Vitamin D Study

Measurement and other methods studies of vitamin D

Some epidemiologic studies have suggested that low vitamin D (25(OH)D) levels are associated with a wide range of cancer outcomes Because the evidence for the relationship between vitamin D and many cancers is limited, we and others in DCEG are engaging in a number of division studies, as well as participating in a multi-cohort pooling project, to assess the relationship between circulating vitamin D levels and subsequent cancer diagnoses.

In addition, because some benefits of vitamin D are firmly established, e.g., prevention of osteoporosis, and evidence is accumulating for the protective effects of vitamin D on other outcomes (e.g., colorectal cancer, heart disease), there are strong public health reasons for understanding how vitamin D status varies with outdoor time, diet, supplement use, etc. The USRT project is also planning a study to assess the determinants of circulating vitamin D by examining self-reported host skin characteristics, sun exposure, and supplement and dietary behavior.

The published and ongoing epidemiologic 25(OH)D studies differ in several potentially important methodological issues, including: (1) the time between blood collection and the centrifuging of the blood to separate out white and red cell components; (2) the type of collection tube and preservative used (no anticoagulant vs. heparin vs. EDTA); and (3) the type of assay used to measure 25(OH)D (radioimmunoassay (RIA) vs. Chemiluminescence (CLIA/Liason)). We are currently undertaking a small study to examine these three issues in blood samples donated by a group of 20 volunteers.