Nitrates in drinking water are at the heart of many discussions. In France, regulations limit the nitrate level to 50mg/l. But beyond the numbers, what is the true impact of nitrates on our health?
Nitrates: definition, sources, benefits, and harms
Nitrates are natural chemical substances, more precisely salts (or esters) of nitric acid containing the anion NO 3. In simple terms, they are composed of the element nitrogen (N) and oxygen (O). Nitrates are naturally present in the environment and are also produced by human activities.
Natural origins
Nitrates are naturally present in soil, water, and certain foods, particularly leafy green vegetables such as spinach and lettuce. They are the result of the decomposition of organic matter by bacteria.
In humans, our main sources of nitrates are plant-based foods: Beets, lettuce, spinach, potatoes, etc. For example, consuming 50 g of spinach provides 250mg of nitrate, equivalent to 5 liters of water at 50 mg/l of nitrate.
Their use in agriculture
Nitrates are commonly used as fertilizers (in the form of Calcium Nitrate, Potassium Nitrate, or Ammonium Nitrate) in agriculture because they are an excellent source of nitrogen for plants.
But this is where the problem lies. It is indeed intensive agriculture that exposes the dark side of nitrate usage. Modern agriculture is a scourge for the environment: a heavy rain following fertilizer application can bury most of the fertilizer content in groundwater.
Nitrate pollution in water
Thus, the excess of nitrates in water, often due to agricultural runoff, is a major environmental concern. Indeed, high concentrations of nitrates in water can lead to algal blooms. The overabundance of these algae creates dead zones where marine life cannot survive due to lack of oxygen.
For example, the large amount of nitrate that Brazil discharges into the Amazon River endangers the ecosystems of Martinique and Guadeloupe. This is a proven fact and a real environmental catastrophe.
On the other hand, the ingestion of this product by the human body, within reasonable limits, compared to the intake from vegetables, is not dangerous at all; quite the opposite.
Also read: Pesticide residues in tap water: How to protect yourself?
Nitrates, environment, and health: let us not confuse them!
As we have seen, while an excess of nitrates in a watercourse can trigger the proliferation of harmful green algae for ecosystems, the ingestion of nitrates, at doses comparable to our plant intake, is not harmful. On the contrary, they can be beneficial for our body.
The benefits of nitrates
That is why modern science considers nitrates to be friends (not to be confused with nitrite salts, a controversial preservative in processed meats. But we will return to that).
For example, in the human body, nitrates are converted into nitrites, which can then be transformed into nitric oxide, a molecule that plays a key role in the dilation and relaxation of blood vessels.
In fact, the benefits of nitrates are so well-known that medications have been manufactured from them, available by prescription! They are used to treat heart failure, hypertension, or to help athletes breathe better at altitude and deliver oxygen to muscles.
Finally, they reduce stress and lower blood pressure.
However, it is important to remember that it is all a matter of balance: high levels of nitrates can be harmful, particularly for infants, as they can cause a condition called methemoglobinemia. But in moderate amounts, they are not necessarily to be avoided.
We refer you to these 2 articles to learn more:
- Nitrates: beware, they are good for health!
- Nitrates, good for health: from a medical standpoint, the debate is closed!
WHO Standards vs French Standards
The World Health Organization (WHO) limits nitrates to 50mg/l without specific provisions for children or pregnant women. However, in France, they are perceived as risky for infants under six months. It is therefore essential to highlight this difference in perception.
Nitrates Vs. Nitrites
As we have seen, at reasonable concentrations (and they are for tap water in France), nitrates themselves are not directly toxic.
So where does the danger lie?
The risks associated with nitrates (NO3) are actually those posed by nitrites (NO2), which are themselves formed from nitrates under the action of bacteria.
As mentioned earlier, in the human body, a small amount of nitrates can be converted into nitrites. These can then react with other compounds to form potentially harmful substances. But it is primarily from certain diets that the problem arises.
Use of nitrites in food
Indeed, nitrites are commonly used as preservatives in the food industry and can come in various forms. Here are some of the most common forms:
- Sodium nitrite: This is one of the most commonly used forms in the food industry. It is often added to processed meats for its ability to prevent bacterial growth and to give a pink color to meats. [you will spot them on the packaging with the code E250]
- Potassium nitrite: Although it is less common than sodium nitrite, potassium nitrite is sometimes used as an alternative, especially in organic foods. [you will spot them on the packaging with the code E249]
- Organic nitrites: Some vegetables, such as lettuce, spinach, and beets, naturally contain nitrites. Upon ingestion, these nitrites can be converted into nitrosamines in the stomach, especially in the presence of specific amines.
Health risks associated with nitrites
It is essential to note that, although nitrites are used to prevent the growth of dangerous bacteria such as botulism, excessive consumption can be concerning for health.
Indeed, once formed, nitrites can cause the formation of “methemoglobin” in the blood, a modified version of hemoglobin that cannot transport oxygen effectively. As mentioned earlier in this article, this can be particularly problematic in infants, who may develop a condition called “infant methemoglobinemia.”
However, in a healthy adult, stomach acidity limits bacterial growth, thereby reducing nitrite production. On the other hand, infants are more vulnerable due to the immaturity of their digestive system. Nevertheless, if the nitrate content in water does not exceed 50 mg/L, this risk for babies is considered minimal.
How to reduce individual exposure to nitrites?
In conclusion, if you want to reduce your exposure to nitrates and nitrites at all costs, you should focus on your consumption of red meats and other processed meats!
The ANSES (French Agency for Food, Environmental and Occupational Health & Safety) recommends 150 grams of processed meat per week and 500 grams of red meat per week. https://www.anses.fr/fr/content/le-point-sur-les-nitrites-et-les-nitrates-en-10-questions
How to remove nitrates from tap water? (Even if it’s unnecessary…)
While the presence of nitrates and nitrites in our diet is accepted, their presence in our water is often a source of concern.
Thus, you will find many products on the market promising to rid your tap water of the ‘nasty’ nitrate ion. Let us take a closer look at 2 types of water filters and their effects on your tap water.
The case of filter jugs
Some carafes, through the action of their filter, replace nitrates with sodium ions.
Indeed, be aware that in the filters of filtering carafes, beads filled with resin are inserted to replace nitrates with sodium ions (table salt, which is already consumed in excessive amounts in ultra-processed food!).
Of course, calcium is also reduced by 90%, which is largely bioavailable in water and necessary for our health. It allows, for example, the transmission of commands from the brain to the muscles.
Obviously, these beads, loaded with nitrates, become very difficult to recycle. In fact, they are generally not recycled, as it would be too costly.
Also read: The filtering carafe: a good idea?
The reverse osmosis system
Another device in the family of tap water purifiers will promise you the elimination of nitrates from drinking water: the reverse osmosis system.
Also read: A reverse osmosis system, for what use?
The reverse osmosis system is a device used to purify water through a process called reverse osmosis. Reverse osmosis is the process by which water is forced through a semi-permeable membrane in order to separate and remove impurities, salts, and other contaminants present in the water.
Nitrate molecules, which are larger than water molecules, are prevented from passing through and are therefore removed from the water. Generally, a reverse osmosis system will eliminate between 90% and 99% of the nitrates present in the water.
The result is therefore demineralized water (goodbye essential minerals) and nitrate-free, which are good for health and whose initial concentration is completely safe and regulated / controlled!
Also read: Limestone / calcium ion in drinking water, the whole truth!
Therefore, it is crucial to understand the impacts of the solutions we adopt for the purification of our water. In the case of filter jugs and the reverse osmosis system, in seeking to eliminate a supposedly harmful substance, we impoverish the quality of tap water while worsening its environmental impact!
Moderation and diversity!
I conclude with a note of common sense: a substance, nitrates, which is beneficial (and essential) for health provided by our vegetables, can hardly be dangerous when absorbed in liquid form in good water.
To claim otherwise would be like saying that the vitamin C contained in cabbage is good, but that taking a vitamin C tablet would be dangerous…
In (bio) chemistry, everything is a matter of quantity; nothing should be abused, but healthy and varied products should be consumed, which provide us with what we need to build our body and our immunity.
To your health!
