Sports nutrition, get the facts!

I received this in my Medical Nutrition Therapy II class. I figured some of you might like to read it because it will clear the air about some of the beliefs about nutrition and exercise. It's long so you might want to print it. Be safe and good luck!

SPORTS NUTRITION
Concept # 1:
You want to overall eat healthy to optimize baseline nutritional status.
Example:
• For energy metabolism in general: need B vitamins
• For strong bones: need Ca, vitamin D, Mg (fluoride)
• To make red blood cells (which carry oxygen in the blood): need iron, B-12, Zn, Copper, etc.
• For better immunity need many nutrients (Zn, Fe, Se, Mg & vitamin A, B, C, D)

Concept # 2:
Maintain optimum hydration during practice & competition:
The # 1 deficiency causing ↓performance is lack of water. First symptom = fatigue.
• Even a 1-2 % loss in water can ↓ performance
o I.e. for a 130 lbs runner, losing 1 ½ lb during a competition (i.e. 1 ½ lb sweat) would significantly impact performance
• Severe dehydration occurs at 5% or more of bodyweight lost to sweat.
o (example for 130 lbs person = 6.5 lbs)
• Body can absorb about 1 quart fluid per hour, but you can sweat up to 2 qts per hour
• Some people sweat more than others
• By weighing yourself before and after workout you will get an idea of how much fluids you will need (depends on temp. & intensity & duration)
• 1 lb loss from sweat = 2 cups fluid.

WHAT KIND OF FLUID?
• Want the fluid to be absorbed rapidly
• Temperature of fluid matters:
o Cool temperatures are faster absorbed than warm fluids. (however, outdoors in winter it may be better to provide warm fluids to help maintain body temperature)
• Plain water is best for hydration if exercise less than 45 minutes
o Water is faster absorbed than sports-drinks.
o Carbohydrates (incl. sugar) and electrolytes (sodium, salt, potassium, etc) slows stomach emptying, i.e. slows the water absorption

WHEN IS IT BENEFICIAL TO USE A SPORTS-DRINK (containing carbohydrate and electrolytes)?
• If exercise for more than 45 minutes: may be beneficial with some carbohydrate in the drink.
o The carbohydrate will help maintain your blood sugar level and spare glycogen stores  you can exercise longer
o Optimum sugar concentration 2.3 – 8 %.
o Higher than 8 % slows the stomach emptying
o Most sports drinks are about 6 %
 13 GRAMS CARB/ 1 CUP = 5 ½ % ; i.e. max 14 g / 8 oz
o Some athletes feel 6% is a bit high, often common to dilute sports-drink with half water. (depends on the person and their preferences)

DO YOU NEED ELECTROLYTES?
o It depends.
o Sports-drinks contain electrolytes (sodium, potassium, chloride)
o Electrolytes are lost in sweat,
o Providing small amounts of electrolytes(like in sports-drinks) may be useful when
 exercising more than 45 minutes,
 especially if more than 60-90 minutes
o Electrolyte loss are more of a concern if there is a lot of sweating or exercise for 3 hrs or more.
 can lose up to 2 grams of salt per 1 qt sweat
o Salt tablets: avoid
o Avoid drinking much more plain water than you need during duration exercise  may dilute your blood sodium level

GUIDELINES TO ENSURE PROPER HYDRATION:
• 2 hrs before exercise : Drink 2-3 cups water
• 15-30 minutes before exercise: Drink 1 - 2 cups water
• During exercise: Every 15-20 minutes: Drink ½ - 1 cup
o About 4 cups / hr can be absorbed
o Water absorption is faster when drinking every 15-20 minutes
o Absorption is more rapid right after water hits the stomach, then it slows a bit
o Smaller amounts of fluids are absorbed quicker and also better tolerated than large amounts
• Remember: during exercise: thirst becomes detectable only after fluid stores are depleted.  do not rely on thirst to start drinking. You have lost 2 cups of fluid before feeling thirsty
• After exercise: drink 2-3 cups for every 1 lb lost.

Concept # 3:
Optimize your glycogen stores.
o The more you can ↑your glycogen stores  the better your endurance.
o The more you can spare your glycogen stores  the better your endurance
o Glycogen stores run out after about 2 hrs of vigorous exercise, but training & diet can impact this.
o (Less than 2000kcal is stored as glycogen)
o Training 
o ↑ ability to store glycogen;
o ↑ aerobic pathways: ↑# mitochondria,↑ enzymes involved; ↑O2 vol; ↑heart capacity;
o ↑ability to mobilize fat for energy  spares glycogen
o ↑Ability to clear lactate
HOW is DIET INVOLVED?
To spare your glycogen  consume carbohydrates during exercise if more than 45 minutes
To ↑ your overall glycogen stores:
• Training and adequate rest for restitution
o rebuilds your glycogen stores & ↑ability to store glycogen
• High carbohydrate diet days before event (maximizes glycogen stores)
• Consume carbohydrates after the exercise (within 2 hrs of exercise, ideally within 30 minutes, because our body’s production of glycogen is especially productive during this time & supplying carbohydrate will optimize this. Recommendation is for 1-1.5 grams carbohydrate per kg bodyweight within 30min / 2 hrs).
o I.e. eat about 60 grams of carbs or more within 2 hours of exercise
 16 oz chocolate milk (low-fat)
 16 oz sports-drink and one PB & jelly sandwich
 8 oz fruit juice and 1 banana with PB + handful pretzels
o For muscle refuel / rebuilding: also helpful to take in some protein within the two hours following exercise, such as complete protein that will include branched chain amino acids.


FUEL DURING EXERCISE SUMMARY:
Anaerobic fuel: fuel that can be used without oxygen:
• First 3-15 seconds of max effort:
o Use ATP & CP stored or made in muscle
• First 1-3 minutes:
o Glucose used to produce energy,
o much of the glucose will be changed into lactic acid because not enough oxygen is available.
o Too much lactic acid  ↓ muscle performance

Aerobic fuel: If longer duration type of exercise of lower intensity: aerobic pathways used to create energy: (i.e. energy is created using chemical that need oxygen)

First 10 minutes:
o Muscles rely mostly on glycogen stored within the muscle
o glycogen is the storage form of glucose.
After 10 minutes:  start taking up more glucose from the blood .
After 20 minutes  muscles start to rely more on fat than on glucose for fuel.

Key concept:
• Muscles still need glucose to utilize fat for energy.
• Muscles can not burn fat for fuel without the presence of glucose
• Once glycogen stores are empty  muscles run out of energy
o because it can not burn fat for fuel  exhaustion

Concept # 4:
Pregame meal: Eat smart prior to exercise / competition to optimize performance.
o Easily digested foods;
o about 3 – 4 hrs before exercise.
o Should be high in complex carbohydrates, and low in fiber and fat ( i.e. avoid high-fiber cereals, large tossed salads). Moderate protein (FYI see pg 390 for some ideas)
o Avoid high sugar / fat intake close to event
o Example:
o 300 kcal: 1 large apple, 4 saltine crackers, 1 Tb PB
o 500 kcal: 1 PB jelly sandwich, 1½ c skim milk
o If eating 1 hr before: size of a tennis ball



Concept # 5:
Athletes have higher needs for protein
o DRI = 0.8 grams protein per kg body weight (i.e. 0.36 grams protein / lb)
o For athletes: 1.2 – 1.7 grams per kg bodyweight (1.7 g / kg = 0.73 grams / lb), both endurance and strength athletes
o Strength / speed power being at higher end of this range.
o Intakes higher than 2 grams protein per kg (0.9 grams / lb) does not seem to ↑ muscle growth
o High protein diets will create more Nitrogen waste and stress kidneys. Also associated with increased Calcium excretion and osteoporosis.
o Endurance athletes: 1.2–1.6 g/kg
o Strength athletes: 12-20 hrs/week: 1.6–1.7 g/kg
o If elite endurance athlete >20hr/week: 1.7 – 2.0 g protein / kg (2.2 g / kg = 1 g / lb)
o I.e. 1 gram protein / lb is OK,
o Do not go higher than 1.5 g / lb (translates to 3 g / kg and about 35% of kcal from protein)

Concept # 6:
Athletes need higher amounts of many vitamins and minerals
o However, these needs are met by diet because of higher calorie intake
o Iron: need is ↑ to make myoglobin (carries oxygen inside the muscles) and hemoglobin (carries oxygen in the blood). Some iron is lost in sweat.
o Especially teenage girl athletes are at risk for iron deficiency due to ↑ iron needs.
o Eating an overall well balanced diet should ensure adequate intake of all nutrients.
o If a supplement is desired: take a one-a –day type multivitamin mineral supplement, avoid > 100 % RDA in the supplement, unless you have been diagnosed with a deficiency.

Concept # 7:
Avoid illegal substances
Avoid unsafe substances

For Caffeine :
o max intake of 800 mg (no more than 5-6 cups of strong brewed coffee within 1 hr of exercise).
o Some endurance athlete studies: 2 cups coffee 1 hr before event may help performance, other studies : no effect.
o Remember that caffeine is a diuretic.