New research has found that people who consume higher levels of nitrate from vegetables have a lower risk of developing dementia, while those who get more nitrate and nitrite from animal-based foods, processed meats, and drinking water face a higher risk of dementia.
New findings from Edith Cowan University (ECU) and the Danish Cancer Research Institute (DCRI) explore how nitrate and nitrite intake from different dietary sources relates to the risk of developing dementia.
Dementia develops through a mix of genetic and lifestyle influences, and diet may play a meaningful role, said Dr. Nicola Bondonno, a Postdoctoral Research Fellow at ECU’s Nutrition & Health Innovation Research Institute (NHIRI) and the DCRI.
One chemical, very different outcomes
In the study, researchers tracked more than 54,000 adults in Denmark for up to 27 years, examining how nitrate and nitrite from specific sources were linked to both overall and early-onset dementia. The analysis showed that where these compounds come from in the diet matters greatly.
Participants who consumed higher amounts of nitrate from vegetables were less likely to develop dementia. In contrast, higher intake of nitrate and nitrite from animal products, processed meats, and drinking water was associated with a greater risk of the condition.
Why do vegetables behave differently
ECU Associate Professor Catherine Bondonno explained that nitrate from vegetables has consistently been linked to better brain health outcomes. This benefit is thought to arise because nitrate from plant foods is converted in the body into nitric oxide, a compound that supports healthy blood flow and cellular function.
“When we eat nitrate-rich vegetables, we are also eating vitamins and antioxidants which are thought to help nitrate form the beneficial compound, nitric oxide, while blocking it from forming N-nitrosamines, which are carcinogenic and potentially damaging to the brain.
“Unlike vegetables, animal-based foods don’t contain these antioxidants. In addition, meat also contains compounds such as heme iron which may actually increase the formation of N-nitrosamines. We think this is why nitrate from different sources has opposite effects on brain health, but we need laboratory studies to confirm exactly what’s happening,” she said.
An unexpected signal from drinking water
This is the first time that nitrate from drinking water has been linked to higher risks of dementia. The study found that participants exposed to drinking-water nitrate at levels below the current regulatory limits, had a higher rate of dementia, however, Dr. Bondonno stressed that this was only one study, and more research was required.
“Water doesn’t contain antioxidants that can block the formation of N-nitrosamines. Without these protective compounds, nitrate in drinking water may form N-nitrosamines in the body,” she said.
In Denmark and the EU, the limit for nitrate in groundwater and drinking water is set at 50 mg/L, but the researchers observed a higher risk for drinking water containing as low as 5 mg of nitrate per liter.
“Importantly, our results do not mean that people should stop drinking water. The increase in risk at an individual level is very small, and drinking water is much better for your health than sugary drinks like juices and soft drinks. However, our findings do suggest that regulatory agencies should re-examine current limits and better understand how long-term, low-level exposure affects brain health.”
Interpreting risk with caution
She simultaneously emphasizes that this is an observational study, which cannot establish that nitrate directly causes dementia. The results must therefore be confirmed in other studies, and it cannot be ruled out that other factors in participants’ diets or lifestyles contribute to the association.
Dr. Bondonno said the take-home results from the study are fairly simple: people who consume more nitrate from vegetables, equating to around one cup a day of baby spinach, had a lower risk of dementia.
On the other hand, people who consumed more nitrate from animal-based foods, particularly red and processed meat, had a higher risk.
“Eating more vegetables and less red meat and processed meat is a sensible approach based on our findings and decades of other research on diet and health,” she added.
Reference: “Source-specific nitrate intake and incident dementia in the Danish Diet, Cancer and Health Study” by Catherine P. Bondonno, Pratik Pokharel, Dorit Wielandt Erichsen, Liezhou Zhong, Jörg Schullehner, Cecilie Kyrø, Kirsten Frederiksen, Peter Fjeldstad Hendriksen, Frederik Dalgaard, Lauren C. Blekkenhorst, Stephanie R. Rainey-Smith, Samantha L. Gardener, Torben Sigsgaard, Ole Raaschou-Nielsen, Anne Tjønneland, Jonathan M. Hodgson, Christina C. Dahm, Anja Olsen and Nicola P. Bondonno, 19 December 2025, Alzheimer’s & Dementia.
DOI: 10.1002/alz.70995
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