OBJECTIVE: This meta-analysis examined the relationship between excess body weight or body mass index (BMI) and risk of thyroid cancer. METHODS: PubMed ® , MEDLINE ® , EMBASE™ and Academic Search™ Premier databases were searched to identify cohort studies examining the effect of being overweight or obese on the risk of thyroid cancer. RESULTS: The inclusion criteria were met by seven cohort studies (total number of thyroid cancer cases, 5154). The pooled relative risk (RR) of thyroid cancer was 1.13 (95% confidence interval [CI] 1.04, 1.22) for overweight. Obesity was also linked with increased thyroid cancer risk in males and females, the strength of the association increasing with increasing BMI. The combined RR of thyroid cancer was 1.18 (95% CI 1.11, 1.25) for excess body weight (overweight and obesity combined). Being overweight was associated with a significant increase in thyroid cancer risk among non-Asians, but not among Asians. Overweight, obesity and excess body weight were all associated with papillary thyroid carcinoma risk. CONCLUSIONS: The association between overweight/ obesity/excess body weight and thyroid cancer risk was confirmed.

To provide a quantitative assessment of the association between iron intake, serum iron indices and the risk of colorectal adenoma (CRA), we summarised the evidence from observational studies. Relevant studies were identified in MEDLINE and EMBASE until 31 March 2015. Summary relative risks (SRRs) with 95% confidence intervals (CIs) were pooled with a random-effects model. A total of 10 articles, involving 3318 subjects with CRA, were used in this meta-analysis. The SRR of CRA was 0.83 (95% CI: 0.71-0.98; P = 0.694, I = 0) for the highest versus the lowest level of dietary iron intake. The SRR was 0.93 (95% CI: 0.62-1.42) for total (dietary and supplemental) iron intake, 1.23 (95% CI: 1.03-1.48) for haem iron intake and 0.73 (95% CI: 0.54-0.97) for supplemental iron intake. Serum iron indices were not associated with CRA risk (serum ferritin: SRR = 1.16, 95% CI: 0.81-1.66; serum iron: SRR = 1.02, 95% CI: 0.75-1.38; serum transferrin saturation: SRR = 1.01; 95% CI: 0.82-1.50). Increased intake of haem iron is associated with significantly increased risk of CRA, whereas intake of non-haem or supplemental iron is inversely associated with risk of CRA. Limited data indicate null associations between serum iron indices and CRA risk.