Vitamins by wanghonghx

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									      Nutrition for Athletics


                Presented by
        Janice Hermann, PhD, RD/LD
OCES Adult and Older Adult Nutrition Specialist
Nutrition for Athletics
 Being physically active has many health
  benefits, and good nutrition plays an
  important role in athletic performance.
 While the USDA MyPyramid provides the
  foundation for a healthy diet, there are some
  special dietary considerations for athletics.
Nutrition for Athletics
 Nutrition can affect body weight, body
  composition and athletic performance.
 As interest in nutrition for athletic
  performance has increased so have
  promotions for ergogenic aids, supplements
  and herbal products claiming to improve
  athletic performance.
Calories
 Meeting calorie needs is a priority for athletic
  performance.
 Inadequate calories can hinder athletic
  training and performance. Inadequate
  calories can result in loss of muscle as well as
  body fat.
 Muscle loss can result in loss of strength and
  endurance. In addition, inadequate calories
  can result in poor nutrient intake.
Calories
 Calorie needs are affected by an individual’s
  age, gender, body size, muscle mass, as well
  as the frequency, intensity and duration of
  physical activity.
 One way to determine if adequate calories
  are consumed is if body weight and
  composition are maintained.
Weight Change
 Athletes often want to increase or decrease
  their body weight to meet sports demands.
 Weight change should occur slowly during the
  off-season, or beginning of the beginning
  before composition begins.
Weight Change
 Weight gain can be accomplished by an
 increase in calorie intake by 500 to 1,000
 calories per day in combination with an
 increase in strength training which can result
 in an increase in muscle mass.
Weight Change
 Weight loss can be accomplished by
  decreasing calorie intake by 500 calories per
  day while maintaining a healthy diet.
 Weight loss should be gradual, approximately
  1-2 pounds/week.
 Slow weight loss contributes to a loss in body
  fat while maintaining muscle. Rapid weight
  loss increases the risk of losing muscle and
  regaining weight.
Weight Change
 The best combination for weight loss is a
 regular fitness program along with a well-
 balanced, low-fat diet following the USDA
 MyPyramid.
Weight Change
 Weight loss may seem small at first when
  using a combination of diet and increased
  physical activity, because muscle mass
  increases at the same time body fat
  decreases.
 However, greater weight loss becomes
  apparent as body fat loss continues and
  muscle gain levels off.
Weight Change
 Weight loss techniques involving loss of body
  water are dangerous.
 Water loss results in decreased blood volume
  and reduced blood flow to the kidneys, skin,
  and muscles.
 This hinders the body’s ability to sweat and
  regulate body temperature, and increases the
  risk of dehydration.
Weight Change
 Determining a healthy body weight is critical.
 A healthy weight is one that can be
 realistically maintained, allows for positive
 increases in athletic performance and
 minimizes risk of injury.
Weight Change
 Pressure to achieve unrealistic body weights
  can lead to chronic dieting and eating
  disorders in severe cases.
 In addition, pressure to loss weight can
  encourage athletes to follow unhealthy
  weight loss methods.
Weight Change
 Excessive weight loss can especially be a
  problem for female athletes.
 In females, low calorie intakes in combination
  with high energy expenditures can lead to
  amenorrhea and loss of or failure to gain
  bone mass.
Body Composition
 Body weight and composition are two major
  factors that affect athletic performance.
 Body weight can affect speed, endurance, and
  power; whereas body composition can
  influence strength, agility and appearance.
Body Composition
 Most athletes need a high strength-to-weight
  ratio to enhance athletic performance.
 Because body fat adds to weight without
  adding strength, a low percentage of body fat
  is often emphasized; however, too little body
  fat can also hinder performance and health.
Body Composition
 Optimal body weight and composition differs
  based on an age, gender, genetics, and type
  of athletic event.
 Yet some athletic events set weight criteria
  that may not be optimal for an individual
  athlete – such as wrestling which may require
  athletes to lose or gain weight for specific
  weight categories.
Body Composition
 Other athletic events such as dance and
  gymnastics may pressure athletes to lose
  weight and have low body fat to have a lean
  physique that may not be ideal.
 Extreme calorie restrictions can result in a
  decreased in both body fat and muscle which
  can hinder athletic performance.
Body Composition
 Optimal body fat percentages vary depending
  on gender and the type of athletic event.
 Athletes who try achieve unrealistic
  inappropriate body weight or body fat levels
  may be at risk for eating disorders or other
  health problems related to inadequate
  calories or nutrients.
Macronutrients
 There isn’t evidence that athletes need a diet
 significantly different from that
 recommended in the Acceptable
 Macronutrient Distribution Ranges:
  45-65% carbohydrate
  10-35% protein
  20-35% fat
Protein
 Protein needs for athletes have received a lot
  of investigation, not only in terms of whether
  protein needs are increased, but also in terms
  of whether individual amino acids are
  beneficial.
 Athletes do have slightly higher protein
  requirements to support increased muscle
  mass and muscle repair.
Protein
 The amount of increase depends on the type
  of athletic activity, intensity, duration, and
  possibly the gender.
 Protein requirement may vary from 1.2 g/kg
  for endurance athletes to 1.7 g/kg for
  bodybuilders and strength athletes.
    General adult RDA for protein 0.8 g/kg

 Increased protein beyond recommended
 levels is unlikely to result in additional
 increases in muscle mass.
Protein
 It is important to realize that if calorie intake
  is not adequate, protein will be used for
  energy.
 It is also important to realize that most typical
  diets provide enough protein to cover even
  the increased protein needs of athletes.
Protein
 The effect of using individual amino acids to
  improve athletic performance has been
  inconsistent.
 Because the safety and efficacy of individual
  amino acid mixtures has not been
  established, their use cannot be
  recommended.
Vitamins and Minerals
 Vitamins and minerals have important roles in
  athletic performance for energy production,
  hemoglobin synthesis, bone health, immune
  function, and protecting body tissues from
  oxidative damage.
 Vitamins and minerals are also required to
  help build and repair muscle.
Vitamins and Minerals
 Although theoretically, physical activity may
 increase or alter vitamin and mineral
 requirements; it is assumed that the current
 Dietary Reference Intakes (DRIs) are
 appropriate for athletes unless otherwise
 stated.
Vitamins and Minerals
 Athletes at risk for poor vitamin and mineral
 intakes are those who severely limit calories,
 eliminate one or more of the food groups
 from their diet, or consume high-
 carbohydrate, low nutrient dense diets.
Vitamins and Minerals
 Athletes participating in the previous types of
  behaviors may need to use a
  multivitamin/mineral supplement to improve
  their overall nutritional status.
 Supplementing single vitamins and minerals is
  discourages unless there is a clear medical or
  nutritional reasons; such as an iron
  supplement for iron deficiency anemia.
Vitamins and Minerals
 The B-complex vitamins; thiamin, riboflavin,
 niacin, vitamin B-6, pantothenic acid and
 biotin are involved in energy production and
 folate and vitamin B-12 are needed for the
 production or red blood cells, protein
 synthesis and tissue maintenance and repair.
Vitamins and Minerals
 There is limited research available to
  determine if athletes need more B-complex
  vitamins; however, the some research
  suggests athlete may have a slightly higher
  need for these vitamins, perhaps up to twice
  the recommended amount.
 However, these increased needs can generally
  be met by athletes higher calorie needs to
  maintain body weight.
Antioxidant Nutrients
 Antioxidant nutrients such as vitamins A, E,
  and C, beta-carotene, and selenium have
  important roles in protecting cell membranes
  from oxidative damage.
 Because physical activity increases oxygen use
  it has been hypothesized that intense physical
  activity produces “oxidative stress.”
Antioxidant Nutrients
 Thus, at this time there is no clear consensus
  on whether athletes need additional
  antioxidant nutrients.
 Athletes at greatest risk for poor antioxidant
  status are those who limit calories, consume a
  low-fat diet, or limit fruit and vegetable
  intake.
Minerals
 Minerals typically low in athletes diets,
  especially for females, include calcium, iron
  and zinc.
 Low intake of these minerals is usually due to
  low calorie intake or limiting animal products
  such as meat, fish, poultry, and dairy
  products.
Calcium
 Calcium is important for building and
  repairing bone and maintaining blood calcium
  levels.
 Inadequate calcium intake increases the risk
  of low bone mineral density and stress
  fractures.
 Female athletes are at greatest risk for low
  bone mineral density if calorie intake is low,
  dairy products are omitted from the diet, and
  amenorrhea is present.
Vitamin D
 Vitamin D is needed for calcium absorption,
  regulation of blood calcium levels, and bone
  health.
 Two main sources of vitamin D are fortified
  foods, such as milk, and production of vitamin
  D by sunlight exposure on the skin.
Vitamin D
 Athletes living in northern regions, who train
  and compete indoors throughout the year
  such as gymnasts and figure skaters are at
  greater risk for poor vitamin D status if they do
  not consume foods fortified with vitamin D.
 These athletes may benefit from vitamin D
  supplementation at the recommended DRI
  level.
Iron
 Iron has an important role in the formation of
  hemoglobin and myoglobin, which carry
  oxygen in the body, and for enzymes involved
  in energy production.
 Iron depletion is a common nutrient problem
  among athletes, especially females.
Iron
 If iron depletion progresses to iron deficiency
  anemia, athletic performance can be
  hindered.
 Iron depletion is usually due to low calorie
  intake, limiting meat, fish and poultry that
  contain iron in the readily available heme
  form, vegetarian diets that contain foods with
  low iron bioavailability, or increased iron
  losses.
Iron
 Female athletes and long-distance runners
  should be periodically screened to evaluate
  their iron status.
 Because iron deficiency anemia can take
  three to six months to reverse early
  nutritional intervention is beneficial.
Iron
 Some athletes may develop a transient
  decrease in hemoglobin when they begin
  training as a result of the increase in blood
  volume which dilutes hemoglobin.
 This situation doesn’t appear to hinder
  athletic performance.
Zinc
 Most dietary zinc comes from animal foods
  and a majority of people consume less than
  DRI amounts recommended.
 Because zinc has important roles in growth,
  building and repairing muscle tissue, and
  energy production, it is prudent to evaluate
  zinc status, especially among female athletes.
Fluids
 It is well known that dehydrate can hinder
  athletic performance.
 In addition, dehydration can increase the risk
  of heat stroke which is potentially life-
  threatening.
 Thus athletes need to keep well-hydrated
  before and during physical activity.
Fluids
 One way the body cools itself by vaporizing
  water.
 Sweat rates vary depending of body size,
  exercise intensity, temperature, humidity and
  acclimation but can exceed 1,800 mL/hour.
 In addition, to water, sweat contains
  substantial amounts of sodium and modest
  amounts of potassium.
Fluids
 Fluid balance is maintained if fluid intake and
  absorption equals fluid loss through sweating,
  and in longer events – urination.
 Fluid balance during physical activity is not
  always possible because maximum sweat
  rates exceed maximum stomach emptying,
  which limits fluid absorption.
Fluids
 However, usually athlete’s fluid intake during
  physical activity is less that the amount that
  can be emptied from the stomach and
  absorbed.
 Athletes often consume less than 500
  mL/hour during competition and the stomach
  emptying rate is more than 1 L/hour.
Fluids
 Stomach emptying is increased when the
  amount of fluid in the stomach is high.
 Stomach emptying is decreased with
  concentrated fluids, carbohydrate
  concentration is greater than or equal to 8%.
Fluids
 Dehydration, hypohydration, and
  hyponatremia are all distortions in fluid and
  electrolyte balance that can be life-
  threatening.
 Dehydration can occur when fluid losses
  exceed fluid intakes.
 Hypohydration can occur when athletes
  dehydrate themselves before beginning an
  event – such as to make a weight category.
Fluids
 Hyponatremia (low blood sodium
  concentrations) can occur due to prolonged,
  heavy sweating without replacing sodium, or
  when excess water is retained in the body.
 Although endurance athletes are more likely
  to suffer from dehydration than from
  hyponatremia (overhydration), hyponatremia
  is not uncommon.
Fluid and Electrolyte Recommendations
 Before Activity: Athletes should be well-
  hydrated before physical activity.
 Recommendations are to drink generous
  amounts of fluid 24 hours before an event,
  and 400 to 600 mL of fluid 2-3 hours before
  an event (1.5-2.5 cups).
 This amount should maximize hydration while
  still allowing enough time for excess fluid to
  be excreted in the urine.
Fluid and Electrolyte Recommendations
 During Activity: During an event athletes
  should try to drink enough fluid to maintain
  fluid balance.
 Even partial dehydration can hinder athletic
  performance.
Fluid and Electrolyte Recommendations
 During Activity: If fluid balance cannot be
  maintained, the maximal amount of fluid that
  can be tolerated should be consumed.
 Athletes can optimize hydration by drinking
  150 to 350 mL of fluid (approximately 6-12 oz)
  every 15 to 20 minutes during the event.
Fluid and Electrolyte Recommendations
 Beverages contain carbohydrate at
  concentrations of 4-8% are recommended for
  events lasting longer than one hour.
 These type of beverages are also acceptable
  for hydration during events lasting less than
  one hour although plain water is also
  appropriate under these conditions.
Fluid and Electrolyte Recommendations
 Little need to replace electrolytes for events,
  less than 3 to 4 hours, especially if pervious
  meal contained sodium.
 However, consuming beverages containing
  modest amounts of sodium is recommended
  during events lasting longer than one hour
  because it may increase acceptability and
  desire to drink, thus increasing the amount of
  fluid consumed.
Fluid and Electrolyte Recommendations
 Consuming beverages containing sodium may
  also help prevent hyponatremia in susceptible
  people.
 Although most athletes who consume more
  fluid than they lose in sweat excrete the
  excess fluid as urine, some people retained
  fluid.
Fluid and Electrolyte Recommendations
 Beverages containing sodium could help
  prevent dilution of blood sodium levels, thus
  decreasing the risk of hyponatremia.
 Limiting fluid intake so that it does not exceed
  losses from sweat can also decrease the risk
  of hyponatremia.
Fluid and Electrolyte Recommendations
 After Activity: Usually athletes do not consume
 enough fluids during activity to balance fluid
 losses.
  As a result most athletes are dehydrated to some
   extent at the end of athletic events.
 Consuming up to 150% of weight lost during an
 activity may be needed to replace losses in
 sweat and urine. Including sodium in fluids
 reduces diuresis that occurs with plain water.
Fluid and Electrolyte Recommendations
 After Activity: Sodium also helps the body
  rehydrate by maintaining blood osmolality
  and thus the desire to drink.
 Because most commercial beverages do not
  contain enough sodium to maximize post
  activity fluid replacement, sodium containing
  beverages should be consumed in
  combination with a sodium containing meal.
Weather Conditions
 Hot and humid weather: The risk of
  dehydration and heat related injury increases
  dramatically in hot and humid weather.
 If outside temperature exceeds body
  temperature, heat cannot be released by
  radiation.
 If humidity is high, the ability to remove heat
  by sweat evaporation decreases.
Weather Conditions
 Hot and humid weather: If both temperature
  and humidity are high, there is a very high risk
  of heat related illness and athletic events
  should be delayed.
 If athletic activities do occur under these
  conditions, precaution should be taken to be
  sure that athletes consume plenty of fluids
  and are monitored for heat related illness.
Weather Conditions
 Cold weather: Although the risk of
  dehydration is greater in hot weather,
  dehydration is not uncommon in cold
  weather.
 Factors can contribute to dehydration in cold
  temperatures include respiratory fluid losses
  in cold dry temperatures, as well as sweat
  losses that may be high if insulated clothing is
  worn during intense athletic events.
Weather Conditions
 Cold weather: Dehydration can also occur
  due to low fluid intake.
 Low fluid intakes can occur if an athlete is
  cold and available fluids are cold, which can
  reduce the athlete’s desire to drink.
 In addition, difficulty removing multiple layers
  of clothing to urinate may cause some
  athletes to voluntarily limit fluid intake.
Weather Conditions
 Altitude: Altitudes higher than 8,200 feet may
  result in fluid losses beyond those due to
  physical activity.
 These losses occur due to mandatory diuresis,
  high respiratory water losses, and decreased
  appetite.
Weather Conditions
 Altitude: Under circumstances of weight
  maintenance, diuresis in about 500 mL/day
  and lasts for about 7 days.
 Respiratory water losses may be as high as
  1,900 mL/day in men and 850 mL/day in
  women.
 Thus, fluid intake should be increased at high
  altitude to as much as 3 to 4 L per day to
  assure optimal kidney function.
Training Diet
 Portion of calories from protein, fat, and
  carbohydrate for athlete’s training diets don’t
  differ substantively from current
  recommendations for the general population.
 Thus athlete’s training diet should follow the
  guidelines recommended by the Dietary
  Guidelines for Americans and the USDA
  MyPyramid.
Training Diet
 The main differences between an athlete’s
  diet and that of the general population are
  that athletes need additional fluid to cover
  sweat losses and calories to for the physical
  activity itself.
 Much of additional calorie needs should be
  supplied by carbohydrate.
Training Diet
 Although in some cases the need for other
  nutrients may also increase (protein, B-
  complex vitamins), the increase in calorie
  needs appear to exceed the increased need
  for other nutrients.
 As a result, as calorie needs increase, athletes
  should first try to consume the recommended
  amount of foods from the MyPyramid food
  groups.
Training Diet
 Another issue for athletes is the timing of
  meals and snacks.
 For the most part foods and fluids consumed
  around athletic activities need to be
  determined on an individual basis and will
  partly depend on an athlete’s gastrointestinal
  characteristics and activity intensity.
Training Diet
 An individual may be able to handle a snack
  of milk and a sandwich one hour before a
  light activity, but would be uncomfortable if
  the same snack was consumed before a very
  hard activity.
 Athletes in heavy training or participating in
  multiple daily workouts may need to eat more
  than 3 meals and 3 snacks per day.
Pre Activity Meal
 Eating before physical activity has been
  shown to improve athletic performance
  versus being in a fasting state.
 A meal or snack before and event or an
  intense workout should prepare the athlete
  for the event, not leave them hungry or with
  undigested food in their stomach.
Pre Activity Meal
 Recommendations for meals and snacks
 before events are that they should provide
 enough fluid to maintain hydration, be low in
 fat and fiber to help gastric emptying and
 lower gastrointestinal distress, be high in
 carbohydrate to maintain blood glucose and
 maximize glycogen stores, be moderate in
 protein, and contain foods the athlete is
 familiar with.
Pre Activity Meal
 The size and timing of pre-competition meals
  are interrelated.
 Because most athletes do not like to compete
  on a full stomach, smaller meals should be
  consumed closer to the time of the event to
  allow for gastric emptying, whereas larger
  meals can be consumed if adequate time is
  available before competition.
Pre Activity Meal
 The amount of carbohydrate consumed in
 studies in which athletic performance is
 enhance range from approximately 200 to
 300 g carbohydrate for meals consumed 3 to
 4 hours before the competition.
Pre Activity Meal
 Recommendations on the amount of
  carbohydrate consumed within one hour
  before an event is controversial.
 Early research suggested this could lead to
  hypoglycemia and premature fatigue;
  however, more recent studies have reported
  either no effect or beneficial effects of pre-
  event carbohydrate intake on performance.
Pre Activity Meal
 The form of pre-competition meals and
  snacks depends on athlete’s individual
  tolerances.
 Some athletes can handle regular meals 2 to 4
  hours before exercise; however, this may
  cause severe gastrointestinal distress for
  others and they may do better with liquid
  meals.
During Activity
 Consuming carbohydrate in amounts typically
  supplied in sports drinks (4-8%) improves
  performance in events lasting one hour or
  less has been controversial.
 Current research now supports the benefit of
  this practice, especially in athletes who are
  physically active in the morning after an
  overnight fast when liver glycogen levels are
  low.
During Activity
 For longer events, consuming 0.7 g
  carbohydrate/kg body weight per hour
  (approximately 30 to 60 g carbohydrate per
  hour) has been shown to extend endurance
  performance.
 Consuming carbohydrate during physical
  activity is even more important for athletes
  who have not carbohydrate-loaded,
  consumed a pre-event meal, or restrict calorie
  intake for weight loss.
During Activity
 Carbohydrate intake should begin shortly
  after the onset of physical activity.
 Research has shown that consuming a larger
  amount of carbohydrate after 2 hours of
  physical activity is not as effective as
  consuming the same amount of carbohydrate
  in 15 to 20 minute intervals during the first 2
  hours of physical activity.
During Activity
 The type of carbohydrate should provide
  primarily glucose; fructose alone is not as
  effective and may lead to diarrhea, although
  mixtures of glucose and fructose seem to be
  effective.
 The form of carbohydrate, solid food or liquid
  doesn’t seem to matter and is more a matter
  of personal preference.
Post Activity Meal
 Timing and composition of the post activity
 meal or snack depends on the length and
 intensity of the physical activity (whether
 glycogen stores are depleted) and when the
 next intense physical activity will occur.
Post Activity Meal
 After a marathon most athletes will have
  depleted glycogen stores; whereas after a 60
  minute training session, glycogen stores may
  not be depleted.
 However, most athletes after completing a
  marathon won’t be competing in another
  marathon the next day.
Post Activity Meal
 As a result, the timing and composition of
  post activity meals for these athletes is less
  important because they have time to restore
  glycogen store.
 However, post event recovery is very
  important for athletes who participate in
  multiple events in one day or have a short
  recovery time between events.
Post Activity Meal
 Timing of post activity carbohydrate affects
  glycogen stores. Carbohydrate consumed
  immediately after physical activity (1.5 g
  carbohydrate/kg at 2 hour intervals) results in
  higher glycogen stores than if carbohydrate
  intake is delaying for 2 hours.
 Timing of post activity carbohydrate is not as
  critical for athletes who have one or more
  days between intense events.
Post Activity Meal
 If adequate carbohydrate is consumed over a
  24 hour period, the timing of carbohydrate
  intake does not appear to affect the amount
  of glycogen stored.
 However, consuming a meal or snack close to
  the end of physical activity may be important
  for athletes to meet their carbohydrate and
  calorie needs.
Post Activity Meal
 The type of carbohydrate consumed can also
  affect post exercise glycogen stores.
 In regards to simple sugars, glucose and
  sucrose are equally affective if consumed at a
  rate of 1.5 g/kg body weight for 2 hours;
  however, fructose alone is less effective.
Post Activity Meal
 In regards to whole foods, consuming foods
  with a high glycemic index produces higher
  muscle glycogen stores 24 hours after activity
  as compared to the same amount of
  carbohydrate from foods with a lower
  glycemic index.
 However, the usefulness of these findings
  must be considered in terms of the overall
  diet.
Post Activity Meal
 When similar amounts of carbohydrates or
  carbohydrates, protein and fat are provided
  following activity, glycogen synthesis is similar.
 Although including protein doesn’t appear to
  enhance glycogen stores, including protein in a
  post activity meal may provide needed amino
  acids for muscle protein repair.
Ergogenic Aids
 Marketing of ergogenic aids (items claiming to
  increase athletic performance) preys on
  athletes.
 The 1994 Dietary Supplement Health and
  Education Act allows supplement
  manufactures to make claims regarding the
  effect of products on the structure/function
  of the body.
Ergogenic Aids
 Ergogenic aids must be carefully evaluated in
 terns of the validity of the claim relative to
 the science of nutrition, athletic performance
 and health consequences.
Ergogenic Aids
 In general, most ergogenic aids fall into one of
 the following categories:
   those that perform as claimed
   those that may perform as claimed but for which
    there is insufficient evidence of efficacy at this
    time
   those that do not perform as claimed
   those which are dangerous, banned, or illegal, and
    should not be used.
Ergogenic Aids
 Use of ergogenic aids is controversial.
 Some health care professionals discourage
 use of all ergogenic aids whereas others
 suggest they be used with caution but only
 after athletes have carefully evaluated of the
 product for safety, efficacy, potency and
 legality and discussed the use of the product
 with a qualified nutrition or health
 professional.

								
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