Are dietary antioxidant intake indices correlated to oxidative stress and inflammatory marker levels?

Epidemiologic and experimental studies have shown that a high intake of individual dietary antioxidants is associated with a reduced risk of cancers. Few studies, however, have investigated the influences of a combination of dietary antioxidants. We evaluated the association of two dietary antioxidant indices, the Dietary Antioxidant Quality Score (DAQS) and the Composite Dietary Antioxidant Index (CDAI), with 10 oxidative stress or inflammation biomarkers (urinary F2-isoprostanes [15-F2t-IsoP]; urinary F2-isoprostane metabolites [15-F2t-IsoPM]; urinary prostaglandin E2 metabolite [PGEM]; C-reactive protein [CRP]; interleukin-1beta [IL-1β]; interleukin-6 [IL-6]; tumor necrosis factor-alpha [TNF-α]; soluble TNF-receptor 1 [sTNF-R1]; soluble TNF-receptor 2 [sTNF-R2]; and soluble GP130 [sGP130]) in 3853 participants of the Shanghai Women's Health Study (SWHS). We found the DAQS and CDAI to be highly correlated (r=0.72), and both were inversely associated with levels of IL-1β (ptrend=0.02 and 0.03, respectively) and TNF-α (ptrend=0.005 and 0.003, respectively). In addition, IL-6 and sTNF-R2 levels were inversely associated with the DAQS score; β-coefficient(±SE) for average-quality and high-quality group versus low-quality group were -0.22(±0.13) and -0.30(±0.13) (ptrend=0.06) for IL-6; -0.06(±0.04) and -0.10(±0.04) (ptrend=0.01) for sTNF-R2. Neither the DAQS nor CDAI score was significantly associated with oxidative stress or other inflammatory biomarkers. Our observations lead us to hypothesize that these two indices offer a potential aggregate method of measuring dietary anti-inflammation, but not anti-oxidation properties.