Minerals
Hypocalcemia, or low blood calcium, is uncommon because the body works hard to maintain a constant supply of calcium in the blood. Signs and symptoms of hypocalcemia include muscle spasms and convulsions. Even though hypocalcemia is rare and occurs mainly in disease states, calcium deficiency in the general population, as well as with athletes, is still one of the most common deficiencies in the United States. Hypercalcemia, or high blood levels of calcium, can be caused by cancer or the overproduction of the parathyroid hormone, often signaled by fatigue, constipation, and loss of appetite.
Amounts of calcium greater than 500 milligrams are not well absorbed when consumed at one time; therefore, it is best to spread supplements throughout the day. Calcium is absorbed best when broken down first by stomach acids; calcium supplements should be taken with a small bit of food to stimulate the secretion of digestive juices. calcium competes closely with iron and zinc, altering the absorption of all nutrients involved and potentially creating other problems. Avoid calcium supplements that are derived from oyster shells or bone meal because they may be contaminated with lead.
Selenium-associated enzymes have also been linked to proper thyroid and immune function, as well as to the healthy development of fetuses. Selenium's role in immune function has led to cancer risk reduction claims. In general, selenium research is still in its infancy, with all roles, mechanisms, and health/performance effects still under investigation. For example, in areas of China with selenium-poor soil, selenium-deficient residents are more susceptible to a form of viral cardiomyopathy called Keshan disease. Selenium has recently been recognized as an antioxidant mineral, raising questions about the effects of suboptimal intake on cardiovascular parameters and cancer risk. The trace minerals include iron, zinc, chromium, fluoride, copper, manganese, iodine, molybdenum, and selenium.
Athletes should strive to consume these nutrients from whole foods first, and rely on supplements only when individually indicated. Consumption of selenium in excess of the upper limit can cause brittle hair and nails; if toxic levels continue to be consumed, the loss of hair and nails can occur. Selenium is found mainly in meats, organ meats, seafood, and grains.
Sodium and potassium, the main electrolytes (minerals) lost in sweat, must be replaced on a daily basis as well as during endurance and ultra-endurance sports to optimize performance and prevent medical complications. Unlike carbohydrates, fats, proteins, and vitamins, minerals are not organic molecules. They are basically inorganic elements or atoms. Also, unlike the macronutrients, minerals contain no calories and, although essential, are needed by the body in very small amounts (i.e., milligrams or micrograms).
Because of their stability, minerals are unaffected by cooking techniques, digestive processes, and/or exposure to enzymes. In other words, unlike many nutrients, minerals remain unaltered from food source to the human cells. inorganic A descriptor given to a compound that does not contain carbon atoms in its molecular structure.
The RDA for men and women is 700 milligrams per day. Phosphorus combines with lipids to form phospholipids, which provide integrity to cell membranes. Phosphorus activates and deactivates enzymes through phosphorylation. In regard to athletic performance, phosphorus is a component of ATP, which provides energy for all forms of cellular function. Phosphorus is also needed for the formation of creatine phosphate (CP). In quick, explosive movements, CP provides an immediate form of energy for cells. During endurance activities, phosphorus buffers acidic end products of energy metabolism, allowing an athlete to sustain his or her effort and delay fatigue. Finally, phosphorus plays a role in energy production by phosphorylating glucose, preparing it to proceed through glycolysis.
Certain disease states, hyperparathyroidism, and taking large doses of antacids (which decrease phosphorus absorption) can contribute to phosphorus deficiencies, producing symptoms such as bone malformation, bone pain, and muscle weakness. Americans consume plenty of phosphorus but not enough calcium. This intake imbalance can lead to altered calcium metabolism and an increased risk for osteoporosis. Phosphorus is found predominantly in animal proteins including meat, fish, eggs, and dairy. abundant in the U.S. food supply. Meats, legumes, nuts, dairy products, and grains tend to have more phosphorus than fruits and vegetables.
Potassium, magnesium, protein, and fiber also have been linked to blood pressure regulation, and therefore intake of all nutrients should be addressed. Some research also shows that high intakes of sodium may lead to increased calcium excretion, thus contributing to osteoporosis. In activities lasting more than 4 hours, such as long-distance triathlons or adventure racing, sodium supplements may be indicated. As the major extracellular anion, chloride is primarily involved in fluid balance within the body; Chloride (Cl) is widely recognized as the partner to sodium (Na) in salt (NaCl), which in fact is the main source of chloride in the American diet.
Chloride acts as a "disinfectant" to maintain health inside the body. Chloride combined with hydrogen forms hydrochloric acid. In the stomach, hydrochloric acid helps to kill harmful bacteria that have been consumed. White blood cells also use chloride to kill invading bacteria throughout the body. In neurons, the movement of chloride, as well as calcium, sodium, and potassium, allows for the transmission of nerve impulses throughout the body. Low chloride levels can be caused by frequent vomiting, which removes hydrochloric acid from the stomach. high intake of both sodium and chloride may cause hypertension. The upper limit for chloride has been set at 3600 milligrams per day.
Changes in macronutrient metabolism can ultimately decrease endurance performance, as well as the body's ability to build and repair muscle during and after exercise. One side effect of chronic high intake of chromium that has been noted is interference with iron and zinc absorption. Typically the claims focus on chromium's ability to enhance insulin action, which in theory might increase muscle anabolism and improve body composition. More than 98% of the fluoride in the body is found in the skeleton. It has also been suggested that fluoride may help strengthen the resistance of interosseous ligaments or muscle tendons during dislocations and sprains and prevent tendonitis in athletes. fluorosis A condition resulting from the overconsumption of fluoride that can lead to pitting and discoloration of the teeth and/or bone and joint problems.
Copper converts ferrous iron to ferric iron, enabling iron to be transported in the blood by transferrin, thus aiding in oxygen metabolism and preventing anemia. Copper is an integral part of a variety of antioxidant enzymes, Copper also participates in the electron transport chain. Menkes syndrome is a rare genetic disorder that involves a failure to absorb copper. Wilson's disease is a genetic disorder characterized by an excessive accumulation of copper, which leads ultimately to anemia, as well as to liver and neurological problems. They found that copper intake, serum copper, and ceruloplasmin levels were adequate in this population. In addition, high doses of copper can become toxic, leading to side effects such as nausea and
In addition to its enzymatic role, zinc is critical for optimal health by: Playing a role in wound healing, which enhances immune function Aiding in the synthesis of RNA and DNA, thus influencing gene expression Ensuring the growth and maintenance of various tissues zinc is a component of various enzymes related to carbohydrate, protein, and fat metabolism, especially during exercise. Zinc also interacts with insulin and increases the affinity of hemoglobin for oxygen. Athletes on calorie-restricted diets or poorly planned vegetarian diets may be at increased risk for zinc deficiency resulting from low zinc intake. Similar to iron, if the body detects a low level of zinc, it compensates by increasing the intestinal absorption of the mineral. In regard to endurance training, plasma zinc levels have been reported to remain unchanged in response to chronic training,
Despite the fact that some studies have reported decreases in plasma zinc levels after endurance-type exercise, the decreases do not appear to lead to long-term zinc deficiencies in endurance athletes, unless athletes are following a calorically restricted diet or are vegetarians. High doses in supplement form can impair iron and copper absorption, which over time may contribute to anemia. Zinc supplements are often marketed for common cold prevention and remedy—a claim that is still under investigation. Chromium is now receiving more attention in the health maintenance and diabetes prevention arenas. The major function of chromium appears to be its ability to enhance the action of insulin. In other words, chromium increases the effects of insulin on the metabolism of carbohydrates, fats, and proteins. Because of its association with insulin, chromium deficiency has been proposed as one cause for high blood glucose, which in the long term may lead to type 2 diabetes.
The theory is that because iron is a pro-oxidant, it may contribute to cell damage, leading to cancerous growths in the colon, or it may accelerate the oxidization of LDL cholesterol, leading to atherosclerosis. The two types of iron are heme and nonheme. Heme iron is found only in animal foods such as beef, poultry, and fish and boasts a greater bioavailability than nonheme iron, which is primarily found in plant foods such as soy products, dried fruits, legumes, whole grains, fortified cereals, and green leafy vegetables. Nonheme iron's bioavailability can be enhanced when sources are consumed with either a meat product or a vitamin C source. Iron absorption can be inhibited by calcium, tannins in tea, phytic acid in grains, or excessive fiber. Iron is found in red meats, certain seafoods, vegetables, and legumes and is added to enriched grains and breakfast cereals.
If an athlete is diagnosed with iron-deficiency anemia, iron supplements are typically suggested, and normalizing iron status will improve performance and endurance. Individual iron supplements should be taken only under the care of a physician. Identifying athletes at risk for anemia via ferritin testing can allow for early intervention. Zinc is important for every living cell in the body. zinc goes to work to enhance health and athletic performance. Zinc is involved in a huge variety of bodily processes and, impressively, is associated with more than 200 enzymatic systems. In addition to its enzymatic role, zinc is critical for optimal health by: Playing a role in wound healing, which enhances immune function Aiding in the synthesis of RNA and DNA, thus influencing gene expression
Deficiencies of sulfur are rare, unless a protein deficiency is also present, which would include a deficiency in methionine and cysteine. When sulfur is present in suboptimal levels, cysteine is required for the production of PAPS, thus sacrificing protein synthesis. There have been reports of individuals suffering from osmotic diarrhea after consuming large quantities of sulfur. Athletes should include sulfur-containing foods on a daily basis in addition to consuming adequate levels of protein. The major minerals include calcium, phosphorus, magnesium, sodium, chloride, potassium, and sulfur. Iron is absorbed in the small intestine, but it must first be prepared for optimal absorption in the stomach. The gastric acids of the stomach help to dissolve iron and convert ferric iron into ferrous iron, which is more readily absorbed through the intestines. elderly individuals with low production of gastric acid, will have compromised iron absorption.
Iron deficiency is one of the most common nutritional deficiencies in the United States and therefore deserves special mention and attention. Red blood cell count : Counts the number of red blood cells in the blood, which reflects iron status because of the need for iron to produce red blood cells. The total number of red blood cells is also related to hemoglobin levels. Transferrin saturation : Transferrin is the transport protein for iron in the blood. The transferrin saturation reflects the percentage of transferrin saturated with iron. Iron is best known for aiding in the formation of compounds essential for transporting and utilizing oxygen; thus, it is critical for aerobic activities and endurance training. Iron depletion : Iron stores are depleted from the bone marrow, which is indicated by a low blood ferritin level. Iron-deficiency erythropoiesis : Blood results will show a continued decline in serum ferritin and an increase in serum transferrin, while hemoglobin levels remain in the normal range. Athletes will begin to feel the effects of iron deficiency through decreased physical performance results.
iron-deficiency anemia A clinical condition commonly resulting from poor iron intake that affects the red blood cells and their ability to transport oxygen. It is important to realize that there are several types of anemia, and it is critical to diagnose the correct one to ensure that individuals receive proper treatment. They state that three groups of athletes appear to be at greatest risk for developing altered body iron: female athletes, distance runners, and vegetarian athletes. In fact, similar reports state that as many as 26-60% of female athletes are affected by iron deficiency. Although female athletes, distance runners, and vegetarian athletes may be at higher risk, they are not the only athletes at risk. Many athletes consume less than their daily requirements for both total calories and iron. Those following an omnivorous diet appear to be at lower risk for deficiency.
Loss through sweat : This factor may have a greater impact on the iron status of males because men tend to sweat more than women. Sports anemia is a unique condition and not a true anemia. It is theorized to occur because the red blood cells become very efficient at carrying and releasing oxygen to the tissues and therefore do not require a high level of concentration in the blood. The upper limit for iron is 45 milligrams per day. Consult with an athletes physician. Perform a diet analysis : Review iron intake from foods and supplements, the types of iron sources consumed (heme and/or nonheme), and dietary factors that are enhancing or inhibiting iron absorption at meals and snacks. Consider the athlete's primary sport and level of training : Impact versus nonimpact sport. Excessive iron can cause decreased absorption of other nutrients, such as copper. For those who are genetically predisposed, high iron intakes can contribute to a condition termed hemochromatosis .
Magnesium blocks the stimulating effect of calcium, allowing muscles, particularly in the arterioles, to relax, thereby decreasing blood pressure. Insufficient magnesium intake will allow calcium's contracting effect to dominate, and higher blood pressure will ensue. Hypermagnesemia, or high blood levels of magnesium, is uncommon except for those with kidney diseases or malfunction. The upper limit of 350 milligrams per day refers to the maximum daily dosage of magnesium only from supplements and medicines. Magnesium is widely distributed in foods but is concentrated in plant-based sources. Whole grains, green leafy vegetables, legumes, nuts, and seafood are all good sources of magnesium.
Overall, research has found the greatest benefit of supplementation in those who are currently consuming low dietary levels of magnesium. if an athlete is deficient in magnesium, achieving an optimal intake may be helpful in resolving poor performance or deficiency symptoms such as muscle weakness, muscle cramps, and irritability. The most current recommendation sets the AI for sodium at 1500 milligrams per day. Sodium is important for maintaining blood pressure, nerve impulse transmission, and muscle contraction. Sodium is most noted for its role in blood pressure. A consistently high intake of sodium has been directly linked to high blood pressure.
A lower sodium intake has been the mantra of health professionals for many years, and it will be renewed when statistics become available in upcoming years on Americans' massive sodium consumption as compared to the new stricter DRI guidelines (the current AI is 1500 milligrams; the previous recommendation was 2400 milligrams). At the other end of the spectrum, sodium is crowned as a hero for its role during exercise, and its intake is often encouraged. Sodium aids in the absorption of glucose, which makes it a key component of sports beverages designed to provide energy during exercise. Sodium also serves as one of the body's electrolytes. Electrolytes are minerals that become positively or negatively charged ions when dissolved in the fluid medium of the body.
Sodium is lost in sweat during exercise. If the loss is excessive, without replacement, a life-threatening condition called hyponatremia can result. hyponatremia Low blood sodium levels resulting from sodium deficiency and/or the intake of large volumes of water. Signs and symptoms of low blood sodium (hyponatremia) include cramping, nausea, vomiting, dizziness, seizures, coma, and—left untreated—death. Hyponatremia can also be caused by consuming only water, versus sports beverages, during long-duration exercise or by routinely avoiding foods and beverages containing sodium.
Potassium supplements are not needed and can cause harm in large doses. For athletes, the emphasis should be placed on food sources of potassium because adequate potassium intake is easily attainable through a balanced diet. Large doses of supplemental potassium, at levels of 18,000 milligrams or higher, can disrupt muscle contraction and nerve transmission, ultimately leading to a heart attack. Regardless of the lack of hard numbers, sulfur or sulfate is a nutrient that athletes should consume on a daily basis for proper bodily functioning.
Sulfur is a component of hundreds of compounds in the body. The body synthesizes the majority of these compounds using the sulfur consumed in the diet and from sulfur produced in the body from degradation of the amino acids methionine and cysteine. The most notable sulfur-containing compound in the body is 3-phosphoadenosine-5-phosphosulfate (PAPS). Sulfate derived from methionine and cysteine found in dietary proteins and the cysteine component of glutathione provide sulfate for use in PAPS synthesis. PAPS, in turn, is then used in the biosynthesis of other essential body compounds.
High-fiber foods contain compounds that can bind to certain minerals, thus preventing their absorption during passage through the intestines. In some instances, high doses of one mineral, which can occur during supplementation, can cause competition for absorption and thus decrease intestinal uptake of other minerals.
The major minerals include calcium, phosphorus, magnesium, sodium, chloride, potassium, and sulfur. Minerals are classified as "major" if they are required by the body in amounts greater than 100 milligrams per day. The trace minerals include iron, zinc, chromium, fluoride, copper, manganese, iodine, molybdenum, and selenium. Minerals are classified as trace if they are required by the body in quantities less than 100 milligrams per day. Both major and trace minerals are stored in the body; when consumed in excess, stored levels can build and become toxic to the body (e.g., high doses of iron can cause hemochromatosis, a condition discussed later in this chapter). Toxic levels can be achieved through dietary intake, but toxicity is much more likely to be caused by high-dosage supplements.
The RDA for calcium for men ages 19 to 70 years is 1000 milligrams per day. 1 The RDA for women ages 19 to 50 years is 1000 milligrams per day. Daily recommendations are increased to 1200 milligrams per day for men older than 70 years and for women older than 50 years. Blood clotting : Calcium helps to produce fibrin, the protein responsible for the structure of blood clots. Nerve transmission : Calcium is required for proper nerve function, releasing neurotransmitters that facilitate the perpetuation of nerve signals and activation. Muscle contraction : Calcium is pumped into and out of muscle cells to initiate both muscle contraction and relaxation in smooth muscle, skeletal muscle, and the heart.
The Dietary Approaches to Stop Hypertension (DASH) study developed the DASH diet, which encourages a balanced diet focusing on calcium, magnesium, and potassium because of their role in moderating blood pressure. The DASH diet recommends consuming a minimum of three servings of low-fat dairy products every day. Colon cancer research has focused on the action of calcium combining with bile salts, which are then excreted from the body, thus protecting the cells within the colon from damage. Weight-bearing exercises such as walking, running, and weightlifting can create stress that strengthens and builds bone.
Magnesium is involved in hundreds of enzymatic reactions, bone health, blood clotting, and the regulation of blood pressure. Magnesium is involved in more than 300 enzyme functions, including DNA and protein synthesis as well as proper blood clotting. Magnesium helps to maintain bone strength through its role in bone metabolism. Magnesium has an inverse relationship with blood pressure, with adequate daily intakes protecting an individual from hypertension. Inside the mitochondria, magnesium is essential for the aerobic production of ATP via the electron transport chain.
The important roles that magnesium plays in muscle function and bioenergetics are the driving force behind the development and marketing of sports-related supplements containing magnesium. Magnesium deficiency has been shown to cause a variety of problems such as altered cardiovascular function, including hypertension, as well as impaired carbohydrate metabolism. Some of the symptoms of magnesium deficiency include loss of appetite, muscle weakness, and nausea.
Salt, or sodium chloride (NaCl), is the richest source of chloride in the American diet. Chloride can also be found in small amounts in fruits and vegetables. Even though chloride is lost in sweat, athletes generally consume plenty of chloride through a balanced diet. Chloride supplements do not appear to enhance physical performance and therefore are not recommended. Potassium is involved in the regulation of many bodily processes, including blood pressure. The most recent dietary recommendations for potassium have increased, creating a large gap between the typical American intake and the recommended values. This gap is caused in large part by the increased consumption of processed foods in the United States, which are generally low in or devoid of potassium. All individuals, including athletes, need to put a stronger emphasis on eating potassium-rich foods on a daily basis.
The interchange and flow of potassium and sodium in and out of cells are responsible for the transmission of nerve impulses and muscle contractions. Potassium is one of the intracellular electrolytes that is critical for fluid balance in the body, especially during exercise. Athletes need to make an effort to choose potassium-rich foods while keeping sodium intake under control. A rapid change in potassium status or long-term low potassium levels can lead to heart arrhythmias. However, in those with impaired kidney function, high intake of potassium (combined with low excretion) can lead to hyperkalemia. High potassium levels in the blood over time can lead to a slowing and eventual stopping of the heart. Meat, milk, coffee, and tea are also significant sources. Food processing tends to remove potassium and add sodium, thereby contributing to the imbalanced intake of these two minerals. The best food sources of potassium are fresh fruits and vegetables, and certain dairy products and fish.
Manganese activates a variety of health-related enzymes that are involved in skeletal growth, protein and hemoglobin synthesis, metabolism of lipids and carbohydrates, and antioxidant functions. One of these enzymes is superoxide dismutase, which is important for its antioxidant properties. Manganese is also involved in energy metabolism and fat synthesis. Iron and calcium supplements should be taken between meals to avoid nutrient-nutrient interactions. Iodine has the glory and recognition of being the first vitamin or mineral to be incorporated into a successful fortification program. T4 and T3 are involved in the metabolism of all cells of the body during the growth process and in the development of most organs, particularly the brain.
The only documented case of acquired molybdenum deficiency occurred in a patient with Crohn's disease on long-term total intravenous nutrition that was not supplemented with molybdenum. The connection between human health and selenium intake was made in 1979 after scientists discovered that Keshan disease could be prevented by providing children in China with selenium supplements. Since then, selenium has quickly climbed the ranks of nutritional importance to become a member of the highly regarded antioxidant category of nutrients. selenium form associated with glutathione peroxidase, an antioxidant enzyme that helps to combat free radical damage to cells. Through this breakdown of free radicals, glutathione peroxidase actually helps to spare vitamin E, allowing the vitamin to continue on its free radical scavenger hunt.
