Nitrite Additive Exposure Linked to Increased Type 2 Diabetes Risk

Bernard Srour, PhD, PharmD

New research does not support any potential benefit for dietary nitrites or nitrates in the prevention of type 2 diabetes (T2D), with exposure to both foods and water-originated and additives-originated nitrites associated with higher T2D risk.

On the other hand, no evidence for an association between total, foods and water-originated, or additives-originated nitrates and T2D risk was reported in the findings.

“This is the first large-scale cohort study to suggest a direct association between additives-originated nitrites and T2D risk,” wrote corresponding author Bernard Srour, PhD, PharmD, Nutritional Epidemiology Research Team (EREN-CRESS) of Inserm, INRAE, Cnam, and Sorbonne Paris Nord University. “It also corroborates previously suggested associations between total dietary nitrites and T2D risk.”

Naturally present in water and soil, both nitrates and nitrites are commonly ingested from drinking water and miscellaneous dietary sources. Often, this includes being used as food additives, as they can be used as a preservative to improve shelf life. However, there is a lack of human-focused data on the role of dietary nitrites and nitrates in metabolic dysfunction and the onset of T2D.

As numerous public health organizations around the world question a possible suspension of nitrites and nitrates as food additives, Srour and colleagues aimed to investigate whether dietary exposure to nitrites or nitrates was associated with T2D risk in the large, prospective from the NutriNet-Sante cohort. The NutriNet-Sante study is an ongoing web-based cohort launched in May 2009 in France and participants aged 15 years or older with access to the internet are continuously recruited.

At the baseline, participants completed a bath of 5 questionnaires related to sociodemographic and lifestyle characteristics, anthropometry, physical activity, health status, and dietary intake. Investigators averaged dietary intakes from all 24-h dietary records available during the first 2 years of each participant’s follow-up and determined the exposure to total nitrites/nitrates, reflecting the exposure from both foods, water, and food additives.

Investigators studied the associations between self-reported exposure to nitrites and nitrates and risk of T2D through cause-specific multivariable Cox proportional hazard models adjusted for known risk factors. The study population comprised a total of 104,168 participants (79.1% female, mean age, 42.7 years) reporting no prevalent T2D at baseline with at least 2 valid 24-h dietary records during their first 2 years of follow-up.

Over a median follow-up of 7.3 years, 969 cases of incident T2D were identified. In the fully adjusted model, total nitrates and food and water-originated nitrites were both positively associated with a higher T2D risk (HR, 1.27 [95% CI, 1.04 to 1.54]; P = .009 and 1.26 [95% CI, 1.03 to 1.54]; P = .02, respectively).

Those with higher exposure to nitrites from food additives had a higher T2D risk compared with those who were not exposed to additives-originated nitrates (HR, 1.53 [95% CI, 1.24 to 1.88]; P <.001), particularly those with higher exposure to sodium nitrate (HR, 1.54 [95% CI, 1.26 to 1.90]; P <.001).

Investigators noted there was no association between total, foods and water-originated, or additives-originated nitrates and T2D.

“These results provide a new piece of evidence in the context of current discussions regarding the need for a reduction of nitrite additives’ use in processed meats by the food industry and could support the need for better regulation of soil contamination by fertilizers,” Srour added. “In the meantime, several public health authorities worldwide already recommend citizens to limit their consumption of food containing controversial additives, including sodium nitrite.”

Srour noted that further research may be required to validate the results, as data were self-reported, and investigators could not confirm specific nitrite/nitrate exposure using biomarkers due to underlying biological challenges. Residual confounding may additionally have impacted the outcome due to the observational design of the study.

The study, “Dietary exposure to nitrites and nitrates in association with type 2 diabetes risk: Results from the NutriNet-Sante population-based cohort study,” was published in PLOS Medicine.