Nitrate is often discussed as a single compound, but new research suggests that its health effects may depend heavily on where it comes from.
In a large observational study following more than 54,000 Danish adults for up to 27 years, researchers found that people who consumed more nitrate from vegetables had a lower risk of developing dementia. In contrast, higher nitrate intake from drinking water and certain animal-based foods was associated with a higher risk. The findings were published in Alzheimer’s & Dementia and draw on data from the Danish Diet, Cancer and Health Study.
The researchers examined nitrate and nitrite intake from a wide range of sources, including vegetables, processed meats, animal-based foods and drinking water. According to the authors, the differences seen across sources reinforce the idea that nutrients do not act in isolation. Instead, the broader food matrix and accompanying compounds appear to shape how the body processes them over time.
“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,” said Associate Professor Catherine Bondonno.
Animal-based foods do not contain the same antioxidant profile.
“In addition, meat also contains compounds such as heme iron which may actually increase the formation of N-nitrosamines,” she said.
The researchers believe these differences may help explain why nitrate from vegetables has been linked to health benefits in previous studies, while nitrate from other sources may be associated with harm.
One of the more novel findings involved nitrate exposure from drinking water. Participants exposed to drinking water nitrate at levels below current regulatory limits still showed a higher rate of dementia compared with those exposed to lower levels. In Denmark and across the EU, the regulatory limit for nitrate in drinking water is 50 mg per liter, but higher dementia risk in this study was observed at levels as low as 5 mg per liter.
The researchers emphasized that this finding does not mean people should avoid 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,” said Dr. Nicola Bondonno. “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.”
The authors also stressed that the study was observational, meaning it cannot establish cause and effect. It remains possible that other dietary or lifestyle factors contributed to the associations observed, and the findings will need to be confirmed in additional populations and experimental studies.
Taken together, the practical takeaway aligns closely with existing dietary guidance. People who consumed more nitrate from vegetables, roughly the amount found in about one cup of baby spinach per day, had a lower risk of dementia. Meanwhile, higher nitrate intake from red and processed meats was associated with 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,” Dr. Bondonno said.
Rather than focusing on single nutrients in isolation, the study reinforces a broader theme in nutrition science: where nutrients come from, and what comes with them, may matter as much as the nutrients themselves.
This research was conducted as part of the Danish Diet, Cancer and Health Study and was supported by public and nonprofit research funders, including the Danish Cancer Society, the World Cancer Research Fund and Independent Research Fund Denmark. Additional support came from BERTHA, a Danish research center focused on environmental and health data, funded by the Novo Nordisk Foundation.
Several authors received individual research fellowships or grants from Australian public health agencies and nonprofit foundations, including the National Health and Medical Research Council of Australia, the Western Australian Future Health Research and Innovation Fund and the National Heart Foundation of Australia.