Major minerals

The main minerals are calcium, phosphorus, magnesium, sulfur, potassium, sodium and chlorine.

• Calcium

Calcium is one of the most studied minerals in the human body. Calcium makes up about 40% of the total amount of all mineral substances. 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:

• bone metabolism;
• blood clotting;
• neuromuscular excitability;
• cell adhesion;
• transmission of nerve impulses;
• maintenance and function of cell membranes;
• active reaction of enzymes and secretion of hormones.

Calcium homeostasis. Serum calcium levels in the range of 2.2-2.5 mmol/kg are controlled by parathyroid hormone (PTH), vitamin D, and calcitonin. If calcium levels fall below normal, PTH increases the synthesis of calcitriol in the kidneys, resulting in the following events:

• increased calcium reabsorption in the kidneys;
• increasing calcium absorption in the intestine;
• increased activity of osteoclasts in bones (release of calcium into the circulatory system).

If the serum calcium level is higher than normal, calcitonin causes the following phenomena:

• increased excretion of calcium by the kidneys;
• decreased intestinal absorption of calcium;
• decreased osteoclast activity.

Average calcium intake. Women generally consume less calcium 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 requirement for women aged 20-29 is 778 mg per day.

For women over 65, 600 mg per day is the usual daily requirement.

If a person is physically active, calcium intake below the norm will lead to negative effects in the body, as calcium is excreted through sweat and urine. The application contains calcium standards.

Recommendations for physically active individuals. Physically active individuals should consume at least the standard amount of calcium. If a person sweats heavily and/or exercises in hot conditions, the calcium requirement will be higher than the current standards, since much calcium is lost through sweat.

Sources: Dairy products contain the highest amount of calcium. If a person does not consume enough calcium in the diet, calcium citrate or calcium carbonate supplements are the best. Calcium supplements containing bone meal, oyster shell, and shark cartilage should be avoided due to their high lead content, which can cause toxic effects in the body. Calcium supplements are best absorbed when taken in doses of 500 mg or less between meals. In older adults who may suffer from achlorhydria, calcium carbonate is best consumed with food. Calcium citrate does not require stomach acid for optimal absorption, so it is considered the best calcium supplement for older women.

Factors Affecting Calcium Absorption. A number of factors can inhibit or enhance calcium absorption. High-protein and sodium diets increase urinary calcium excretion. Although phosphorus can reduce urinary calcium loss, high levels can lead to hyperparathyroidism and bone loss. Dietary fiber and caffeine have little negative effect on calcium loss; a cup of coffee results in a loss of 3.5 mg of calcium, which can be compensated for by adding milk. Phytins, however, greatly reduce calcium absorption, and oxalates greatly reduce its bioavailability. Conversely, vitamin D, lactose, glucose, and a healthy digestive system and high nutritional requirements (eg, pregnancy) enhance calcium absorption.

• Phosphorus

Phosphorus is the second most abundant mineral in the human body. About 85% of it is found in bone, mostly as hydroxyapatite crystals. Phosphorus is essential for bone mineralization in both animals and humans. Even with high calcitriol levels, rickets can occur in humans if phosphorus is deficient. Although phosphorus is essential for bone growth, excess phosphorus can cause skeletal disorders, especially if calcium intake is low. Excess phosphorus and protein are negatively correlated with radius bone mineral density.

High phosphorus intake reduces serum calcium, particularly when phosphorus intake is low, because phosphorus is involved in calcium transport into soft tissues. The resulting hypocalcemia activates PTH secretion, which increases bone calcium loss (resorption) to maintain serum calcium homeostasis. High phosphorus intake may also reduce vitamin D production, further affecting calcium absorption and causing secondary hyperparathyroidism. Optimal Intake: Standards for phosphorus are provided in the Appendix. Phosphorus intakes generally exceed recommended standards. For women aged 20–29 years, the mean phosphorus intake has been reported to be 1137 mg/day.

Recommendations for physically active individuals. Most people consume sufficient amounts of phosphorus from food, especially from soft drinks, which contain a lot of phosphates and usually replace milk. Excessive phosphorus intake is becoming a concern. Retrospective studies by Wyshak et al. show that athletes who drink carbonated drinks suffer more fractures than those who rarely or never drink them. Thus, the 300% increase in carbonated drink consumption over the past three decades, combined with a decrease in milk consumption, may lead to serious health complications in people.

Another way athletes consume excess phosphorus is through "phosphate loading." This loading is thought to reduce the formation of hydrogen ions, which increase during exercise and have a detrimental effect on energy production. The results of phosphate loading as an ergogenic effect are questionable; however, athletes who train hard may benefit by adjusting the dose. No long-term negative effects of phosphate loading on bone mineral density have been documented. Phosphorus is most abundant in protein.

• Magnesium

About 60-65% of all magnesium in the human body is in bone, about 27% in muscle, 6-7% in other cells, and 1% in extracellular fluid. Magnesium plays an important role in a number of metabolic processes, such as mitochondrial function, protein, lipid, and carbohydrate synthesis, energy transfer, and neuromuscular coordination. Standards for magnesium are provided in the Appendix.

Recommendations for physically active individuals. Magnesium excretion in urine and sweat may be increased in people who exercise. A tennis player suffering from magnesium deficiency was given 500 mg of magnesium gluconate daily, and it relieved her muscle cramps [96]. Athletes who train intensively every day, especially in the heat, and who consume an inadequate amount of kilocalories, lose large amounts of magnesium in sweat. The clinical signs of magnesium deficiency - muscle cramps - should be monitored. However, magnesium deficiency during exercise is the exception rather than the norm. Table 5.6 lists some food sources of magnesium.

• Sulfur

Sulfur in the human body is in non-ionic form and is a component of some vitamins (e.g. thiamine and biotin), amino acids (e.g. methionine and cystine) and proteins. It also participates in maintaining acid-base balance. If protein needs are met, there is no need for a special diet for sulfur, since it is contained in protein foods.

Recommendations for physically active individuals. There is no data on the effect of sulfur on indicators or its loss during physical activity. Sources. Sulfur is present in foods rich in protein.

• Potassium

As one of the three major electrolytes, potassium is the most important intracellular cation. The total amount of potassium in the human body is approximately 3000-4000 mmol (1 g equals 25 mmol). Maintaining intracellular ionic strength and transmembrane ionic potential are two of the main roles of potassium in the body.

Optimal intake. There is no RDA or standard for potassium. The 1989 estimated minimum requirements are still used today and are 2000 mg per day.

Recommendations for physically active individuals. Several studies have been conducted on the electrolyte balance of potassium. After a 42.2 km run, plasma potassium concentrations in runners increased significantly, which is explained by a shift of potassium from the intracellular to the extracellular space. In addition, Zjungberg et al. reported a significant increase in potassium concentrations in the saliva of marathon runners, which returned to baseline levels one hour after the marathon. Millard-Stafford et al. also found that female runners had a greater increase in serum potassium than male runners after a 40 km run in hot and humid conditions. Therefore, serum potassium is likely to shift to the extracellular space during and immediately after exercise. However, this shift is likely transient, since most studies report a return to baseline serum extracellular potassium concentrations one hour or more after exercise. A temporary shift in potassium may result in higher than recommended potassium intakes by physically active individuals. If there is an excess or deficiency of potassium in the human body, cell function may be impaired. Therefore, if the potassium shift is not temporary, it may have serious consequences. However, since potassium is found in all foods, additional intake is not required. Moreover, with light physical activity (walking, gardening, warm-up jogging), there is no significant shift in serum potassium concentration.

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