Tea consumption and oxidative stress: a cross-sectional analysis of 889 premenopausal women from the Sister Study

Br J Nutr. 2018 Dec 20;1-23. doi: 10.1017/S0007114518003732. Online ahead of print.

Abstract

In experimental and clinical studies, green or black tea consumption has been shown to reduce oxidative stress. However, these studies involved high levels of tea consumption and may not reflect patterns in the general population. Here we examined the association between black or green tea consumption and oxidative stress in a cross-sectional study of 889 premenopausal U.S. women aged 35–54 years. Tea consumption was measured using the Block-98 food frequency questionnaire. Urinary 8-iso-prostaglandin F (F2-IsoP) and 2,3-dinor-5,6-dihydro-15-F2t-isoprostane (15-F2t-IsoP-M) were used as biomarkers of oxidative stress. These compounds were measured by mass spectrometry and normalized to creatinine. Linear regression was used to calculate geometric mean differences (GMD) and 95% confidence intervals (95% CI) for log-transformed urinary F2-IsoP or 15-F2t-IsoP-M in relation to black or green tea consumption. We further examined whether adjusting for caffeine impacted associations between tea and oxidative stress. Geometric means of urinary F2-IsoP and 15-F2t-IsoP-M were 1.44 (95% CI 1.39–1.49) and 0.71 (95% CI 0.69–0.73) ng/mg Cr, respectively. Overall, green tea consumption was not associated with urinary F2-IsoP or 15-F2t-IsoP-M. High-level black tea consumption (≥5 cups/week compared to 0) was associated with higher 15-F2t-IsoP-M concentrations (aGMD=0.10, 95% CI 0.02–0.19) but not F2-IsoP. Adjusting for caffeine nullified the association between black tea and 15-F2t-IsoP-M. Our findings do not support the hypothesis that dietary tea consumption is inversely associated with oxidative stress.