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Chapter 7
Lecture Slides
What are vitamins and how do they work?
Vitamins – Major Functions
Coenzyme Functions
B Vitamins
What are vitamins and how do they work?
Vitamins – Major Functions
Coenzyme Functions
B Vitamins
Antioxidant Functions
Beta-Carotene (Vitamin A)
Vitamin C
Vitamin E
Free Radicals
• Reactive oxygen species (ROS)
– Superoxide radical
– Hydroxy radical
• Reactive nitrogen species (RNS)
– Interaction of nitric oxide (NO) with superoxide
• Free radicals are produced during normal metabolic processes and are involved in normal cell functioning, but may be produced in excess under certain circumstances and be damaging to cellular constituents
Figure 7.2
What are vitamins and how do they work?
Vitamins – Major Functions
Coenzyme Functions
B vitamins
Antioxidant Functions
Beta-Carotene (Vitamin A)
Vitamin C
Vitamin E
Hormone Functions
Vitamin D
Essential vitamins
• Cannot be synthesized in the body in sufficient quantity
• Causes deficiency symptoms when intake is inadequate
• Alleviates deficiency symptoms when added back into the diet
• Some substances, such as CoQ10, have been attributed with vitamin-like activity, but are not essential vitamins
What vitamins are essential to human nutrition?
• Water-soluble vitamins
– Thiamin
– Riboflavin
– Niacin
– Vitamin B6
– Vitamin B12
– Folate
– Biotin
– Pantothenic acid
– Choline*
– Vitamin C
• Fat-soluble vitamins
– Vitamin A
– Vitamin D
– Vitamin E
– Vitamin K
* Not classified as a vitamin
Foods rich in VitaminsStarches
and Grains
Fruits, citrus and others
Vegetables, dark green and others
Meat, fish,
poultry
Milk and dairy
products
Fats and Oils
B1
B2
Folate
E
β-carotene
C
β-carotene
Niacin
B6
Folate
C
E
K
B1
B2
Niacin
B6
B12
Folate
A
B2
B12
A*
D*
E
* Fortified milk
Notes: (1) Vitamin D is synthesized in the skin from sunlight (2) Vitamin K is
synthesized in the intestines by bacteria (3) β-carotene may be converted to
vitamin A (4) Some foods are fortified with up to 100% of the RDA for vitamins
and minerals.
Food Labels - Vitamins
• Vitamins A and C listed
– % of Daily Value
• Others may be listed
In general, how do deficiencies or excesses of vitamins influence health or physical performance?
• Four stages of vitamin deficiency
– Preliminary stage
– Biochemical deficiency stage
– Physiologic deficiency stage
– Clinically manifest deficiency stage
Example of stages of vitamin deficiency(Vitamin B12)
• Preliminary stage
– Individual switches to a vegan diet and avoids fortified foods
• Biochemical deficiency stage
– Serum levels of vitamin B12 decrease
• Physiologic deficiency stage
– General feelings of weakness occur
• Clinically manifest deficiency stage
– Pernicious anemia develops
Note: First 3 stages represent Subclinical Malnutrition
Excessive intake of vitamins
• RDA for some vitamins now being considered for health promotion
• Hypervitaminosis
– Not likely to occur from natural foods
– Most likely due to excessive intake • Vitamin supplements
• Fortified foods
• Combination of the two
– Vitamins begin to function as drugs
– UL has been established for 7 of the 13 essential vitamins
Format for vitamins
• Name; terms
• DRI
• Food sources
• Major functions
• Deficiency
– Health
– Performance
• Supplementation
– Health
– Performance
• Prudent recommendations
Fat-Soluble Vitamins
• Vitamins A, D, E, and K
• Soluble in fat, but not in water
• Found in foods with some fat content
• Several may be manufactured in the body
• Excessive intake of several may be toxic
Essential Fat-soluble Vitamins
Essential Fat-soluble Vitamins
Vitamin A
Name (synonyms):
– Retinol (preformed vitamin A)
– Provitamins; carotenoids such as beta-carotene
Dietary reference intakes (DRI):
– Retinol equivalents (RE) or retinal activity equivalents (RAE)
– 1 RAE = 1 mcg retinal or 12 mcg beta-carotene
– RDA = 900, 700 RAE or 3000, 2300 IU (1 RAE = 3.3 IU)
– UL = 3 mg/day, or 10,000 IU
– DV is 5000 IU (1/2 the UL)
Vitamin A
Good food sources:
– Vitamin A in animal foods; liver, butter, fortified milk
– Beta-carotene in dark-green, yellow-orange vegetables; some fruits
Major functions in humans:
– Maintenance of epithelial cells; Vision – night and
peripheral; bone development; immune system;
antioxidant
Vitamin A
Deficiency - effects on health:
– Night blindness; skin lesions; impaired growth; blindness from xerophthalmia (destruction of cornea)
Deficiency - effects on sport performance:
– Theoretical problems with impaired gluconeogenesis, synthesis of muscle protein, or night vision in sports, but no data are available to support these contentions
•
Vitamin A
Supplementation - effects on health (beneficial or detrimental):
– Not recommended unless under medical guidance;
– Hypervitaminosis A: weakness, nausea, headache, joint pain, skin peeling; may lead to bone loss; hip fractures; liver damage; in pregnancy excess A may be teratogenic
– Beta-carotene; harmless yellowing of skin in excess
– Note: Antioxidant effects on health covered later in chapter
Vitamin A
Supplementation - effects on sport (beneficial or detrimental):
– Little theoretical value; no beneficial effect
– Note: Antioxidant effects of beta-carotene on exercise performance and prevention of muscle tissue damage covered later in the chapter
Vitamin A
Prudent recommendations:
– Supplementation in excess not recommended; excesses of both vitamin A and beta-carotene (discussed later) may be harmful to one’s health.
Vitamin D (cholecalciferol)
Name, terms:
– Cholecalciferol (vitamin D3)
– Calcitriol – Physiologically active hormonal form
DRI (In the absence of adequate sunlight):
– AI = 5 mcg, or 200 IU (1 mcg = 40 IU)
– AI = 400-600 IU for older individuals
– DV = 400 IU (Twice the AI)
– UL = 2,000 IU
Vitamin D
Food sources
– Most foods contain no vitamin D
– Fatty fish (salmon, sardines) contain 200-500 IU in 3 oz
– Egg yolks contain about 25 IU
– Mushrooms, Shitake; 3 contain about 250 IU
– Fortified foods (milk; cereals) may contain 50-100% of RDA
Supplements
– D2, ergocalciferol; D3, cholecalciferol
• D3, cholecalciferol, is the recommended form
– Normally contain 200-600 IU
– Some contain 5,000 IU
Vitamin D
Exposure to sunshine– Swimsuit with no sunscreen
• 20,000 – 30,000IU in 30 minutes
– Hand, arm and face exposure • RDA with 10-20 minutes in the summer sun
– Need longer exposure time in the winter
• May be difficult to obtain sufficient amounts in northern latitudes
Vitamin D
• Major functions:
– Bone metabolism
• Works with parathormone (parathyroid gland)
• Absorb Ca++ from intestines and kidney
• Helps regulate phosphate metabolism
– Appears to be important in muscle function
– Involved in the development of the skin
– May help inhibit cell proliferation
Vitamin D
Deficiency – Health effects
– Some contend vitamin D deficiency is widespread and is associated with serious health problems
– Increased losses of calcium from bone
• Rickets in children; osteomalacia in adults
– Muscle weakness: impaired calcium metabolism in muscle
• Increased risk of falls in older individuals
– Relation of sun exposure to cancer development
• Epidemiological research shows risk of certain cancers with adequate exposure to sunshine; vitamin D may inhibit cell proliferation
Vitamin D
• Deficiency – Physical Performance– Although vitamin D deficiency may cause muscle
weakness, few data are available relative to the effects of vitamin D deficiency on exercise performance
Vitamin D
• Supplementation – Health effects
– Bone health
• Combined with calcium appears to help decrease fractures in postmenopausal women
• May also lower the risk of fractures in the elderly by increasing muscle strength and preventing falls
– Cancer
• Epidemiological studies show reduced risk of colorectal cancer with vitamin D and calcium intake
• Prospective studies are equivocal, but some find reduced cancer risk. Research is ongoing.
Vitamin D
• Supplementation – Health effects
– Diabetes
• May enhance immune functions to prevent autoimmune diseases
• Supplementation suggested to help prevent type I diabetes in children
Vitamin D
• Supplementation – Health effects
– Kidney stones and other adverse effects
• Excess calcium may combine with some salts, such as oxalates, to form kidney stones
• Excess calcium may lead to calcified plaque in arteries
• Excess vitamin D may cause vomiting, weight loss, and loss of muscle tone
Vitamin D
• Supplementation – Effects on exercise performance
– Research is very limited, only a few studies
• No ergogenic effects of single megadose
• No ergogenic effects of supplementation over the course of 2 years
– Little is known of the vitamin D status of athletes
Vitamin D
• Prudent recommendations
– Obtain at least the RDA for your age
• Foods rich in or fortified with vitamin D and adequate sunshine
– Some health professionals recommend 1,000 to 2,000 IU daily
• Supplement with vitamin D, preferably D3
• Canada recommends supplement for elderly over 50
• Take no more than 2,000 IU daily
• Consult physician if at risk for kidney stones
Vitamin E
Name, terms:
– RRR-alpha-tocopherol
• d-alpha-tocopherol (natural form)
• dl-alpha-tocopherol (synthetic form)
– RRR-gamma-tocopherol
DRI:– RDA = 15 mg RRR-alpha-tocopherol
– 1 mg = 1.5 IU
– DV = 30 IU
– UL = 1,000mg or 1,500 IU
Vitamin E
Food sources:
– Polyunsaturated vegetable oils; margarine
1 tablespoon contains 3-5 IU
– Fortified cereals; wheat germ oil
Fortified cereals contain 10-45 IU
– 1 tablespoon wheat germ oil contains 40 IU
Moderate amount in meats, dairy, fruits and vegetables
Vitamin E
Supplements:
– May contain natural or synthetic sources
– Synthetic form (dl-) not the same as natural form (d-)
– Need 40-50% more of synthetic to match natural source
Vitamin E
• The total function of vitamin E in human nutrition is unknown
– “A vitamin looking for a disease”
• Major function is to serve as an antioxidant
– Prevent oxidation of cell phospholipids
• Red blood cells
• LDL-cholesterol
– Prevent oxidation of vitamin A
Vitamin E
Deficiency – Health:
– Deficiency is rare
– May result from a genetic deficiency to absorb fat
– May result from very low fat diets
– Free radical damage could cause cancer, heart disease (oxidized LDL) or anemia
Deficiency – Physical Performance
– Anemia could impair performance; few data available
Vitamin E
• Supplementation – Effects on health
– Antioxidant effects theorized to help prevent heart disease and cancer
– Research findings discussed later with other antioxidants
Vitamin E
• Supplementation – Effects on exercise performance
– Theorized to maintain integrity of RBC and O2
delivery by preventing RBC membrane oxidation
– Possible benefits
• Altitude (1-3 miles)
• High-smog areas
– No apparent ergogenic effect at sea level
– Antioxidant effect on muscle tissue damage later in chapter
Vitamin E
• Prudent recommendations
– Diets rich in vitamin E may be healthful
– Supplements taken for purported health benefits should be used with caution
– Supplements are not ergogenic for physically active individuals
Vitamin K
Name, terms:
– Vitamin K is the generic term for menadione (K3)
• Phylloquinone (K1) – plant form
• Menoquinone (K2) – animal form
DRI:
– AI = 120 and 90 mcg/day for males and females
– DV = 80 mcg
– No UL
Vitamin K
Food sources:
– Plant foods: Vegetable oils; green leafy vegetables
• Main dietary source
• 3 oz spinach contain 380 mcg
– Animal foods: Meats and milk
• Lower concentrations
• 3 oz meat contain 1 mcg
Synthesis in body:
– Intestinal bacteria form menoquinone (MK)
Vitamin K
• Major functions:
– Essential in two steps of the blood clotting process
– May enhance function of osteocalcin, a protein with an important role in bone formation
Vitamin K
Deficiency – Effects on health
– Uncommon, but may occur with antibiotics
– May cause impaired blood clotting; hemorrhage
Deficiency – Effects on exercise performance
– No data available
•
Vitamin K
Supplementation – Effects on Health:
• Emerging data of a beneficial role on bone health
– Pharmacological doses effective to enhance bone mineralization in patients with osteoporosis
– Supplements (K1) may help prevent bone loss, particularly when taken with vitamin D
• Effective dose of 150-250 mcg/day
Vitamin K
Supplementation – Effects on exercise performance
• No studies have evaluated the ergogenic effects of vitamin K supplementation
• One short-term study reported an increased index of bone formation markers in female athletes, but some of the subjects were vitamin-K deficient before the supplementation protocol
• A long-term study found no beneficial effects on bone loss in female endurance athletes
Vitamin K
Prudent recommendations:
– Individuals desiring to use vitamin K supplements should do so only under the guidance of a physician
– One-a-day supplements may contain 0 to 120 mcg
Water-soluble Vitamins
• Nine vitamins
– B complex (8 individual vitamins)
– Vitamin C
• Deficiency symptoms may be noted in 2-4 weeks for some B vitamins
– May impair energy production for exercise
Figure 7.3
Essential Water-soluble Vitamins
Essential Water-soluble Vitamins
Thiamin
Name, terms:
– Vitamin B1
– Antiberiberi vitamin
– Antineuritic vitamin
DRI:
– RDA = 0.5 mg per 1,000 Calories
– 1.2 mg/day males; 1.1 mg/day females
– UL – None
– DV = 1.5 mg
Thiamin
• Food sources:
– Widely distributed in plants and animal foods
– Whole wheat, pork
– Fortified cereals contain 100% of RDA
• Major functions:
– Energy substrate coenzyme for carbohydrate
• Needed to convert pyruvate to acetyl-CoA
• Normal functioning of the nervous system
Thiamin
• Deficiency – Health:
– Symptoms may occur in several weeks
– Mental confusion; muscular weakness
– Beriberi: Damage to nervous system and heart
• Deficiency – Physical Performance
– Thiamin needs are increased with exercise and a high-carbohydrate diet
– Deficiency impairs endurance performance
• Deficiencies are rare
Thiamin
• Supplementation: Effects on health
– No benefits to well nourished individuals
– No UL has been established for thiamin
• Supplementation: Effects on exercise performance
– No beneficial effects on performance• World War II studies
– Recent study suggests reduced subjective complaints of fatigue following strenuous exercise; needs confirmation
– Thiamine derivatives, allithiamine: no ergogenic effects
Thiamin
• Prudent recommendations:
– Supplements not recommended
– Athletes should consume nutrient-dense foods
Riboflavin
• Name, terms:
• Vitamin B2
•
• DRI:
• RDA = 1.3 mg/day males; 1.1 mg/day females
• UL – None
• DV = 1.7 mg
Riboflavin
• Food sources:
– Widely distributed in plants and animal foods
– Milk, dairy products, whole wheat
• Major functions:
– Needed for oxidative enzymes - flavoproteins
– Important for carbohydrate, fat and protein metabolism
– Healthy skin tissue
Riboflavin
• Deficiency : Effects on health
– Glossitis; skin cracks; dry skin
• Deficiency : Effects on exercise performance
– Deficiency could impair endurance capacity
– Athletes may need more than the RDA during training
• Deficiencies are rare
Riboflavin
• Supplementation: Effects on health
– Has no health benefits for well-nourished individuals
– No UL has been set for riboflavin
• Supplementation: Effects on exercise performance
– Only one reputable study conducted and reported no beneficial effects on performance
Riboflavin
• Prudent recommendations:
– Supplements not recommended
– Athletes should consume nutrient-dense foods
Niacin
Name, terms:
– Nicotinic acid; nicotinamide; anti-pellagra vitamin
DRI:
Niacin equivalents (NE)
– RDA = 16 NE adult males; 14 NE adult females
– 1 NE = 1 mg niacin or 60 mg tryptophan
– UL = 35 mg
– DV = 20 mg
Niacin
• Food sources:
– Foods with high protein content
– Meat, fish, poultry, whole grains, legumes
•
• Major functions:
– Coenzymes for glycolysis and fat synthesis
• Nicotinamide adenine dinucleotide (NAD)
– Important for both aerobic and anaerobic energy
processes
Niacin
Deficiency – Effects on health
– Skin rashes, mental confusion, lack of energy, muscle weakness
– Pellagra: severe dermatitis, diarrhea, dementia
Deficiency – Effects on exercise performance
– Could impair aerobic and anaerobic endurance performance, but no research involving niacin alone has been conducted
•
Niacin
Supplementation – Effects on health
– Various forms
• Immediate release
• Sustained release
• Extended release
– May cause flushing, burning and tingling sensation
– High doses may improve serum lipid profile
• Reduce total and LDL-cholesterol and triglycerides
• Increase HDL-cholesterol
– Excess may cause liver damage
– Use only under medical care
Niacin
Supplementation – Effects on exercise performance
– Several studies report no ergogenic effect
• 10-mile run
• Prolonged cycling
– Not recommended
• May impair endurance performance by interfering with fat metabolism during exercise
– One study suggests niacin may be helpful as a means to dissipate body heat during exercise
Niacin
Prudent recommendations:
– Supplements not recommended
– Use for lipid lowering only under care of a physician
Vitamin B6
Name, terms:
– Pyridoxine, pyridoxal, pyridoxamine
DRI:
– RDA = 1.3 mg/day age 19-50
– 1.7 and 1.5 for males and females > age 50
– UL = 100 mg/day
– DV = 2 mg
Vitamin B6
Food sources:
– Widely distributed in protein foods
– Meat, fish, poultry, whole grains
Major functions:
– Coenzyme for protein metabolism; 60 enzymes
• Tryptophan to niacin
• Formation of proteins, such as hemoglobin
– Neurotransmitter formation
– Glycogenolysis and gluconeogenesis
Vitamin B6
Deficiency – Effects on health
– May occur in those on low-protein diets
– Skin disorders, mouth sores, mental depression, anemia, epileptic-like seizures
Deficiency – Effects on exercise performance
– Could impair endurance performance
• Anemia
• Impaired carbohydrate metabolism
– Some suggest impairment in fine motor control sports
Vitamin B6
Supplementation – Effects on health
– May be useful in treatment of PMS symptoms
– May lower homocysteine
• Discussed later relative to CHD
– Prolonged excessive intake (> 100 mg) may cause neural damage
• Loss of sensation from limbs
• Impaired gait
Vitamin B6
Supplementation – Effects on exercise performance
– Physically active individuals may need 1.5 to 2.5 the current RDA to maintain good B6 status
– Research suggests supplementation does not affect performance positively or negatively
Vitamin B6
• Prudent recommendations:
– Supplements not recommended for health or enhanced exercise performance
– Consume nutrient-dense foods
– Excess consumption over time may lead to adverse health effects
Vitamin B12
Name, terms:
– Cobalamin
DRI:
– RDA = 2.4 mcg/day
• Over age 50 should obtain B12 from fortified foods or supplements
– UL = None
– DV = 6 mcg
Vitamin B12
• Food sources:
– Only found in animal foods; meat, fish, poultry, milk
– Vegans need fortified food source or supplement
– Found in fortified foods, such as breakfast cereals
Major functions:
– Part of coenzyme critical to formation of DNA; works with folate
– Red blood cell formation
– Formation of myelin sheath on nerve fibers
Vitamin B12
Deficiency – Effects on health
– Deficiency is rare
• Liver stores may last for years
– Elderly may experience inadequacies
• Decrease enzyme to release B12 from food
• Decrease in transport proteins in intestines
– Adverse health effects
• Anemia (pernicious)
• Neural damage; paralysis
• Birth defects
Vitamin B12
Deficiency – Effects on exercise performance
– Anemia could impair endurance performance
Vitamin B12
• Supplementation – Effects on health
– May help treat pernicious anemia
– No apparent adverse effects of large doses
• Supplementation – Effects on exercise performance
– No apparent effect on endurance performance
– Senior athletes should consume fortified cereals or take a supplement
Vitamin B12
• Prudent recommendations:
– Supplementation not normally warranted
– Consumption of fortified foods or vitamin supplements may be recommended for vegans and older persons
Folate
• Name, terms:
– Folate (natural form)
– Folic acid (synthetic form)
– Folacin (collective term)
• DRI:
– Dietary folate equivalents (DFE)
– RDA = 400 DFE/day; 600 DFE in pregnancy
– 1 DFE = 1 mcg food folate
= 0.6 mcg in fortified foods (1 mcg = 1.7 DFE)
= 0.5 mcg in supplement (1 mcg = 2.0 DFE)
– UL = 1,000 mcg (1 mg) DFE/day
– DV = 400 mg
Folate
• Food sources:
– Green, leafy vegetables, like spinach
– Whole grains, legumes
– Fruits and vegetables
– Fortified grains (140 mcg/100 grams of food)
• Major functions:
– Coenzyme critical to formation of DNA
– Needed during periods of rapid cell division
• Red blood cell formation
• Early pregnancy
– Involved in homocysteine metabolism
Folate
• Deficiency – Effects on health
–Deficiencies may occur
• Alcoholics
• Females on oral contraceptives
– Decreased absorption of folate
Folate
• Deficiency – Effects on health
– Impair DNA formation
• Pernicious anemia; increased homocysteine
• Increased risk of cancer
• Increased levels of homocysteine
– Associated with several vascular diseases, including CHD and stroke
– May be just a marker for disease
– Research is ongoing
• Increased risk of neural tube defects
Folate
• Deficiency – Effect on exercise performance
– Anemia could impair endurance performance
Folate
• Supplementation – Effects on health
–May help prevent neural tube defects (NTD)
– Food fortification studies
• ↓ incidence of NTD up to 78%
–All women of childbearing age should obtain 400 mcg as folic acid, plus food folate
Folate
• Supplementation – Effects on health
– Research findings equivocal relative to homocysteine and vascular disease
• A meta-analysis reported a reduced risk of first stroke by 18%
• Another meta-analysis found no effect on CHD or all-cause mortality in patients with heart disease
• AHA does not classify homocysteine as a risk factor
– A recent 10-year study suggested folic acid supplementation (1 mg/day for 10 years) may increase the risk of some forms of cancer
Folate
• Supplementation – Effects on health
– Large doses of folic acid may mask a vitamin B12 deficiency
• Pernicious anemia will not develop, but damage to the myelin sheath will continue and may not be recognized until irreparable damage is done
Folate
• Supplementation – Effects on physical performance
– No apparent effect on endurance performance
– Folate supplementation may increase serum folate, but has no effect on hemoglobin, VO2max, or endurance running time
Folate
• Prudent recommendations:
– All women in childbearing years should obtain 400 DFE/day from fortified foods and supplements, in addition to food folate
– Current advice suggests males and postmenopausal women might use caution so as not to take excessive folic acid through fortified foods and supplements
Pantothenic acid
• DRI
– AI = 5 mg
– DV = 10 mg
– UL = None listed
• Food sources
– Distributed widely in all natural animal and plant foods
– Major losses in highly processed foods
• Major functions:
– An essential component of coenzyme A
– Acetyl CoA from carbohydrate, fat and protein
Pantothenic acid
• Deficiency – Health and exercise performance
– Deficiencies are very rare
– Experimentally induced deficiencies cause
• Fatigue
• Muscle cramping
• Impaired motor coordination
– A deficiency could impair energy metabolism if adequate acetyl CoA was not available
Pantothenic acid
• Supplementation – Health and exercise performance
– Current research indicates that supplementation with pantothenic acid has no ergogenic effect on various tests of aerobic endurance performance in runners and cyclists
Pantothenic acid
• Prudent recommendations
– A balanced diet should provide adequate pantothenic acid for the healthy, physically active individual
Biotin
• DRI
– AI = 30 mcg
– DV = 300 mcg
– UL = None listed
• Food sources
– Organ meats, egg yolk, legumes, green leafy vegetables
– Also synthesized in the intestines by bacteria
• Major functions:
– Coenzyme for enzymes involved in protein metabolism
– Involved in gene expression
– Involved in gluconeogenesis
Biotin
• Deficiency – Health and exercise performance
– Deficiencies are rare, but may occur in diets rich in raw egg whites
– Symptoms may include
• Loss of appetite,
• Mental depression
• Muscle pain
– No studies relative to deficiency states in athletes
Biotin
• Supplementation – Health and exercise performance
– No evidence that biotin supplementation enhances health or exercise performance is available
– Supplements appear to be harmless, with no adverse effects up to 200 mg daily
Biotin
• Prudent recommendations
– Supplements are unnecessary for the physically active individual
Choline
• DRI:
– AI = 550 mg/day males; 425 mg/day females
– UL = 3.5 grams/day
– DV = None
• Sources:
– Animal foods as lecithin; plants as free choline
• Major functions:
– Precursor for lecithin; formation of acetylcholine
•
Choline
• Deficiency – Health:
– Deficiency is very rare
– Experimental deficiency: Fatty liver and liver damage
•
• Deficiency – Physical Performance
– Plasma levels reduced in marathon; no adverse effects noted
•
Choline
• Supplementation -- Health
– Not apparently beneficial, as deficiency is rare
– Excess may cause GI distress, low blood pressure
• Supplementation – Physical Performance
– Preliminary studies have shown supplementation will ↑ serum choline
– Preliminary field and laboratory studies found an ergogenic effect
– More recent studies reveal no ergogenic effect on endurance performance
•
Choline
• Prudent recommendations:
– Supplementation not warranted
•
Vitamin B Complex
• Eight vitamins in the B complex
• Function together in energy metabolism important to exercise
Vitamin B Complex
• Deficiency – Health
– A deficiency would impair overall health status.
– The homocysteine issue
• Deficiency increases plasma homocysteine
• High levels of homocysteine may predict heart attacks and strokes
• May be a result of disease, not a cause
Vitamin B Complex
• Deficiency - Exercise performance
– A deficiency of 4-8 weeks could impair both exercise performance
– World War II starvation studies
– Netherlands studies created deficiency over 4 weeks
• Impaired aerobic and anaerobic performance
Vitamin Deficiency: Effect 3-weeks deficiency of B vitamins and
vitamin C
• Decreased aerobic energy production
• Decreased anaerobic energy production
• In general, correcting a vitamin deficiency associated with impaired performance will enhance subsequent performance
Vitamin B Complex
• Supplementation - Health
– In 2004, Consumers Union noted some evidence that vitamin B, especially folate and B6, could reduce blood pressure and stroke risk
– Experimental study, Vitamin Intervention for Stroke Prevention (VISP) • Lowered serum homocysteine
• No effect on stroke, coronary events, or death
– Meta-analysis• No effect on progression of atherosclerosis
– American Heart Association• Does not recommend widespread use of vitamin B to reduce the
risk of heart attack or stroke
Vitamin B Complex
• Supplementation – Exercise performance
– Sport nutritionists recommend adequate vitamin B• Metabolic pathways using vitamin B may be stressed
• Adaptations to training increase requirements
• Strenuous exercise may increase turnover in sweat
• May be needed in the repair of muscle tissue
– B supplementation may be recommended to athletes in high energy expenditure sports who do not consume a nutrient-dense diet
– Some research reports B1, B6, B12 supplementation improves pistol shooing; needs confirming research
Vitamin B Complex
• Prudent recommendations
– Consume a balanced diet with natural, wholesome foods
– Fortified cereals provide substantial amounts of the B vitamins
– Women of childbearing age should obtain adequate folate and folic acid
– Athletes who train intensely for endurance sports and eat mainly highly processed foods should consider a B vitamin supplement
Vitamin C
• Name, terms:
– Ascorbic acid
• DRI:
– RDA = 90 mg/day males; 75 mg/day females
– UL = 2,000 mg/day
– DV = 60 mg
• Sources:
– Fruits and vegetables; citrus fruits
– One orange or glass of orange juice contains the RDA
Vitamin C
• Major functions:
– Synthesis of collagen
– Formation of hormones and neurotransmitters;
– Helps absorb iron (non-heme iron)
– RBC formation
– Functions as an antioxidant
Vitamin C
• Deficiency – Health:
– Rare in industrialized societies
– Smoking, aspirin, oral contraceptives increase need
– Major deficiency disease is scurvy• Bleeding gums
• Weakness
• Muscle cramps
• Impaired wound healing
• Anemia
– Epidemiological research• Higher incidence of CHD and cancer
Vitamin C
• Deficiency – Exercise performance:
– Weakness could impair exercise performance
– Anemia could impair endurance performance
– World War II starvation studies
• Minnesota starvation studies: Ancel Keys
Vitamin C
• Supplementation -- Health
– Antioxidant effects discussed later
– Controversial opinions on safety of megadoses
• Undesirable side effects– Diarrhea
– ↓ bioavailability of B6, B12, copper
– ↑ urinary calcium oxalates (short-term studies with 1,000 mg)
» Possible kidney stones
– Iron storage; oxidative effect of iron
– Rebound scurvy
• No adverse side effects– Excess amounts are excreted by the kidneys
– Long term study shows no increase in kidney stones
Vitamin C
• Supplementation – Exercise performance
– Antioxidant effects discussed later
– Early research indicates improvement in individuals who are vitamin-C deficient
– Some studies indicate reduced severity of upper respiratory tract infections (URTI) following ultraendurance exercise
– Current research shows no benefit to immune system functions after endurance exercise
– No apparent effect on exercise performance
Vitamin C
• Prudent recommendations;
– Obtain vitamin C naturally through foods
• Eat more fruits and vegetables
– May maintain plasma saturation with 200 mg/day
Vitamin Supplements:Ergogenic Aspects
• Many athletes use vitamin supplements
• Dietary supplements are marketed to physically-active individuals – Individual vitamins
– Multivitamins
– Antioxidants
– Vitamin-like substances
Should physically active individuals take vitamin supplements?
• Some possible reasons
– Weight-control sports
– Poor dietary habits
– Pregnancy
– Elderly, senior athletes
– Consult with your health professional
Can the antioxidant vitamins prevent fatigue or muscle damage during training?
• Exercise training may increase total antioxidant capacity– Superoxide dismutase
– Glutathione peroxidase
• Such adaptations provide protection against free radical damage
• Antioxidants not shown to improve exercise performance– Individual antioxidants
– Antioxidant cocktails
Antioxidants:Muscle damage during training
• Strenuous exercise may generate ROS to overwhelm the body’ natural antioxidant defense system
• Equivocal research and review findings relative to the effects of antioxidant supplementation– Some studies show reduction in markers of muscle tissue damage
– Other studies show no benefits
– Several studies found adverse effects of supplements
– Some suggest older athletes may benefit
• Most scientists recommend– More research is needed
– Athletes obtain antioxidant from natural foods
Antioxidant VitaminsMuscle Tissue Damage – Key Reviews
• Several antioxidants, vitamin C and, especially vitamin E, have been shown to decrease the exercise-induced increase in the rate of lipid peroxidation. Trained athletes who received antioxidant supplements have shown evidence of reduced oxidative stress, , which could help prevent muscle tissue damage.
• Aging lessens the exercise training-induced improvement in natural antioxidant enzymes and one prominent sports scientist suggests exercise training in older athletes might be assisted with antioxidant supplementation in attempts to optimize antioxidant defense.
• Whether the body’s own natural antioxidant defense system is sufficient to combat oxidative stress during prolonged exercise or whether antioxidant supplements are needed is unknown. More evidence is needed to support a recommendation for antioxidant supplements for those engaged in prolonged aerobic exercise.
Antioxidant Vitamins• Although some studies have indicated that supplementation
with vitamin E and vitamin C may decrease exercise-induced oxidative stress to muscle cells in humans, little evidence shows that antioxidant supplementation can improve human performance
How effective are the special supplements marketed for athletes?
• Multivitamin-mineral supplements
• Bee pollen
• CoQ10
• Quercetin
Multivitamin-mineral supplements
• Multivitamin-mineral supplementation (100-6000% of the RDA) has not been shown to enhance VO2max and aerobic capacity, as well as laboratory and field tests of anaerobic and aerobic endurance, such as 400-meter and 15K run performance, in elite athletes.
• Some athletes may be advise to take a simple one-a-day multivitamin-mineral
Bee pollen
• Marketed specifically to runners
– No specific physiological mechanism
– Not effective as ergogenic aid
– May cause allergic reaction
CoQ10
• Coenzyme Q10 (CoQ10)
– A lipid with characteristics of a vitamin
– Involved in oxidative processes; serves as an antioxidant
– Used in treatment of cardiovascular disease
– Use as an as ergogenic aid
• Studies cited in a book show ergogenic effects
• Well-controlled studies show no effects– VO2max
– Exercise time to exhaustion
– Muscle tissue damage
– May cause muscle tissue damage; prooxidant
Quercetin
• A dietary flavonol
• Functions as an antioxidant
• Marketed in some energy drinks
• Studied for effects on immune function in exercise
– Findings equivocal
• Research relative to ergogenic effects is limited
– Results not sufficient to support an ergogenic effect
• Additional research merited
What’s the bottom line regarding vitamin supplements for athletes?
• Some athletes may need supplements
• Some health professionals recommend a
one-a-day multivitamin-mineral
Vitamin Supplementation: Key Points
• A vitamin deficiency can impair physical performance• Correcting a vitamin deficiency returns performance to
normal• In general, supplementation to an athlete on a well-balanced
diet does not enhance performance• Obtaining adequate amounts of the antioxidant vitamins via a
healthful diet may benefit some athletes– Additional research appears to be warranted:
• Vitamin E and endurance at high altitude• Antioxidants and prevention of muscle catabolism; older athletes
• Some endurance athletes may need vitamin supplements– Weight-loss dieting– Females of childbearing age– Older athletes– Vegans who do not consume fortified foods (B12)– Poor dietary habits
Vitamin Supplements:Health Aspects
• Vitamin supplements
– Most popular of all dietary supplements
– Multibillion dollar industry
Can I obtain the vitamins I needthrough my diet?
• Vitamin intake may be inadequate for various reasons
– Food refining process may remove vitamins
• Food processing may help or hurt
– Improper home storage or preparation of foods
• Key point
– Consume a balanced diet of natural foods with high nutrient density
– Obtain your vitamins from foods
• Athletes in particular
Why are vitamin supplements often recommended?
• May be important for some individuals, including athletes, to consume supplements or fortified foods
– Women who are pregnant or lactating
– Individuals with certain diseases or disorders
– Individuals taking certain drugs
– Elderly individuals, who have higher RDA or AI
– Vegans who consume no vitamin B12
– Individuals on weight-loss diets
– Athletes who do not consume enough energy
– Individuals intolerant to certain foods
– Individuals who make unwise food selections
Why do individuals take vitamin overdoses?
• Vitamins marketed for health reasons
• Some use vitamins as drugs
Do foods rich in vitamins, particularly antioxidant vitamins, help deter chronic
diseases?• Epidemiological studies support the viewpoint that diets rich
in fruits, vegetables, whole grains and other plant foods may exert protective health effects– Heart disease
– Various cancers
• Such diets are rich in vitamins, including antioxidant vitamins, and other phytonutrients
• Underlying mechanism not known– Protective effect of antioxidants on immune functions
– Phytochemicals block tumor formation
Do vitamin supplements help deter disease?
• Many studies were epidemiological in nature
• More recent experimental studies with some disease processes
• NIH State-of-the-Science conference on vitamin and mineral supplements and health in 2006; analyzed only randomized controlled trials (RCTs)
– Cardiovascular disease and stroke
– Cancer
– Eye health
– Mental health
– General health
Cardiovascular disease and stroke
• Theories
– Vitamin E can prevent oxidation of LDL-cholesterol
– Antioxidants may exert anti-inflammatory effects
– B vitamins decrease homocysteine
• Most supportive evidence was epidemiological
• RCTs
– Do not support beneficial effect of antioxidants or B vitamins
– Some studies have shown increased risk of CHD and mortality
Cardiovascular disease and stroke
• Criticism of RCTs
– Done with CHD patients, not healthy individuals
– Vitamin E studies used mainly alpha-tocopherol, not the gamma form, which may lower serum cholesterol
• American Heart Association
– Does not recommend B vitamin supplementation to prevent CHD or stroke
– Recommends against antioxidant supplements
Cancer
• Theories
– Preventing DNA damage
– Strengthen immune system
• Epidemiological studies are inconsistent against various forms of cancer
Cancer
• Recent major reviews
– NIH State-of-the-Science Report and the American Institute of Cancer Research report on Nutrition and Prevention of Cancer
• NIH - Effects of vitamin/mineral supplements on cancer are inconsistent and data are insufficient to recommend for or against multivitamin use
• AICR - May be increased risk of some cancers with supplements. Does not recommend vitamin supplements for cancer prevention
• Recent Selenium and Vitamin E Cancer Trial (SELECT)
– Stopped early; increased risk of prostate cancer
Eye health
• Theories
– Prevent oxidation, a contributing factor to cataracts and Age Related Macular Degeneration (ARMD)
• NIH review indicates results are inconsistent, but one well designed study (AREDS) supports beneficial effects
– Vitamins C, E, beta-carotene; zinc and copper
– Consumers Union recommends use of a vitamin/mineral supplement for those in the intermediate stage of ARMD
• Some antioxidant phytonutrients now under study
Mental health
• Theory
– Brain cells susceptible to oxidative damage
– Vitamin E may prevent vascular damage caused by peptides
• Research findings
– Epidemiological research supports some beneficial effects of vitamin E from supplements and food
– Results from RCTs are inconsistent
– May delay onset of Alzheimer’s
• More research necessary
General health
• NIH report
– The present evidence is insufficient to recommend either for or against the use of multivitamins/minerals by the American public to prevent chronic disease
– Need advanced research
• Large-scale, long-term studies
How much of a vitamin supplement is too much?
• The Tolerable Upper Intake Level (UL)
• Set for 7 vitamins and choline
– Fat-soluble vitamins A, D, E
– Water-soluble vitamins niacin, folate, B6, C
• Not usually dangerous when consumed as natural foods
How much of a vitamin supplement is too much?
• Excessive intake may occur with supplements and fortified foods
– 20 milligrams of niacin in some breakfast cereals
– More than 50% the UL for adults
• Excessive vitamins in the body
– May be excreted in the urine
– May be stored in some body tissue
– May function in uncharacteristic ways
• Example: Teratogenic effects of excess vitamin A
Vitamin SupplementsA Current Recommendation
“Most people do not consume an optimal amount of all vitamins by diet alone . . . It appears prudent for all adults to take vitamin supplements.”
JAMA, 2002
The typical one-a-day multivitamin/multimineral
tablet may be sufficient.
If I want to take a vitamin-mineral supplement, what are some prudent guidelines?
• Most health professionals recommend against single vitamins
• A basic one-a-day multivitamin/mineral tablet may be recommended
• The ADA recommends low levels that do not exceed the RDA or AI
Vitamin/mineral supplements
• Check the Daily Value; look for 100% of DV
• Buy the inexpensive house brand, but be leery of some bargain brands, such as those in dollar stores
• Stick with the basics; 11 vitamins and 7 minerals
Vitamin/mineral supplements
• Vitamin A
– Buy a supplement low in vitamin A, no more than 3,000 IU of retinol
– Select those with beta-carotene
• Vitamin D
– Select one with 400-600 IU if elderly, a vegan, or postmenopausal and do not obtain enough in the diet
– Select vitamin D3 which is more effective than D2
Vitamin/mineral supplements
• Vitamin E
– Buy at least the DV, or 30 IU
– Doses of 100-200 IU appear to cause no risk
– Avoid doses higher than 400 IU
• Vitamin K
– Buy a supplement with K
– Not all supplements contain vitamin K
– The AI is 120 mcg, but DV is only 80 mcg
Vitamin/mineral supplements
• B vitamins
– Buy a supplement that contains 100 percent of thiamin, riboflavin, niacin, folic acid, B6 and B12.
– You can ignore biotin and pantothenic acid
– Senior citizens should buy a supplement with 25 mcg
• Vitamin C
– Buy a supplement with 100-200 percent of the DV
– RDA is 90 and 75 mg, but DV is only 60 mg
Vitamin/mineral supplements
• Calcium
– Buy a supplement with calcium if you are female or elderly and do not obtain adequate amounts in the diet
– Most supplements contain 200-300 mg
• Iron, copper, zinc
– Buy a supplement limited in these minerals, with no more than 100 percent of the RDA for each
– Iron DV is 18 mg, but male and postmenopausal female RDA is only 8 mg
Vitamin/mineral supplements
• Magnesium and phosphorus
– Buy a supplement containing no more than 100 mg of magnesium and limited in phosphorus
• Chromium and selenium
– Buy a supplement containing 100 percent of the AI for chromium and RDA for selenium
Vitamin and mineral supplementation
• Think food first!
• Foods contain numerous phytonutrients in addition to vitamins and minerals