Review Cite This: J. Agric. Food Chem. 2019, 67, 7205−7222
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Nitrate and Nitrites in Foods: Worldwide Regional Distribution in View of Their Risks and Benefits Zeynep Kalaycıoğlu and F. Bedia Erim* Istanbul Technical University, Department of Chemistry, Maslak, Istanbul, Turkey
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ABSTRACT: Nitrate and nitrite ions are used as food additives to inhibit the growth of microorganisms in cured and processed meats. Vegetables contain significant quantities of nitrate and nitrite. Actually, the vast majority of consumed nitrate and nitrite comes from natural vegetables and fruits rather than food additives. For years, the cancer risks of these two ions have been discussed, since they potentially convert into the carcinogenic nitrosamines. However, recently, these two ions have been considered essential nutrients which promote nitric oxide production and consequently help cardiovascular health. It seems that the role of these two ions in our diet is important now from a different point of view. In this review, the nitrate and nitrite contents of food products from different countries are displayed globally in order to reinterpret the risks/benefits of our consumption quotations. This review article is based on Science Citation Index (SCI) articles reported between 2008 and 2018. KEYWORDS: nitrate, nitrite, food, vegetable, meat, health risk, health benefit
1. INTRODUCTION Sodium nitrate/E251 or potassium nitrate/E252 and sodium nitrite/E250 or potassium nitrite/E249 are added to cured and processed meat to inhibit the growth of microorganisms, notably Clostridium botulinum, which is the cause of botulism, a rare but serious illness. Moreover, nitrite gives the typical reddish color and flavor to processed meat. The nitrate ion is not considered toxic, but nitrate added to food is converted into nitrite by commensal bacteria in the mouth and gastrointestinal tract, and nitrite ion can be converted into nitrosamines, which are considered carcinogenic. It is also claimed that the consumption of nitrite causes methemoglobinemia (blue baby syndrome) in children younger than 6 months. Therefore, the nitrite and nitrate additives in meat products are restricted in many countries. However, limiting values vary from country to country. On the other hand, it should be considered that the initial amounts of both components in food may vary depending on the storage conditions. During this period at ambient temperature, a significant decrease in nitrate levels and a significant increase in nitrite levels of vegetables were observed. In contrast, nitrate and nitrite levels remained constant under refrigerated storage conditions.1 It was noted that the additive nitrite concentration in processed meat products is reduced over time.2,3 However, it was suggested that nitrate inhibits the nitrite autodecomposition in the cooked cured pork, controlling the rate of residual nitrite depletion and decrease in color stability.3 On the other hand, the analysis of these two ions in processed meat products and natural vegetables with the same analytical methods shows that the amount of nitrate in vegetables is significantly above the content of nitrate additives in meat products.4 Actually, it is foreseen that 60% of dietary nitrates is taken from vegetables.5 Both ions are of great interest in the scientific literature. Some of the scientific publications on nitrate and nitrite ions are based on the development of new analytical methods. The purpose of these © 2019 American Chemical Society
studies is to develop faster methods with high repeatability and accuracy for the simultaneous analysis of these two ions. It appears that the analytical methods concentrate on the spectroscopic, chromatographic, or capillary electrophoretic methods with the different modifications and have been collected up to now in two review articles.6,7 Another group of scientific articles aims to create data on the nitrate and nitrite contents of consumed food on a country basis and to estimate the dietary exposure of nitrate and nitrite. Of late, there is increasing scientific and medical interest in the benefits of dietary nitrite and nitrate. As discussed in many medicinal studies in recent years, dietary nitrite and nitrate have cardiovascular protective effects.8−12 Both in vivo and in vitro studies show that dietary nitrate has an effect similar to that of nitric oxide (NO) on lowering blood pressure, gastric injury, and bleeding, by way of gradual chemical reduction of nitrate to nitrite and, finally, to nitric oxide. It has been shown that the consumption of nitrate-containing vegetables frequently decreased hypertension risk in adults. Moreover, some new epidemiological cohort studies reject the association between the consumption of nitrite and nitrate and stomach cancer.13,14 Nitrate and nitrite contents of breast milk are higher than those in most commercial products. It was reported that the nitrite and nitrate contents of breast milk contributes to the growth and development of the neonate.15 The favorable effects of dietary NO3− supplements on the physiological performances of older adults are indicated in current literature.16 The health beneficial effects of both ions, which have gained importance in recent years, have been summarized Received: Revised: Accepted: Published: 7205
February 20, 2019 May 27, 2019 June 5, 2019 June 5, 2019 DOI: 10.1021/acs.jafc.9b01194 J. Agric. Food Chem. 2019, 67, 7205−7222
Review
Journal of Agricultural and Food Chemistry
Figure 1. (a) Number of Web of Science (WOS) papers on nitrite and nitrate analysis between 2008 and 2018. (b) Distribution of these articles in different food types.
in review articles.17−20 These new and growing research results need a reconsideration of nitrite and nitrate safety. It seems that the consumption of nitrate and nitrite for our health will continue to be a matter of debate for many years. When diet plans are made on the basis of these two ions, it is necessary to know the contents of ions in different food products. Due to the global trade, the quantities of products from different regions are also relevant to the global consumer. The aim of this study is to display the nitrate and nitrite contents of food products in different countries and regions. In the study, the publications that appeared in SCI journals between the years 2008 and 2018 were scanned. Between 2008 and 2018, 838 SCI journal articles that directly dealt with nitrite and nitrate analysis in foods were published. As seen from Figure 1a, a more or less homogeneous distribution was monitored in regard to years. The distribution of these articles in meat, vegetables, dairy products, baby foods, fish, and other food products is seen in Figure 1.b. A high percentage of the analyzed foods belongs to meats and vegetables. Studies reporting nitrate and nitrite contents worldwide for a significant number of food products have been included in this review article. This review does not include articles with the purpose of improving the method of analysis and which provide nitrate and nitrite contents of a limited number of food products, except for a few studies on a small number of products that have not been previously reported. Three tables were created for visually quick interpretation of the data. Table 1 includes only meat-based products, Table 2 shows studies on vegetables, fruits, dairy products, and other natural food products, and Table 3 gives nitrate and nitrite contents in baby and infant foods.
De Gonzalez et al. evaluated the nitrite and nitrate contents of cured meat products from five different regions in the United States.22 Conventional products (C) and organic/ natural/uncured/indirectly cured products (ONC) were compared according to their nitrite and nitrate contents. In all cases except fermented/acidified sausages, no difference was found between the nitrite levels of C and ONC products. Nitrite levels in the analyzed meat products were below 10 mg kg−1. Nitrate concentrations of fermented/acidified sausages of C and ONC were almost same. Volatile N-nitrosamine, biogenic amine, and nitrite/nitrate levels were determined in 101 dry fermented sausages from the Belgian market.23 Nitrite and nitrate concentrations were detected between
