Transcript Sports Nutrition

Nutrition for
Athletes
Determinants of the Athlete’s
Energy Requirements
• During intense exercise
– Carbohydrate stored in muscles and liver (glycogen)
is predominant fuel source
• During prolonged exercise
– Fat stores are predominant fuel source
• Fitness level of the athlete
– Well trained endurance athletes burn fat more
efficiently, sparing limited glycogen stores
Easy Formula for Estimating the
Body’s Calorie Requirements
• Sedentary person
– Weight (kg) x 25
• Moderately active person
– Weight (kg) x 30
• Active person (endurance athlete)
– Weight (kg) x 40
• Underweight person
– Weight (kg) x 45
• kg = lbs / 2.2
Recommendations for Athletes
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Carbohydrate intake
Pre-exercise meal
Carbohydrate loading
Protein intake
Fat intake
Carbohydrates
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Non-essential nutrient (human body can make sugar)
Simple (sugars) and Complex (starches)
Major fuel source for exercising muscle
Athletes should ingest 6 to10 g/kg/day
– 60 to 70% of total calories should come from carbohydrates
– Complex carbohydrates (starches) are preferable
• During exercise
– Athletes should consume 25 to 30 g of carbohydrate for every 30
minutes of exercise (100-120kcal)
– Athletes should drink 6 to 8 ounces of water or sports drink for
every 10 to 15 minutes of exercise
Carbohydrates
• After exercise
– Athletes should consume 1.0 to 1.5 g/kg
immediately post exercise and again one hour
later
• To replace muscle glycogen stores
• To prevent gradual depletion of muscle glycogen stores
over time caused by repetitive daily bouts of heavy
exercise
• To decrease muscle breakdown
Why Complex Carbohydrates?
• Compared to ingesting simple carbohydrates,
ingesting complex carbohydrates:
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Increases muscle glycogen stores better
Improves performance and delays fatigue
Promotes faster stomach emptying
Causes less stomach upset and indigestion
Leads to lower blood sugar and insulin levels
Provides other beneficial nutrients
• Fiber, vitamins and minerals
Pre-exercise Meal
• Importance
– Less hunger before and during exercise
– Maintains optimum glycogen stores
• Recommendations
– Emphasize complex carbohydrates (starches)
• 1 to 4 g/kg about 1 to 4 hours prior to event
• Consume less closer to event
– Avoid high fat and high protein foods
• Slower gastric emptying can cause stomach upset
– Avoid high fiber or gas forming foods
• Can lead to cramping abdominal pain
Carbohydrate Loading
• Increases the body’s pre-exercise glycogen
stores by 50 to 100%
• Benefits endurance athletes who compete
for longer than 90 minutes
– Can increase endurance up to 20%
– Can increase performance by 2 to 3%
Carbohydrate Loading:
One Example of How
Days prior to event
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5
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Exercise duration
90 minutes
40 minutes
40 minutes
20 minutes
20 minutes
rest
Carbohydrate intake
5 g/kg/day
5 g/kg/day
5 g/kg/day
10 g/kg/day
10 g/kg/day
10 g/kg/day
Protein
• Athletes require more protein than non-athletes
– 12 to 18% of total calories should come from protein
– Protein intake should be tailored to type of training
• 1.2 to 1.4 g/kg/day recommended for endurance athletes
• 1.7 to 1.8 g/kg/day recommended for strength athletes
• Average American diet provides 1.4 g/kg/day
• Adequate calorie intake is just as important as adequate
protein intake for building muscles
• Too much protein intake can be bad
– Excess protein calories are stored as fat
– Excess protein intake can lead to dehydration and may
contribute to kidney problems
Fat
• Major source of energy
• 25 to 30% of total calories should come from fat
– Less than 10% of total calories should come from saturated
fats
• Cholesterol intake should be less than 300 mg/day
• Average American diet provides 37% of total calories
from fat
Nutritional Supplements
• 1994 Dietary Supplement Health and Education Act
– Definition of a supplement
• Any product that contains vitamins, minerals, amino
acids, herbs, botanicals or a concentrate, metabolite,
constituent, extract or combination of any of these
ingredients
– Removed dietary supplements from FDA regulation on the
front end
– FDA must prove a supplement is dangerous before its sale
can be prohibited
Nutritional Supplements
• 1994 Dietary Supplement Health and Education
Act (USA)
– Manufacturers do not have to provide scientific proof
of claims
– Manufacturers cannot state product is meant to
diagnose, treat, prevent or cure a disease but can
make indirect suggestions
– Created a multi-billion dollar industry that continues
to grow rapidly
• Canada has implemented laws over the past 6
years much like the FDA but much stricter at the
advertising level
Vitamins and Minerals
• Essential nutrients
– Human body needs these to produce energy
• No evidence in North American studies that taking vitamin
and mineral supplements improves athletic performance
– Being deficient in vitamins or minerals is rare in the U.S.
compared to the rest of the world
• A few studies outside North America showed an effect
– Did population studied have some baseline deficiency treated
with these supplements?
• Vegetarian athletes are at risk for being deficient in
vitamins B12, D, riboflavin, iron, zinc and calcium
– Athletes who are strict vegetarians should take a multivitamin to
prevent deficiencies and a calcium supplement (1000 mg/day) to
help prevent bone loss
Vitamins and Minerals
• Specific vitamins and minerals studied
– Vitamin A and Vitamin D
• No evidence of increased performance
• May have toxic effects at high doses
– Vitamin E
• No evidence of increased performance
• Toxic effects are rare
– Vitamin C
• Anti-oxidant effect may help decrease exercise related muscle
soreness
• No effect on strength
• Possible toxic effects at high doses
Vitamins and Minerals
• Specific vitamins and minerals studied
– Vitamin B6
• No evidence of increased performance
• Toxic over 200 mg/day (nervous system side effects)
– Other anti-oxidants (Betacarotene, Bioflavinoids,
Copper, Cysteine and Glutathione)
• May help to protect against exercise induced muscle damage
• Study results are conflicting
• Should not exceed 100% of the RDA of anti-oxidants
• Buyer beware!
– Some supplements have been found to contain up to
3000% of U.S. RDA for vitamins and minerals
Creatine
• Chemical name: Creatine-Monohydrate
• Naturally available in meat and fish
• NCAA study found creatine supplements used by 12% of
college athletes
• A subsequent survey of high school athletes showed
similar usage rates
• Does it work to
– Increase muscle mass?
– Increase strength?
– Increase performance?
• Is it safe?
Creatine
• I found 9 studies showing (+) effects in healthy subjects published
between July 1997 and November 2001
– Increased high intensity, intermittent exercise performance in squash
players
– Increased cell hydration status and performance variables in Division I
college football players more than training alone
– Augments repeated sprint cycle performance in hot environment
without altering thermoregulatory responses
– Increases indices of high intensity exercise performance for both
males and females
– Increased capacity of human muscle to perform work during
alternating intensity contraction
Creatine
• Recent studies with (+) effects (continued)
– Ergogenic effect in elite ice hockey players
– Loading improves intermittent sprint capacity at end of endurance
exercise to fatigue
– Adding creatine to glucose, taurine and electrolyte supplement
promoted greater gains in fat and bone free mass, isotonic lifting
volume and sprint performance during intense resistance and agility
training
– Helped to prolong time maximal rate of power output could be
maintained
Buyer Beware!
• IOC funded study by Shanzer (Germany) from 10/00 to 11/01
– Analyzed 634 products labeled as non-hormonal nutritional supplements
from 13 countries and 215 different suppliers
• 94 products (14.8%) were found to be “positive supplements” (contained
anabolic steroid precursors not declared on the label)
• Anabolic androgenic steroid concentrations ranged from 0.01 to 190 micrograms
per gram of supplement
• 23 products contained steroid precursors of nandrolone and testosterone
• 64 products contained steroid precursors of testosterone only
• 7 products contained steroid precursors of nandrolone only
• Percentage of positive supplements per country
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25.8% of products bought in Netherlands
22.7% of products bought in Austria
18.8% of products bought in UK
18.8% of products bought in US (45 positive out of 240 tested)