ex nutr c9-vit mineral1 vitamins water-soluble, fat-soluble reusable coenzymes in many metabolic...
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Ex Nutr c9-Vit Mineral 1
Vitamins
Water-soluble, fat-soluble Reusable coenzymes in many metabolic
reactions Generally, exercise ↑vitamin requirement
↓absorption from GI tract ↑excretion from sweat ↑turnover (degradation) ↑requirement (retention) because biochemical
adaptation to training (↑ mitochondria density, muscle hypertrophy)
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Ex Nutr c9-Vit Mineral 6The roles of water-soluble vitamins in energy metabolism
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Assessing vitamin status Difficult to determine accurately Diagnosis of vitamin deficiency needs to
COMBINE following information Blood analysis: plasma concentration and/or
activity of functional enzyme(s) Dietary intake: tedious and inaccurate Clinical symptoms: unspecific
Most studies showed that athletes do NOT have lower vitamin status Except with extremely low dietary energy intake
or very imbalanced diet
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Recommended intakes of vitamins
Estimated average requirement (EAR): normally distributed Amount of nutrient sufficient to meet the needs of
average individual in certain age and gender Recommended daily allowance (RDA): cover
97.5% of all healthy individuals Athletes have higher requirement for vitamins, but
also consume more foods/energy If energy intake match energy requirement, athletes
consume reasonably balanced diet, they can get all vitamins they need from food
No need for supplements
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Risk group for low vitamin intake Low-energy or unbalanced diet Very high energy intake (>4800 kcal/day)
Consume large ‘in between meals’ and high-energy sport drinks
Low in vitamins/minerals Vegetarians: B12 Vitamin loss in sweat negligible NO increased vitamin excretion in urine and feces
in athletes Vitamin turnover usually unaffected by exercise
Acute exercise may change plasma concentrations Mainly due to redistribution of labile pools
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Ex Nutr c9-Vit Mineral 20Effect of exercise on mineral requirements
Temporary depression of free (unbound) plasma concentrations of some minerals after prolonged exercise Fe, Zn, Cu Redistribution of different tissue compartments Release of proteins from liver/neutrophils that
chelate ( 螯合 ) minerals, part of acute-phase response to inflammation
Ex Nutr c9-Vit Mineral 21Dietary surveys of mineral intakes in elite athletes
Difficult Differences in bioavailability in various foods Not all foods have analyzed for their mineral contents Mineral contents may depend on their content in soil
Plasma concentrations usually do NOT represent body pool
Low iron stores Middle- and long-distance runners, adolescent athletes,
female athletes Low Ca intake: female and adolescent athletes Low Zn, Mg intake: female athletes
Ex Nutr c9-Vit Mineral 22Effect of exercise on iron requirements
Iron loss in sweat Previous studies: can reach 0.3 mg/L Extra ~12 mg
iron from food (10% absorbed) Recent studies: 6-11% iron absorbed each day lost in
sweat per hour of exercise Higher sweat rate and higher iron loss in men
Increased iron requirement ↑Myoglobin, red cell mass GI bleeding: irritation of stomach lining or hemorrhage
of colon caused by ischemia Elite male distance runners loss 6 ml blood/day from GI
during training and racing
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Iron Iron depletion (serum ferritin 儲鐵蛋白 < 12 ug/L)
common in female athletes Iron depletion without anemia ↑lactate during max exercise,
↑subjective feeling of exercise overload in elite athletes ↑performance by iron supplementation in Iron depletion without
anemia Anemia reduce athletic performance
Insufficient oxygen delivery, breathlessness, mental dysfunction, impaired temperature control, ↓immunity
Periodic screening of serum ferritin in athletes Higher absorption rate for heme 血基質 -iron
Vitamin C absorption ↑ rate for nonheme-iron Anemia also result from deficiency in B6, B12, folate
For nucleic acid and red blood cell production
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Phytate: 植酸 ; Tannins: 單寧酸 ; phosphate 磷酸根
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Calcium and bone health Ca intake closely related to total-energy intake Female athlete triad: amenorrhea, oligomenorrhea
associated with high risk of early osteoporosis Chronically low estrogen Low body fat, low energy intake, high physical activity Eating disorder Gymnastics, swimming, long-distance running, dancers ↑Ca consumption to 120% RDA help maintain bone
density and development in amenorrhea Use low-fat dairy products
Sweat concentration 0.1-1.0 mM Lost 4 L sweat lost 2 mmol (80 mg) Ca 200 mg
Ca intake (40% absorption)
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Micronutrients as antioxidants Exercise ↑free radical (unpaired electron) production
Demonstrated in vivo studies Mainly through electron leakage from electron transport chain, 3-5%
oxygen consumed at rest Damage to lipid, protein, DNA
Antioxidant defense system eliminate/quench free radicals Prevent/reduce oxidative stress
Vitamin C, E, beta-carotene Cu, Zn, Selenium: as cofactors for antioxidant enzymes Glutathione: glycine, cysteine, glutamine Polyphenols 多酚類 : tea, red wine, fruits, vegetables
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Antioxidant and muscle damage Unaccustomed exercise or eccentric actions damage
myofibers Muscle pain, soreness, stiffness, ↓range of motion,
↓glycogen resynthesis Damaged muscle tissue cause initial activation of
immune system WBC attracted to damaged muscle breakdown of
damaged fibers, initiate repair process Occur within fist hour after eccentric exercise, followed
by infiltration of monocyte and macrophage, reaching max at 24-72 after exercise
Repaired process involve production of reactive oxygen species (ROS) by invading leukocytes
ROS cause muscle soreness, ↑creatine kinase, oxidative damage to DNA and proteins
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Antioxidant mechanisms
Prevent ROS formation Intercept ROS attack by scavenging Binding transition metal ion, such as Cu, Fe,
to prevent initiation of free radical reactions React with chain-propagating radicals Provide favorable environment for effective
functioning of other antioxidants Free radical really a bad thing? Or a signal
for exercise adaptation?
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Vitamin C
Vitamin Ebeta-carotene
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Polyphenols
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Regeneration of GSH
Glutathione reductase
Glutathione
(GSH)
Ex Nutr c9-Vit Mineral 36Possible risks of high-doseantioxidant supplementation
Antioxidants inhibit apoptosis (programmed cell death) Important defense mechanism, inhibit tumor
development by eliminating new mutated cells In situations with high DNA damage
Exercise, heavy smoking Administration of large amounts of antioxidants may
prevent effective removal of damaged cells May ↑cancer risk
Insufficient data to recommend antioxidant supplements for athletes Usually NO effect on exercise performance
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Athletes need more antioxidants? Higher antioxidant required in athletes to reduce
oxidative damage induced by exercise Dietary sources of antioxidants are preferable to
single/combined supplements Based on epidemiological studies on adverse health
outcomes Pro-oxidant effects with prolonged use of high-dose
antioxidant supplements May need 3X of RDI Supplements may be necessary if RDI can not be met
Antioxidant supplements on human performance usually negative
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