In addition to the basic food substances that are sources of energy and plastic material, food contains substances that do not provide energy but are necessary in minimal quantities to sustain life. These include vitamins. These substances are essential because they are not synthesized or hardly synthesized by the body's cells. Their most important biological role is usually associated with the fact that they are part of biological catalysts of enzymes or hormones, which are powerful regulators of metabolic processes in the body.
Currently, several dozen vitamins are known, but not all of them are necessary.
Based on their physical and chemical properties and the nature of their distribution in natural products, vitamins are usually divided into water-soluble and fat-soluble. The first group includes vitamin C (ascorbic acid) and a wide group of B vitamins (B1, B2, PP, folic and pantothenic acids, pyridoxine and others). The second group includes vitamins A, D, E and K. This division of vitamins is not accidental, it helps to find natural sources of their production in food and to understand how vitamins are absorbed in the intestine. Food products may contain not only vitamins but also their precursors, or so-called provitamins, from which the vitamins are formed in the body. A long-term lack of vitamins in the diet leads to a characteristic disease called avitaminosis, severe forms of which are rarely encountered today. Much more often, a doctor encounters so-called hypovitaminosis conditions, the development of which is associated with a lack of vitamins in food. In summer and autumn, food is richer of vitamins than in winter and spring. This is why hypovitaminosis states are seasonal and most commonly seen in winter and spring.
It is known with increased physical and mental work, under the influence of unfavourable effects on the body, with overheating and hypothermia, under the influence of pathogenic factors, with impaired absorption of vitamins, as well as in such physiological conditions as pregnancy, child feeding the need for vitamins increases significantly.
Most hypovitaminosis is characterized by common signs: increased fatigue, weakness, apathy, decreased efficiency, fall resistance to colds and infectious diseases. But in addition to these general signs for each of the vitamins are known and specific signs of its deficiency.
- Vitamin A deficiency is characterized by deterioration of twilight vision: a person at dusk quickly loses orientation, sees objects indistinctly, and his visual reactions are slowed down.
The yellow pigment pro-vitamin A, called carotene, contained in many fruits and vegetables plays a major role in meeting human vitamin A requirements. Large amounts of carotene are in carrots, red peppers, sorrel, green onions. Interestingly, the carotene content depends greatly on the colour of the vegetable. Red carrots have 9 times more than yellow carrots, and red peppers 50 times more than green peppers
Remember that vitamin A, like other fat-soluble vitamins, is much better absorbed with fat. This means that for a more complete absorption in the intestines it is advisable, for example, to stew the product in oil beforehand.
- Bread and cereal products are the primary sources of Vitamin B. It should be borne in mind that the main amounts of this vitamin are contained in the outer layers of the grain, most of which are lost in the production of higher grades of flour, polished rice and other refined products. Therefore, bread products made of coarse flour, especially bran, have a higher vitamin value.
Since vitamin B1 is highly soluble in water and easily oxidized by oxygen, long soaking of foods or leaving them in the air in crushed form should be avoided to preserve it.
- Deficiency of Vitamin B2 (riboflavin) is manifested in growth retardation, disorders of the skin and mucous membranes (formation of cracks, ulcers in the corners of the mouth, peeling skin, inflammation of the mucous membranes of the eyes, etc.). The adult requirement for this vitamin is 2.5-3.5 mg per day. Good sources of vitamin B2 are milk, cottage cheese, cheese, eggs, liver, meat: especially yeast.
- Vitamin C deficiency is manifested in inflamed gums, increased fragility and bleeding of blood vessels, and reduced resistance to colds and infectious diseases. Biochemical studies show that low ascorbic acid content in the blood, especially in the winter-spring period.
An adult's vitamin C requirement is 70-100 mg per day, depending on the nature of the work. An excellent source of vitamin C is blackcurrant, red rose hips, red pepper, green onions, cabbage and other vegetables, berries and fruits. When vegetables are processed, vitamin C is destroyed relatively quickly, so it's important to know the correct cooking methods. Vitamin C is readily soluble in water and has little resistance to oxygen and heat.
- Calcium and phosphorus are very important components of food. They form the mineral basis of the skeleton, which is why their requirements are particularly high during the growth period. Calcium is also necessary for normal nervous system excitability and muscle contractility. Occurring in the disease of the parathyroid glands seizures are associated with a sharp decrease in calcium in the blood. In addition, calcium serves as an activator of some enzymes.
An adult person should receive approximately 0.8-1.0 g of calcium per day; children and teenagers 1-2 g, pregnant women and breastfeeding mothers - up to 2 g. The degree of calcium absorption depends on its correlation with other salts, especially phosphates and magnesium, as well as on the body's supply of vitamins and magnesium. The degree of calcium assimilation depends on its correlation with other salts, especially with phosphates and magnesium, as well as on the provision of the organism with vitamins and magnesium, and in particular on the provision of the organism with vitamins of the D group. It is no coincidence that milk and dairy products are excellent sources of easily digestible calcium and phosphorus. Practically half a litre of milk or 100 g of cheese satisfies the daily calcium requirement of an adult.
Of the trace elements - substances that in very small amounts (mg or even fractions of mg) are necessary for maintaining health is iron, the most important component of haemoglobin. On average, an adult should receive about 15 mg of iron daily. The main sources of iron are meat products, especially liver and lungs, and specialised products enriched with blood. The advantage of these products over other foods is that the organic iron compounds they contain are much better absorbed by the human body.
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