Food components: from nutrients to contaminants
All substances entering the body with food can be divided into natural and foreign.
Natural substances include nutritional nutrients (proteins, fats, carbohydrates, vitamins, minerals) and flavoring compounds (organic acids, esters, tannins). Natural products also contain anti-nutritional substances (antienzymes, antivitamins). They are not toxic, but are capable of blocking or inhibiting the absorption of beneficial components.
In contrast, xenobiotics present a serious ecological problem. These are extraneous contaminants entering food due to external factors. The main reasons for their appearance in food:
- Violations of agricultural practices and the use of unapproved food additives (preservatives, antioxidants).
- Use of toxic containers and packaging materials.
- Introduction of genetic engineering, new technologies of microbiological synthesis, and livestock farming.
- Incorrect culinary processing (for example, frying and smoking).
- Global environmental pollution (air, water, and especially soil).
Migration pathways and cumulation in food chains
Foreign substances are distributed by entry pathways as follows: humans receive 20% of toxins via air, 10% via water, and 70% via food. Toxicants migrate through complex ecological chains. Most often they follow the route: air/water → soil → plants → animals → humans.
某些药物极其危险的一个特性是蓄积作用——即在生物体内积聚并在每个后续阶段（营养级）使浓度成倍增加的能力。DDT（滴滴涕，即二氯二苯三氯乙烷）杀虫剂是生物富集的经典例证。历史上，它曾帮助战胜了斑疹伤寒和疟疾的传播媒介（其发明者因此获得诺贝尔奖），但后来人们发现它具有极其顽固的持久性。
DDT accumulation scheme:
- Silt at the bottom of a water body — conditional concentration of $1 \times 10$.
- Algae — $10 \times 10$.
- Small crustaceans — $100 \times 10$.
- Small fish — $1000 \times 10$.
- Predatory fish — $10\ 000$.
As a result, humans or animals consuming predatory fish receive massive, toxic doses of the insecticide.
Main types of food xenobiotics
In addition to pesticides (such as DDT), food safety is threatened by numerous other contaminants:
- Mercury. Often enters nature from fungicides used to treat seed grain against pathogenic fungi. Eating such grain by birds leads to the death of both the seed-eaters themselves and predators, and the toxin accumulates massively in chicken eggs. When mercury is washed into water bodies, seals feeding on contaminated fish die from it.
- Heavy metals. Include lead and cadmium, which easily penetrate crops from contaminated soil.
- Hazardous chemical compounds. Polycyclic aromatic hydrocarbons (PAHs), dioxins, nitrosamines.
- Veterinary and agricultural preparations. Hormones (estrogens) are often used to stimulate growth in slaughter livestock, beta-blockers to relieve stress before slaughter, and antibiotics to prevent infections. Predictably, residues of these substances end up on the consumer's table.
Hygienic standardization of toxicants
Due to the enormous variety of foods, establishing a single standard for FCS content in all foods is impossible. Therefore, hygienists use the concept of MPC (maximum permissible concentration).
It is calculated based on two main values: ADI (acceptable daily intake) or PTDI (provisional tolerable daily intake). These values are derived from threshold doses of the toxicant, which are additionally reduced by a strict safety factor.
When approving hygienic standards, four main indicators are taken into account:
- Organoleptic (preservation of taste, color, and odor).
- General hygienic (prevention of a decrease in biological value).
- Technological (compliance with production regulations).
- Toxicological (guarantee of health safety).
Ideally, food should meet the status of an ecologically pure product — being wholesome, biologically complete, and completely devoid of xenobiotics or containing them in safe, sub-threshold concentrations.
简述：主题相关问答
Which heavy metals are subject to mandatory hygienic standardization in food products?
Sources indicate the following controlled toxic elements for food products:
- lead;
- arsenic;
- cadmium;
- mercury.
In methodological manuals, these substances are listed as toxic elements; the classification of arsenic specifically as a heavy metal is not established in the cited sources.
What toxic effects and diseases are caused by chronic dietary intake of cadmium?
Chronic dietary intake of cadmium causes a number of severe diseases and pathological conditions. The main toxic effects include:
- Itai-itai disease — accompanied by severe impairment of the musculoskeletal system functions (occurs upon consumption of contaminated rice).
- Anemia — develops in children and pregnant women.
- Congenital malformations — occur when the toxicant affects the body of expectant mothers.
- Neoplasms — cadmium has a pronounced carcinogenic effect.
What specific disease is caused by chronic alimentary poisoning with mercury compounds?
The specific name of the disease is not indicated in the sources. Mercury compound poisoning occurs when consuming organisms living in contaminated water bodies. In water bodies, mercury accumulates in aquatic plants and fish.
Which classes of hazardous chemical compounds are classified as food contaminants?
Food contaminants (foreign chemical substances) include the following classes of hazardous compounds:
- Pesticides — residual amounts of insecticides (e.g., DDT).
- Heavy metals — salts of lead, cadmium, and mercury.
- Chemical compounds — polycyclic aromatic hydrocarbons (PAHs), dioxins, and nitrosamines.
- agricultural and veterinary substances — hormones (estrogens), beta-blockers, and antibiotics.
- Radionuclides — radioactive isotopes.
- Biological toxins — mycotoxins and alkaloids.
- Food additives — when used in elevated doses or without approval.
To memorize the main food chains of toxin migration, remember the rule: "As the soil is, so are the products." All pollutants from the air and water settle in the soil, from where they pass into flora, then into fauna, and culminate in humans.
课堂与考试常见问题
What is the difference between anti-nutritional substances and xenobiotics?
Anti-nutritional substances are natural components of a natural product and are not toxic; they only temporarily inhibit the absorption of nutrients. Xenobiotics are foreign chemical pollutants that cause direct toxic harm to the body.
Why is the alimentary route of toxin intake considered dominant?
Up to 70% of foreign substances enter with food because agricultural lands (soil) serve as a huge natural depot for toxic wastes from the atmosphere and groundwater.
What is the calculation of MPC for food products based on?
MPC (Maximum Permissible Concentration) is determined by calculation based on the Acceptable Daily Intake (ADI) of the substance and the amount of a specific contaminated product in the human daily diet.
该主题的其他拓展内容
- The global socio-economic problem of food security and world hunger statistics.
- Demographic forecasts and the depletion of agricultural land area.
- Mechanisms of the influence of various culinary processing methods on the formation of toxicants in food.
- Specific features of the action of mycotoxins and alkaloids as specific contaminants.
- Classification of anti-nutritional substances: anti-enzymes, anti-vitamins, and demineralizing compounds.
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