Vitamin and Minerals at a Glance

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Fat-soluble vitamins include A, D, E, and K, while vitamin C and the B vitamins are water-soluble. We need only tiny amounts of vitamins in our diet. In fact, in a year, you need less than a pound of vitamins compared to the two thousand pounds of food we eat. But even they are essential for life, as our bodies cannot manufacture vitamins and minerals.

Most vitamins play some role in muscle contractions or the ability to convert food into energy and in energy metabolism. Several B vitamins are necessary for storing excess calories as fat; breaking down glycogen into glucose; aerobic metabolism (oxidative metabolism); and the digestion and absorption of nutrients. Folic acid and B12 also are necessary for red blood cell development; without enough, anemia can result.

Water-Soluble Vitamins

Vitamin B1 (Thiamine)

Required for energy, the production of branched-chain amino acids, and carbohydrate metabolism, it is thought that B1 requirements may be slightly higher for individuals who have high energy expenditures. Overall, however, physical activity does not appear to significantly increase the body's requirement for thiamine. But for those engaged in intense training, higher levels of intake may be required. However, of the few studies conducted with athletes supplemented with thiamine, none has found conclusive evidence that exceeding the RDA value for B1 provides a performance benefit.

Vitamin B2 (Riboflavin)

Riboflavin is involved in metabolic reactions for energy production. While there are no data to suggest that athletes need more than the RDA of riboflavin in their diet for optimal performance, research does suggest that riboflavin requirements may be higher for athletes than for the general population.

Niacin

Niacin is actually a family of molecules that also includes nicotinic acid and nicotinamide. The B vitamin is needed for glucose metabolism and energy production. Either too much or too little can be detrimental to performance. A deficiency can affect glycolysis and the oxidation process affecting both anaerobic- and aerobic-type performance. At high doses it may shift metabolism to utilize carbohydrate and decrease free fatty acids, potentially impairing endurance performance. The requirement for niacin is usually linked to energy intake, which means that athletes who have high energy intakes will have a proportionately higher need for niacin. Overall, there is no evidence to support higher amounts of niacin above the RDA for a performance benefit.

Vitamin B6 (Pyridoxine)

Also referred to as pyridoxal, this B vitamin is essential for about a hundred reactions in the body, including the production and metabolism of carbohydrates, fats, and proteins. It also is involved in the manufacture of compounds necessary for hemoglobin, the compound that carries oxygen through the bloodstream. While some initial studies suggested that endurance athletes may have increased needs for B6, more recent data suggest that the RDA is adequate.

Vitamin B12 (Cyanocobalamin)

This B vitamin is necessary for DNA synthesis and for the formation and function of red blood cells; deficiencies can lead to anemia. Because of its role in oxygen-bearing red blood cells, it has been suggested that additional B12 might improve performance in athletic events in which oxidative metabolism is important. However, there is no evidence that B12 supplements or injections improve performance. And B^ deficiency among athletes is rare. Since B12 is found only in animal-based products, vegan athletes need to take B12 supplements or include B12-fortified foods in their diets. Supplementing with large doses of other vitamins, such as vitamin C, may actually decrease vitamin B12 availability and lead to a B12 deficiency.

Folate (Folacin, folic acid)

This B vitamin is also involved in DNA synthesis and the formation of amino acids and is important during times of growth and development. A

deficiency of this nutrient can lead to anemia. Recent Centers for Disease Control and Prevention data have shown that a growing percentage of women in the United States have deficient blood folate levels. However, there is no evidence that in the absence of a deficiency, supplemental folate can improve athletic performance. Athletes should strive to meet the RDA for folate.

Pantothenic Acid

Pantothenic acid is necessary for energy production from proteins, carbohydrates, and fats. Few studies have been conducted to determine if athletes have increased requirements for pantothenic acid. For optimal performance, athletes should strive to meet the AI for pantothenic acid. Pantothenic acid is present in virtually all plant and animal foods, so inadequate intake is rare.

Biotin

This vitamin serves as a coenzyme in many metabolic reactions and is essential for carbohydrate, fat, and amino acid metabolism. Biotin is needed in energy production, suggesting that inadequate intake could affect performance, but to date, no studies have been conducted to determine if athletes require additional biotin above the AI level.

Vitamin C (Ascorbic acid, ascorbate)

This antioxidant vitamin is necessary for collagen synthesis, breaking down fatty acids, and forming neurotransmitters in the brain and nervous system. There are data to suggest that vitamin C helps protect against upper respiratory tract infections (URTIs) or common colds among endurance and ultraendurance athletes.

Athletes competing and training in ultraendurance events may benefit from taking five hundred milligrams a day of vitamin C, and those in other nonendurance activities may benefit from at least a hundred grams a day. There is no evidence that doses at higher amounts will provide additional benefits, and they may have adverse effects.

Fat-Soluble Vitamins

Vitamin A (Retinol) and Beta-carotene

This antioxidant vitamin is best known for its role in maintaining healthy vision, but it is also needed for reproduction and bone formation. Beta-carotene serves as a precursor to vitamin A, meaning that when the body needs vitamin A, it will convert beta-carotene into vitamin A. Beta-

carotene is just one of the hundreds of carotenoids that have been identified, including lutein and lycopene.

Carotenoids are also antoxidants and are thought to have potential anti-cancer activity when consumed in foods, but supplements appear to be less helpful and in some cases have been found to be potentially harmful. There is some evidence that supplemental beta-carotene may have adverse effects on lung tissue, so it is not recommended that athletes supplement their diets with beta-carotene unless suggested by a health care professional.

There is no evidence to suggest that athletes should consume more than the RDA for vitamin A or beta-carotene. Since vitamin A is stored in the body, it can have negative health effects. Studies show that excessive amounts can reduce bone-mineral density, among other negative effects.

Vitamin D

This hormone/vitamin is unique in that the body can generally manufacture enough on its own if the skin is exposed to adequate sunlight. Vitamin D is essential for calcium metabolism and bone health. Emerging research shows it to be involved in a much wider spectrum of body functions, from helping prevent certain types of cancer and type 2 diabetes. However, there has been little research to investigate the effects of physical activity on vitamin D requirements or the effects of vitamin D on exercise performance. While there is no evidence that athletes are at special risk for vitamin D deficiency or that they need additional vitamin D, it is important for athletes in weight-sensitive sports (gymnasts, distance runners, and cyclists) to take adequate vitamin D to help maintain healthy bones. In recent years, as Americans have become more aware of the harmful effects of UV rays from sunlight, vitamin D status has declined. By blocking the sun's UV rays, sunscreens are blocking the trigger that allows the body to manufacture vitamin D.

More recent research has linked diets rich in vitamin D to a reduced risk for certain cancers, diabetes, and overall death rates. Most of the research on vitamin D has occurred in the past five years, and it is thought that the current recommendation of 400 IU per day used on food labels as the daily value may be too low; four to six times that amount may be optimal. While it's too early to recommend vitamin D as a preventive measure against disease, ensuring that you have foods that contain vitamin D in your diet is essential. Only a few foods naturally contain vitamin D, and only dairy products and a few 100 percent fruit juices are fortified with the nutrient. In addition, expose your skin to sunshine for small, safe amounts of time to manufacture the nutrient. Spending 15 minutes in the summer sun can enable the body to produce 15,000 IU of vitamin D or more than thirty-seven times the RDI of 400 IU.

Vitamin E (Tocopherols, Tocotrienols)

Vitamin E is actually a family of eight compounds known as tocopherols and tocotrienols. As an antioxidant, vitamin E helps to protect cell membranes from oxidative damage and is known to help protect the immune system. Vitamin E has long been thought to possess cardioprotective qualities, but recent research on vitamin E supplements and heart disease has been less conclusive.

Several studies of marathon runners have evaluated the effects of vitamin E supplementation before marathons or other ultraendurance events, such as the Marathon des Sables, a six-stage running event across the Sahara. French researchers randomly assigned runners to either an antiox-idant group, who took twenty-four milligrams of vitamin E (along with vitamin C and beta-carotene) daily for three weeks before the event, or to a control group. Blood was taken from the athletes two days prior to the race, after the third stage, then again at the end. The researchers found that athletes who took the supplement did not have elevated TBARS (a measure of oxidative stress) compared to the control subjects, who exhibited elevated TBARs during the race.

Other studies have found similar results. Because vitamin E protects muscle from free radical damage, it has potential as an ergogenic aid for athletes. However, research suggests it holds more promise as a way to prevent oxidative damage as a result of exercise, rather than actually improving exercise performance. There is no conclusive data to suggest that vitamin E acts as a performance enhancer, but since many athletes don't get enough of this nutrient, it's important to pay close attention to the level of E in your diet or to consider a supplement containing vitamin E.

Vitamin K

Vitamin K is the fat-soluble nutrient best known for blood clotting. What's less known is that vitamin K is also required for the formation of osteocalcin, a compound necessary for optimal bone growth and density. Deficiencies of vitamin K may be more common than previously thought due to diets high in refined carbohydrates and megadoses of vitamins A and E. Antibiotics also can impair vitamin K status by decreasing intestinal bacterial function responsible for the production of vitamin K.

Athletes at risk for low bone density and bone mass may need additional vitamin K in their diets over and above the current AI.

Major Minerals

Minerals are inorganic compounds classified by the amount required in the body: macrominerals are required in amounts ranging from hundreds to thousands of milligrams, while trace minerals are required in amounts of only a few milligrams or even micrograms. Sodium, potassium, calcium, phosphorus, and magnesium are macrominerals, while iron, zinc, selenium, and others are trace minerals.

Sodium, Potassium, and Chloride

Sodium, potassium, and chloride are the three major electrolytes in the body that maintain electrical signaling between the outside and the inside of every cell in the body. Sodium and chloride are in the fluid outside of the cells, in the extracellular fluid, while potassium is in the intracellular fluid. They are involved with maintaining fluid balance, nerve transmission, and muscle contractions.

Sweating increases the need for sodium because the average sodium loss ranges from 460 to 1,840 mg of sodium per liter of sweat and can only get worse in the heat.

Exercise-induced low-plasma sodium, also called hyponatremia (sodium concentration of <130 mmol/l, normal range 135 to 146 mmol/l), has been observed with increasing frequency during the past decade, with reports of up to nearly 30 percent of endurance athletes being affected. Hyponatremia has been reported in many endurance athletes, from marathoners to Ironman competitors, and is thought to occur when athletes become dehydrated and drink water only without additional sources of sodium (i.e., sports drinks, bars, or gels).

Most athletes get enough sodium, potassium, and chloride in their diets as they eat more calories and naturally get more salt (sodium chloride) in their diets than do nonathletes. However, endurance athletes need to pay special attention to their sodium and chloride intake before, during, and after training and racing to ensure that they are replenishing what is lost in sweat.

For the endurance athletes, loss of fluid and sodium can affect performance because of the dreaded heat cramps—which seem to be different from cramps due to fatigue. Fatigue cramps are localized muscle cramps related to being too tired or working too hard. The best remedy for these cramps is stretching, icing, and massaging. Heat cramps, on the other hand, occur during prolonged exercise in hot conditions and may have more to do with large losses of fluid and sodium due to heavy sweating. Endurance athletes tend to be heavy sweaters who lose large amount of sodium through sweat.

Electrolytes Lost in Sweat

Sodium: 40-80 mmol/L or 920-1840 mg/L Chloride: 30-70 mmol/L or 1062-2478 mg/L Potassium: 4-8 mmol/L or 156-312 mg/L Calcium: 3-4 mmol/L or 120-160 mg/L Magnesium: 1-4 mmol/L or 24-96 mg/L

Average Amounts of Electrolytes Lost in 1 Liter (33.8 ounces) of Sweat

Sodium: 1,380 mg Chloride: 1,770 mg Potassium: 234 mg Calcium: 140 mg Magnesium: 60 mg

Calcium

Calcium is the most abundant element in the body. We have a few pounds of it in our body at any given time, with 99 percent of the body's calcium providing structure to our bones and teeth, with the remainder in our blood, body fluids, muscles, and other soft tissues. The mineral is necessary for bone metabolism, blood, neuromuscular function, muscle contractions, cell membranes, and hundreds of other reactions in the body.

Calcium is often lacking in athletes' diets, and some evidence suggests that athletes who sweat a lot in the heat may have additional calcium losses in sweat and may need more than the AI for calcium in their diets; a calcium supplement may be needed. Keep in mind that the efficiency of absorption of calcium from supplements is greatest when calcium is taken in doses of no more than five hundred milligrams at a time.

Phosphorus

As the second most abundant mineral in the body, 85 percent is in our bones and teeth, and the remaining 15 percent help with many other functions, including energy production. Phosphorus is in muscles as part of the high-energy compounds phosphocreatine and adenosine triphos-

phate (ATP). ATP is the supplier of energy for muscle contractions. Phosphorus also is involved in buffering of the acid end products of energy metabolism, which is why you may have heard of phosphate-loading. This was a technique designed to buffer lactic acid buildup but was found not to provide performance-enhancing benefits.

While phosphorus is essential for healthy bones, too much of the nutrient actually weakens bones. High phosphorus intakes can decrease vitamin D production, affecting calcium absorption. Phosphorus is in many foods in the diet, so overconsumption is more of an issue for athletes than not getting enough of the nutrient. Drinking too many carbonated beverages, which are high in phosphorus, can increase risk of bone fractures. There is no evidence to support getting more than the RDA for phosphorus for active individuals.

Magnesium

Magnesium is a mineral essential for energy production and is involved as a cofactor in more than three hundred enzyme systems in the body. It also is needed to manufacture glycogen, the storage form of blood glucose in the muscles and liver. In addition, it works with calcium and phosphorus to maintain bone health. In fact, 60 to 65 percent of the body's magnesium is in bone. Magnesium also works in conjunction with sodium and potassium to maintain blood pressure.

Of the studies conducted on magnesium supplementation with athletes, there is inconclusive evidence that the nutrient acts as a performance enhancer. However, studies show that loss of magnesium in the urine and sweat is higher in people who exercise, especially in hot conditions. Obtaining the RDA for the nutrient is considered adequate.

Iron

Iron is key for athletes because it is needed to form hemoglobin in red blood cells and myoglobin in muscle. Iron helps increase the oxygen-carrying capacity of blood, which is critical for muscles to extract oxygen for energy production. In addition to supplying oxygen to cells, iron helps facilitate energy transfer within cells. Training, regardless of the type, increases iron requirements due to increased iron turnover in tissues, iron losses in sweat, and the breakdown of red blood cells during training.

Many athletes—especially female athletes, runners, and vegetarians—are at risk for low iron, which will result in a reduced amount of hemoglobin in the blood. In fact, iron depletion is relatively common among athletes, and as a result, it has been suggested that athletes need much more than the

RDA for iron. Some have recommended seventeen to eighteen milligrams per day for men and twenty-three milligrams per day for women who are menstruating. Some studies have found that as many as 60 percent of female athletes may be at risk for anemia. For those identified as anemic, a doctor may recommend up to one hundred milligrams of iron per day—at this level, you need to have a doctor prescribe it; don't do this on your own.

Iron-deficiency anemia causes loss of appetite, fatigue, sluggishness, and a high rate of perceived exertion when working out. Endurance athletes, vegetarians, and females should have their iron levels and hemat-ocrit levels checked annually or twice a year to detect if iron levels are sufficient. Ferritin is the storage form of iron, while hematocrit is a measurement of red blood cells, which carry iron. As the iron supply decreases, the serum iron concentration falls, and the saturation of transferrin (the amount of iron it stores) is decreased. Though no single test tells the whole story, low hematocrit and low hemoglobin together typically signal anemia. Low serum ferritin with normal hemoglobin suggest early-stage iron deficiency (borderline anemia).

Iron supplements are commonly used among athletes. If you have low iron, it's almost impossible to reverse in a timely fashion (fewer than one to two years) without supplementation. Taking an iron supplement daily can help improve anemia in about three months. Since excess iron can be toxic for people who suffer from hemochromatosis or iron overload, it is best to have your blood levels of iron checked frequently to ensure that you are not at risk for iron overload.

Signs of Iron Deficiency

  • Pale skin
  • Elevated resting heart rate
  • Feeling run-down
  • Weakness or lethargy
  • Lack of motivation
  • Mood changes
  • Loss of appetite

For those striving to get more iron, it's important to know that only about 10 percent of the iron you eat is absorbed. And what you eat or drink can further diminish how much iron your body absorbs. Heme iron, or iron from animal foods, has the highest absorption and is affected little by dietary factors. For best absorption of other foods and supplements, consume iron supplements or iron-containing plant foods with a vitamin C source and avoid phytate- or polyphenol-rich options at about the time you have an iron-rich meal or supplement.

Iron enhancers include vitamin C-containing foods such as citrus fruit and juices that enhance iron absorption. Several compounds in foods inhibit iron absorption: phytate in whole grains, wheat bran, wheat germ, seeds, soy, oatmeal, and lentils; polyphenols (tannins) in tea, red wine, cocoa, and coffee; excess intake of other minerals (zinc, calcium, magnesium); oxalates from spinach, rhubarb, Swiss chard, and dark chocolate; and excess use of antacids.

Zinc

Zinc is ubiquitous in our bodies; about 60 percent of the mineral is in muscle, 29 percent in bone, and the remainder in the GI tract, skin, kidneys, and other major organs. Zinc has a role in more than three hundred reactions in the body, is associated with keeping the immune system healthy, and is involved in gene expression. Zinc also affects metabolic rate, thyroid hormones, protein utilization, and glycogen storage.

Zinc is lost through urine and sweat. However, consumption of the RDA appears to be enough for athletes; zinc status has not been found to be negatively affected by exercise training when zinc intake is adequate, and additional zinc will not provide a performance-enhancing benefit. However, athletes maintaining low body weights, such as wrestlers, dancers, and gymnasts, may not meet their zinc requirements. And the zinc requirement for strict vegetarians may be as much as 50 percent greater than for nonvegetarians.

Selenium

This antioxidant nutrient is essential for normal immune system and thyroid hormones, and some research suggests it has anticancer properties. Selenium supplements have been studied for endurance athletes to see if selenium reduces oxidative damage. However, research does not support the need for selenium in the diet above the RDA.

Chromium

Chromium is involved in carbohydrate, fat, and protein metabolism. Chromium is thought to stimulate insulin and therefore increase protein synthesis in muscle and help regulate blood sugar. At health food stores, chromium is often sold as chromium picolinate, a highly absorbable form of chromium, and marketed to increase lean body mass. However, studies have found mixed results; overall there appears to be some benefit for strength- or power-focused athletes but little or no benefit for endurance athletes.

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