Michikawa 2011.

Study characteristics
Methods	Cohort study in Japan
Participants	Participants: 140,420 (male/female: 68,722/71,698), with 61,595 from cohort 1 and 78,825 from cohort 2 and 100,507 (male/female: 48,802/51,705) participants with complete data. Inclusion criteria: aged 40‐59 years, from 5 Public Health Centre areas (Iwate, Akita, Nagano, Okinawa and Tokyo) for cohort 1, and aged 40‐69 years for cohort 2 from 6 Public Health Centre areas (Ibaraki, Niigata, Kochi, Nagasaki, Okinawa and Osaka), respondent at 5‐year follow‐up. Katsushika Public Health Centre was excluded due to missing cancer data. Parent cohorts Cohort 1: Japan Public Health Centre‐based Prospective Study (JPHC)‐I Cohort 2: Japan Public Health Centre‐based Prospective Study (JPHC)‐II Recruitment: from 1990 for cohort 1 and 1993/1994 for cohort 2
Interventions	N/A
Outcomes	Number of cases Outcome assessment: 31 December 2007 Thyroid cancer: 159 (male/female: 26/133) cases, including 133 cases of papillary carcinoma, 7 cases of follicular carcinoma, 1 case of anaplastic carcinoma and 18 cases of other or unknown histologic types
Green tea in exposure categories	Exposure assessment: green tea drinking Lowest exposure: < 1 cup/d Intermediate exposure 1: 1‐2 cups/d Intermediate exposure 2: 3‐4 cups/d Highest exposure: ≥ 5 cups/d
Notes	Funding: Grant‐in‐Aid for Cancer Research from the Ministry of Health, Labour and Welfare, Japan (until 2009) and by Management Expenses Grants from the Government to the National Cancer Center (since 2010). It has also supported by a Grant‐in‐Aid for the Third‐Term Comprehensive Control Research for Cancer from the Ministry of Health, Labour and Welfare, Japan and by a Grant‐in‐Aid from Keio Medical Association. Statistical methods: Cox proportional hazard regression Variables controlled in analysis: age, area, smoking history, passive smoking in the workplace, alcohol consumption, BMI, consumption of green vegetable and seaweed, health screening in the previous year and coffee consumption. For women, additionally adjusted for menopausal status and use of exogenous female hormones. Variables controlled by matching: ‐