Tea consumption, oxidative stress, and breast cancer risk Public Deposited

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  • March 21, 2019
  • Zhang, Dongyu
    • Affiliation: Gillings School of Global Public Health, Department of Epidemiology
  • Purpose: Oxidative stress, which features the imbalance between reactive oxygen species and antioxidant defenses, is associated with carcinogenesis. Tea contains natural antioxidants and has anti-tumor properties. However, limited epidemiologic studies investigated the association between tea and oxidative stress. Previous epidemiologic studies investigating tea and breast cancer risk have not addressed the potential for associations to vary by breast cancer subtype. Methods: The Sister Study is a nationwide cohort study that enrolled women across the US and Puerto Rico from 2003-2009. In aim 1, we included 889 premenopausal women from a nested case-control study within the Sister Study and investigated associations between black or green tea and oxidative stress which was measured by urinary F2-isoprostane (F2-IsoP) and a primary metabolite, 2,3-dinor-5,6-dihydro-15-F2t-isoprostane (15-F2t-IsoP-M). In aim 2, we investigated the association between black or green tea and breast cancer risk in the full cohort of 49,214 women. The analysis addressed variation by estrogen receptor (ER) status and other biologically important factors. Results: (Aim 1) We observed green tea was not associated with urinary F2-IsoP and 15-F2t-IsoP-M. Black tea was not associated with urinary F2-IsoP. However, drinking at least 5 cups of black tea per week (compared to 0 cup/week) was associated with a higher level of urinary 15-F2t-IsoP-M (geometric mean difference (GMD)=0.09, 95% CI 0.01, 0.17). Additionally adjusting for caffeine intake attenuated the association towards null (GMD=0.07, 95% CI -0.02, 0.16). (Aim 2) A total of 3,044 breast cancer patients were diagnosed from 49,214 participants. High-level black (hazard ratio (HR)=0.86, 95% CI 0.76, 0.98, ≥5 compared to 0 cups/week) and green tea (HR=0.84, 95% CI 0.73, 0.97, ≥5 compared to 0 cups/week) consumption were associated with a lower breast cancer risk. Both black and green tea consumption were inversely associated with ER+ breast cancer risk. Associations with ER- breast cancer risk were similarly inverse but non-significant. Conclusions: Contrary to previous experimental and clinical studies, we did not find an inverse association between black or green tea and oxidative stress. However, drinking at least 5 cups of black or green tea per week (compared to 0) was associated with a lower breast cancer risk.
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  • In Copyright
  • Troester, Melissa
  • Cai, Jianwen
  • Nichols, Hazel
  • Ferguson, Kelly
  • Bensen, Jeannette
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2018

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