Nutrition

Overview• Proper nutrition forms foundation for physical

performance:

- Provides fuel for biological work- Chemicals for extracting & using potential

energy within fuel- Repair existing cells & synthesize new tissue

Carbohydrates

• Monosaccharides

Glucose, fructose, galactose

• Glucose:1. Becomes available as energy source for cellular metabolism

2. Forms glycogen for storage in liver & muscle 3. Converts fats to glycerol

• Disaccharides:

• Sucrose = Glucose + Fructose (e.g. cane sugar)• Lactose = Glucose + Galactose (e.g. milk sugar)• Maltose = Glucose + Glucose (e.g. beer, cereal)

• Polysaccharides:

• Complex carbohydrates (e.g. starch)

• Fibre:e.g. whole grain cereal fibres

• Exclusively in plants – gives bulk to food in intestinal tract aids digestion

scrapes gut wall, binds harmful chemicals, shortens transit time for food residues

• Western diet: Loss of natural plant fibre through processing

• Recommendations:>38g for men>25g for women

• Not all carbs are physiologically equal:

-Foods containing dietary fibre = slow digestion & minimize surges in blood sugar (glucose)

- Low fibre, processed foods = digest quickly & enter blood stream rapidly

Blood sugar surges

• Refined, processed starch & simple sugars = over production of insulin

• Fibre-rich Low GI carbs:-Lowers blood glucose & insulin response after eating- Improve blood lipid profile- Increase insulin sensitivity

Role in obesity

• Insulin resistant individuals = greater risk for weight gain if consistently eat carbs with rapid absorption rate

Excessive insulin facilitates glucose breakdown at expense of FA breakdown

Regular exercise improves insulin sensitivity

Recommended intake of carbs

• Western diet: 40-50% total calories

• Physically active: 60% (predominantly unrefined, fibre-rich grains, fruits, veg)

• Intense training: 70%

• American Sodas = 33% sugar

Contemporary approach• Tim Noakes:

Low Carb, High Fat diet (LCHF)

• <15g carbs per day in diet - Liver will produce carbs needed for energy

Role of Carbs

1. Energy Source- Maintain glycogen stores (muscle & liver)

2. Protein sparer- Preserve tissue protein (maintenance, repair, growth)

- Starvation, reduced energy/calories/carb intake affects metabolism & energy production

reduces lean muscle mass & add solute load to kidneys = forced to excrete nitrogen-containing by-products

3. Metabolic Primer- Substrate for oxidation

4. Fuel for CNS- CNS uses glucose – uninterrupted supply to nervous system

Carbs in dynamic exercise

• High intensity – glucose from liver• Glycogen – carbs used as energy source during early

stages of exercise

carbs rapidly supply ATP (compared to fats & protein)

• Increase carbs before exercise = improves endurance performance

• Carb deficient diet = rapidly depletes muscle & liver glycogen -ve for performance

Lipids (Fats & Oils)

• Most are insoluble in water

Include:i) triglycerides (fats & oils)ii) phospholipids (lipids that contain phosphorus)iii) steroidsiv) fatty acids and v) fat-soluble vitamins (vitamins A, D, E, & K)

• Triglycerides are most plentiful in body & diet• Are the body’s most highly concentrated form

of chemical energy• Have twice as much energy as Carbs• Stored in tissue called adipose• Excess Carbs, proteins, fats &oils are stored as

triglycerides in adipose tissue.• They may be saturated, monounsaturated

&polyunsaturated

Simple lipids

• Broken down by Lypolysis = Free fatty acid taken up by muscles for energy storage

Saturated Fatty Acids:• Mainly animal products: Egg yolk, dairy milk,

butter• E.g. Beef = 52% saturated

fatty acid

Unsaturated Fatty Acids:• Contain double bonds

1. Monounsaturated Fatty Acids:- 1 double bond- Peanuts, olive oils, avocados

2. Polyunsaturated Fatty Acids:- 2 or more double bonds- Sunflower oil, corn oil

• Maximum saturated FA = 10% of total daily intake (30 – 35g) for young adults

• Positive health benefits:- Omega 3 FA: Prevents blood clots, improves mental health

Recommended lipid intake

• Physically active: 34 -38% total caloric intake• Not more than 20% for inactive – reduce risk

of cancer

Role of lipids in the body

• Energy source & reserve (storage) provides 80-90% of energy required at rest

• Protection of vital organs 4%• Thermal insulation• Vitamin carrier & hunger suppressor

• 1g = 9kCal (38KJ) {Twice as much as carbs provide}

• Fats used as fuels ‘spares’ proteins = proteins can carry out NB functions

• Exercise:-Increases blood flow through adipose tissue = increases release of FFA’s for delivery to and use by muscle

-Fat contributes 50-70% of energy requirements during light – mod exercise

-Stored (intramuscular fat) play NB role during prolonged exercise

Proteins

• Composed of Amino Acids• Contain nitrogen

• Body’s structural materials (muscles, skin, hair)

• Body requires AA to produce new protein & replace damaged proteins lost in urine

• Average adult: 10 -12kg protein located in skeletal muscle

• Protein 10-15% total caloric intake

• Sources: Eggs, milk, meat, fish, poultry, beans, nuts

Protein in Sports• Sedentary & recreational athletes have same

protein requirements

• ± 1g of protein per kg of body mass

• Exercise at higher intensities = greater protein requirement (esp. when building muscle bulk)

• Type of sports which need high protein: Elite endurance athletes, weight lifters, power sports (rugby/ football).

Recommended dietary intake

• ±0.83 kg per kg body mass• Growing children: 2 – 4kg per body mass• Pregnant women: Increase intake by 20g

• Stress, disease & injury = increase protein requirements

• Inadequate protein & energy intake = lose muscle protein

• Athletes:Resistance training stimulates muscle growth

• Athletes increase food intake compensates for increased energy expenditure in training

• Body builder & power lifters = 4x RDA

Vitamins

• Micronutrients

Types:Fat soluble (A, D, E, K)Water soluble (B, C)

Fat soluble Vitamins

• Dissolve in body’s fat tissue = body does NOT need to digest them

• Consuming a “fat-free diet” = fat soluble vitamin insufficiency

• Should not be consumed in excess above RDA- e.g. high doses of vitamin A during pregnancy = birth defects

Water Soluble Vitamins

• Act as coenzymes participate directly in chemical reactions

• Dissolve in bodily fluids without being stored• Generally excess intake of water soluble

vitamins lost in urine• Insufficiencies seen after 4 weeks (if less than

50% of vitamin is obtained)• Exert influence for 8-14 hours after ingestion

Role of Vitamins

• Vitamins contain no useful energy for the body

- Act as essential links- Regulators in metabolic reactions that release

energy from food- Control tissue synthesis- Protect plasma membranes of cells

Minerals

• Make up enzymes, hormones, vitamins

• Combine with other chemicals e.g calcium in bone, iron in blood

Role of minerals

1. Provide structure in forming bone & teeth

2. Help maintain normal heart rhythm, muscle contractility, acid-base balance

3. Regulate cellular metabolism by becoming constitutes of enzymes & hormones that regulate cellular activity

Calcium

• Body’s most abundant mineral

• Combines with phosphorus to form bones & teeth

• Assists with muscle stimulation, blood clotting, transmission of nerve impulses, transportation of fluids across cell membranes

Osteoporosis

• Calcium availability significantly affects the dynamics of bone remodeling

• Generally young adults require 1300mg of calcium per day (±5 glasses of milk)

• Deficiency in calcium leads to osteoporosis (porous bone)

• Causes bone to lose mineral density (calcium mass) = becomes more porous and brittle

Exercise & Osteoporosis

• Mechanical loading slows rate of skeletal aging

• Active lifestyle increases bone density (adults & children)

• Short sessions of intense mechanical loading with dynamic exercise 3-5x week will increase load on bones = increase bone density

Iron• Iron combines with hemoglobin

in red blood cells increases bloods O2 carrying capacity

• Component of myoglobin (O2 storage in muscle)

• Insufficient iron = anemia

• Anemia: sluggish behaviour, loss of appetite, brittle nails, pale, headaches, dizziness, reduced exercise capacity

Iron & Females

• Anemia = common in physically active women & pregnant women

• Menstrual cycle 30 - 60ml blood lost (15 – 30mg of iron)

• Therefore, increase iron intake (5mg) during menstruation

Exercise-induced anemia

• Sports anemia• Reduced hemoglobin levels – approaching

anemia due to training• Intense exercise = increased demand for iron

that exceeds intake• Puts strain on iron reserves = decreased

hemoglobin synthesis & decreased function of energy systems

• Intense training theoretically increases iron demand by:

1. Small loss of iron in sweat

2. Loss of hemoglobin in urine from red blood cell destruction with increased temperature & circulation rates (+ mechanical trauma from feet pounding on ground foot strike hemolysis)

3. Gastrointestinal bleeding with distance running

Water• 40 – 70% of body mass

• Water intake should replace output• Intake: sedentary: 2.5L per day

:Active: 5 – 10L per day

• Contemporary theory: drink to thirst

• Water intake from 3 sources:1. Foods2. Liquids3. Metabolism

• Water is lost:1. Urine2. Through skin (sweat)3. Water vapour (moisten inhaled air)4. Feces

Too little water = hyponatremia Too much water = hypernatremia (water intoxication)