The health effects of nitrites and nitrates have become a growing concern in recent years, frequently discussed in the media and debated by health organizations. In France, the issue has been taken seriously at the political level.
In France, a parliamentary bill was passed in 2022 to gradually reduce the use of nitrites in processed meats such as ham and sausages. In March 2023, the government introduced a plan aiming to reduce nitrite levels by 20–25%, though it did not propose a full ban. Despite additional proposals in 2023 and 2024 to prohibit nitrite use entirely, the French Parliament rejected them. As of now, nitrite use is not banned but is being progressively limited.
This article explores what nitrites and nitrates are, where they come from, how they affect human health, and what steps we can take to reduce potential risks.
Sources, Dietary Exposure, and Potential Health Effects
Nitrates and nitrites occur naturally in water and soil, because of the nitrogen cycle, therefore in our vegetables, fruits and drinking water too. They are also frequently used as food additives to increase shelf life and avoid bacterial growth and to provide red coloration to processed meats products. Their use of additives is massive, however up to %80 of nitrites and nitrates comes with the natural sources.
The nitrate content in fruits and vegetables can vary significantly from region to region due to several factors such as lighting conditions, soil properties, humidity, and fertilization practices. One study found a significant association between nitrate/nitrite concentrations in produce and environmental factors like annual rainfall, average temperature, and fertilizer application. Nitrate levels were highest in regions with high annual rainfall and increased further with rising average temperatures.(3)
After being ingested, nitrates are absorbed through the digestive system and enter the bloodstream, where they mix with nitrates naturally produced by the body. While most of the nitrate is excreted through urine, about a quarter is taken up by the salivary glands. There, it reaches the mouth and is converted by oral bacteria into nitrite. Once swallowed, this nitrite is further transformed in the stomach’s acidic environment into nitric oxide and other nitrogen-based compounds, including potentially harmful N-nitrosamines. (8)
Experimental studies highlighted the fact that nitrites from N-nitroso compounds (NOCs) in the digestive tract considered as a potential carcinogen in human and proven carcinogen in a number of animal species. These compounds could result from endogenous synthesis. Indeed, a high-red-meat diet led to the endogenous synthesis of NOCs in the colon during an experiment on healthy volunteers. They can also result from exogenous exposure from nitrites and nitrates converted by the oral microbiota.
In fact the natural sources of nitrites and nitrares such as vegatables and fruits contain antioxidants also that naturally inhibit the formation of NOCs and may reduce the risk of carcinogenic potential of natural sources.
As food additives nitrites and nitrates can be named ;
- Potassium nitrite (e249),
- Sodium nitrite (e250),
- Sodium nitrate (e251)
- Potassium nitrate (e252)
Most of the reference studies did not distunguish natural or food additive nitrites and nitrates. But one study with 101 056 participants compared the cancer risks for non consumers and consumers of the food additives to distinguish the effects of natural sources and food additives. In this large prospective cohort study, food additive
nitrates intakes, in particular potassium nitrate (e252), were associated with increased breast cancer risk, specifically pre-menopausal breast cancer, and nitrite additives
intakes, especially sodium nitrite (e250), were positively
associated with prostate cancer risk. No association was detected for
nitrites or nitrates from natural sources. (1)
In another study, researchers examined the associations between nitrite and nitrate intake from processed meat and diastolic blood pressure. They found that higher nitrite intake was associated with increased diastolic pressure, even after accounting for sodium intake. The effect was particularly pronounced when nitrite and sodium were consumed together. (2)
One systematic review and meta-analyses showed that Glioma, bladder, and stomach cancer risks were higher, but pancreatic cancer risk was lower with higher nitrite intakes. Thyroid cancer risk was higher, but kidney and bladder cancer risks were lower with higher nitrate intakes. But there were some limitiations for this review. There are only a few studies available for each type of cancer, and this study was also unable to examine the effects of naturally occurring forms of vitamins—such as C, D, and E—that can inhibit NOCs, as well as the overall intake of these vitamins from individuals' daily diets. (4)
Another systematic review and meta-analyse found out that nitrate intake from diet was associated with risk of colorectal cancer but nitrite in diet was not significantly associated with risk of colorectal cancer. Nitrate in water did not show an association with risk of colorectal cancer. (5) The last finding about drinking water made me think that the amount of nitrites and nitrates are not that much high in the drinking water unless if there is not a great pollution in it. So this may can cause to not to find an association between them. On the other hand another systematic review and meta-analyses study in 2022, found out an association of nitrate in drinking water with gastric cancer. (7)
CONCLUSION:
More research is needed to fully understand the effects of nitrites and nitrates on human health. But all these research are sufficient for us to consider its harmful effects and take individual precautions and action. As a practical first step, reducing processed meat consumption and increasing the intake of fruits and vegetables—rich in antioxidants that can counteract the potential harmful effects of these compounds—can be beneficial. For example, if you choose to include processed meat in a meal, adding vegetables to your plate may help neutralize some of the negative impacts. Aim to consume at least 3–4 portions of vegetables and 2–3 portions of fruits each day for better overall health.
This model visually demonstrates the ideal balance of food groups on a single plate. Half of the plate is filled with vegetables and fruits. The other half is divided equally between whole grains and protein sources. You can see this model in many nutritional national guidelines, promoting variety and moderation.
REFERENCES:
1) Nitrites and nitrates from food additives and natural sources and cancer risk: results from the NutriNet-Santé cohort, Int J Epidemiol. 2022 Aug 10;51(4):1106-1119. doi: 10.1093/ije/dyac046.
2) Nitrite and nitrate intake from processed meat is associated with elevated diastolic blood pressure (DBP), Clin Nutr. 2023 May;42(5):784-792. doi: 10.1016/j.clnu.2023.03.015. Epub 2023 Mar 21.
3) A worldwide systematic review, meta-analysis and meta-regression of nitrate and nitrite in vegetables and fruits, Ecotoxicol Environ Saf. 2023 Jun 1:257:114934. doi: 10.1016/j.ecoenv.2023.114934. Epub 2023 Apr 19.
4) Association between Dietary Nitrate, Nitrite Intake, and Site-Specific Cancer Risk: A Systematic Review and Meta-Analysis, Nutrients. 2022 Feb 4;14(3):666. doi: 10.3390/nu14030666.
5) Nitrate-nitrite exposure through drinking water and diet and risk of colorectal cancer: A systematic review and meta-analysis of observational studies, Clin Nutr. 2021 May;40(5):3073-3081. doi: 10.1016/j.clnu.2020.11.010. Epub 2020 Nov 28.
6) Dietary nitrate and nitrite and human health: a narrative review by intake source, Nutr Rev. 2022 Mar 10;80(4):762-773. doi: 10.1093/nutrit/nuab113.
7) Nitrate and nitrite contamination in drinking water and cancer risk: A systematic review with meta-analysis, Environ Res. 2022 Jul:210:112988. doi: 10.1016/j.envres.2022.112988.
8) Leafy Vegetable Nitrite and Nitrate Content: Potential Health Effects, Foods. 2023 Apr 15;12(8):1655. doi: 10.3390/foods12081655.
Photo taken from : https://food-guide.canada.ca/en/tips-for-healthy-eating/make-healthy-meals-with-the-eat-well-plate/
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