Nitrates: a danger on the plate

The nitrogen that is incorporated into our body usually does so as part of the proteins but, unlike this way of assimilation, there are other ways of ingesting it that are not only unnecessary, but are not recommended. This is the case when it is part of the nitrates.

Where are nitrates found?

The human exposure to nitrates It is produced mainly through the consumption of vegetables and, to a lesser extent, from water and other foods that incorporate additives:In vegetables, especially in green leafy vegetables, such as chard, spinach and lettuce.In water, where the content can be highly variable. Both the WHO and Spanish legislation establish a maximum value of 50 mg/liter of nitrates.In preservative additives. Sodium nitrite (E249), potassium nitrite (E250), sodium nitrate (E251) and potassium nitrate (E252) are commonly used. All of them are specific inorganic preservatives for meat products and additionally for some cheeses and fish products, because they prevent the multiplication of the bacteria that cause botulism.

What health problems do nitrates cause?

Although nitrates themselves are relatively non-toxic, their metabolites and reaction products, eg nitrites, may be implicated in adverse health effects. It is the case of the methemoglobinemia (when hemoglobin does not release oxygen in body tissues) and the carcinogenesis.

The infants and young children Those who ingest high concentrations of nitrates in the diet can more easily exceed the figure of 3.65 mg of nitrates per kilogram of body weight.

The problem of the conversion of nitrates into nitrites

Nitrate can be transformed into nitrite by bacterial reduction both in food –during processing and storage– and in the body –in saliva and the digestive tract–.

Also, nitrates react with amino acids in food in the stomach, generating nitrosamines and nitrosamides of proven carcinogenic effects.

How are nitrates avoided?

The 3 basic measures to reduce the intake of nitrates are:

1. Prefer vegetables that contain them in low amounts

They have a higher level of nitrates chard, with about 1,700 mg/kg. Next are beets, lettuce, celery and spinach, all exceeding 1,000 mg/kg on average. They are closely followed by pumpkin and then, with values ​​of about 650 mg/kg, turnip.

Wash in plenty of water can reduce nitrate levels by 10-15%, and by cook them in water decreases from 15 to 80%. Other measures to consume these foods with less nitrates is:

Choose them from organic farming and moderate those grown in greenhouses. Remove the outermost and green leaves. Keep cooked vegetables (whole or pureed) in the refrigerator if they are to be consumed the same day; if not, freeze them. Avoid vegetables packed in plastic.

The Spanish Agency for Food Safety and Nutrition (AESAN) points out that for an average consumption of chard or spinach with an average level of nitrates, it is unlikely that there is a concern for health; however, in cases of high consumption it is publicly recognized that there would be a risk.

The AESAN recommends do not include spinach or chard in purees before the first year of age and, if it does, that its content does not exceed 20% of the total puree. Do not give more than one serving of these vegetables a day to children between one and three years of age, or to children with gastrointestinal infections.

They are low in nitrates. in descending order, carrot, cucumber, potato, onion, pepper, tomato and pea, all below 300 mg/kg. Zucchini, leeks and green beans can present medium levels (between 420 and 320 mg/kg).

The European Food Safety Authority recommends eating about 400 grams of vegetables (fruits and vegetables) per day. With this amount, the acceptable daily intake (ADI) of nitrates (3.65 mg/kg of body weight) is not exceeded and its benefits are ensured.

2. Drink water with a minimum content of nitrates

Health authorities control the nitrate content of drinking water. For this reason, in principle, the presence will not be greater than 50 mg/liter.

The problems with water and nitrates occur in populations that obtain it from aquifers that can be contaminated with nitrates from livestock farms.

3. Avoid foods with additive nitrates and nitrites

Additives should be avoidedsodium nitrate (E251) and potassium nitrate (E252), just like him sodium nitrite (E249) and the potassium nitrite (E250). At least two of these additives are found in practically all products of animal origin (meat and fish).

All of them are specific inorganic preservatives for meat products and additionally for some cheeses and fish products, because they prevent the multiplication of the bacteria that cause botulism.

In general, foods of animal origin cured, salted and smoked they are rich in exogenous nitrosamines and nitrites, which are in turn precursors of endogenous nitrosamines in the stomach.

Epidemiological studies suggest that consumption of smoked, pickled, and salted foods increases the incidence of esophageal and stomach cancer.