WASHINGTON – One of the many advertised benefits of vitamin D and fish oil supplements is that they reduce systemic inflammation, which in turn could help prevent certain chronic illnesses. However, a first-of-its-kind study published in AACC’s journal Clinical Chemistry has discovered that these two supplements do not actually reduce inflammation in healthy individuals, a finding that could help consumers make more informed choices about which supplements they decide to take.

Even though many supposed benefits of dietary supplements are unsubstantiated, these over-the-counter health aids are still wildly popular, with approximately half of all adult Americans taking at least one. Two of the most widespread supplements are vitamin D and marine omega-3 fatty acids taken in the form of fish oil. Both are touted for a wide variety of benefits, from improving bone health (in the case of vitamin D) to mental health (in the case of fish oil)—and the wellness industry has promoted both supplements as key to reducing systemic inflammation. Systemic inflammation occurs when the body chronically releases chemicals that are normally released during infection or injury, and it is a major underlying contributor to cardiovascular disease, diabetes, and other chronic conditions. The verdict is still out, however, on whether vitamin D and fish oil supplements truly lessen inflammation or if this claim is just another instance of the hype surrounding supplements. A number of small studies have tried to answer this question, but have yielded mixed results. 

In an effort to bring consumers more clarity on this issue, a team of researchers led by Karen H. Costenbader, MD, MPH, of Brigham and Women’s Hospital in Boston, Massachusetts, completed the largest study to date investigating the effect of vitamin D and fish oil supplements on systemic inflammation. This study involved 1,561 older Americans (defined as men age 50 and older, and women age 55 and older). For one year, 392 of the participants took both vitamin D and omega-3 fatty acids, 392 took vitamin D alone, 392 took omega-3 fatty acids alone, and 385 took a placebo. At the start and end of the study, the researchers measured participants’ vitamin D and omega-3 fatty acid levels for comparison purposes. They also assessed changes in participants’ levels of interleukin-6 (IL-6), tumor necrosis factor-receptor 2 (TNFR2), and high-sensitivity C-reactive protein (hsCRP), all of which are biological molecules that increase along with systemic inflammation.

From this, the researchers found that participants taking supplements experienced a 39% rise in vitamin D levels and a 55% rise in omega-3 fatty acid levels. However, TNFR2 and hsCRP levels did not significantly change over the course of the year in participants taking supplements, and IL-6 levels actually rose by 8% in participants taking vitamin D compared with those on the placebo. Altogether this indicates that, while vitamin D and fish oil supplements might still have other health benefits, they do not reduce inflammation in the general population and healthy individuals should not take them for this purpose.

“Vitamin D and marine omega-3 fatty acids are widely consumed supplements advertised to prevent disease and reduce systemic inflammation. Their purported health benefits have received enormous attention in the medical and popular presses,” said Costenbader. However, “in this study … neither vitamin D 2000 IU per day nor [omega-3 fatty acid supplements] reduced systemic inflammation biomarkers over one year. Thus, it is unlikely that these supplements, taken widely in the general population, have major anti-inflammatory effects.”

About AACC

Dedicated to achieving better health through laboratory medicine, AACC brings together more than 50,000 clinical laboratory professionals, physicians, research scientists, and business leaders from around the world focused on clinical chemistry, molecular diagnostics, mass spectrometry, translational medicine, lab management, and other areas of progressing laboratory science. Since 1948, AACC has worked to advance the common interests of the field, providing programs that advance scientific collaboration, knowledge, expertise, and innovation. For more information, visit www.myadlm.org.

Clinical Chemistry (clinchem.org) is the leading international journal of laboratory medicine, featuring nearly 400 peer-reviewed studies every year that help patients get accurate diagnoses and essential care. This vital research is advancing areas of healthcare ranging from genetic testing and drug monitoring to pediatrics and appropriate test utilization.