No abstract

Animal models have suggested the carcinogenic effect of iron due to its oxidative potential. The lung is particularly vulnerable to oxidative stress. However, epidemiological studies investigating the association between dietary iron and the risk of lung cancer have reported inconclusive results. In this systematic review and meta-analysis, we aimed to clarify this association. Methods: We searched PubMed, Web of Science, Scopus and Google scholar for eligible articles published through May 2023 reporting the Relative Risk (RR), Hazard Ratio (HR) or Odds Ratio (OR) with 95% confidence interval (95% CI). Case-control and cohort studies that examined the relationship between dietary iron and lung cancer risk were included and review and meta-analyses articles, experimental studies, abstracts, letters to editor and studies with insufficient data were excluded. Finally, three case-control studies and 6 cohort studies were included. Random effect models were used to calculate the pooled results. Results: Nine studies (cases n=21,943, participants n=1,542,993) were included. There were no significant associations between the highest dietary total iron (heme and non-heme) (RR: 1.09, 95% CI: 0.78 to 1.51) or heme iron (RR: 1.01, 95% CI: 0.73 to 1.38) intake compared to the lowest intake with lung cancer risk. Null-associations were also observed in the subgroup analysis based on smoking status and lung cancer histology. However, in the subgroup of women (cases n=5074), heme iron was associated with a 14% increase in the risk of lung cancer (RR: 1.14, 95% CI: 1.01 to 1.29). Conclusions: The current results demonstrated that there is no significant relationship between dietary iron intake and the risk of lung cancer. However, a positive association was observed between dietary heme iron and the risk of lung cancer in women, which may require further investigation.

Background Given the role of insulin resistance in several cancers, we hypothesized that the risk of colorectal cancer and colorectal adenoma may be lessened by following a diet that improves insulin resistance. Therefore, we conducted the current study to examine the association between dietary diabetes risk reduction and the odds of colorectal cancer and colorectal adenoma. Method This hospital-based case-control study was conducted on 129 newly diagnosed colorectal cancer patients, 130 newly diagnosed colorectal adenoma cases, and 240 healthy age- and sex-matched hospitalized controls. We used a valid and reliable 148-item food frequency questionnaire (FFQ) to collect the dietary intake of subjects. Multivariate logistic regression was used to estimate the association between DDRRs and the odds of colorectal cancer and adenoma. Results After adjusting for confounding variables, individuals in the highest tertile of the DDRR score were 0.13 and 0.22 times less likely to have colorectal cancer (OR = 0.13, 95% CI: 0.06–0.25) and adenoma (OR = 0.22, 95% CI: 0.12–0.41) respectively Conclusion Current results demonstrated that a high DDRR score was associated with a lower risk of colorectal cancer and adenoma.