Value of food

Examples: 8 000 kJ = 1 900 kcal
                 1 600 kJ = 380 kcal

Nutritional value of food must be according to Act no. 152/1995 Codex on foodstuffs visible on the food packaging. In addition, since 2016, the following should be indicated on the packaging:

Macronutrients

In the following text we will focus on the importance of macronutrients (carbohydrates, fats, proteins) in human food.

• Proteins - polypeptides composed of more than 100 amino acid residues linked by a peptide bond – specifically spatially arranged. Their daily intake should be 0.75g per kg of human weight for 24 hours. In childhood, pregnancy, breastfeeding, high physical activity and convalescence, their intake should be increased to 2.5 g. They perform a wide range of tasks in the body – from tissue construction, through defense of the organism to coding of genetic information. Thanks to their complex structure, they enable them to perform a wide range of tasks in the body, from tissue construction through nutrient transport to encoding genetic information. Important sources of protein are meat (especially beef), eggs, milk and dairy products, but also soya.

• Fats – organic compounds composed of glycerol and higher carboxylic acids (so-called fatty acids). Fats make up about 30% of the body‘s energy needs. They are an essential component of each cellular structure (including nerve cells). They are also an important energy reserve of the organism. Without a certain proportion of fat reserves, women would not start a menstrual cycle. They also provide mechanical and thermal protection of the organism. Their presence in the diet is also important because of the solubility of some vitamins (A, D, E, K). The sources of polyunsaturated fatty acids are mainly walnuts, sunflower, sesame, flax and pumpkin seeds and sea fish (salmon, tuna, mackerel).

• Carbohydrates – organic compounds that consist of oxygen, hydrogen and carbon. The daily intake of carbohydrates should be in an average of 200-500g. Overall, they represent approximately 0.3-1% of the human body weight. They cover up to 60% of energy needs, with carbohydrate energy being used first. We recognize monosaccharides (glucose, fructose and galactose), oligosaccharides (consisting of 2-10 carbohydrate units, e.g. sucrose, maltose, lactose) and polysaccharides (more than 10 carbohydrate units, e.g. starch). In excess, carbohydrates are stored (eg in the form of glycogen). Monosaccharides and disaccharides (simple carbohydrates) are simple carbohydrates (mono- and disaccharides) that serve as a fast energy source (but they cannot feed a person for a long time – so-called fast carbohydrates). Foods are referred to as sugars and are particularly glucose, fructose and sucrose.

Vitamins

Vitamins are organic substances important for living even we need them (comparing to macronutrients) in minimal amounts. They are not formed in the animal organism (or only inadequately). Their importance in the human body is mainly in terms of energy management and tissue construction. We know about 20 vitamins, of which 15 are important for humans.

A) Fat soluble vitamins – A, D, E, K

B) Water soluble vitamins – e.g. B1 thiamine, B2 riboflavin, H biotin, B12, etc

Basal metabolism

In addition to energy metabolism, we distinguish basal (basic) metabolism, which means the least amount of energy necessary to maintain vital functions (breathing, digestion, regulation of body temperature, etc.) with complete physical and mental peace, without movement, in sleep. It is clear from this that a person needs a certain amount of energy to provide vital functions even in complete peace (e.g. during sleep).

Basal metabolism and its level are influenced by factors such as:

• Gender – men have higher BM (+ 5–7%).
• Age – decreases with age (decrease by approx. 2% in 10 years), child between 6 and 12 years of age uses 50% of energy for basal metabolism.
• Body surface – the direct proportion of the body surface to the level of metabolism; also associated with thermoregulation / heat loss.
• Hormonal status, for example during stress the hormone adrenaline increases metabolism.

The total energy expenditure of an average adult over a day, including basal metabolism, can be illustrated as follows: