Carolina Baraúna de Assumpção1, José Luiz Nascimento2, Ândrea Ribeiro dos Santos1, André Salim Khayat1, Bruna Meireles Khayat1, Caroline Aquino Moreira-Nunes1,3, Ney Carneiro dos Santos1, Gregory Riggins4, Rommel Rodríguez Burbano1*, Paulo Pimentel de Assumpção1,5
1Nucleus of Research in Oncology, Federal University of Para. Belem, PA 66073000, Brazil
2Biological Science Institute, Federal University of Para. Belem, PA 66075110, Brazil
3Research Laboratory in Hemoglobin apathies & Genetics of Hematologic Diseases, Federal University of Ceara, Fortaleza, CE, 60430-370, Brazil
4Johns Hopkins University, Baltimore, Maryland 21218, USA
5Brazilian Gastric Cancer Association. Sao Paulo, SP 01318-901, Brazil
Received: 28 November, 2015; Accepted: 05 March, 2016; Published: 07 March, 2016
Rommel Mário Rodriguez Burbano, Human Cytogenetics Laboratory; Institute of Biological Sciences , Federal University of Para, Augusto Correa Street 01, Guama, CEP 66075-110, Belem, Para, Brazil, Tel: +55-91-3201-7930; Fax: +55-91-3201-7568; E-mail:
de Assumpção CB, Nascimento JL, dos Santos ÂR, Khayat AS, Khayat BM, et al. (2016) Nitrite Levels Before and after Washing in Salted Fish. Arch Clin Gastroenterol 2(1): 007-009. 10.17352/2455-2283.000011
© 2016 de Assumpção CB, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Cancer; Environmental health; Gastroenterology
Background: Gastric adenocarcinoma is the fourth most common malignancy worldwide and is globally the second leading cause of cancer-related deaths each year. Salted foods and exposure to H. pyloriinfection during the infancy have been considered the most important environment risk factors for gastric cancer. Despites increased access to electric energy, allowing the use of refrigerators to better conserve foods, many people keep consuming salted food, by washing them before eating with the intention of reducing salted flavor and also supposing to decrease or avoid risk of diseases. The aim of this study was to investigate the efficacy of reducing nitrites levels in salted fish by washing the fish before consuming, to find if washing salted food should be an efficient measure to reduce, or even avoid, the nitrites related gastric cancer risk.
Methods: Nine paired samples of fresh and salted fish and 20 additional samples of salted fish were taken for analyses. The nine paired samples were used to comparison of nitrites levels between salted and fresh fish, and the 20 additional salted fish samples for analyses of the effect of washing the fish in reducing nitrites levels. To simulate the usual procedure of living salted fish submersed in fresh water before consumption, we kept the salted samples under water during different periods of time and checked the nitrites levels at each “washing time”. For every experiment a p value of 0•05 was considered, and t-student tests were performed.
Results: The washing procedure did not reduce significantly the nitrites levels in salted fish, even after long periods of immersion (p=0•807), and the levels of nitrites in washed salted fish remained much higher than that of the fresh samples, maintaining the consumers exposed to nitrites, known carcinogens related to gastric cancer, and giving an equivocal and hazard feeling of protection to the population.
Conclusion: Salted fish has higher concentration of nitrites compared to fresh. Washing, or living salted fish under water, does not provide significant decrease of the nitrites levels.
Gastric adenocarcinoma is the fourth most common malignancy worldwide and is globally the second leading cause of cancer-related deaths each year [1,2].
The death rate from gastric cancer has gradually declined over the last several decades in the United States and worldwide, indicating that environmental factors (e.g. diet) play a critical role in the etiology of this malignancy .
However, in undeveloped regions, incidence and mortality remain very high  and opportunities for research on cancer prevention include investigating specific circumstances of exposure to known carcinogens .
Salted foods and exposure to H. pyloriinfection during the infancy have been considered the most important environment risk factors for gastric cancer, and several new meta-analyses support the carcinogenic effect of high salt intake in the context of Helicobacter pylori infection [6,7].
Despites increased access to electric energy, allowing the use of refrigerators to better conserve foods, many people keep consuming salted food. Cultural habits and lack of information regarding the hazards of salting foods seem to be responsible for the high intake of these types of food. Even having available fresh foods, and refrigerators at home, many people, usually prefer to consume salted food.
Nevertheless, before eating salted food, people wash the food with the intention of reducing salted flavor and also supposing to decrease or avoid risk of diseases related to salted food, as is the case of gastric cancer.
With the aiming of investigate the efficacy of reducing nitrites levels in salted fish by washing the fish before consuming, we decided to conduce a high controlled experiment, simulating the washing procedure, and compared the nitrites levels of salted fish before and after washing the fish, to find if washing salted food should be an efficient measure to reduce, or even avoid, the nitrites related gastric cancer risk.
Material and Methods
Samples from both fresh and salted Pirarucu, a traditional Amazonic fish, were obtained at Ver-o-Peso marked, the most famous fish market in Belém, the capital of Pará state, in Brazil.
Nine paired samples of fresh and salted fish and 20 additional samples of salted fish were taken to Neurochemistry Lab, at Federal University of Pará, and analyzed in several manners as described below.
The 29 samples of salted food have been salted 8 days before, as usual, taking the proportion of 1kg (2·2lbs) of salt to each 4kg (8·8lbs) of fish. The nine samples of fresh fish were taken for analyses at the same day that the fish were catched.
The nine paired samples were used to comparison of nitrites levels between salted and fresh fish, and the 20 additional salted fish’s samples for analyses of the effect of washing the fish in reducing nitrites levels.
Assay of nitrite level
Samples were initially diluted 1:2 in PBS (phosphate buffer saline) and then 500µl of each diluted sample were mixed with the same volume of Griess reagent (0·1% naphtylethylen + 1% sulfanilamide in 5% phosphoric acid). The nitrites levels were analyzed using a spectrophotometer with a wave length of 540nm, measured and referred to a standard curve of known concentrations of Sodium nitrite .
To simulate the usual procedure of living salted fish submersed in fresh water before consumption, we kept the salted samples under water during different periods of time and check the nitrites levels at each “washing time”.
We established four washing protocols: 15 minutes, 60 minutes, 360 minutes and 720 minutes of “washing time”. The 20 salted samples were divided in four groups of five samples, and each group was analyzed before and after washing, according to the protocols.
The nitrites levels of the nine paired samples were compared taking the average levels of nitrites of each group (salted and fresh fish).
The nitrites levels of each salted sample group submitted to the washing protocols were measured before and after each defined washing time and the results were compared.
For every experiment a p value of 0·05 was considered, and t-student tests were performed using SPSS 17.0 pack (SPSS Ins. Chicago, IL, USA).
The nitrites levels (µM) of the nine fresh fish samples, used for the first experiment of comparing salted and fresh fish, varied from 4·54 to 8·49 (mean 6·32, SD 1·40), and from 16·40 to 31·67 (mean 24·76, SD 6·15) in the nine salted fish. The nitrites levels of salted fish were superior to that of the fresh fish, and these results were statistically significant (p<0·05) (Figure 1).
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