Source-specific nitrate intake and incident dementia in the Danish Diet, Cancer and Health Study

INTRODUCTION: Dietary nitrate, through conversion to nitric oxide, which supports vascular and nervous system function, may lower dementia risk but may also form neurodegenerative N-nitrosamines, depending on the nitrate source. METHODS: We investigated associations between source-specific nitrate and nitrite intake and incident and early-onset dementia (<65 years) in 54,804 dementia-free participants from the Danish Diet, Cancer and Health Cohort Study over ∼27 years. Nitrate and nitrite intakes were derived from food frequency questionnaires and nitrate and nitrite databases. RESULTS: Higher plant-sourced nitrate intake was non-linearly associated with lower rates of incident dementia (fifth vs first quintile hazard ratio 95% confidence interval: 0.90 [0.83, 0.98]), while increased risk was seen for higher intakes of animal-sourced, additive-permitted meat-sourced, and tap water-sourced nitrate. Similar associations were seen for source-specific nitrite intake and were more pronounced for early-onset dementia. No clear effect modification was observed. DISCUSSION: These findings highlight the importance of nitrate source in dementia risk and warrant further investigation. Highlights: Plant nitrate is associated with a lower risk of incident and early-onset dementia. Animal and tap water nitrate are associated with an increased risk of dementia. Encouraging consumption of plant-based nitrate sources may lower risk of dementia.