The main minerals are calcium, phosphorus, magnesium, sulfur, potassium, sodium and chlorine.
Calcium is one of the most studied minerals in the human body. Calcium is about 40% of the total amount of all minerals. 99% of calcium is contained in bones and teeth, and the remaining 1% is distributed in extracellular fluids, intracellular structures, cell membranes and various soft tissues.
The main functions of calcium are as follows:
- bone metabolism;
- blood clotting;
- neuromuscular excitability;
- cell adhesion;
- transmission of nerve impulses;
- preservation and function of cell membranes;
- active enzyme reaction and secretion of hormones.
Homeostasis of calcium. The serum calcium level in the range 2.2-2.5 mmol-kg is controlled by parathyroid hormone (PTH), vitamin D and calcitonin. If the calcium level falls below normal, PTH enhances the synthesis of calcitriol in the kidneys, resulting in the following phenomena:
- increased reabsorption of calcium in the kidneys;
- increase of calcium absorption in the intestine;
- increased activity of osteoclasts in the bones (liberation of calcium in the circulatory system).
If the level of calcium in the serum is higher than normal, calcitonin causes the following phenomena:
- increased excretion of calcium by the kidneys;
- reduction of calcium absorption by the intestine;
- decreased activity of osteoclasts.
Average intake of calcium. Women usually consume calcium less than men.
Half of all teenage girls consume less than 2/3 of the recommended dose.
Half of adult women consume less than 70% of the recommended dose.
The average calcium level for women 20-29 years is 778 mg per day.
For women over 65, 600 mg per day is the usual daily rate.
If a person is physically active, calcium intake below normal will lead to negative effects in the body, since calcium is excreted with sweat and urine. The application contains standards for calcium.
Recommendations for physically active persons. Physically active persons should consume, at least, a standard rate of calcium. If a person sweats heavily and / or trains in conditions of high temperatures, then the need for calcium for him will be higher than the available standards, since a lot of calcium is excreted with sweat.
Sources. Dairy products contain the greatest amount of calcium. If a person does not consume enough calcium with food, then the best additives are citrate or calcium carbonate. Calcium supplements containing bone meal, oyster shells and shark cartilage should be avoided because of the high content of lead in them, which can cause toxic effects on the body. Calcium supplements are best absorbed if taken 500 mg or less in between meals. In older people who may suffer from achlorhydria, calcium carbonate is best consumed with food. Calcium citrate does not require gastric acid for optimal absorption, so it is considered the best calcium supplement for older women.
Factors affecting the absorption of calcium. A number of factors can inhibit or enhance calcium absorption. High-protein and sodium diets cause an increase in the release of calcium in the urine. Although phosphorus can reduce calcium loss in the urine, its high level can lead to hyperparathyroidism and bone loss. Dietary fiber and caffeine have a weak negative effect on calcium loss; a cup of coffee gives a loss of 3.5 mg of calcium, which can be compensated by adding milk. Fitins, however, greatly reduce the absorption of calcium, and oxalates greatly reduce its bioavailability. Conversely, vitamin D, lactose, glucose, as well as a healthy digestive system and a high need for food (for example, pregnancy) - enhance calcium absorption.
Phosphorus is the second most common mineral in the human body. About 85% of its quantity is in bones, mainly in the form of crystals of hydro-xyapatite. Phosphorus is of great importance for the mineralization of bone tissue in both animals and humans. Even in the presence of high content of calcitriol, with a lack of phosphorus in humans, rickets may occur. Although phosphorus is essential for bone growth, excess of it can cause disturbances in skeletal tissue, especially if calcium intake is low. Excess phosphorus and protein are in negative correlation with the density of minerals in the radius.
A large intake of phosphorus reduces the serum calcium content, especially when its consumption is low, because phosphorus is involved in the transfer of calcium into soft tissues. As a result, hypocalcemia activates the secretion of PTH, which increases the loss of bone calcium (resorption) to maintain calcium homeostasis in the serum. A large intake of phosphorus can also reduce the production of vitamin D, continuing to affect calcium absorption and generating secondary hyperparathyroidism. Optimum consumption. The Appendix contains standards for phosphorus. The consumption of phosphorus usually exceeds the recommended standards. There are data that for women aged 20-29 years, the average consumption of phosphorus is 1137 mg per day.
Recommendations for physically active persons. Most people consume enough phosphorus with food, especially with soft drinks that contain a lot of phosphate and usually replace milk. Excess consumption of phosphorus becomes a matter of concern. Retrospective studies Wyshak et al. Show that athletes who drink carbonate drinks are more likely to suffer from fractures than those who use them rarely or do not use them at all. Thus, the 300% increase in the consumption of carbonate drinks in the last three decades combined with a decrease in the consumption of milk can lead to serious complications in people's health.
Another way of excess phosphorus intake by athletes is "phosphate load". It is believed that this load reduces the formation of hydrogen ions, the number of which increases during the performance of exercises that have a harmful effect on the generation of energy. The results of studies of the phosphate load as an ergogenic effect are highly questionable; However, intensely trained athletes can benefit by selecting the appropriate dose. The long negative effects of phosphate loading on the density of minerals in the bones are not documented. The greatest amount of phosphorus is in protein.
About 60-65% of the total magnesium in the human body is found in the bones, about 27% in the muscles, 6-7% in other cells, and 1% in the extracellular fluid. Magnesium plays an important role in a number of metabolic processes, such as the functions of mitochondria, the synthesis of protein, lipids and carbohydrates, energy transfer processes and neuromuscular coordination. The Appendix lists the standards for magnesium.
Recommendations for physically active persons. The excretion of magnesium in the urine and then in the training people can be increased. A tennis player suffering from a lack of magnesium was given 500 mg of glucon-ta magnesium per day, and he took muscle spasms from her . Athletes who train intensively every day, especially in the heat, and consuming an inadequate amount of calories, lose a lot of magnesium with sweat. Clinical signs of magnesium deficiency - muscle spasms - should be kept under control. However, the lack of magnesium during physical exertion is, rather, the exception, than the norm. In Table. 5.6 shows some food sources of magnesium.
Sulfur in the human body is in a non-ionic form and is a component of some vitamins (for example, thiamine and biotin), amino acids (for example, methionine and cystine) and proteins. It also participates in maintaining the acid-base balance. If the protein needs are met, then there is no need for a special diet for sulfur, since it is contained in protein foods.
Recommendations for physically active persons. Data on the effect of sulfur on the indices or loss of it during physical exertion are not available. Sources. Sulfur is present in foods rich in protein.
Being one of the three basic electrolytes, potassium is the most important intracellular cation. The total amount of potassium in the human body is about 3000-4000 mmol (1 g equals 25 mmol). Maintaining intracellular ionic strength and transmembrane ionic potential is the two main roles of potassium in the body.
Optimum consumption. For potassium, there are neither RDNs nor standards. The estimated minimum requirements of 1989 are used to date and are 2000 mg per day.
Recommendations for physically active persons. A number of studies have been carried out concerning the electrolyte balance of potassium. After running for 42.2 km, the concentration of potassium in the blood plasma of runners increased significantly, which is explained by the transfer of potassium from the intracellular space to the extracellular space. In addition, Zjungberg et al. Reported a significant increase in the concentration of potassium in saliva marathoners, which restored its initial level one hour after the marathon. Millard-Stafford et al. Also found that in female runners, the increase in serum potassium concentration is higher than that of male runners after 40 km of run in hot and humid conditions. Therefore, the serum potassium moves to the extracellular space, apparently during and immediately after exercise. However, this movement is probably temporary, as most researchers indicate a restoration of the initial level of concentration of extracellular serum potassium in an hour or more after physical exertion. Temporary movement of potassium may cause a higher intake of it by physically active persons than recommended. If there is a surplus or a lack of potassium in the human body, there may be a disruption in the functions of the cells. Therefore, if the movement of potassium is not temporary, it can cause serious consequences. However, since potassium is found in all foods, consumption of its additional amount is not required. Moreover, with little physical exertion (walking, gardening, warm-up running), there is no significant shift in serum potassium concentration.
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