Nitrate is a natural compound. You’ll find it in all surface and groundwater. However, you’ll see higher levels where farmers use fertilizers. The government set a limit for nitrate in public drinking water to protect babies from methemoglobinemia, but they didn’t really consider other health issues. Drinking nitrate might increase your risk of certain cancers and birth defects. That’s because when you drink nitrate, it turns into nitrite. This nitrite can then react with other compounds to form N-nitroso compounds, which are known to cause cancer in animals. This study wanted to see if there’s a connection between nitrate in drinking water and cancer risk in people.

Methods

We did a systematic review, following PRISMA and MOOSE guidelines. We searched PubMed, EMBASE, the Cochrane Library, Web of Science, and Google Scholars for relevant papers from their start dates up to January 2020. We used STATA version 12.0 for meta-regression and a two-stage meta-analysis.

Results

We ended up using 48 articles that looked at 13 different cancer types. Our meta-regression showed a link between stomach cancer and the average nitrate dose from drinking water (t = 3.98, p = 0.0001, and adjusted R-squared = 50.61%). Other cancer types didn’t show this connection. The first part of our meta-analysis found a link between brain cancer and glioma (OR = 1.15, 95% CI: 1.06, 1.24), and colon cancer (OR = 1.11, 95% CI: 1.04, 1.17) and nitrate consumption when we compared the highest and lowest risks. The second part of the analysis found a link only between colon cancer risk (OR = 1.14, 95% CI: 1.04, 1.23) and nitrate consumption, comparing all higher risks combined against the lowest.

Conclusion

This study suggests a link between nitrate in drinking water and certain cancers in people. What’s the best way to keep nitrate levels down in your drinking water? Stop the contamination in the first place. We definitely need more research on this topic.