Biomarkers A venous blood sample was collected at the start, at the change of filter types (end of week 3) and at end of the intervention (end of week 6). Samples were transported to the Human Nutrition Research Center on Aging (Tufts University, Boston campus), where they were processed to plasma and stored at minus 80 ºC within 1-3 h of collection. Participants were instructed to fast overnight prior to the blood draws (79% confirming fasting), which occurred between 8 and 10 AM. Samples were assayed in batches using immunoassay kits for TNF-RII (Quantitative, R&D Systems, Minneapolis, MN, USA) and IL-6 (Quantitative HS, R&D Systems). High sensitivity CRP (hsCRP) was measured by a solid-phase, two-site chemiluminescent immunometric assay, (IMMULITE 2000, Siemens Healthcare Diagnostics, Los Angeles, CA 90045). These biomarkers are a measure of the levels of systemic inflammation.