title: Seaweed consumption and the risk of thyroid cancer in women:  the Japan Public Health Center-based Prospective Study.
abstract: Iodine is a suspected risk factor for thyroid cancer. Seaweed accounts for about 80% of Japanese people's iodine intake. We examined the association between seaweed consumption and the risk of thyroid cancer in Japanese women. Women participating in the Japan Public Health Center-based Prospective Study (n=52 679; age: 40-69 years) were followed up for a mean of 14.5 years; 134 new thyroid cancer cases, including 113 papillary carcinoma cases, were identified. Seaweed consumption was assessed using a food-frequency questionnaire and divided into three categories: 2 days/week or less (reference); 3-4 days/week; and almost daily. The Cox proportional hazards model was applied to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). Seaweed consumption was clearly associated with an increased risk of papillary carcinoma (HR for almost daily consumption compared with 2 days/week or less=1.71; 95% CI: 1.01-2.90; trend P=0.04). After stratification for menopausal status, an increased risk was observed in postmenopausal women (papillary carcinoma HR for almost daily consumption compared with 2 days/week or less=3.81, 95% CI: 1.67-8.68; trend P<0.01), but not in premenopausal women (HR=0.91, 95% CI: 0.44-1.91; trend P=0.76). This study identified a positive association between seaweed consumption and the risk of thyroid cancer (especially for papillary carcinoma) in postmenopausal women.
authors.affiliation: Epidemiology and Prevention Division, Research Center for Cancer Prevention and Screening, National Cancer Center, 5-1-1 Tsukiji Chuo-ku, Tokyo, Japan.
authors.forename: Takehiro
authors.initials: T
authors.lastname: Michikawa
authors.forename: Manami
authors.initials: M
authors.lastname: Inoue
authors.forename: Taichi
authors.initials: T
authors.lastname: Shimazu
authors.forename: Norie
authors.initials: N
authors.lastname: Sawada
authors.forename: Motoki
authors.initials: M
authors.lastname: Iwasaki
authors.forename: Shizuka
authors.initials: S
authors.lastname: Sasazuki
authors.forename: Taiki
authors.initials: T
authors.lastname: Yamaji
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Tsugane
mesh_terms: D000328:Adult; D000368:Aged; D002291:Carcinoma, Papillary / Q000209:etiology*; D004032:Diet / Q000009:adverse effects*; D004034:Diet Surveys; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007455:Iodine / Q000008:administration & dosage / Q000009:adverse effects*; D007564:Japan; D008875:Middle Aged; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012307:Risk Factors; D012624:Seaweed / Q000737:chemistry*; D013964:Thyroid Neoplasms / Q000209:etiology*
chemical_list: D007455:Iodine