Occasional excess of nitrite from foods
Finns get most of their nitrate intake from vegetables, fruit and water. Some of it is converted into nitrites in the body. Nitrates and nitrites are also used as food additives to prevent the growth of bacteria that cause food poisoning. On the other hand, an excessive intake is considered to cause negative health impacts.
In a scientific risk analysis project lasting several years, the Finnish Food Safety Authority Evira investigated the exposure to nitrates and nitrites of Finnish children aged 1, 3 and 6 and Finnish adults aged 25 to 74 through various foods and household water. The results of the study have been published in a report.
Nitrates mostly from fruit, vegetables and household water
Most of the intake of nitrates comes from natural sources such as vegetables, fruit and water. The intake is highest for those who favour vegetables with a high nitrate content, such as salads, rocket, spinach and red beet.
People who eat a lot of vegetables with a high nitrate content may exceed the acceptable daily intake (ADI) for nitrates, which is 3.7 mg of nitrate ions per kg of body weight per day.
“Temporarily exceeding the ADI does not in itself translate into a health risk, because ADIs are determined using wide safety margins,” says Senior Researcher, Docent Johanna Suomi from Evira.
Preparation of vegetables – washing and peeling – lowers nitrate content, as does cooking in most cases. Nitrate levels depend on the type of fruit or vegetable and the climate conditions in the place of cultivation. It is possible to reduce levels slightly through good agricultural practice.
Nutrition benefits exceed disadvantages
It is generally considered that the nutrition benefits of eating fruit and vegetables exceed any disadvantages that may be caused by nitrates.
“In 2008, the European Food Safety Authority (EFSA) estimated that if one eats fruit and vegetables according to the recommendations, the health benefits will be greater than any adverse impact possibly caused by exceeding the ADI for nitrates on a temporary basis,” says Suomi.
Nitrate levels in household water are generally low, but locally higher levels may occasionally occur. Nitrates used as additives in meat products, cheeses and pickled herring contribute only a very small part of the total exposure.
Nitrites mostly from food additives
The most important source of nitrite exposure for Finns is sausages, particularly cooking sausages, because they are used often and in large quantities. Nitrates and nitrites are used as food additives to prevent the growth of bacteria that cause food poisoning. The heat treatments usually used in the preparation of Finnish processed meat products are not sufficient to destroy the spores of the Clostridium botulinum bacteria that cause botulism.
Nitrite use is necessary to ensure consumer safety especially in products with a low salt content and a long shelf life. If nitrite levels were to be reduced from the present, hygiene requirements and cold chain management would have to be tightened. Nitrites also affect the colour and taste of sausages. The use of additives is governed by decree, specifying maximum levels and products in which they may be used.
The level of nitrites in household water is governed by the Household Water Decree. However, household water contributes substantially less to consumers’ exposure to nitrites than food additives.
Levels of nitrites used as food additives decrease over time
In the study, nitrite levels were measured at the probable average time of consumption, about one week before the sell-by date. It was estimated that exposure to nitrites from food additives for children aged 1 remained below the ADI, which is 0.07 mg of nitrite ions per kg of body weight per day.
However, in the research material it was found that exposure to nitrites from food additives and household water exceeded the ADI for about 0.2% of adults, about 14% of children aged 3 and 11% of children aged 6 in Finland. Long-term exposure consistently exceeding the ADI translates into a potential health risk, the likelihood of which increases as the exposure increases.
High levels of nitrates and nitrites may inhibit oxygen transfer in the body. Exposure to nitrites is also suspected of elevating the risk of diabetes, coronary disease and cancer, but the research findings so far have been contradictory, and no causal link between exposure to nitrites and these conditions has been proven. In the risk assessment conducted by Evira, the risk was assessed on the basis of acceptable daily intake (ADI), regarding the values of which there is a general scientific consensus. The safety and ADI of nitrates and nitrites used as food additives will be re-evaluated in the EU by the end of 2015.
Long-term exposure of Finns to nitrates and nitrites was estimated probabilistically using the Monte Carlo method, based on levels measured in foods and on individual food consumption data. The consumption data was collected as part of the FinDIET 2007 project and the DIPP project in which the predicting and preventing of type 1 diabetes were studied.
Read the report: Kvantitatiivinen riskinarviointi lasten ja aikuisten altistumisesta nitraatille ja nitriitille [Quantitative risk assessment on dietary exposure of children and adults to nitrate and nitrite] (PDF, Description in English)
Evira´s press release 13.12.2013: Moderation in consumption of cold cuts and sausages by children
Johanna Suomi PhD, Senior Researcher, Docent, Risk Assessment Research Unit, tel. +358 40 822 5629 (available from 13.00 on 13 Dec 2013)