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From early childhood, we are used to hearing that vegetables need to be eaten because they are healthy. Vegetables contain macro- and micronutrients (carbohydrates, proteins, fats, vitamins and mineral salts, biologically active substances, phytohormones) and natural non-alimentary substances (fiber, cellulose, ballast compounds). In addition to useful and ballast compounds, vegetables may also contain contaminants (pollutants) and food additives (substances artificially added to products to improve or change their properties). Contaminants and food additives are often lumped together under the same term xenobiotics.
The danger of contaminants
Xenobiotics can get into vegetables during their cultivation, storage, transportation or preparation. Pollutants can be natural (natural) and anthropogenic, 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 amounts, such as solanine in potatoes and eggplants, nitrates in beets and carrots, and histamine in red tomatoes.
The most common anthropogenic pollutants of a chemical nature are toxic elements (arsenic, cadmium, copper, lead, mercury), nitrogenous 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 contaminants in vegetables: they get into them during improper cultivation or storage.
Taking into account the peculiarities of the morphological structure of some vegetables, their natural composition, growing conditions and further processing, storage and use, as well as the way they are eaten, root crops (beets, carrots, radishes), leafy green vegetables (lettuce, spinach, sorrel, parsley, dill), early cucumbers, nightshade (eggplants, tomatoes, potatoes, sweet peppers), zucchini, white cabbage.
Let’s try to figure out in detail how these familiar vegetables can be dangerous, and how to avoid serious consequences.
Sources of nitrates and pesticides
Nitrates are an essential waste product of many vegetables. But some of them have the genetic ability to selectively accumulate nitrates. These vegetables include root vegetables (beets, radishes, carrots), green leafy vegetables, zucchini, early cucumbers, tomatoes, and cabbage. At the same time, in beets, carrots and radishes, more contaminants are concentrated near the “tail” and root, in cabbage – in the stalk and upper leaves, in green leafy vegetables – in stems and petioles. Less nitrates are found in late (ground) fruits.
Why are nitrates in vegetables dangerous? Improper storage of vegetable products (at high humidity or temperature) leads to the activation of microorganisms on their surface. In the process of reducing reactions, bacteria convert nitrates that are inert to the human body into dangerous nitrites.
Nitrites, getting into the blood, bind to erythrocyte hemoglobin and form methemoglobin, which is not able to perform its oxygen-transporting function. As a result, human cells and tissues experience oxygen starvation, which is especially dangerous for nervous tissue and heart muscle. When high concentrations of nitrites enter the blood, a person develops acute hypoxia, which can be fatal.
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 among the plants that increase the production of histamine, although they themselves do not contain it. At the same time, eggplants, soybeans and their products, sauerkraut are themselves sources of histamine and, in the presence of hypersensitivity in a person who consumes 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.
The conditional vegetable allergen also includes solanine, an alkaloid contained in the green fruits of vegetables of the nightshade family: green potato tubers, immature fruits of tomato, eggplant and sweet pepper. This compound, having entered the human body in moderation, can cause digestive disorders, and in large quantities – a violation of the mental state.
Mycotoxin “bomb”
Mold often develops when stored improperly. Molds in the course of their life produce toxins, which are called mycotoxins. They are formed at different stages of vegetable production: during cultivation, storage, transportation, processing. Factors that contribute to the formation of toxin in mold fungi are:
- high or low temperature;
- excess moisture;
- free access to oxygen;
- damage to the protective cover of vegetables;
- contamination 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 mycotoxicoses – severe poisoning that affects the liver, kidneys, gastrointestinal tract, central nervous, immune, and reproductive systems. In this case, the disease can be acute or chronic, provoke reversible or irreversible changes with various outcomes: from mild malaise to death.
biological pollution
Biological contamination, as a rule, infection with helminths and their eggs, E. coli and other fecal flora, is most often exposed to green leafy vegetables (lettuce, spinach, sorrel, parsley) and white cabbage. Between the leaves of these cultures, comfortable conditions are created for the reproduction of helminths and bacteria, therefore, if they are used in an unwashed or insufficiently washed form, you can simply 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 abandoned. Knowing how to reduce the content of contaminants, each person will be able to protect himself and his loved ones when eating their favorite vegetables.
Control of nitrates and pesticides
The ideal preventive method of poisoning with nitrates and nitrites is to purchase a device for home use – a nitrate meter. You can go to the market and the store with it: just turn on the nitrate meter, select the desired type of fruit on the display and immerse the probe of the device for a few seconds inside the vegetable. Modern devices have a display on which both the result of an express analysis and its comparison with the maximum permissible concentrations for a given type of product are displayed (more often in the form of a light indication). The only drawback of nitrate meters 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 chemical and radioactive pollutants. The waiting rule is also acceptable for ground vegetables: the longer they are stored, the less contaminants remain in them.
To reduce chemical contamination of early vegetables, they should be thoroughly washed and soaked in cold water for 20-30 minutes. Peeling fruits also reduces the concentration of nitrates and pesticides in them.
Nitrate and pesticide poisoning can be avoided by primary and thermal cooking of vegetables, as well as by observing moderation in the use of young (greenhouse) plants. Root crops can be boiled (contamination level is reduced by 40-70%) or blanched (up to 50%).
But such a method of processing vegetables as drying leads to an increase in the concentration of nitrogenous compounds, pesticides and radionuclides due to the removal of moisture in which they are dissolved, so you should not use it for harvesting vegetables.
Prevention of allergies and poisoning
Allergic reactions can only be avoided by avoiding the foods that cause them. Allergy sufferers should be aware of their allergies and exclude vegetables and canned foods that are dangerous for them from their diet.
To prevent poisoning with solanine, green or sprouted potato tubers and unripe eggplants should not be eaten. To reduce the solanine content in eggplants and sweet peppers, they need to be peeled and soaked in salt water. Another way to reduce the level of solanine in nightshade fruits is salting, so salted green tomatoes, eggplants or peppers can be eaten without fear.
Mycotoxicosis prevention
To prevent mycotoxins from entering the human body, it is necessary to avoid vegetables affected or in contact with mold. Removing moldy areas does not lead to the complete removal of harmful microorganisms and mycotoxins, but only reduces their number. Heat treatment of vegetables also does not destroy mycotoxins, so it is not advisable to choose boiling or frying vegetables as a way to prevent mycotoxicoses.
Vegetables should be bought only in grocery stores, where a special place is allocated for them, in which temperature and humidity storage conditions are observed. Visually, vegetables should not be covered with dirt or mold. It is strictly forbidden to sell vegetables with broken shells, cuts or removed sections in the distribution network: mycotoxins easily penetrate the fruit from its affected surface and continue to develop inside it.
At the same time, the softer the fruit, the greater the likelihood of microorganism contamination of its pulp.
Prevention of infection with helminths and bacteria
Vegetables must be washed before eating. It is necessary to brush off the remnants of the earth from the root crops with a brush, then rinse under running warm water, after which 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 a container with cool water for several minutes, stirring from time to time with your hand so that the remnants of the earth from them settle at the bottom of the bowl. After that, the greens should be washed again under cool running water.
When buying vegetable products, you need to pay attention to the availability of accompanying documentation from sellers. Conscientious sellers must have documents confirming the quality and safety of vegetables sold: their large batch must be tested for nitrates, salts of heavy metals, pesticides, mycotoxins and radionuclides. Such large-scale studies are usually carried out by vegetable producers or their major suppliers. The results of the research are formalized by the expert opinion of Rospotrebnadzor.
Each small batch of vegetable products must additionally be accompanied by a quality certificate.
Legislative regulation
In the Russian Federation, the content of contaminants is regulated at the federal level: Sanitary rules and norms SanPiN 2.3.2.1078-01 “Hygienic requirements for the safety and nutritional value of food products” have been developed and implemented, which must be observed by individuals and legal entities in the process of growing, transporting, storing, distribution and processing of food products, including vegetable raw materials.
However, no matter how strict the laws and other regulatory documents are, no matter how conscientiously their manufacturers and sellers observe them, the responsibility for their own health lies directly with the consumer himself. “Trust, but verify” – this rule should become for each consumer his personal law.