Iron Metabolic Biomarkers and the Mortality Risk in the General Population: A Nationwide Population-Based Cohort Study

Dietary factors and cancer outcomes in individuals with type 2 diabetes: A systematic review and meta-analysis of prospective observational studies

INTRODUCTION

Cancer is a major health concern in persons with type 2 diabetes (T2D). Diet plays an important role in progression of diabetes and cancer. We aimed to systematically summarize the evidence on diet and cancer in individuals with T2D.

METHODS

PubMed and Web of Science were searched until August 2023 and followed up via PubMed alert until December 2024. Prospective studies investigating any dietary factor in association with cancer in individuals with T2D were eligible.

RESULTS

We identified 68 studies and conducted 20 meta-analyses. A general low-carbohydrate diet was not associated with cancer outcomes, whereas an inverse association was found for vegetable-based low-carbohydrate diet (HR per 5 points [95 % CI]: 0.90 [0.84, 0.97]; n = 2). We found indications of lower cancer incidence for higher adherence to Dietary Approaches to Stop Hypertension diet, (Alternate) Healthy Eating Index, higher intakes of n-3 fatty acids (0.73 [0.55, 0.98]; n = 2) and higher serum vitamin D (0.95 [0.93, 0.97]; n = 2), as well as a positive association for serum manganese concentrations (1.44 [1.11, 1.87]; n = 2), rated with low to very low certainty of evidence.

CONCLUSION

So far, the certainty of evidence is very limited due to the small numbers of primary studies. There is an indication of a possible association between diet and cancer risk among persons with T2D, but further well-designed prospective cohort studies are warranted.

Iron Metabolic Biomarkers and the Mortality Risk in the General Population: A Nationwide Population-Based Cohort Study

Context

Iron is an essential element in the human body and plays a critical role in many physiological and cellular processes. However, the association between iron status and the risk of all-cause or cause-specific mortality has not been well-investigated. And it is unclear whether the association between iron metabolic biomarkers and the risk of mortality differs between people with and without diabetes mellitus (DM).

Objective

This work aimed to investigate associations between iron metabolic biomarkers and all-cause and cause-specific mortality risk in the general population, and heterogeneities in the associations among population with and without DM..

Methods

A total of 29 166 adults from the National Health and Nutrition Examination Survey (NHANES) III and NHANES 1999 to 2010 were included, with linkage to the National Death Index to December 31, 2019. Cox proportional-hazard models and Fine-Gray subdistribution hazard models were used to estimate associations between iron metabolic biomarkers and outcomes.

Results

During a median follow-up of 18.83 years, 9378 deaths were observed, including 3420 cardiovascular disease (CVD) deaths and 1969 cancer deaths. A significant linear association between serum ferritin (SF) and all-cause mortality was observed among the overall population and those without DM. J-shaped associations between transferrin saturation (TSAT) and all-cause and CVD mortality were observed among all populations. In the overall population, compared to the first quartile (Q1) group, the adjusted hazard ratio (HR) (95% CI) for all-cause mortality was 1.07 (1.00-1.15), 1.05 (0.98-1.12), 1.13 (1.05-1.21) in Q2, Q3, and Q4 groups for SF, while the HR was 0.94 (0.88-0.99), 0.92 (0.86-0.97), and 0.93 (0.88-0.99) for TSAT. In individuals without DM, the adjusted HR of the Q4 of SF were 1.19 (1.03-1.37) for CVD mortality and 1.25 (1.05-1.48) for cancer mortality. In individuals with DM, the adjusted HRs of the Q4 of TSAT were 0.76 (0.62-0.93) for CVD mortality and 1.47 (1.07-2.03) for cancer mortality.

Conclusion

Iron metabolism abnormalities increase mortality risk in the general population. The associations of iron status with mortality were significantly different between individuals with and without DM, which indicated tailored strategies for iron homeostasis are needed.