Adolescent and mid‐life diet and subsequent risk of thyroid cancer in the NIH‐AARP diet and health study

Although thyroid cancer is suspected to have a nutritional etiology, prospective studies examining the relationship between diet and thyroid cancer are lacking. During 1996–1997, NIH‐AARP Diet and Health Study participants, ages 51–72 years, completed a 37‐item food frequency questionnaire about diet at ages 12–13 years (adolescence) and 10 years before baseline (mid‐life). Over a median 10 years of follow‐up, 325 individuals (143 men and 182 women) were diagnosed with thyroid cancer. Multivariable‐adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated for intakes of foods and food groups comparing the highest to the lowest quartiles. Adolescent intakes of chicken/turkey (HR = 1.59, 95% CI: 0.97–2.60; p_trend < 0.01) and sweet baked goods (HR = 1.59, 95% CI: 1.09–2.34; p_trend = 0.04) were positively associated with thyroid cancer risk, while intake of butter/margarine was inversely associated with risk (HR = 0.64, 95% CI: 0.44–0.91; p_trend < 0.02). Similar to adolescent diet, mid‐life intake of sweet baked goods was nonsignificantly associated with an increased risk of thyroid cancer (HR = 1.39, 95% CI: 0.96–2.00; p_trend = 0.11), but intake of butter/margarine was inversely associated with risk (HR = 0.66, 95% CI: 0.46–0.95; p_trend = 0.03). Among men, higher adolescent consumption of canned tuna was positively associated with risk of thyroid cancer (HR = 1.69, 95% CI: 1.01–2.83; p_trend = 0.03), and greater mid‐life intake of broccoli was associated with a twofold increased risk (HR = 2.13, 95% CI: 1.13–3.99; p_trend < 0.01). This large prospective study suggests that several components of the adolescent and mid‐life diet, including iodine‐rich foods and goitrogens, may influence thyroid cancer risk.