vitamins & minerals chapter 9. vitamins organic compounds that are essential for the optimal...
TRANSCRIPT
Vitamins & Minerals
Chapter 9
Vitamins
• Organic compounds that are essential for the optimal functioning of many different physiological processes in the body
• Major Functions– Coenzymes– Hormones– Neurotransmitters– Antioxidants
Vitamin Categories
• Water Soluble– Vitamin C– B-Vitamins (thiamin, riboflavin, niacin, B6, B12,
folic acid, pantothenic acid, biotin)
• Fat Soluble – Vitamin A (Retinol or beta carotene)– Vitamin D (calciferol)– Vitamin E (-tocopherol)– Vitamin K (menaquinone)
Exercise and Vitamin Requirements
• Inadequate vitamin status impairs performance
• Dies exercise increase vitamin requirement– Decreased absorption?– Loss in sweat?– Increased mitochondrial density?– Muscle hypertrophy?– Anti-oxidant requirement?
Athletes at Risk
• Low energy intake– Females– Gymnasts, dancers, wrestlers
• Unbalanced diet
Vitamin Supplementation Above the DRI or RDA
• Vitamin B6 may improve aerobic power
• Vitamin C may enhance heat acclimatization
• Vitamin E may enhance aerobic power at altitude
• B-complex vitamins may increase short term performance/recovery in hot climates
Antioxidants & Free Radicals
• Oxygen Free Radicals – Molecules with an unpaired electron in their
outer orbit– Produced by the reduction of molecular
oxygen, and ongoing process during normal cellular respiration
– Examples are superoxide (O2-), hydrogen
peroxide (H2O2), and hydroxyl radical (OH-)– Between 2-5% of the total electron flux during
normal metabolism generate free radicals
Consequences of Free Radicals
• Deterioration of membrane lipids
• Changes in membrane protein structure
• Mitochondria appear to be most susceptible to free radical damage
• Free radical damage has been implicated in diseases such as heart disease, cancer, diabetes, immune dysfunction, accelerated aging
Exercise and Free Radicals
• Increase in cellular respiration increases FR production
• Increase in body temperature increases rate of FR formation
• Increase in catecholamines increases FR formation
Natural Defenses Against Free Radicals
• Protective antioxidant enzymes
• Exercise training increases the level of antioxidant enzymes but oxidative potential of the muscle increases more
• Nutritional antioxidants work with the enzymes
• Primary nutritional antioxidant vitamins are C, E, and beta-carotene
Recommended Intake of Antioxidant Vitamins
• Beta-Carotene– DRI: 10-11 mg– Recommended: 20 mg
• Vitamin C– DRI: 75-90 mg– Recommended: 250 mg
• Vitamin E– DRI: 22.5 IU– Recommended: 150 IU
Minerals
• Minerals are inorganic solid elements found in nature in plants, animal tissue, and water.
• 15 known essential minerals and 5 nonessential composing less than 4% of the body weight
Functions of Minerals
• Building blocks for body tissues such as bones, teeth, & muscles
• Components of metalloenzymes which regulate metabolism
• Exist as ions or electrolytes involved in metabolism & body water regulation
• Components of hormones
Classification of Minerals
• Macrominerals– RDA or ESADDI is > 100 mg per day or body
contains more than 5 grams– Calcium, phosphorus, magnesium, potassium,
sodium chloride, sulfur
• Trace Minerals– Needed in quantities < 100 mg– Iron, copper, chromium, selenium, boron,
vanadium, cobalt, fluoride, iodine, manganese, molybdenum
Calcium
• Major Functions– Bone formation– Enzyme activation– Nerve impulse transmission– Muscle contraction– Cell membrane potentials
Current DRIs for Calcium
• Ages 9-18– Males: 1300 mg– Females: 1300 mg
• Ages 19-50– Males: 1000 mg– Females: 1000 mg
Factors Altering Ca Absorption/Utilization
• Dairy sources absorbed better than plant– Vitamin D and lactose increase– Phytates in plants decrease
• Fiber decreases
• Excessive protein decreases
• Excessive coffee decreases
• Excessive alcohol decreases
Consequences of Low Ca
• Low serum calcium is rare because of the ability to absorb Ca from bones– Muscular cramping– Impaired muscular contraction
• Colon Cancer
• Osteoporosis
Consequences of Too Much Ca
• Abnormal heart rhythms
• Kidney stones
• Reduces iron and zinc absorption
Calcium Supplements
• Calcium citrate, carbonate, lactate, gluconate, antacids
• Citrate is the best for absorption
• Taken with meal is best
• Taken in 200-300 mg doses is best
Female Athlete Triad
• Disordered eating
• Secondary amenorrhea due to hormonal deficits and imbalances
• Osteoporosis
Iron
• Major Functions– Used to form hemoglobin, cytochromes, and
Kreb-cycle metalloenzymes• 70% is activety used• 30% is stored as ferritin
– As many as 90% of females get less than RDA but body partly compensates by increasing absorption
– 16% of females have iron-deficiency anemia
RDA for Iron
• Ages 9-13 yr– Males: 8 mg– Females: 8 mg
• Ages 14-18 yr– Males: 11 mg– Females: 15 mg
• Ages 19-50 yr– Males: 8 mg– Females: 18 mg
Types of Iron
• Heme iron– Animal sources– Best absorption: 10-30%– Animal sources are 40% heme, 60% non-
heme
• Non-heme iron– Plant sources– Poorly absorbed: 2-10%
Factors Affecting Iron Absorption
• Increases absorption– Vitamin C for non-heme iron– MPF for both heme and non-heme
• Decreases absorption– Tannins in tea (by 60%)– Phytic acid in whole grains– Oxalic acid in green leafy vegetables– Calcium for non-heme
Sources of Iron
• Animal– 4 oz liver- 10 mg– 4 oz beef, pork, dark poultry – 5-6 mg– 4 oz white poultry – 1 mg
• Plant– 8 oz prune juice – 3 mg– 1/3 cup dates, raisins, prunes – 1 mg– ½ cup spinach, beans, broccoli – 2 mg
Iron Deficiency
• Stage 1– Depletion of bone marrow stores and decrease in
serum ferritin• Stage 2
– Further decrease in serum ferritin and loss on some Hb, but Hb still normal
– 30-50% of female and 15-30% of male distance runners are in this stage
• Stage 3 (iron-deficiency anemia)– Very low serum ferritin and low Hb– < 13 grams Hb for males– < 11 grams Hb for females
Sports Anemia
• Low Hb levels due to expanded blood volume
• Iron stores are normal
Iron Supplementation and Performance
• Iron supplementation will improve performance in iron-deficiency anemia
• Iron supplementation will improve iron status in iron deficiency (stage 2) without anemia but may not improve performance
• Iron supplementation will not improve performance when iron stores are normal
Sodium or Natrium (Na+)
• Functions– Primary electolyte in extracellular fluid– Fluid balance and osmotic pressure– Nerve conduction and muscle contraction
Recommended Na+ Intake
• No RDA
• Minimal requirement is 500 mg
• Salt is 40% sodium
• Most recommendation is < 3000 mg/day
Effects of High N+ Intakes
• Associated with high BP in ~ 20% of population
• Water retention
Effects of Low Na+ Intakes
• Muscle cramps????
• Disruption of cardiac electrical activity which can result in death
Sources Containing 300 mg Ca
• 8 oz of milk
• 1.5 oz of cheese
• 1 cup yogurt
• 1.75 cups ice cream
• 8 oz fortified OJ
• 1 serving fortified cereal