Nitrites and nitrates

What are?

Nitrite (NO ₂ ) and nitrate (NO ₃ ) are substances composed of nitrogen (N) and oxygen (O) normally present in nature.

The former derive from nitrous acid and the latter from nitric acid.

Their presence is essential for the growth of plants which, thanks to sunlight, use nitrogen to synthesize their protein structures.

Man has learned to enrich the soil of these substances through the use of natural and chemical fertilizers, thus ensuring optimal crop growth.

In a second moment the usefulness of nitrites and nitrates has been exploited also in the alimentary field preserving the characteristics of some foods and at the same time increasing their shelf life.

The human being has thus succeeded in polluting two of the fundamental elements for its survival: on the one hand the aquifers with nitrogen fertilizers and on the other the foods with artificial preservatives.

Nitrites and nitrates, why are they dangerous?

NITRATES: in themselves they are harmless but in particular conditions they can turn into nitrites (long periods of storage, heat, acid pH). This percentage is normally around 20-30% and makes them much less dangerous than nitrites.

NITRITES: they have the ability to bind to hemoglobin (the blood protein that carries oxygen in our body), transforming it into methaemoglobin and consequently reducing the transport of oxygen to the tissues.

This aspect is particularly dangerous for children and newborns who absorb greater quantities of nitrites from the diet. Poor oxygenation can, in these cases, cause asphyxia and breathing difficulties.

The ability of nitrites to combine with amines (organic compounds found especially in protein foods, such as meat, cured meats and cheeses) generates carcinogenic substances called nitrosamines .

These substances are already formed in the oral cavity by some salivary enzymes. In the stomach, the acid environment further favors its formation.

A small amount of vitamin C (or ascorbic acid) is also secreted at the gastric level, which significantly reduces the synthesis of nitrosamines; however, a recent scientific study has shown that in the presence of lipids in the stomach (10%), vitamin C could have a favorable effect on the synthesis of nitrosamines.

Nitric oxide is generated by the reaction between nitrites and vitamin C in the stomach; this could however spread into lipids and interact with oxygen to form nitrosamine-generating chemicals. However, in the literature a general consensus can still be found about the protective effects of vitamin C on nitrosamine synthesis.

The American Food and Drug Administration recognized nitrosamines as "... one of the most powerful groups of carcinogens ever discovered". Dr. William Lijinsky reported the results of his studies by introducing nitrosamines into the feeding of some animals he wrote: "in six months the presence of tumors was found in 100% of the guinea pigs. The cancerous manifestations are present in every part of the body: in the brain, in the lungs, in the pancreas, in the stomach, in the liver and in the intestines."

According to the AIRC (Ass. It. Cancer Research) the consumption of sausages with preservatives is one of the ascertained causes of stomach cancer, so that in Italy this disease is more widespread in regions where the consumption of these products is greater.

Where are?

FOOD: they are used as additives in canned meats, cured meats, marinated fish and sometimes also in dairy products. Except for rare exceptions, foods with the highest levels of nitrites and nitrates added are the cured meats.

VEGETABLE: the concentration of nitrates in foods of vegetable origin is particularly high in some vegetables. In particular, their presence depends on:

quantity and quality of fertilizers used; for this reason the plants coming from organic and / or not intensively fertilized crops contain a lower percentage of nitrates
amount of light absorbed: as we have already mentioned, plants need sunlight to use the nitrogen contained in nitrates. It follows that plants grown in greenhouses or exposed to light only contain more nitrates than seasonal ones grown in the fields.

Types of vegetables:

high in nitrates: lettuce, kohlrabi, cappuccino lettuce, watercress, chard, radish, horseradish, rhubarb, beetroot, spinach
medium nitrate content: turnip top, endive, fennel, kale, celery, white cabbage, savoy cabbage, courgette
low in nitrates: eggplant, green bean, cauliflower, broccoli, chicory, pea, cucumber, potato, sprouts, carrot, pepper, mushrooms, leek, Brussels sprout, red cabbage, bitter root, asparagus, tomato, onion.

The distribution of nitrates in the vegetable is also variable, with higher concentrations in the stems, in the ribs, in the outer leaves and in the rind.

However, it is interesting to note that these vegetables are particularly rich in vitamin C and poor in amines, a winning mix that prevents the transformation of nitrates into nitrites and the latter into nitrosamines.

WATER: water can enrich itself with nitrites following their absorption from the land, or because it is particularly rich in bacteria capable of producing nitrites from nitrates.

CONTINUES: Nitrites and nitrates, regulations and food labels »