Calcium also plays an important role in skeletal muscle contraction and relaxation. In a week study on young women involved in intense endurance training Dressendorfer, R, et al, Int.

Sports Nut. and Exer. Calcium intake for endurance athletes needs to be adjusted upwards. This mineral is of critical importance to anyone who exercises, and is of critical importance to athletes and endurance athletes.

Magnesium is a component of more than enzymes involved in energy metabolism. Magnesium is involved in the production of adenosine triphosphate ATP from fatty acid oxidation see diagram below.

ATP stores energy and is present in all cells, especially muscle cells. Low magnesium levels can contribute to early fatigue, nausea, and muscle cramps. Magnesium is involved in a multitude of processes that impact muscle function, including oxygen uptake and electrolyte balance, in addition to energy production.

Iron is of critical importance for athletic or sports performance. It is a component of hemoglobin, myoglobin, cytochromes, and other enzymes in the muscle cells. All of these substances are involved in the transport and metabolism of oxygen for energy required for aerobic performance during endurance exercises.

Studies have shown that athletes can experience depletion of iron [J Int Sports Nutr ; 2 1 ]. An hour of weight training can deplete 5. Losing too much iron stores can lead to iron deficiency, which causes fatigue and saps endurance.

It has also been shown that iron deficiency without anemia impairs favorable adaptation to aerobic exercise Brownlie, T. Athletes who train for 6 or more hours per week often have iron deficiency anemia and should be checked yearly for the condition.

Med Sci Sports Exer Sep; 24 9 Suppl : S ]. This mineral electrolyte is stored within muscle fibers along with glycogen. According to Jonathan Toker, Ph. It is responsible for regulating total body water, as well as stabilizing voluntary and automatic muscle contractions.

It works with sodium and chloride to control fluid and electrolyte balance, and assists in the conduction of nerve impulses. Potassium is needed to repolarize the cell membrane after nerve conduction, resetting the nerve for its next activity.

Potassium deficiency can be induced by extreme training or athletic performance, especially in hot climates, and has been implicated in muscle injury. The symptoms of potassium deficiency include nausea, slower reflexes, vomiting, muscle weakness, muscle spasms, cramping, and rapid heart rate.

As one can see, potassium is a critically needed electrolyte for athletic performance, and measures need to be taken to maintain a safe body level of this mineral electrolyte. Selenium is a component of several enzymes, and is essential to the production of the antioxidant enzyme glutathione peroxidase SeGPx.

It is believed that selenium supplementation could prevent peroxidation of the RBC membrane and muscle cell substructures involved in oxygen metabolism. In an animal study, reducing the level of muscular SeGPx resulted in an increase in cellular damage from prolonged exercise, supporting the theory that muscle damage due to free radicals causes muscle fatigue [Venditti P.

Int J Sports Med ct;18 7 : ]. Research has also shown that selenium supplementation increases SeGPx status and reduces lipid peroxidation during prolonged aerobic exercise.

Person-Moschos M. Maintaining optimal zinc levels is imperative to maximize athletic performance. Zinc is needed by more than enzymes to repair the body and protect against immune invaders. It also helps synthesize proteins and helps cells reproduce.

Zinc plays important roles in the production of testosterone, insulin-like growth factor, and growth hormone. All of these have great impact on increasing the building of muscle, increased strength, and improved recovery time. These effects have been seen in men and women.

This will cause a decline in energy and endurance. Zinc is essential for an effective immune system. Athletic performance leads to the production of harmful free radicals.

Zinc functions as a powerful intracellular antioxidant, aiding in the reduction of free radicals, which helps athletes recover more quickly from athletic performance. Zinc has a positive impact on insulin release in response to increased blood glucose and aids in improved insulin sensitivity, helping the uptake of glucose by muscle cells.

For most athletic performances, hyponatremia is not a problem. Sodium helps cells retain water and prevents dehydration. It also helps ATP generation. Inadequate energy intake or avoidance of animal products are typically the culprits.

It has many other important tasks, such as regulation of muscle contraction, nerve conduction, and blood clotting. There are two main forms of calcium supplements, if supplementation is needed: carbonate and citrate.

Both forms are well absorbed, but individuals with reduced levels of stomach acid can absorb the citrate form more easily.

Calcium carbonate is commonly available and inexpensive, and its absorption rate is most efficient when taken with food. Calcium citrate is absorbed equally effectively when taken with or without food.

No more than milligrams of calcium should be taken at a time to ensure optimal absorption and utilization. When this goal is not achieved, performance declines because of less than optimal levels of hemoglobin, as well as changes in the muscle—reduced amounts of myoglobin and iron-related enzymes that are involved in energy production.

Hemoglobin and myoglobin are both oxygen-carrying proteins. The capacity to carry oxygen is essential for endurance exercise as well as for normal function of the nervous, behavioral, and immune systems. Iron deficiency, with or without anemia, can impair muscle function and limit work capacity.

Iron depletion is typically related to inadequate energy intake. There are other factors that can affect iron status, including following a vegetarian diet with poor iron availability, times of rapid growth in adolescence, training at high altitudes, and increased losses sweat, urine, feces.

It is prudent to perform routine iron screenings, including serum ferritin levels, to determine possible supplementation needs. Also note that reversing iron deficiency anemia can take three to six months.

Good sources of iron include chicken and beef liver, Cream of Wheat, dried fruits, oatmeal, beans, lentils, and meats. Certain forms of iron from non-meat sources are absorbed more readily when foods with vitamin C are consumed at the same time.

Also important to consider is that absorption is decreased when taken with tea, coffee, chocolate, dark leafy greens, whole grains, soda, and certain minerals. A good rule of thumb if iron stores are low is to consume calcium-rich foods and tea between meals.

Also, focus on getting vitamin C-rich foods at meal times, especially when consuming non-meat iron sources. Basal metabolic rate, thyroid hormone levels, and protein utilization have been shown to be directly affected by zinc status. Athletes, especially women, who are at risk for impaired zinc status are those who consume a diet low in overall energy needs and animal protein, but high in fiber.

Athletes should be cautioned against single-dose zinc supplements because they often exceed the UL of 40 mg. Consuming too much zinc can lead to low HDL cholesterol and nutrient imbalances by interfering with absorption of other minerals, such as iron and copper.

Endurance performance is impaired by magnesium deficiency because of increasing oxygen requirements to complete submaximal exercise. Inadequate magnesium intake is typically related to overall energy deficit and an inadequate balance of food groups. The B vitamins thiamin, riboflavin, niacin, B6, pantothenic acid, and biotin are involved in energy production during exercise.

Folate and B12 are required for the production of red blood cells, protein synthesis, and in tissue repair and maintenance. There has been some data to suggest that exercise may double the need for B vitamins. Severe deficiency of B12, folate, or both may result in anemia and reduced performance.

In terms of supplementation, B vitamins are water-soluble, thus are not stored in the body in the same way as fat-soluble vitamins.

Also know that excess intake can lead to problems. Although technically not a vitamin, this hormone is necessary for the absorption of calcium, making it essential for bone health. It also plays an important role in immune function and reducing inflammation. In recent years, more research has been done on the consequences of vitamin D deficiency in athletes.

It has been shown that low levels can decrease physical performance and increase the incidence of stress fractures. The RDA was increased from IU to IU in as more information about the prevalence of deficiency and its role in maintaining good health and optimal athletic performance was uncovered.

It has been hypothesized that frequent exercise produces a chronic oxidative stress on the muscles since exercise increases oxygen consumption, and thus ups the need for antioxidants.

This idea remains controversial. There is some evidence that a combination of antioxidants may be helpful at reducing inflammation and muscle soreness.

Athletes need to be advised to not exceed the UL for any antioxidant because higher doses could be pro-oxidative with possible negative effects. With our student-athletes at Texas, the goal is that they meet increased micronutrient needs through food alone. But that can be difficult to achieve consistently.

This is especially true with athletes who have restricted eating patterns intentional or unintentional , such as severe weight loss practices, disordered eating, a food allergy, or by following fad diets.

A balanced, varied diet can also be tough for athletes with poor eating habits, inadequate finances, or an overcommitted lifestyle that causes erratic meal patterns.

In some cases, here at Texas, individual nutrient supplementation, such as iron, calcium, or vitamin D, is recommended based on our protocols and my assessment of the athlete. Another strategy I often use is to fill the nutritional gaps with fortified sports bars and other fortified foods that provide micronutrients.

This issue will not be discussed in detail here, but there are some important points to consider:. For more in-depth information about dietary supplements, visit the helpful website www.

Teaching athletes the importance of an overall adequate diet is the key to long-term success. They include: Recommended Dietary Allowance RDA : average daily level of intake sufficient to meet the nutrient requirements of nearly all 97 to 98 percent healthy people.

Adequate Intake AI : established when evidence is insufficient to develop an RDA and is set at a level assumed to ensure nutritional adequacy. Tolerable Upper Intake Level UL : maximum daily intake unlikely to cause adverse health effects. Pack a punch In the above list, I put nutrient density first because it is the most important.

Adding vitamin supplements With our student-athletes at Texas, the goal is that they meet increased micronutrient needs through food alone. This issue will not be discussed in detail here, but there are some important points to consider: Look for third party verification, such as Informed-Choice or NSF, which helps to ensure the safety of the dietary supplement.

Avoid supplements marketed to burn fat, increase energy, or promise anything that sounds too good to be true. Avoid supplements that offer mega-doses of vitamins and minerals. Amy Culp, RD, CSSD, LD, is an Assistant Athletics Director and the Sports Dietitian at the University of Texas.

She has been coaching athletes on all aspects of fueling for optimal performance and health for more than a decade. Tags: nutrition , vitamins.

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