Nitrates/Nitrites in Food—Risk for Nitrosative Stress and Benefits

Abstract

In the context of impact on human health, nitrite/nitrate and related nitrogen species such as nitric oxide (NO) are a matter of increasing scientific controversy. An increase in the content of reactive nitrogen species may result in nitrosative stress—a deleterious process, which can be an important mediator of damage to cell structures, including lipids, membranes, proteins and DNA. Nitrates and nitrites are widespread in the environment and occur naturally in foods of plant origin as a part of the nitrogen cycle. Additionally, these compounds are used as additives to improve food quality and protect against microbial contamination and chemical changes. Some vegetables such as raw spinach, beets, celery and lettuce are considered to contain high concentrations of nitrates. Due to the high consumption of vegetables, they have been identified as the primary source of nitrates in the human diet. Processed meats are another source of nitrites in our diet because the meat industry uses nitrates/nitrites as additives in the meat curing process. Although the vast majority of consumed nitrates and nitrites come from natural vegetables and fruits rather than food additives, there is currently a great deal of consumer pressure for the production of meat products free of or with reduced quantities of these compounds. This is because, for years, the cancer risks of nitrates/nitrites have been considered, since they potentially convert into the nitrosamines that have carcinogenic effects. This has resulted in the development and rapid expansion of meat products processed with plant-derived nitrates as nitrite alternatives in meat products. On the other hand, recently, these two ions have been discussed as essential nutrients which allow nitric oxide production and thus help cardiovascular health. Thus, this manuscript reviews the main sources of dietary exposure to nitrates and nitrites, metabolism of nitrites/nitrates, and health concerns related to dietary nitrites/nitrates, with particular emphasis on the effect on nitrosative stress, the role of nitrites/nitrates in meat products and alternatives to these additives used in meat products.

The Effects of Processing and Preservation Technologies on Meat Quality: Sensory and Nutritional Aspects

“…Nitrites react with amines and amino acids leading to the formation of N-nitrosamines, which are chemical agents with potentially carcinogenic, mutagenic and teratogenic activities. For this reason, alternatives are being sought to reduce or eliminate the addition of nitrites in meat products and reduce health risks [ 201 ].…”

Beetroot, A Remarkable Vegetable: Its Nitrate and Phytochemical Contents Can be Adjusted in Novel Formulations to Benefit Health and Support Cardiovascular Disease Therapies

“…In contrast, the enzymatic activity of bacteria in the mouth and conversion of NO 3 − to NO 2 − may be disrupted by antibiotic use or mouth rinsing with an anti-bacterial mouthwash. Oral nitrate-reducing microbiota are beneficial to the host and participate in the control of cardiovascular NO homeostasis [ 6 , 192 , 193 ].…”

“…In addition to dietary sources, NO 3 − and NO 2 − can be endogenously originated from NO synthetized by the three isoforms of the nitric oxide synthase (NOS), family from the amino acid L-arginine and O 2 , namely the neuronal (nNOS or NOS-I) and endothelial (eNOS or NOS-III) isoforms, both constitutive and dependent on Ca 2+ -calmodulin, and the inducible isoform (iNOS or NOS-II). In addition, L-arginine is metabolized by arginase to L-ornithine and urea to eliminate excess nitrogenous compounds [ 193 ].…”

“…This radical character confers high reactivity to this compound, since it rapidly oxidizes to NO 2 − and NO 3 − . NO displays an affinity for lipophilic environments and accumulates in the lipid milieu, such as cell membranes and lipoproteins [ 193 ]. In human physiology, NO can exert antioxidant functions and is considered a secondary messenger, acting on the vascular endothelium, central and peripheral neurons, and immune system, inhibiting platelet activation, adhesion, and aggregation, modulating vascular tone, and improving human skeletal muscle function [ 5 , 27 , 194 , 195 ].…”

Alternative Curing Methods

“…After adding nitrite to the mildly acidic meat matrix (pH 5.5), it is reduced to nitric oxide (NO) [6]. NO is gaseous and interacts with the heme subunit of myoglobin [2] forming the "nitrosomyoglobin" complex responsible for the typical reddish-pink color of cured meat [2,[6][7][8]. To induce this effect, more than 20 ppm are needed.…”