additional research is required to confirm our findings, our study provides clinically valuable insights to help guide patient management until these other trials are performed."
Written by Grace Rattue