Basics of nutritional physiology
The human diet is a form of interaction with the environment that obeys strict biological rules. Ignoring any of them inevitably leads to the development of alimentary diseases.
- Energy adequacy: the caloric content of incoming food must precisely cover the energy expenditure of the body.
- Substrate adequacy: the composition of food must correspond to the metabolic and morphofunctional characteristics of a person.
- Plastic adequacy: nutrients must ensure the synthesis exclusively of the body's own structures, excluding foreign ones.
- Adequacy to biorhythms and developmental cycles: the menu must be adapted to age periods and specific activities (e.g., night shift work).
- Biotic safety: consumed foods must be completely harmless.
Impact of nutritional disorders on health
Despite high tolerance to starvation compared to thirst or hypoxia, food remains a critical factor in maintaining health. Pathologies provoked by nutrition are divided into two categories.
Direct consequences:
- Heart and vascular diseases (hypertension, atherosclerosis, coronary artery disease).
- Gastrointestinal pathologies (peptic ulcer disease, intestinal and hepatic lesions, oncological processes).
- Metabolic disorders (diabetes mellitus, obesity, the full spectrum of vitamin imbalances).
- Genitourinary system diseases (urolithiasis).
- Oral cavity lesions (dental caries).
Indirect impact: An inadequate diet severely depresses the immune system. A decrease in overall resistance paves the way for numerous other pathologies not directly related to nutrition.
Xenobiotics and food safety
A huge threat is posed by xenobiotics — foreign chemical substances that require continuous monitoring. The most common include:
- Mycotoxins: metabolic products of mold fungi. They cause alimentary mycotoxicoses and have mutagenic and carcinogenic effects. For example, aflatoxins (produced by Aspergillus) lead to GI tract tumors, while ergot alkaloids (Claviceps purpurea) affect the blood vessels of the legs.
- Nitrates and nitrites: nitrogen-containing compounds. Nitrates (from fertilizers) are reduced to nitrites, which are used as preservatives. They enhance the synthesis of methemoglobin and carcinogenic N-nitrosamines.
- Polycyclic aromatic hydrocarbons (PAHs): potent carcinogens, the indicator of which is benzo(a)pyrene. They are formed during hot smoking, charcoal grilling, and also come from exhaust gases and industrial emissions.
- Food additives: added to alter taste or prolong shelf life. In the Russian Federation, their consumption is strictly regulated (special attention is paid to sorbic and benzoic acids).
Toxic heavy metals
Among many metals, lead, mercury, cadmium, and antimony are classified as absolute xenobiotics.
- Mercury: has a high capacity for accumulation. Humans most often receive it through aquatic food chains via seafood (in particular, it accumulates in tuna meat) or from terrestrial ecosystems via pesticides.
- Lead: lead ions bind to sulfhydryl groups of enzymes, blocking their function. It is deposited in bones. Main sources: aquatic organisms from polluted water bodies, substandard tin cans (seams, lacquer), and vegetables grown near highways.
- Cadmium: enters food due to phosphate fertilizers, wastewater, and the solder of tin cans.
Briefly: answers to topical questions
Which mycotoxins contaminate food products and cause alimentary mycotoxicoses?
Food products are contaminated by various mycotoxins that cause alimentary mycotoxicoses.
- Aflatoxins — produced by mold fungi of the genus Aspergillus (A. nigra and A. flavus), possess hepatotropic properties and a carcinogenic effect.
- Ergot alkaloids (ergotoxin, ergotamine, ergometrine) — produced by the fungus Claviceps purpurea, cause a hallucinogenic effect and affect the vascular system.
- Toxins of fungi of the genus Fusarium — cause alimentary-toxic aleukia.
- Other representatives — deoxynivalenol, zearalenone, patulin, sterigmatocystin, ochratoxin A, T-2 toxin.
What specific syndromes develop in severe protein-energy malnutrition?
In severe protein-energy malnutrition, specific clinically significant forms of pathology develop.
- Kwashiorkor — a form of pathology caused by a violation of protein-energy status.
- Alimentary dystrophy (alimentary marasmus) — a combined form of deficiency resulting from a severe deficit of proteins, energy, vitamins, and minerals. It is characterized by extreme exhaustion of the body.
- Marasmic kwashiorkor — a specific form of severe deficiency.
In children older than two years, alimentary marasmus represents the extreme degree of protein-energy malnutrition.
What methods exist for reducing the concentration of nitrates in plant products?
To reduce the concentration of nitrates in plant products, heat treatment is used, which lowers their concentration.
Class and exam questions
Are all food additives harmful to the body?
No. Ideally, additives are biologically inert. More than 200 of them are integrated into normal metabolism, while the rest are successfully excreted following hydrolysis, conjugation, or oxidation reactions. Their use is permitted only after safety verification.
How can the amount of nitrates in vegetables be reduced?
The simplest and most effective method is heat treatment, which reliably reduces the concentration of nitrates in food.
What is the mechanism of the toxic action of lead?
Lead ions form stable compounds with sulfhydryl groups of proteins. This leads to the blockade of the body's most important enzyme systems.
What else to study on this topic
- Mechanisms of biotransformation of food additives
- Toxicokinetics of heavy metals: deposition and elimination
- Alimentary mycotoxicoses: pathogenesis and clinical presentation
- Ecological methods for obtaining safe food raw materials
- The process of synthesis of N-nitroso compounds in the body
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Other topics in "Chapter 5. Ecological and hygienic problems of population nutrition"
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