Exposure to nitrate from food and drinking-water in New Zealand. Can these be considered separately?

Abstract

Recent epidemiological studies have reported associations between colorectal cancer incidence and nitrates in drinking-water, but not from the diet. The toxicokinetics of nitrates were reviewed and exposure data from New Zealand were analysed. Dietary (including drinking-water) exposure of New Zealanders to nitrates was found to be very similar to most other countries and within internationally-established acceptable daily intakes. Less than 10% of nitrate exposure was from drinking-water, with little difference between adults and children. Approximately half of the total water-based exposure is through water alone, the remainder was consumed as tea and coffee (adults), or water-based fruit drinks (children). For children, drinking-water as a beverage is generally consumed close to a meal time, with 83% of servings consumed within an hour of eating. For adults, this is reduced to 51% of servings consumed within an hour of a meal. Only 2.6% of nitrate exposure for adults and 0.7% of nitrate exposure for children is from drinking-water consumed on its own and not in close temporal association to food consumption. It was concluded from the combination of the biology and the exposure assessment that there is little reason to differentiate between drinking-water and food nitrate exposure.

Keywords:

• Nitrate
• nitrite
• colorectal cancer
• dietary exposure
• risk assessment

Acknowledgements

The authors wish to acknowledge the New Zealand Food Safety Science and Research Centre, the Ministry of Business, Innovation and Employment and Fonterra Co-operative Group for funding this study and the New Zealand Ministry of Health as owner of the copyright and funders of the 1997–1998 National Nutrition Survey, the 2008–2009 Adult Nutrition Survey and the 2002 National Children’s Nutrition Survey and to thank them for access to food consumption information (24-hour dietary recall) from these surveys.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The authors wish to acknowledge the New Zealand Food Safety Science and Research Centre, the Ministry of Business, Innovation and Employment and Fonterra Co-operative Group for funding this study.