We are used to hearing from early childhood that you need to eat vegetables because they are healthy. Vegetables contain macro- and micronutrients (carbohydrates, proteins, fats, vitamins and mineral salts, biologically active substances, phytohormones) and natural non-nutritional substances (fiber, cellulose, ballast compounds). In addition to useful and ballast compounds, vegetables can also contain contaminants (pollutants) and food additives (substances introduced into products artificially to improve or change their properties). Contaminants and nutritional supplements are often combined under the same term “xenobiotics”.
The danger of contaminants
Xenobiotics can get into vegetables during their cultivation, storage, transportation or preparation. Contaminants can be natural (man-made) and man-made, chemical and biological. The amount of pollutants that enter the body with plants depends on their type and growing conditions. Natural chemical contaminants are present in fruits in varying quantities, for example, solanine in potatoes and eggplant, nitrates in beets and carrots, histamine in red tomatoes.
The most common anthropogenic pollutants of a chemical nature are toxic elements (arsenic, cadmium, copper, lead, mercury), nitrogen compounds (nitrates, nitrosamines, nitrites), pesticides, aromatic hydrocarbons, radionuclides, dioxins.
Biological contaminants include microorganisms (salmonella, yersinia, staphylococcus, mold, fungus), their metabolic products (botulinum toxin, mycotoxins), helminths (their eggs, larvae). Normally, there should be no biological pollutants in vegetables: they get into them if grown or stored improperly.
Given the morphological structure of some vegetables, their natural composition, growing conditions and further processing, storage and use, as well as the method of eating, root vegetables (beets, carrots, radishes), leafy green vegetables (lettuce, spinach, sorrel, parsley, dill), early cucumbers, nightshade (eggplant, tomatoes, potatoes, bell peppers), zucchini, white cabbage.
Let’s try to understand in detail what these familiar vegetables may be dangerous and how to avoid serious consequences.
Sources of nitrates and pesticides
Nitrates are a must for many vegetables. But some of them have the genetic ability to selectively accumulate nitrates. Such vegetables include root vegetables (beets, radishes, carrots), green leafy vegetables, zucchini, early cucumbers, tomatoes and cabbage. Moreover, in beets, carrots and radishes, more contaminants are concentrated near the "tail" and the root, in cabbage - in the stalk and upper leaves, in green leafy vegetables - in the stems and petioles. Less nitrates are found in late (ground) fruits.
What is the danger of nitrates in vegetables? Improper storage of vegetable products (at elevated humidity or temperature) leads to the activation of microorganisms on their surface. In the process of recovery reactions, bacteria turn nitrates inert to the human body into dangerous nitrites.
When nitrites enter the bloodstream, they bind to erythrocyte hemoglobin and form methemoglobin, which is unable to perform its oxygen transporting function. As a result, human cells and tissues experience oxygen starvation, which is especially dangerous for nerve tissue and heart muscle. When high concentrations of nitrites enter the bloodstream, a person develops acute hypoxia, which can end fatally.
Allergens in vegetables
The cause of allergic reactions is the use of vegetable products that contain specific biologically active substances or provoke their production in the human body. For example, tomatoes are plants that enhance the production of histamine, although they themselves do not contain it. At the same time, eggplants, soybeans and products from them, sauerkraut are themselves sources of histamine and, in the presence of hypersensitivity in the person who uses them, can cause food allergies up to life-threatening anaphylactic reactions. The concentration of histamine and histamine-like substances increases many times during canning.
Allergenic products are also "foreign" vegetables that do not grow in our climate zone, or fruits grown in greenhouse conditions. The same imported cabbage, cucumbers or tomatoes with a seemingly identical chemical composition contain an increased amount of allergenic substances such as histamine, tyramine and similar compounds in comparison with domestic ones.
Solanine, an alkaloid contained in the green fruits of vegetables of the nightshade family, is also a conditional vegetable allergen: green potato tubers, unripe fruits of tomato, eggplant and sweet pepper. This compound, when it enters the human body in moderation, can cause digestive upset, and in large quantities, a violation of the mental state.
If vegetables are not stored properly, mold often develops on them. Molds in the course of their life produce toxins called mycotoxins. They are formed at different stages of the production of vegetables: during cultivation, storage, transportation, processing. Factors that contribute to toxin formation in molds are:
- high or low temperature;
- excess moisture;
- free access of oxygen;
- damage to the protective cover of vegetables;
- insemination of the premises with mold spores.
Of vegetable crops, mycotoxins most often appear in beans and legumes, cabbage, tomatoes, and eggplant.
Mycotoxins (aflatoxin, ochratoxin, citrinin and others) in the human body cause mycotoxicosis - severe poisoning that affects the liver, kidneys, gastrointestinal tract, central nervous, immune, reproductive system. Moreover, the disease can be acute or chronic, provoke reversible or irreversible changes with various outcomes: from mild malaise to death.
Biological contamination, as a rule, infection with helminths and their eggs, Escherichia coli and other fecal flora, green leafy vegetables (lettuce, spinach, sorrel, parsley) and white cabbage are most often exposed. Between the leaves of these cultures, comfortable conditions are created for the propagation of helminths and bacteria, so when they are used in unwashed or insufficiently washed form, you can easily become infected.
How to Avoid Killer Vegetables
Despite the possible danger of the gifts of the earth, their use is not necessary and cannot be refused. Knowing how to reduce the content of contaminants, each person will be able to protect themselves and their loved ones by eating their favorite vegetables.
Nitrate and Pesticide Control
The ideal preventive method of poisoning with nitrates and nitrites is the purchase of a device for home use - nitrate meter. With it you can go to the market and to the store: just turn on the nitrate meter, select the desired type of fruit on the display and immerse the probe for a few seconds inside the vegetable. Modern devices have a scoreboard on which the result of the express analysis is displayed at the same time, and its comparison with the maximum permissible concentrations for this type of product (more often in the form of a light indication). The only drawback of nitratomers is their rather high cost (from 5900 rubles).
It is not recommended to purchase the very first early vegetables. It is better to wait a couple of weeks: in later plants there will be less pollutants of a chemical and radioactive nature. The waiting rule is also acceptable for ground vegetables: the longer they are stored, the less contaminants remain in them.
To reduce the chemical contamination of early vegetables, they must be thoroughly washed and soaked in cold water for 20-30 minutes. Peeling fruits also reduces the concentration of nitrates and pesticides in them.
It is possible to avoid nitrate and pesticidal poisoning with the help of primary and thermal cooking of vegetables, as well as observing moderation in the use of young (greenhouse) plants. Root crops can be boiled (the level of contamination is reduced by 40-70%) or blanched (up to 50%).
But this method of processing vegetables, such as drying, leads to an increase in the concentration of nitrogen compounds, pesticides and radionuclides by removing the moisture in which they are dissolved, so you should not use it for harvesting vegetables.
Prevention of allergies and poisoning
Avoid the appearance of allergic reactions can only the rejection of those products that cause them. Allergy sufferers should be aware of their allergies and exclude hazardous vegetables and canned foods from them.
Avoid solanine poisoning, green or sprouted potato tubers and unripe eggplants should not be eaten. To reduce the solanine content in eggplant and sweet pepper, they need to be peeled and soaked in salt water. Another way to reduce the level of solanine in solanaceous fruits is salting, so salted green tomatoes, eggplant or pepper can be eaten without fear.
To prevent mycotoxins from entering the human body, vegetables affected or affected by mold must be avoided. Removing mold-affected areas does not completely remove harmful microorganisms and mycotoxins, but only reduces their number. Heat treatment of vegetables also does not destroy mycotoxins, therefore, it is impractical to choose boiling or frying vegetables as a way to prevent mycotoxicosis.
Vegetables should be bought only in grocery stores, where a special place is reserved for them, in which the temperature and humidity conditions of storage are observed. Visually, vegetables should not be covered with dirt or mold. It is strictly forbidden to sell vegetables with broken shells, slices or remote areas in the distribution network: mycotoxins easily penetrate the fetus from its affected surface and continue to develop inside it.
Moreover, the softer the fetus, the greater the likelihood of seeding of its pulp by microorganisms.
Helminth and bacteria infection prevention
Vegetables must be washed before use. Brush off root crops with a brush, then rinse under running warm water, and then you can start cleaning them. Cabbage should be freed from the upper leaves and rinsed under running warm water. Green leafy vegetables must be washed under running water, soaked in containers with cool water for several minutes, stirring occasionally with your hand, so that the rest of the earth from them settled on the bottom of the vessel. After this, the greens need to be washed again under cool running water.
When buying vegetable products, you need to pay attention to the presence of accompanying documentation from sellers. Conscientious sellers must have documents confirming the quality and safety of vegetables sold: their large batch should be tested for nitrates, salts of heavy metals, pesticides, mycotoxins and radionuclides. Such extensive studies are usually carried out by vegetable producers or their major suppliers. The research results are drawn up by the expert opinion of Rospotrebnadzor.
Each small batch of vegetable products must additionally be accompanied by a quality certificate.
In the Russian Federation, the content of contaminants is regulated at the Federal level: Sanitary rules and norms of SanPiN 184.108.40.2068-01 "Hygienic requirements for safety and nutritional value of food products" that are to be observed by individuals and legal entities in the process of growing, transporting, storage, vacation and processing of food products, including vegetable raw materials.
However, no matter how strict laws and other regulatory documents may be, no matter how faithfully their manufacturers and sellers comply, the consumer himself is directly responsible for his own health. “Trust, but verify” - this rule should become for each consumer his personal law.