MADISON, N.J., July 17, 2012 /PRNewswire/ -- Raising vitamin D to optimal from deficient blood levels may not improve total cholesterol and other blood lipids, key markers of cardiovascular disease risk, according to a study published today in Circulation, a publication of the American Heart Association. The study, by researchers at Quest Diagnostics (NYSE: DGX) and The Rockefeller University, is the first large-scale examination of the clinical impact of correcting vitamin D deficiency on lipid levels and associated cardiovascular disease risk. "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," said lead investigator Manish Ponda, M.D., M.S., assistant professor of Clinical Investigation for The Rockefeller University's Laboratory of Biochemical Genetics and Metabolism. "This 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." An accompanying editorial in Circulation characterizes the study as having "great importance" for demonstrating that biomarkers, such as vitamin D, that are associated with disease risks in certain types of studies may not be found to cause those risks in other types of research. Optimal vitamin D levels associated with favorable lipids Heart disease is the number one killer of men and women in the United States, and individuals with high total cholesterol levels have twice the risk of heart disease as people with optimal levels. Several studies show an unfavorable association between deficient levels of vitamin D and cardiovascular disease markers such as total cholesterol and other lipids. However, randomized controlled studies are pending to assess if vitamin D deficiency is a cause or merely a marker of poor heart health and the effect of therapy to correct a deficiency. The researchers conducted two studies on patients tested for vitamin D and lipids by Quest Diagnostics in the United States. The first study involved a cross-sectional analysis of 107,811 patients to assess differences in lipid levels between those with optimal and deficient vitamin D levels. Cross-sectional studies evaluate a study population in one moment in time. The analysis found that patients with optimal levels of vitamin D, defined as 30 ng/ml or higher, had a statistically significant lower lipid risk profile, including lower overall total cholesterol, LDL ("bad") cholesterol and triglycerides, and higher HDL ("good") cholesterol, compared to those with deficient levels measuring less than 20 ng/ml.