Transcript Exercise, Fiber, alcohol

Protein for Athletes
 American College of Sports Medicine (ACSM) /
American Dietetic Association (ADA)
–Endurance athletes, 1.2 to 1.4 g/kg per day
• Accounts for greater use of protein as fuel for energy
–Strength athletes, 1.2 to 1.7 g/kg per day
• To support muscle growth, particularly during early training phase when gains
are greatest and protein utilization is less efficient
 Clinical studies suggest there is no apparent
benefit at intakes above 2.0 g/kg per day
How much protein for athletes?
• Many athletes may already meet or exceed protein
recommendations
– Definition of “high protein” can be the absolute amount of
protein, % of total energy (calories), or protein ingested
per kg of body weight
• Strength athletes in particular may believe that much
higher protein intakes are needed for muscle building
– Intakes at 4- to 6-g/kg range are not uncommon
– Unlikely to provide benefit beyond 2.0 g/kg
– It is possible that this much protein intake could adversely
affect the nutrient quality of the overall diet
Risks of High Protein
 Hydration status
– Nitrogen that is obtained from consuming protein must be excreted in the
urine as urea
– Increased urinary output due to high protein load may increase chances of
dehydration
 Diets very high in protein may lack appropriate amounts
of carbohydrate, fiber, and some vitamins/minerals
– Could impair exercise performance
– Could increase long-term risk of diseases such as colon cancer
• Possibly due to lack of fiber or increased intake of red meat
 Excessively fatty protein sources could increase risk
of cardiovascular disease
– Choose mostly lean protein sources
• For example, salmon is more desirable than a ribeye steak
Branched Chain Amino Acids
• Make up 40% of the daily requirements of essential amino
acids
Branched Chain Amino Acids
 BCAAs are
 Unlike other amino acids, most BCAA
metabolism occurs in skeletal muscle
– Liver lacks first 2 enzymes in the pathway that break
down BCAAs
 Supplemental free form, bypass the liver and gut
and go directly into the blood stream.
 BCAAs inhibit brains ability to uptake tryptophan
Leucine
– The bodies need for leucine is 25 times greater than
the available free amino acid pool.
– Stimulates protein synthesis by activating insulin
– Insulin increases a.a. uptake
– Incorporation of BCAAs in muscle is IGF-1 dependent
– IGF-1 stimulates muscle synthesis
– Chronic low levels of BCAAs will show up in urine
– β-hydroxy-β-methylbutyrate (HMB) is derived from the
breakdown of leucin
– Some evidence in humans that doses of 3 g/day may
be effective at preventing muscle breakdown
• Additive benefits with creatine
– Some studies suggest that HMB may provide greater
benefit to untrained people who start weight training
compared with previously conditioned athletes
Should athletes Supplement?
 If protein requirements are met, the individual AA
requirements should be met as well
 Estimated that 3-18% of workout energy is provided by
BCAAs
 Leucine increases release of fats for energy
 Claims mainly center on decreasing muscle soreness and
improving either performance or recovery from exercise
 Doses can range from 2 to 7 g/day to more than 20 g/day
taken before during and after
 There are potential risks associated with AA supplements
– Large doses of single AAs can prevent the absorption of other AAs, which may
lead to diarrhea
– Can indirectly cause deficiency of other AAs as a result
Phosphocreatine
• aka creatine phosphate (PCr)
• Rapidly mobilizable reserve
of high energy phosphate for
skeletal muscle (and brain)
• Formed from parts of Arg,
Gly & Met
• Can donate phosphate to
ADP anaerobically in the first
2-7 seconds following an
intense muscular effort
• Forward and reverse reaction
catalyzed by CK, which is a
marker of muscle damage
Alcohol
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Ethanol
Not a nutrient
7 kcal/g
50% alcohol = 100 proof
Alcohol Absorption
• Small amounts absorbed
in mouth and esophagus
• 20% absorbed directly
across stomach wall
• Food delays diffusion
• Most absorbed by simple
diffusion in the upper
small intestine
• Distributed wherever
water is found
Alcohol metabolism
1) Alcohol Dehydrogenase System
- women have less
- varies among ethnic groups
- NADH production turns of TCA cycle
- Excess acetyl CoA converted to FATTY ACIDS
- Fatty liver develops
2) Microsomal Ethanol-oxidizing
System (MEOS)
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When ADH cannot keep up with demand
Occurs in liver, in cytosol of cells
Also used to metabolize drugs and foreign substances
Reduces bodies ability to detoxify drugs  overdose
Increases alcohol metabolism, thus tolerance  leads to weight
loss
3) Catalase Metabolism of Alcohol
• Found in liver
• Minor pathway for alcohol metabolism
H2O2
Ethanol
Catalase
H2O
Acetaldehyde
Alcohol Metabolism
• Depends on:
- Sex
- race
- size
- food
- physical condition
- alcohol content
• Amount of alcohol
dehydrogenase
• Alcohol cannot be
stored and has priority
in metabolism
Negative effects on vitamins and
minerals
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Thiamin
Niacin
B6
B12
Folate
Vitamin C
Vitamin A
Vitamin D
Vitamin K
Vitamin E
• Magnesium
• Zinc
• Iron
Alcoholics and malnutrition
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Poor diet
Alcohol has energy but no nutrients
Lack of interest in food: GI problems
Alcohol interferes with absorption of amino
acids
• Alcohol races blood level of fats
Liver Damage
• Build up of
acetaldehyde
• Production of free
radicals
• Alcohol inhibits
body’s natural
antioxidant systems
• Advanced stages of
liver damage are
not reversible
Fetal Alcohol Syndrome
• Alcohol reaches fetus
• Deprives brain of
oxygen and nutrients
• About 4 drinks a day or
binge drinking while
pregnant
• Prenatal and postnatal
growth retardation
• Brain and CNS
impairment
• Abnormalities of face
and skull
• increased rate of birth
defects
Health Benefits of Alcohol
• Moderate drinking
associated with reduced
mortality
• ≤ 2 drinks for men, ≤ 1
drink for femal
• Reduced cardiovascular
disease
-reduces blood clotting
-increase HDL
-reduced inflammation
• Polyphenols
• Relaxation and
socialization
Fiber
• Plant cell wall contains > 95% of dietary fibers
- cellulose, hemicellulose, lignin, pectins
-Lignin  structural support
-Pectin  intercellular cement
-Cereal bran  hemicellulose and lignin
-Fruit & Vegetables  cellulose and pectin
• Starch  energy storage is found within the
cells walls
Fiber = ability to resist digestion
in the small intestine
Fiber
Dietary + Functional = Total Fiber
• Dietary – Found natuRally in foods
• Functional – forms added to foods
• Insoluble – Not fermented by bacteria
in the colon
• Soluble – Fermentable
Fiber
Soluble
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Pectin
Gums
Mucilages
Some
hemicellulose
Insoluble
• Lignin
• Cellulose
• Some
hemicellulose
Polysaccharides
1. Cellulose
• Polysaccharide of glucose
• Most abundant substance
in plant kingdom
• Β- 1,4 glycosidic linkages
• Water insoluble
• Does not provide energy
• Bran, legumes, nuts peas,
root vegetables, cabbage
• Cotton is pure cellulose
Insoluble fibers – Exterior/hulls &
Structural
2. Hemi-cellulose
• Mixture of
pentoses &
hexoses
• Linked to lignin
in cell wall
• Amorphous
• Partially soluble
in mild alkali
3. Lignin
• Highly branched
• Not digested by
colonic bacteria
• Non-CHO
• Structural support
• Roots vegetables,
carrots, wheat,
fruits with seeds
Soluble Fibers – inside & around plant
4. Pectin
• gel forming
• Amorphous
• Intracellular cement –
spaces b/w cell wall
• Almost completely
metabolized by colonic
bacteria
• Apples, strawberries &
citrus
• Added jellies & jams
5. Gums/Mucilages
• Secreted at the site of
plant injury: tree
exudates
• Highly branched
• Highly fermented by
colon bacteria
• Gum arabic is a food
additive for gelling
• Caramels, gumdrops,
toffee, bakery goods,
salad dressings, oatmeal
Physiological & Metabolic Effects
Effects of Fiber
1. Solubility in water
• delay gastric emptying
• Increase transit time
• Decrease nutrient absorption
2. Water-holding capacity
• Delay gastric emptying
• Reduced mixing of GI contents w/ digestive
enzymes
• Delayed nutrient absorption
• Shortened transit time
Physiological & Metabolic Effects
Effects of Fiber
3. Ability to bind (adsorption) molecules
• Decreased absorption of lipids
• Increased bile excretion
• Lower serum cholesterol
• Altered mineral balance
4. Fermentability by intestinal bacteria
• Microflora produces SCFAs
- energy
- cell proliferation
-increases water absorption in the colon
CO2, H2, CH4
Soluble Fiber
SCFA
Fermented
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Fuel for cells
≈1.5-2.5 kcal/g
Acetic acid
Butyric acid
Proprionic acid
Blood stream
Pre & Pro – biotic Diets
Medical Nutritional Therapy
• Pro-biotic
- ingestion of certain foods with live cultures containing
certain strains of bacteria to increase the counts of
specific microflora of the GI tract
-Yogurt
-survive digestion and then colonize lower GI tract
• Prebiotic
-food ingredients that are not digested or absorbed but
can stimulate the growth/activity of selected types of
bacteria in the colon
- Oligofructose or inulin (non-digestible oligosaccharides)
Health benefits of Dietary Fiber
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Promotes softer, larger stool and regularity
Slows glucose absorption
Increases satiety
Reduces blood cholesterol
Reduces heath disease
Reduces hemorrhoids and diverticula
Nutrition and GI disorders
• Constipation
- reduced by fiber, fluid intake, exercise
• Diarrhea
• Diverticulosis
- Pouches along colon
- high fiber diet reduces formation
Recommended Dietary Fiber Intake
• Adequate intake (14g/1000 kcal):
- 25 g/day for women
- 38 g/day for men
- US intake: 13-17 g/day
• Too much fiber (>60 g/day)
- require extra intake of fluid
- binds to some minerals (Fe & Zn)
- fill the stomach of young child quickly