Harm of nitrates to the body. Study of crop products for the presence of nitrates in winter. Scale of plant needs for nitrogen fertilizers

Of all harmful substances In products in Russia, nitrates are the most well-known. The war with them began during the years of perestroika. I remember now: almost every evening a man came to the news studio with a string bag of vegetables and fruits and a device for measuring nitrates. Like a fiery revolutionary, he told at which market he bought this poison, showing how the needle on the device went off scale from an excess of nitrates. The population also began to buy such dosimeters, and the most suspicious ones completely abandoned vegetables and fruits, replacing them with sausage sandwiches. They didn’t even realize that sausage also contains a lot of nitrates. In fact, this became the first consumer movement in our country, and it began in the era of scarcity.

Is the alarm cancelled?

20 years have passed, and experts say that nitrates are most likely even... beneficial. Is this possible? Scientists have very seriously studied the circulation of nitrates in plants and our bodies and have come to the conclusion that they are not as dangerous as previously thought. But first things first.

About 50 years ago, they tried to limit the consumption of nitrates by introducing strict maximum permissible standards. And there were reasons for this: chemists are well aware that nitrates turn into nitrites (note that the names of both substances differ by only one letter), and from the latter into acidic environment Nitrosamines are formed - real carcinogens. Since stomach juice is acidic, scientists immediately theorized that this terrible substance could be formed from nitrates eaten in vegetables and fruits, all of which contribute to the development of stomach cancer.

“Scientists even confirmed that similar metamorphoses can occur in a living organism, when in an experiment pure nitrates, nitrites and amines necessary for these reactions were introduced into the animals’ stomachs,” says David Zaridze, corresponding member of the Russian Academy of Medical Sciences, director of the Research Institute of Carcinogenesis Oncological scientific center RAMS. - It turns out that vegetables and fruits can really be carcinogenic? It turns out not. In reality, these reactions do not occur in humans. Fruits and vegetables contain antioxidants that block these reactions. Today this problem is closed from a scientific point of view, and vegetables and fruits are considered very healthy.

Formally, the maximum standards for nitrate consumption remain, but increasingly scientists are talking about their meaninglessness. Moreover, our body produces 25-50% of nitrates itself, and we get the rest from food and water (see figure). In addition to vegetables and fruits, there are quite a lot of nitrates in meat products, water, and beer. Almost all sausages and ready-made meat products contain nitrates and nitrites ( nutritional supplements E 249-E 252), which give them a pink meat color and protect them from spoilage. Already in the mouth, under the influence of bacteria, nitrates are converted into nitrites and enter the stomach with saliva. And there, as it turns out, they form not so much carcinogenic nitrosamines, but nitric oxide, which is beneficial for us. It improves blood circulation in the stomach, protecting it from gastritis, ulcers and even from the aggressive effects of drugs such as aspirin. This was recently proven by experiments by Swedish scientists from the University of Uppsala.

Nitrogen and sex

Nitric oxide deserves special mention. This is the main substance in our body that protects blood vessels from damage, improves blood flow and reduces blood pressure. It is also important for the most intimate processes: Viagra and similar drugs do their work largely thanks to nitric oxide, preventing its destruction. And last year, scientists at the University of Texas proved in an experiment on animals that the addition of nitrates and nitrites increases the survival rate of animals during a heart attack by 48%, and reduces the size of a heart attack by 59%. There is work showing that these substances prevent the development of hypertension.

We are sure that nitrates appear in plants from nitrogenous fertilizers. This is not entirely true; fertilizers have very little effect on their content. Most of the nitrates are synthesized by the plant itself; it needs them in the same way as oxygen. Most of them accumulate in leaves and stems, much less in root vegetables and very little in fruits and seeds (tomatoes, cucumbers, peas, etc.). Fruits and berries usually contain much less nitrates than vegetables (rarely more than 10-40 mg/kg). Gifts of nature grown in greenhouses or in insufficient light contain more nitrates.

Where do we get nitrates from?

Vegetables - 50-75%.

Sausages, sausages, ham, brisket and other prepared meat products - 6-10%.

Beer - up to 15%.

Water - 15-22%.

Other products - 4-6%.

In addition to this, our body itself synthesizes nitrates in an amount of 25-50% of consumed foods and drinks.

The quality of drinking water is determined by its organoleptic characteristics. One of the most serious problems is high concentration nitrates - salts nitric acid entering water from wastewater from industrial, domestic and agricultural activities. Nitrates in water can be determined by chemical analysis liquids. Wherein important step is further high-quality cleaning water source.

Excess nitrates are found in underground and surface water sources, less often in wells up to 35 meters deep. In artesian waters, nitric acid salts are contained in minimal quantities or almost absent.

There are three levels of toxicity for compounds that can harm humans. The first level is nitrate, the second is nitrite, the third is dangerous nitrosamine.

The negative impact on the human body and domestic animals is manifested in the following:

1. Nitrates contribute to the formation of a dangerous substance in the blood - methemoglobin, which leads to oxygen starvation. If the methemoglobin level is 15%, this is manifested fatigue, lethargy and dizziness. An increase in methemoglobin up to 60% leads to death.
2. A decrease in hemoglobin levels leads to deterioration in cardiac and vascular system, blockage of blood vessels and capillaries, stroke.
3. Lack of oxygen supply causes severe headaches, migraines, fainting and nausea.
4. Exceeding the concentration of nitrates in water causes poisoning, disruption of the gastrointestinal tract, excretory and endocrine system, destruction of tooth enamel and the appearance of caries.
5. It is dangerous to give water contaminated with nitrates to pets. After all, such a liquid does not undergo heat treatment, so it can lead to serious violations in the functioning of internal organs.

Where do nitrate compounds in water come from?

Wells and wells are the main sources of water for private households, which is used for domestic, household and agricultural needs.

A water source may become polluted in the following cases:

• using household chemicals, discharged into the ground near a hydraulic structure;
• when carrying out agricultural work using fertilizers that contain nitrogen and magnesium in high concentrations;
• when setting up cemeteries for pets and livestock near water intake points.

This leads to saturation of the soil with nitrates, which first penetrate into water horizons and then into private hydraulic structures.

Effective methods of water purification from nitrates

To choose effective method water treatment, you need to know the standard established by WHO for MPC (maximum permissible concentration) of nitrates.

The norm for nitrates in water is 45 mg per liter; in some European countries the norm can be increased to 50 mg per liter. Water for cooking and drinking should not contain more than 10 mg/l of nitrates.

In natural water sources, the content of nitric acid salts does not exceed 2 mg/l.

Nitrates can be quickly and efficiently removed from water using professional reverse osmosis and ion exchange treatment plants.

Reverse osmosis purification

This method allows you to remove most of the nitrates in water extracted from a well using special cleaning elements that effectively filter the incoming liquid. Deep filtration allows you to retain harmful substances and impurities on partition membranes.

The cleaning process is repeated cyclically until clean water, which is discharged into a special tank, and the sediment into a waste tank.

The principle of osmosis is based on separation liquid substance into two solutions having different concentrations. IN working system supported constant pressure osmosis, which determines the rate at which liquid passes through filter membranes.

A reverse osmosis system is an innovative method of water filtration that allows you to reduce increased content existing nitrates in water to normal levels.

The main advantage of reverse osmosis is its reliable design, affordable installation and ease of operation. Install and configure similar system It is quite simple, in addition, it does not require large energy and financial costs for its maintenance.

Reverse osmosis is effective in reducing nitrate levels that exceed 35 g/l, as well as reducing dry matter in water.

The main disadvantage of this cleaning method is the high price of the finished kit. Small-sized units are designed for installation under the kitchen sink, standard units are designed for placement in special rooms. Reverse osmosis systems are no less in demand in city apartments for filtering tap water.

Ion exchange purification

The principle of ion exchange provides for multi-stage filtration of the incoming liquid, as a result of which dangerous ions are replaced by useful compounds.

An ion exchange filter allows you to quickly and efficiently purify water from nitrate and other impurities, as well as reduce its hardness.

Such filtration is successfully used in industry, agriculture and everyday life.

In private households, a single-stage ion-exchange water purification scheme is often used, which has a number of disadvantages. It does not involve a large number of reagents, which require large water resources for washing the ion exchanger from the formed sediment. In addition, such an installation does not guarantee high quality filtration, unlike multi-stage schemes, the effective impact of which depends on the use of acidic hydrogen cations.

To choose the most suitable option for purifying water from nitrites, the following activities are carried out:

• sanitary examination of the water intake point to identify possible sources of water pollution, as well as ways to neutralize them;
• laboratory analysis to determine nitrates in water, as well as the full chemical and bacteriological composition.

Based on the data obtained, a decision is made to select the best way solutions to such a problem.

You can get rid of nitrate compounds in water using other methods. accessible ways, but those indicated in the article are the most effective. To provide a home clean water and protect yourself from negative influence nitrates, it is worth taking care in advance to install an effective and safe water treatment system.

It's no secret for most people: in order to have good health, it is better to eat more vegetables, fruits, and less animal food. As you know, nitrates are considered an indispensable attribute of the nitrogen cycle in nature. This is an important part of nitrogen nutrition for plants, without which the complex biological process of protein synthesis becomes impossible. Nitrates were, are and will be, even if you have to completely abandon the use of fertilizers. Nitrates in plants can be reduced to nitrites, which undergo further transformation and produce ammonia - the basis for plant nutrition. But why did a natural process suddenly become considered harmful to humans?

Everything is good in moderation

The presence of nitrates in plants should in itself be considered a normal phenomenon, but their excessive increase is extremely undesirable. This is due to the fact that nitrates are highly toxic to humans. Although it is more correct to talk about their reduced form - nitrites, which interact with hemoglobin in the blood when massively ingested into the body. As a result, the substance methemoglobin is formed, which is unable to carry oxygen. Violated normal breathing tissues and cells of the body (during the process of tissue hypoxia). As a result, lactic acid accumulates and the amount of protein sharply decreases. Nitrates are especially dangerous for infants, since their enzyme systems are considered imperfect; the reduction of methemoglobin to hemoglobin occurs very slowly.

Harmful properties of nitrates

Nitrates can reduce the content of vitamins in food and affect all types of metabolism. With prolonged intake of nitrates into the human body (even in the smallest doses), the amount of iodine decreases, which can lead to an enlargement of the thyroid gland.

It was possible to establish a connection between nitrates and the appearance of tumors in gastrointestinal tract person.

Nitrates provoke the development of pathogenic (very harmful) intestinal microflora, highlighting toxic substances(toxins) human body. Because of this, autotoxication occurs, the process of poisoning the body.

This happens in a variety of ways:

• through drinking water;
• through food products of animal and plant origin;
• through medications.

Most of the nitrates enter the human body with fresh and canned vegetables (at the level of 40-80 percent of the daily amount of nitrates). A small amount of nitrates can come from fruits, baked goods, and dairy products.

How to fix it

It is very important to introduce more red and black currants, fruits, and other berries into your diet (there are practically no nitrates in hanging fruits). Drink green tea. These are natural neutralizers of nitrates that have entered your body. Vitamin E can also protect the body from the harmful effects of nitrates.

It is no secret that early fruits and vegetables, parsley, dill, as well as brightly colored foreign fruits can contain “nitrates that are very harmful to human health.” When purchasing fruits and vegetables at markets, buyers often hear from sellers that their products do not contain nitrates, because they do not use fertilizers during the growing process. Is it really possible to grow decent vegetables and fruits without the use of nitrates?

What are nitrates

Nitrates are salts of nitric acid. Unfortunately, it should be noted that the sellers at the market are simply deceiving you: all living organisms contain a certain amount of nitrates. In order for the plant to grow and develop well, as well as to provide it with normal nutrition, you cannot do without these compounds!

Nitrates enter our body with food and also with water. The danger is not the content of nitric acid salts in products itself, but their excessive amounts in the juice and pulp of vegetables and fruits.

Why are nitrates dangerous?

Since the fifties of the last century, scientists began to study the impact of these compounds on human health and life. The researchers analyzed the collected information regarding rare disease– methemoglobinemia. A person suffering from this disease experiences oxygen starvation. This happens due to the conversion of hemoglobin to methemoglobin. If the first actively participates in gas exchange, delivering oxygen to all cells and tissues, then the second does not take part in the transport of oxygen. As a result of the experiments, it turned out that the cause of this disease is too much nitric acid salts in the water that people used for drinking and cooking. Somewhat later, in the sixties, scientists studied how nitrates enter the human body along with food.

Experts in Russia consider it normal if no more than 3.7 mg of nitrates per 1 kg of body weight enters the body per day human body. In other states, the permissible standards are slightly different. In Germany, for example, these standards are more stringent. It is clear that doses of nitrates causing poisoning, much higher than the established limits.

Let us remember that these compounds enter the human body along with water and food. Getting sucked into the walls small intestine, they get into the blood. Nitrates leave the body with urine, and in nursing mothers they also enter milk. At bad work the kidneys and digestive system, accordingly, almost no harmful substances are eliminated. The same thing happens when there are too many nitrates in the foods you eat.

Particularly dangerous are nitrites, which are formed from nitrates during metabolic processes. It is nitrites that react with hemoglobin, resulting in the formation of another compound - methemoglobin. If the new compound is in the blood in an amount of up to 2%, then this is normal. A person begins to feel symptoms of poisoning if the methemoglobin level rises to 30%. The body may die if the amount of this compound in the blood reaches 50%. The conversion of nitrates into nitrites occurs as a result of the activity of microbes in the large intestine. In case of insufficient acidity gastric juice, due to gastritis or due to individual characteristics, bacteria in the large intestine are able to enter various organs of the digestive system, producing large amounts of nitrites. These compounds combine with amines and amides resulting from digestion rich in protein food. Accordingly, nitrosamines and nitrosamides appear, which, according to scientists, are carcinogens.

Symptoms of nitrate poisoning

How to determine that a person has been poisoned by nitrates? What are the symptoms of this poisoning? Do you suspect that you feel unwell after eating a questionable vegetable (fruit)? Know: the time for signs of poisoning to appear will depend on how sensitive your body is, on your weight, on the number of years you are and, of course, on how much of these vegetables (fruits) you ate.

So, a person may immediately feel sick, then vomiting and diarrhea begin. A special sign of nitrate poisoning is an enlarged and dense liver with painful sensations. The therapist or emergency doctor will immediately determine the nature of the poisoning based on the condition of this organ. By the way, in case of ordinary poisoning with stale or poor-quality food, such transformations definitely do not happen to the liver.

Then the pulse weakens and becomes arrhythmic. Decreasing arterial pressure, breathing quickens, limbs become cold. If first aid is not provided on time, the head begins to hurt and there is noise in the ears. Facial muscles contract convulsively, movements become uncoordinated. Observed brightly severe weakness. At severe form poisoning, a person loses consciousness and may even fall into a coma. Mental depression is also observed. It happens that poisoning with nitric acid salts can manifest itself only as slight diarrhea and a drowsy, apathetic state.

How nitrates get into our body

It is no secret that the path of nitrates into vegetables and fruits is through fertilizers. In order to reap a decent harvest, gardeners are forced to additionally feed the plants, since the land Agriculture completely exhausted, and they had already given away everything they could a long time ago.

Different varieties of plants are cultivated using special technologies developed at one time by specialists in the field of botany, biology, and chemistry. Agronomists and agricultural technicians also made a significant contribution to this matter.

These same technologies impose strict regulations on the amount of fertilizers that are applied to the soil; the quality and volume of nitrates are also determined. Unfortunately, technological rules are often not followed. In pursuit of “quick” fruits, bright color, correct form and the large weight of vegetables and fruits, dishonest farmers, almost without using potassium and phosphorus fertilizers, abuse nitrogen fertilizers with might and main. This is the reason for the excessive accumulation of nitric acid salts in various parts of the plant. There are especially many of them in fruits, stems and leaves. The situation is further aggravated by a lack of lighting, as well as if the crops are too thick.

It is common for almost all plants to store nitrates. initial stage growth. The accumulated salts of nitric acid are a source of nutrition in the future; with the help of these compounds they grow and bear fruit. If the plants are fertilized, adhering to the technological rules, most of these substances will be used up, and vegetables and fruits will delight with a pleasant taste and bring only benefits. Of course, you won’t be able to monitor how well farmers grow fruits and vegetables, but it is within our power to be vigilant and prudent in stores and markets.

How to choose nitrate-free products

The least harmful compounds are found in medium-sized, fully ripened fruits. (The size of the fruit is considered relative to other fruits of the same variety). This means that tomatoes that are too large, unless they are the “Bull’s Heart” variety, should not be taken. Most likely, they were raised with the help of growth stimulating agents. Do not eat too small fruits, there is a possibility that they simply did not have time to spend the nitrates accumulated for development. When looking closely at radishes, opt for the round-fruited variety. A long-fruited variety usually accumulates more nitric acid salts. Remember that fruits that taste sour always contain harmful substances. in miniscule quantities. Thanks to vitamin C, which is rich in the juice and pulp of these fruits, nitrates cannot be converted into nitrites.

The longer the fruits are stored, the less nitric acid salts remain in them. For example, after six months from the start of storage, the amount of nitrates in potatoes is reduced to 30%, in carrots - to 50%. Such a positive metamorphosis occurs only when proper storage, namely, in a room with good ventilation, a certain temperature and humidity. Conversely, improper storage of vegetables and fruits in rooms where it is too hot and humid creates all the conditions for the conversion of nitrates into nitrites. Remember: only dry, undamaged and clean vegetables can be lowered into the cellars.

An interesting fact: salted and canned fruits have fewer harmful substances than fresh ones. The fact is that a certain proportion of nitrates ends up in the brine. To achieve a reduction in the amount of nitric acid salts, vegetables need to be soaked in a solution of salt or vinegar for at least a week.

It should be noted that different parts of plants accumulate different amounts of harmful substances. Here helpful information, which will definitely come in handy in the kitchen. You want the dishes you prepare to be not only appetizing, but also beneficial to your body?

Where are the most nitrates?

IN leafy vegetables Most nitric acid salts accumulate in the stem and roots. In this regard, the stems of table greens and aromatic herbs should be removed, the cabbage stalk should be thrown away, and the thick veins on the cabbage leaves should be cut off. The carrot core is full of nitrates, and closer to the skin there are fewer harmful substances. In radishes and cucumbers, on the contrary, the danger comes from the peel, so before preparing any dish, it would be good to peel these vegetables. By the way, when peeled, they taste better.

In watermelon and melon, an accumulation of nitrates is observed in the pulp immediately under the rind, as well as in those areas that have not yet ripened. It is advisable to trim the stalks of beets, eggplants, radishes, squash and zucchini: it is in this part of them that nitric acid salts accumulate. In almost all fruits, the peel and the pulp underneath are dangerous. Do not be lazy to clean the questionable fruits; in this simple way you can avoid poisoning. Interestingly, fruits contain much less harmful substances than vegetables; this is provided by nature.

How to reduce nitrates in food

Can't live without table greens in early spring? Place the herb brought from the market or supermarket in a jar of water, then place it in direct sunlight for about sixty minutes. To prevent the greens from wilting, carefully sprinkle them with water from a spray bottle. These actions will help the plant use up the supply of substances necessary for life, and the amount of nitrates will, accordingly, decrease.

Vegetables such as beets, pumpkins, eggplants, squash and zucchini can be processed sufficiently in a simple way, as a result of which the amount of nitrates will noticeably decrease. To do this, cut the vegetables into small pieces and put them in cold water for thirty minutes. During this half hour, the water must be changed at least three times.

During the boiling process, vegetables lose not only some vitamins, but also some of the nitric acid salts that were in the juice, as well as in the pulp. For example, when boiled, potatoes lose up to 75% of nitrates, cabbage - 70%, beets - 40%. Salts of nitric acid fall from vegetables into the broth, which, after thirty minutes from the start of boiling, it is advisable to drain, replacing it with fresh boiling water.

You should know that the long process of thawing fruits helps convert nitrates into nitrites. Defrost vegetables using the microwave right before cooking or eating them. Herbs and chopped vegetables can be added directly from frozen to boiled soup.

It is recommended to eat freshly prepared food. If the dish is kept in a room with sufficient high temperature, nitrates begin to be converted into nitrites and nitrosamines. Store vegetables and fruits in the refrigerator. It is also recommended to boil the soup and carefully reheat it prepared vegetables before serving them to the table. Lost when heated a small amount of nitrites.

To prevent poisoning by harmful compounds, it is recommended to consume foods that contain a lot of ascorbic acid every day. You remember that thanks to vitamin C, nitrates do not become more toxic to human body connections.

Buy yourself a test strip, with its help you can easily determine the content of nitric acid salts in fruits. Using it is not at all difficult, you just need to attach the necessary part of the indicator to a new cut of the vegetable, and then all that remains is to check the color of the strip with the color scale. Unfortunately, the accuracy of such a test often leaves much to be desired. You can also purchase an electronic analyzer that will more accurately show the amount of nitrates in a certain product. However, the price of this device is quite high, so such analyzers are rarely used in everyday life.

In the end, I would like to focus your attention on the fact that the safest and useful fruits- these are those that have ripened in your garden or vegetable garden or were grown by people whose integrity you do not doubt. This is the only way you will know for sure what fertilizers the plants were fed with, how much of them were added to the ground, and what the fruits were treated with. In addition, when working in the garden, you will be actively moving, consuming unnecessary calories. Exercise stress It will also help strengthen muscles and improve mood.

It is well known that the most valuable thing a person has is his health, which cannot be bought and which largely depends on proper nutrition his. No wonder there is a proverb: “Tell me what you eat, and I will tell you what makes you sick.”

It is no longer a secret for most that to improve health it is better to eat more fruits, vegetables and less animal food. With rational plant nutrition should be done 10 useful tips that will help a person live longer:

Must be included in daily menu any fruit orange color, which contains beta-carotene, valuable for the body, which reduces the risk of cancer and heart diseases, even among smokers.

Every day on our table there should be fruits and vegetables containing vitamin C. This primarily applies to patients diabetes mellitus, because studies by Italian scientists have found that a daily dose of vitamin C of 1000 mg accelerates the production of the hormone insulin.

Tomatoes, except good taste, have and healing properties thanks to high content they contain lycopene. Daily use tomatoes significantly reduce the risk of colon cancer, oral cavity, stomach, because it neutralizes the effect of nitrosamines, which contribute to the development cancer cells. It has also been noted that those who eat tomatoes in sufficient quantities are much more energetic and active than those who neglect these vegetables.

Fruits should be eaten raw. British scientists presented convincing statistics. Based on data from a 17-year study of residents of England, Scotland and Wales, scientists found that those who ate fresh fruits, reduced the risk of acute heart attacks by 24%, the risk of stroke by 32% and premature death by 21%.

Be sure to eat raisins and dried apricots; they are indispensable for those who want to improve their health and gain more strength and energy, since the potassium contained in them helps better work heart muscle.

Fruit juices are very healthy. However, it should be remembered that fruit juices cannot replace food, which can be abused by children. One glass fruit juice per day for a child is quite enough.

Raw vegetables provide good mood, fresh skin, elegant figure, reduce troubles with the stomach and intestines, because they contain a significant amount of fiber. This is especially important when sedentary life and in the fight against obesity and constipation. The healing powers of the raw plant food have been known for a long time.

Onions and garlic are needed to get rid of rotting in digestive tract as a result poor nutrition, especially during the period of mass spread of influenza.

It is better to eat fruits 0.5 hours before meals, on an empty stomach and without bread.

According to Bragg, 3/5 of the entire diet should be fruits and vegetables: raw, baked and boiled.

So, fruits and vegetables, but they must be healthy and free of substances such as nitrates and nitrites.

Nitrates and nitrites, their role in plants

Nitrogen is one of the most important chemical elements in plant life, because it is necessary for the synthesis of amino acids from which proteins are formed. The plant receives nitrogen from the soil in the form of mineral nitrogen salts (nitrate and ammonia).

In plants, nitrogen undergoes complex transformations. Nitrogen metabolism in plants is a complex process, and nitrates occupy an intermediate position in it:

HNO3 – HNO2 – (HNO)2 – NH2OH + NH3 |

(nitrate) (nitrite) (hyponitrite) (hydroxylamine) (ammonia)

Nitrates in plants are reduced to nitrites. Various metals (molybdenum, iron, copper, manganese) are involved in this process, and intensive consumption of carbohydrates occurs, since restoration requires energy, the source of which is carbohydrates. Nitrites can accumulate in plants and thereby inhibit their growth. But the main part of nitrites, undergoing further transformations, produces ammonia (NH3). Ammonia Russian scientist D.M. Pryanishnikov called the alpha and omega in plant nutrition.

Harmful effects of nitrates on the human body

People first started talking about nitrates in our country in the 70s, when several mass gastrointestinal poisonings of watermelons occurred in Uzbekistan due to their excessive feeding with ammonium nitrate (1).

World science already knew about nitrates much earlier. It is now common knowledge that nitrates are highly toxic to humans and domestic animals:

Under the influence of the enzyme nitrate reductase, nitrates are reduced to nitrates, which interact with hemoglobin in the blood and oxidize divalent iron into ferric iron. As a result, the substance methemoglobin is formed, which is no longer able to carry oxygen. Therefore, the normal respiration of cells and tissues of the body is disrupted (tissue hypoxia), as a result of which lactic acid and cholesterol accumulate, and the amount of protein drops sharply.

Nitrates are especially dangerous for infants, because their enzyme base is imperfect, and the restoration of methemoglobin to hemoglobin is slow.

Nitrates contribute to the development of pathogenic (harmful) intestinal microflora, which releases toxic substances into the human body - toxins, resulting in toxicity, i.e. poisoning of the body. The main signs of nitrate poisoning in humans are:

cyanosis of nails, face, lips and visible mucous membranes;

nausea, vomiting, abdominal pain;

diarrhea, often with blood, enlarged liver, yellowness of the whites of the eyes;

headache, increased fatigue, drowsiness, decreased performance;

shortness of breath, increased heart rate, up to loss of consciousness;

in case of severe poisoning - death.

Nitrates reduce the content of vitamins in food, which are part of many enzymes, stimulate the action of hormones, and through them affect all types of metabolism.

Pregnant women experience miscarriages, healthy men- decreased potency.

With prolonged intake of nitrates into the human body (even in small doses), the amount of iodine decreases, which leads to an enlargement of the thyroid gland.

It has been established that nitrates have a strong influence on the occurrence cancerous tumors in the gastrointestinal tract in humans.

Nitrates can cause a sharp dilation of blood vessels, resulting in a decrease in blood pressure.

With all of the above, it should be remembered that it is not the nitrates themselves that cause harm to the human body, but the nitrites into which they turn under certain conditions.

Permissible norms of nitrates for humans

Maximum for an adult permissible norm nitrates - 5 mg per 1 kg of human body weight, i.e. 0.25 g per person weighing 60 kg. For a child, the permissible dose is no more than 50 mg.

A person can tolerate a daily dose of nitrates of 15–200 mg relatively easily; 500 mg is the limit permissible dose(600 mg is already a toxic dose for an adult). For poisoning infant 10 mg of nitrates is enough.

IN Russian Federation the permissible average daily dose of nitrates is 312 mg, but in the spring it can actually reach 500 – 800 mg/day.

Ways of nitrates entering the human body

Nitrates enter the human body in various ways.

Through food:

of plant origin;

animal origin.

Through drinking water.

Through medications.

The bulk of nitrates enters the human body with canned food and fresh vegetables(40 – 80% of the daily amount of nitrates).

A small amount of nitrates comes from bread products, fruits, with dairy products.

Some nitrates can be formed in the human body itself during its metabolism.

Nitrates also enter the human body with water, which is one of the main conditions normal life person. Contaminated drinking water causes 70–80% of all existing diseases, which reduce human life expectancy by 30%. According to WHO, more than 2 billion people on Earth fall ill for this reason, of which 3.5 million die (90% of them are children under 5 years of age). IN drinking water Groundwater contains up to 200 mg/l of nitrates, much less in water from artesian wells. Nitrates enter groundwater through various chemical fertilizers (nitrate, ammonium), from fields and from chemical plants producing these fertilizers. Largest quantity nitrates are found in groundwater. Typically, city residents drink water that contains up to 20 mg/l of nitrates, while residents rural areas- 20 – 80 mg/l nitrates.

Nitrates are also found in animal foods. Fish and meat products in in kind contains some nitrates (5 – 25 mg/kg in meat, and 2 – 15 mg/kg in fish). But nitrates and nitrites are added to the finished product meat products in order to improve its consumer properties and for longer storage (especially in sausages). Raw smoked sausage contains nitrites 150 mg/kg, and boiled sausage- 50 – 60 mg/kg.

Nitrates also enter the human body through tobacco. It was found that some varieties of tobacco contain up to 500 mg of nitrates per 100 g of dry matter.

The mere presence of nitrates in plants is normal phenomenon, since they are sources of nitrogen in these organisms, but their excessive increase is extremely undesirable, since they (as we already know) are highly toxic to humans and domestic animals.

Nitrates mainly accumulate in roots, root vegetables, stems, petioles and large veins of leaves, and much less in fruits.

There are also more nitrates in green fruits than in ripe ones. The most nitrates are found in lettuce (especially in greenhouse), radish, parsley, radish, beets, cabbage, carrots, dill:

in beets and carrots there are more nitrates in the upper part of the root crop, and in carrots also in its core;

in cabbage - in the stalk, in thick petioles and in the upper leaves.

It was also found that all vegetables and fruits contain the most nitrates in their skin.

According to their ability to accumulate nitrates, vegetables, fruits and fruits are divided into 3 groups (2):

with average content (300 – 600 mg): cauliflower, zucchini, pumpkins, turnips, radishes, White cabbage, horseradish, carrots, cucumbers;

WITH physiological point In terms of vision, the amount of nitrate nitrogen in plants is determined by the ratio:

absorption processes;

transport;

assimilation;

its distribution in different organs and parts of the plant.

And all these processes are determined by a combination of soil-ecological conditions, agrotechnical and genetic factors.

Thus, the accumulation of nitrates in plants depends on a complex of reasons:

from biological features the plants themselves and their varieties. It was found that the most nitrates are contained in the “Red Giant” radish compared to its other varieties (“pink with white tip,” “heat,” etc.).

depending on the age of the plants: there are more of them in young organs (except for spinach and oats). Less nitrates accumulate in hybrid plants. There are more nitrates in early vegetables than in late ones.

on the mineral nutrition regime of plants. Thus, microelements (especially molybdenum) reduce the nitrate content in radishes, radishes and cauliflower; zinc and lithium - in potatoes, cucumbers and corn. The nitrate content in plants decreases and as a result of replacement mineral fertilizers into organic ones (manure, peat, etc.), which gradually decompose and are absorbed by plants. Organic fertilizers have a positive effect on cabbage, carrots, beets, parsley, potatoes, and spinach. Irrational, careless use of chemical fertilizers and excessive doses lead to a strong accumulation of nitrates, especially in table root vegetables.

The nitrate content increases more strongly when using nitrate fertilizers (KNO3, NaNO3, Ca(NO3)2) than when using ammonium fertilizers. Behind last years(according to the head of the laboratory of food toxicology of the Institute of Nutrition T.S. Khotimchenko) there was a significant decrease in nitrates in domestic crop products due to less use of chemical fertilizers due to their high cost. If in 1988–89 the MPC for nitrates exceeded 15% for vegetables, now it is no more than 3%.

from factors environment(temperature, air humidity, soil, light intensity and duration):

the longer the daylight hours, the less nitrates in plants;

during humid and cold summers, the amount of nitrates increased 2.5 times.

when the temperature increased to 20 °C, the amount of nitrates in table beets decreased by 3 times. Normal illumination of plants reduces the nitrate content, so there are more nitrates in greenhouse plants.

When eating fruits, we must carefully monitor their quality. To keep apples longer, they are coated with an emulsion coating and saturated with preservatives. Such apples are very attractive in appearance, but sometimes they have no taste, no smell, no vibrant juiciness, and the preservatives in them kill beneficial microflora in the human intestine. The same preservatives are used to store other products ( vegetable oil, sausages, sausages). Therefore, you need to carefully monitor the certificates of imported products.

The issue of accumulation of nitrates in plants in our region began to be studied by the Sakha Scientific Research Institute of Agriculture since 1989, whose employees found out that on Sakhalin, due to special agrometeorological conditions, the content of nitrates in plants increases:

a large number of days, frequent fogs;

reduced solar radiation;

more low temperatures air and soil;

strong winds.

Ways to reduce the harm of nitrates in plants on the human body

It is very important not only to know which plants, which organs and parts of them contain nitrates, but it is also equally important to know how to reduce the content of these toxic substances for the body, therefore a number of valuable tips are offered:

The amount of nitrates decreases with heat treatment vegetables (13) (washing, boiling, frying, stewing and blanching). So, when soaking - by 20 - 30%, and when cooking - by 60-80%.

in cabbage - by 58%;

in table beets - by 20%;

in potatoes - by 40%.

It should be remembered that with intensive washing and blanching (cooking with boiling water) vegetables, not only nitrates are released into the water, but also valuable substances: vitamins, mineral salts, etc.

To reduce the amount of nitrates in old potato tubers, the tubers should be filled with a 1% solution of table salt.

Zucchini and eggplant need to be cut top part, which is adjacent to the stalk.

Since there are more nitrates in the peels of vegetables and fruits, they (especially cucumbers and zucchini) need to be peeled, and for herbs, their stems should be thrown away and only the leaves should be used.

Both ends of cucumbers, beets, and radishes must be cut off, since they have the highest concentration of nitrates.

Vegetables and fruits should be stored in the refrigerator, because at a temperature of +2 °C it is impossible to convert nitrates into more toxic substances - nitrites.

To reduce the content of nitrites in the human body, it is necessary to use vitamin C in sufficient quantities in food ( ascorbic acid) and vitamin E, because they reduce harmful effects nitrates and nitrites (4).

It was found that when canning, the nitrate content in vegetables decreases by 20–25%, especially when canning cucumbers and cabbage, since nitrates go into the brine and marinade, which must be poured out.

Salads should be prepared immediately before eating and eaten immediately.

Conclusion

The problem of toxic accumulation of nitrate nitrogen on modern stage is one of the most acute and relevant.

Many research institutions around the world are busy solving this problem, but despite close attention to this problem, a radical solution has not yet been found.