Nitrites and nitrates are used as food additives to prevent bacterial growth, mainly in processed meats, and they are also found in foods (mainly green leafy vegetables) and water (nitrates from the use of nitrogen fertilizer can enter the water supply).
The researchers analyzed data from 104,168 participants in NutriNet-Santé who had no diabetes at baseline and who completed 24-hour dietary intake records. They investigated the association between exposure to nitrites and nitrates (in food and water or in additives) and incident type 2 diabetes.
Most nitrites came from food (95.3%), and less often from food additives (4.7%) and water (< 0.01%). The nitrites in foods were mainly from vegetables (60%) and seasonings (23%).
Most nitrates also came from food (93%), followed by water (6.9%) and food additives (0.1%). The nitrates in foods were mainly from vegetables (41%), processed meat (19%), and meat (17%).
During a median follow-up of 7.3 years, there were 969 incident cases of type 2 diabetes.
Compared with individuals in the lowest third of nitrites from food and water, those in the highest tertile had a 27% higher risk of incident type 2 diabetes, after adjusting for multiple variables (hazard ratio, 1.27; P = .009).
The risk of type 2 diabetes associated with the highest intake of nitrites from additives was as previously described, 53% higher, than that for those with the lowest intake.
There was no evidence of an association between nitrates and risk of type 2 diabetes.
The researchers acknowledge that study limitations include potential errors in assessment of nitrate and nitrate exposure, potential selection bias (participants in the web-based study may have had healthier behaviors than the general population), and potential unaccounted confounders (because it was an observational study).
A version of this article first appeared on Medscape.com.