How long do nitrates stay in the body

Bacterial nitrate reductases are noted by the number 2. Mammalian enzymes with nitrite reductase activity are noted by the number 3 [Adapted from Hord et al. Skip directly to site content Skip directly to page options Skip directly to A-Z link.

Environmental Health and Medicine Education. Section Navigation. Facebook Twitter LinkedIn Syndicate. Minus Related Pages. On This Page. Learning Objective. Upon completion of this section, you will be able to Describe what happens to nitrates and nitrites once they enter the body.

Intake of some amount of nitrates is a normal part of the nitrogen cycle in humans. We also know that this may be particularly important in older people, since natural nitric oxide production via arginine tends to drop with ageing. Nitrates in leafy greens are less likely to form cancer-causing nitrosamines and have plenty of health benefits Credit: Getty.

So when most of the nitrates in our diets come from vegetables — and in turn encourage nitric oxide formation — they are probably good for us. But the report also noted that people of all age groups can exceed this ADI quite easily.

Nitrite intakes are generally much lower one estimate of average intake in the UK being 1. As always, dose makes the poison, and levels of grams mg of nitrate can be acutely toxic, causing changes in haemoglobin that present as a blueish tinge to lips and skin.

The upshot? If you want to eat the right kinds of nitrates and nitrites and avoid the potentially carcinogenic ones, then eat a widely varied diet with at least five servings a day of fruit and vegetables, and avoid nibbling on processed meats too often. That way, the benefits of nitrates and nitrates will almost certainly outweigh the downsides. Correction: A previous version of this story stated that the International Agency for Research on Cancer categorises processed meat as a probable carcinogen, when it categorises it as a carcinogen.

We regret the error. If you liked this story, sign up for the weekly bbc. The truth about the nitrates in your food.

Share using Email. By Angela Dowden 13th March Usually associated with processed meats, nitrates and nitrites are potentially cancer-causing compounds. However, this process would be weakened by polyphenols and other antioxidants such as vitamin C. With enough amounts of antioxidants as vitamin C, the nitrosylation of secondary amine through nitrite was inhibited [ 54 , 55 ]. The International Agency for Research on Cancer IARC has concluded that there was no substantial evidence implicating nitrates as animal carcinogens in [ 56 ].

Moreover, in recent epidemiological investigations, dietary nitrate showed no association with gastric cancer or esophageal cancer in humans [ 7 , 57 ]. Some research even showed that nitrate could decrease the occurrence of gastric cancer [ 11 , 58 ], possibly because the main source of dietary nitrate are vegetables, which contain a large amount of fiber, vitamin C, and other reductants.

Liver and kidney tissues were checked after high-dose nitrate feeding for 2 years, and no observed systemic toxicity or damage was found in miniature pigs [ 60 ]. The association of nitrite with cancer seems conflicted [ 11 ]. The correlation between nitrite and gastric cancer is contradictory in different epidemiological surveys [ 57 ].

In , carrying out a large cohort study including approximately individuals, followed up on for almost 10 years, Cross and his teammates concluded that nitrate and nitrite were not associated with esophageal or gastric cancer, whereas positive associations were found between red meat intake and esophageal squamous cell carcinoma [ 62 ]. Some epidemiological studies use processed or smoked meat as a source of exogenous nitrite ignoring complex compounds such as nitrosamines in such foods, resulting in lack of uniformity and scientific accuracy in conclusions.

Therefore, association of exogenous nitrite with cancer seems less likely because large amounts of nitrite are formed endogenously. Besides, people are in contact with nitrosamine in many circumstances, such as through smoke, beer, water, working environment, especially cigarettes which contain about times the level of nitrosamine in the daily diet.

Methemoglobinemia was found to be caused on ingestion of excessive nitrite [ 64 ], whereas ingestion of excessive nitrate did not lead to the disorder. A study in America showed that even though the mother ingested a large amount of nitrate, the baby would not get methemoglobinemia through breast feeding [ 65 ]. On the other hand, dietary nitrate, the source of which is mostly vegetables, which contain a large amount of antioxidants, effectively decreases the occurrence of methemoglobinemia [ 3 ].

Under conditions of illness or senescence, the activity of eNOS was reduced and the production of NO was decreased, as reported [ 46 , 66 , 67 ], thus indicating exogenous source of NO supplement might have a potential therapeutic treatment for patients undergoing illness or senescence.

Nitrate was reported could lower blood pressure in health volunteers [ 68 ] and established in several experiments in human trials [ 69 ]. The aortic pulse wave velocity was improved, and the platelet-monocyte aggregates reduced in nitrate supplemental patients which resulting in decreased blood pressure [ 70 ].

Whilst with positive clinical trials, negative results were reported showing no significant effect was found in lowing blood pressure with nitrate supplement [ 71 , 72 ].

The reason of these complex results was uncertain and more clinical trials were needed for further research. Although many positive effects were found in animal models, the clinical usage of nitrate was quite limited. With increasing awareness on nitrates, nitrates and nitrate-related products are being accepted. As part of their daily diet, people ingest inorganic nitrate mostly through green, leafy vegetables. Apart from their negatives, dietary nitrate and nitrite have been reported as exogenous donors of biological NO, playing an important role in physiological activity.

Furthermore, dietary nitrate supplements seem to have potential protective effect for body balance, improvement of disorders stroke, myocardial infarction, systemic and pulmonary hypertension, etc. Normal dietary nitrate and nitrite showed no harm to human health and no confirmed evidence stated the explicit association of dietary nitrate and cancer.

Most existing research on nitrite and tumors ignored the complicated compounds in target foods, resulting in contradictory conclusions among researchers. Considering the various protective effects, other than the formal harmful suspects, dietary nitrate and nitrite play an important role in physiological functions through the provision of non-enzymatic NO.

With a new understanding of nitrates and nitrites, their biological functions and applications need further investigation in the future. National Center for Biotechnology Information , U. Journal List Aging Dis v. Aging Dis. Published online Oct 1.

Author information Article notes Copyright and License information Disclaimer. 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 that the original work is properly attributed. This article has been cited by other articles in PMC. Abstract The source of dietary nitrate NO 3 is mainly green, leafy vegetables, partially absorbed into blood through intestinal mucosa.

Source of nitrate and nitrite Systemic circulating nitrate is mainly obtained from two sources, diet and oxidation of endogenous NO, which correspond to exogenous and endogenous nitrates, respectively [ 9 ]. Distribution and conversion of nitrate and nitrite Nitrate and nitrite exist widely in the human body, while the distribution is quite different. Circulation of nitrate and nitrite The salivary glands and oral bacteria play an essential role in the circulation and conversion process of exogenous NO 3 - -NO 2 - -NO pathway.

Open in a separate window. Figure 1. Circulation of nitrate in the body The recycling of dietary nitrate is mainly in salivary glands, where sialin plays a key role in active transport and concentration of nitrate. Function of nitrate and nitrite Under conditions of hypoxia and ischemia, the production of endogenous NO from L-arginine is inhibited.

Safety of nitrate and nitrite Previously nitrate and nitrite were considered as precursors of N-nitroso compounds that were classified as human carcinogens. Clinical application of nitrate and nitrite Under conditions of illness or senescence, the activity of eNOS was reduced and the production of NO was decreased, as reported [ 46 , 66 , 67 ], thus indicating exogenous source of NO supplement might have a potential therapeutic treatment for patients undergoing illness or senescence.

Conclusion As part of their daily diet, people ingest inorganic nitrate mostly through green, leafy vegetables. Crit Rev Food Sci Nutr , 56 The increase in plasma nitrite after a dietary nitrate load is markedly attenuated by an antibacterial mouthwash. Nitric Oxide , 19 Roles of dietary inorganic nitrate in cardiovascular health and disease.

Cardiovasc Res , 89 Novel aspects of dietary nitrate and human health. Annu Rev Nutr , 33 Dietary nitrate and nitrite: Benefits, risks, and evolving perceptions.

Meat Sci , Distribution of Seven N-Nitrosamines in Food. Toxicol Res , 31 Ingested nitrate and nitrite and stomach cancer risk: an updated review. Food Chem Toxicol , 50 Sialin SLC17A5 functions as a nitrate transporter in the plasma membrane.

Biology of nitrogen oxides in the gastrointestinal tract. Gut , 62 Evidence that ingested nitrate and nitrite are beneficial to health. J Food Prot , 65 Nutrients , 7 Estimation of dietary intake of nitrate and nitrite in Great Britain.

Food Chem Toxicol , 25 Nitric oxide and quality and safety of muscle based foods. Nitric Oxide , 24 Nitrites and nitrates in the human diet: Carcinogens or beneficial hypotensive agents? J Ethnopharmacol , Health implications of exposure to environmental nitrogenous compounds. Toxicol Rev , 22 Human safety controversies surrounding nitrate and nitrite in the diet.

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