Intake and risk assessment of nitrate and nitrite from New Zealand foods and drinking water

Abstract

Exposure to excess nitrite is a potential health risk for humans. One hundred meat and processed foods and 100 vegetable samples purchased from New Zealand retail outlets were prepared as for consumption and analysed for nitrite and nitrate concentration using a standard, validated methodology. Nitrate concentrations ranged from less than the limit of detection (LOD = 5 mg kg-1) in cheddar cheese and cream cheese-based dips to 3420 mg kg-1 in lettuce. Nitrite was detected in half the processed foods and meats analysed (levels up to 119 mg kg-1), but detected in only one vegetable sample above the LOD (broccoli at 27 mg kg-1 nitrite). Concentration data were combined with 24 h dietary recall information to generate 4398 individual adult daily exposure scenarios for exogenous nitrite and nitrate including a contribution from water assessed from 1021 drinking water samples. The mean adult daily intake of exogenous nitrate and nitrite from food and water combined was 16 and 13% of the Acceptable Daily Intake (ADI), respectively, and therefore should not pose a health risk for the average consumer. A maximally exposed New Zealand adult is estimated to have an intake of up to seven times the ADI for nitrate. When the endogenous conversion of nitrate to nitrite is taken into account, approximately 10% of people with an average rate of conversion and half of all people with a high rate of conversion are estimated to exceed the ADI. Either the ADI is inappropriate and needs to be re-evaluated, or those individuals who have a high rate of conversion of nitrate to nitrite are at risk to adverse effects of nitrite exposure.

Nitrate Content in Potatoes Cultivated in Contaminated Groundwater Areas

“…Depending on dietary habits, potatoes can be the main source of nitrate intake. Namely, vegetables account for 97% of our nitrate intake, of which 32% originates from potato consumption and 29% from lettuce consumption (Santamaria, 2006;Thomson, Nokes, & Cressey, 2007).…”

Contribution of different vegetable types to exogenous nitrate and nitrite exposure

“…Nitrogen fertilisation and light intensity have been identified as the major factors that influence nitrate content in vegetables (Gruda, 2005;Santamaria, 2006). Even among different samples of the same vegetable varieties, the range of concentrations may be large (Prasad & Chetty, 2008;Tamme et al, 2006;Thomson et al, 2007). Variations, within site, for plants growing in the same plot can be explained by differences in soil mineral nitrogen, and individual plant growth in response to localised areas of soil compaction, or variability in soil pH (Weightman, Dyer, Buxton, & Farrington, 2006).…”

“…This value can reach 20% for individuals with a high rate of conversion (Thomson et al, 2007). Methemoglobinemia is another health hazard attributed to nitrite, a condition where reduced iron (Fe 2+ ) in haemoglobin is oxidised by nitrite to Fe 3+ , thus reducing the total oxygen-carrying capacity of the blood (Santamaria, 2006).…”

“…These have been related to an increased risk of gastric, oesophageal, nasopharyngeal and bladder cancers (Choi, Chung, Lee, Shin, & Sung, 2007). For this reason the determination of nitrate and nitrite in food has received increased attention and several recent studies have addressed the dietary exposure of human population to these compounds (Menard, Heraud, Volatier, & Leblanc, 2008;Thomson, Nokes, & Cressey, 2007).…”

Change in Mutagenic Activity of Genistein after a Nitrite Treatment

“…6) The nitrate ingested from foods and water is reduced to nitrite when it comes into contact with the bacteria in oral saliva, about 30% of this nitrate being converted to nitrite. Nitrate and nitrite, after their absorption in the upper gastrointestinal tract, reach the salivary glands via the blood circulation where they are secreted into the oral cavity.…”