Dietary nitrate, nitrite, and nitrosamine in association with diabetes: a systematic review and meta-analysis

Abstract Context Diabetes is a global health concern, and diet is a contributing factor to diabetes. Findings regarding the connection between nitrate, nitrite, and nitrosamine and diabetes risk are inconsistent. Objective The aim was to examine the effects of these dietary compounds on diabetes risk. Data Sources The data were sourced from PubMed, EMBASE, Scopus, and Web of Science until February 28, 2023. Studies that reported individual-level consumption of these compounds were included. Review articles or ecological studies were excluded. Data Extraction The number of events and total observations were recorded. Data Analysis The pooled odds ratio (OR) was calculated and displayed in a forest plot. Subgroup and sensitivity analyses were predefined. A dose–response meta-analysis was conducted to determine the exposure intervals that may increase the risk of disease. Six observational reports that met the inclusion criteria were included, involving 108 615 individuals. Participants in the highest quantile of nitrite intake had a greater risk of diabetes compared with those in the lowest quantile (OR, 1.61; 95% confidence interval [CI], 1.08–2.39; I2 = 74%, P = 0.02). Higher nitrosamine consumption tended to increase diabetes risk (OR, 1.52; 95% CI, 0.76–3.04; I2 = 76%; P = 0.24). The relationship was stronger for type 1 (OR, 1.79; 95% CI, 1.20–2.67; I2 = 58%; P < 0.01) than for type 2 diabetes (OR, 1.42; 95% CI, 0.86–2.37; I2 = 71%; P = 0.17). Additionally, nitrite consumption had a dose-dependent association with both phenotypes. No association was found between diabetes risk and high nitrate intake (OR, 1.01; 95% CI, 0.87–1.18; I2 = 28%; P = 0.87). Conclusion Attention should be paid to the consumption of nitrite-containing foods. Systematic Review Registration PROSPERO registration no. CRD42023394462 (https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=394462).