To trace elements include iron, zinc, copper, selenium, iodine, fluorine, chromium, manganese, boron and vanadium.
The total iron content in the body is about 5.0 and 3.8 mg-kg of body weight. Men and women respectively. Iron takes part in various processes associated with physical activity, such as the synthesis of hemoglobin and myoglobin, and is also part of the cytrochromes and tegamine compounds of iron. Some enzymes, dependent on iron NADH2 and succinate dehydrogenase), participate in oxidative metabolism.
Recommendations for physically active persons. The incidence of anemia associated with iron deficiency is approximately 5-6% 109, these rates may be higher in adults and women due to the needs of growth and menstrual cycles. On the other hand, iron deficiency is quite common among athletes, it ranges from 30 to 50%, especially among female athletes specializing in endurance sports.
Female athletes often consume inadequate amounts of iron with food (as a result of consuming fewer kilocalories and / or reducing meat in food), so iron loss with sweat, gastrointestinal bleeding, myoglobinuria, hemoglobinuria caused by intravascular hemolysis and menstruation can threaten their health and good indicators. Decrease in indicators is associated not only with anemia, reduced aerobic capacity and worsening endurance. Anemia caused by iron deficiency in food has a negative effect on the resynthesis of ATP in skeletal muscles, as well as the ability to tolerate prolonged loads. Recent studies show that in women with iron deficiency, the maximum oxygen consumption (V02max) is reduced, as a result of a reduced iron reserve, rather than a decrease in oxygen transport. Changes in the intensity of metabolism, the status of thyroid hormones and thermoregulation with depletion of iron stores and iron deficiency anemia have been noted. Weak iron deficiency anemia can also have a negative impact on psychomotor development and intellectual abilities.
Iron supplements. For people with iron deficiency anemia, iron supplements in the diet will be most appropriate to increase its reserves and prevent harmful physiological effects. Iron sulphate is the cheapest and most accessible form of iron supplement. Adults with iron deficiency anemia is recommended to take a daily dose of at least 60 mg of iron in a break between meals. It is believed that there are enough arguments for the consumption of controlled iron supplements by all athletes with low serum ferritin levels.
Factors affecting the absorption of iron. As in the case of calcium, some factors inhibit, while others enhance the absorption of iron.
Factors inhibiting iron absorption:
- polyphenols (tannins of tea and coffee);
- adequate supplies of iron in the body;
- excessive consumption of other macro-elements (zinc, calcium, manganese);
- reduced production of hydrochloric acid of gastric juice;
- some antacids.
Factors enhancing iron absorption:
- the corresponding secretion of gastric acid;
- heminic forms of iron;
- increased need of the body for red blood cells (eg, blood loss, height above sea level, training, pregnancy);
- lack of iron in the body;
- factor of meat protein;
- ascorbic acid.
Consuming foods containing vitamin C, or drinks with food, as well as tea or coffee for 1 hour before or after meals increases iron absorption. Such a regime is highly recommended even for those who, with a diagnosis of iron deficiency anemia, take iron supplements.
Zinc is found in all organs, tissues, liquids and secretions. About 60% of all zinc in the body is in the muscles, 29% - in bones and 1% in the gastrointestinal tract, skin, kidneys, brain, lungs and sex glands. Zinc is involved in more than 30 metabolic reactions of the body. Alkaline phosphatase, Zn, Cu-superoxide dismutase are just some zinc metal-enzymes.
Recommendations for physically active persons. Many residents in the US do not consume the required amount of zinc. Young women, for example, take only 9.7 mg of zinc per day, about 50% of women runners also consume zinc less than recommended. More recent studies show that swimmers - men and women - consume zinc in excess of 70% of the recommended rate. Apparently, if the intake of zinc with food is sufficient, then the physical load does not adversely affect its status.
The temporary effect of physical stress on the status of zinc is established. It is shown that the status of zinc directly affects the intensity of the basal metabolism and the level of thyroid hormones in men, which can adversely affect their health indicators. The effect of zinc supplements on the intensity of basal metabolism, the level of thyroid hormones and protein utilization in six young men who participated in a 75-day study of metabolism was studied. At first they were given 16.5 mg of zinc per day for 12 days, then for 54 days they received 5.5 mg per day, which resulted in a zinc deficiency. There was a significant decrease in the intensity of basal metabolism, thyroid hormone levels and protein utilization. This study provides an insight into the relationship between zinc status, basal metabolic rate and thyroid hormone levels. The long-term effect of daily exercises on the status of zinc requires further study to develop more specific recommendations for physically active individuals. In Table. 5.8 some food sources of zinc are given.
In the human body contains from 50 to 120 mg of copper. Copper is involved in the enhancement of iron absorption (using the ceruloplasmin metalloplasma), the formation of collagen and elastin, in the electron transport chain (cytochrome oxidase), and is also an antioxidant (Zn, Cu-superoxide dismutase).
Optimum consumption. RDN for copper is absent. Based on the 1989 recommendations, a safe and adequate daily dietary consumption of copper was developed, in which the recommended adult dose is 1.5-3.0 mg per day.
Sources. The state of the soil has a great influence on the content of copper in food products. Rich sources of copper are: liver, sea products (oysters), cocoa, mushrooms, various nuts, seeds (sunflower seeds), bread, cereals.
Selenium is well known as an antioxidant because it is part of the enzyme glutathione-peroxidase. It takes part in the metabolism of thyroid hormone. Recommendations for physically active persons. Data on the needs of selenium athletes and people leading a sedentary lifestyle are very limited.
It can be assumed that, due to increased oxidation during physical exertion, physically active persons will require more selenium in food. However, studies involving 12 men who used a diet of 180 μg selenomethionine for 10 days and 12 men who received a placebo showed that endurance training increased the antioxidant potential of glutathione peroxidase, but selenium supplements did not affect the performance. Since data on the consumption of selenium are small, physically active persons should consume it no more than indicated in the RDN.
Sources. Food sources, as for copper, vary greatly and depend on the content of selenium in the soil. Sources of food selenium are fish, crustaceans, meat, eggs and milk.
Thyroid hormones are synthesized from iodine and tyrosine, so iodine is needed for normal metabolic rate.
Recommendations for physically active persons. Data on iodine for physically active individuals are not available, however, inadequate intake of iodine can influence the synthesis of thyroid hormones.
Sources. Iodine is found mainly in sea fish, molasses, iodized salt and seafood.
The main function of fluoride is the protection of teeth and bones. It is known that an adequate amount of it in water helps prevent caries. Fluoride stimulates the growth of bones (osteoblasts), increases the formation of trabecular bones and the mineral density of the bones of the spine. The application contains standards for fluoride.
Recommendations for physically active persons. Studies related to the issue of the need for fluoride for athletes, carried out a little. Most studies assess the effect of fluoride on the mineral density of bones and the prevention of osteoporosis.
Given the important role of fluoride in bone metabolism, further research is needed on the role of fluoride for female athletes.
Sources. Food sources of fluoride are limited to tea, seaweed, seafood and fluorinated household water.
Chromium is a well-studied mineral. It enhances the action of insulin and thus affects the metabolism of carbohydrates, lipids and proteins. Chromium also has an anti-atherogenic effect, reducing the level of serum cholesterol, but these data are insufficiently argued. It was proposed to increase the body weight, as well as its reduction. However, the results of a number of studies have not confirmed this assumption.
Optimum consumption. According to the calculation of safe and adequate daily consumption, adults need 50-200 μg of chromium per day. Anderson, Kozlovsky proposed an average value for the consumption of chromium per day - 25 μg for women and 33 μg for men.
Recommendations for physically active persons. Since on the days of training, the release of chromium with urine increases, the diet of the athlete requires an increased content of it. Due to the fact that chromium can change the status of other minerals (eg iron), its consumption is higher than calculated before the completion of further studies is not recommended.
Sources. Food sources of chromium: whole grains, offal, beer, egg yolk, mushrooms and nuts.
Manganese is involved in the antioxidant activity of the body, since it is a part of superoxide dismutase. Manganese also participates in carbohydrate and bone metabolism.
Optimum consumption. According to the calculation of safe and adequate consumption, adults need 2-5 mg of manganese per day.
Recommendations for physically active persons. Data on whether athletes need more manganese in food are not available.
Sources. Food sources of manganese: whole grains, deciduous vegetables, nuts, beans, tea.
Molybdenum interacts with copper and iron. Excess molybdenum can inhibit the absorption of copper. Molybdenum is involved in the metabolism of glucocorticoids.
Optimum consumption. According to the recommended dietary intake norms, adults require 74-250 μg molybdenum per day.
Recommendations for physically active persons. Data on the needs of molybdenum for physically active persons are not available.
Sources. Food sources of molybdenum: beans, nuts, whole grains, milk and dairy products.
At present, boron is not considered an indispensable mineral for humans, but it can make a difference in the metabolism of bone tissue by interacting with calcitriol, estradiol, testosterone, magnesium and calcium. Many athletes believe that boron increases body weight and mineral density of bones. However, recent studies of these boron effects have not revealed.
Optimum consumption. The recommended norms for boron are absent, however, adults can consume 1-10 mg boron per day.
Recommendations for physically active persons. Most of the research is devoted to the study of the influence of boron on bone mineral density and body weight, but it is not established whether athletes need more of this trace element in food.
Sources. Food sources of boron: fruits, vegetables, nuts and beans.
It is shown that, like chromium, vanadium enhances the effects of insulin. Like chlorine, vanadium supplements (vanadyl sulfate) are proposed to increase body weight, but these anabolic effects are not confirmed by studies.
Optimum consumption. Recommendations for food consumption of vanadium are absent. Its needs for adults are defined in the range of 10-100 mcg per day.
Recommendations for physically active persons. No reports of increased demand for vanadium or its ergogenic properties have been identified. Additions of vanadium are not justified.
Sources. Food sources of vanadium: grains, mushrooms and crustaceans.