Introduction to Sports Nutrition

Original Editor - Wanda van Niekerk

Top Contributors - Wanda van Niekerk, Jess Bell and Lucinda hampton  

Basics of Nutrition

Macronutrients

Macronutrients provide calories or energy to the body. Their function is to promote:

• cellular growth
• metabolism
• maintenance of normal bodily functions

Macronutrients are necessary in large amounts to have a full and proper effect. The three types of macronutrients are:

• carbohydrates
• proteins
• fats

Table 1. Summary of macronutrients and their function

Carbohydrates	Proteins	Fats
Body's main fuel source Broken down into blood glucose Red blood cells and the brain only use glucose for energy Types: sugars, starch, fibre	Chemical foundation for all cells, antibodies, enzymes and hormones Amino acids are the building blocks of proteins Promotes wound healing Plays a role in the development and repair of bone, muscle and skin Protein needs are increased during more stressful times and/or during illness Essential for transport of oxygen around the body	An essential nutrient, necessary for the normal functioning of the body Concentrated form of energy Help maintain body temperature and insulation of body organs Necessary for healthy skin and normal nerve function Carry the fat-soluble vitamins A, D, E, and K

Micronutrients

Micronutrients are essential, but we need these in smaller amounts. Micronutrients are necessary for cell growth and function. The human body cannot produce micronutrients, so they must be consumed.

Table 2. Micronutrients in nutrition

Vitamins	Minerals and their function
Fat-soluble - absorbed through intestines with fat (Vitamins A, D, E, K) Water soluble - dissolve in water (Vitamins B complex and C)	Fluid and electrolyte balance (sodium, potassium) Bone health (calcium, magnesium) Oxygenation of blood (iron)

Water

• Water is best for hydration, but any calorie-free, non-caffeinated, non-alcoholic fluid can work
  • Caffeine and alcohol function as diuretics

Food Groups

Table 3. The main food groups and examples

Fruits	Vegetables	Protein	Grains/starch	Dairy	Fats
Apples Strawberries Pears Bananas	Carrots Broccoli Cauliflower Butternut	Plant-based sources beans, lentils, legumes nuts, nut butter, seeds Animal-based sources poultry lean cuts of beef and pork oily fish	Grains/starch whole grains quinoa, oats, barley popcorn potatoes, corn, peas (the nutritional make-up of these foods is more similar to grains than vegetables)	Milk, yoghurt, cheese Non-dairy milk and yoghurt Kefir	Plant-based fats are better avocado, olives, nuts/seeds

MyPlate provides good examples of healthy eating. Read more here.

Sports Nutrition

Energy Balance and Exercise

Some considerations with energy balance and exercise include:

• Energy balance is important for athletes wanting to change their body mass and/or body composition in order to improve performance or make a specified weight category for their sport.
• Insufficient energy consumption in relation to expended energy will result in the effects of training being lost, as muscle and fat will be used as energy sources.
• Restricted energy intake may compromise an athlete's ability to obtain necessary nutrients.
• Athletes need to consume enough energy to cover the energy costs of:
  • daily living
  • their sport
  • building and repairing muscle tissue
• Energy balance = E_in = E_out
  • E_in = energy consumed
  • E_out = expended energy
• Energy balance is a dynamic process
  • for example, if energy intake is changed through a different diet, this can affect the physiological and biological components of energy expenditure.
• Factors that influence energy balance can be:
  • internal
    • genetic
    • epigenetic
    • metabolic
    • hormonal
    • neural
  • external
    • environmental
    • social
    • behavioural

Table 4. Influencing factors on energy intake and expenditure

Energy intake	Energy expenditure
Diet composition Timing of intake Exercise intensity Types of food	Diet composition Exercise intensity Sedentary behaviour Resting metabolic rate

Training Consequences of a Negative Energy Balance

• Increased risk of stress fractures
• Decreased athletic performance
• Slower phospocreatine recovery rates
• Athlete enters a hypometabolic catabolic state (low insulin growth factors, high cortisol-releasing hormone, high cortisol levels), which means it is more difficult for athletes to increase their lean muscle mass.
• Increased risk of injury
• Changes (decrease) in metabolic rate
• Breakdown of lean tissue

How Many Calories Do Athletes Need?

• TEE = REE x AL x TAE
  • TEE = Total energy expenditure
  • REE = Resting energy expenditure
  • AL = Active lifestyle
  • TAE = Training activity energy

• Adequate calories are a vital component of nutrition for athletes
• Quality is just as important as quantity (i.e. what you eat is just as important as how much you eat)

Carbohydrate Intake and Needs for Athletes

Carbohydrate-rich foods:

• Provide energy
• Contribute:
  • dietary fibre
  • Vitamins, for example, vitamin B complex
  • Antioxidants (in fruits and vegetables)

Considerations when discussing carbohydrates with athletes:

• quality of carbohydrates (low versus high quality)
• high versus low glycaemic index
• timing of intake
• variety of sources necessary
  • vegetables, fruits, sweet potatoes, quinoa, brown rice, wild rice, nuts, seeds

Amount of Carbohydrates Required

• Carbohydrate intake ranges from 3 to 10 g/kg BW/day (it may reach 12g/kg BW/day for extreme and prolonged activities) - BW = body weight
• Intake ranges are dependent on:
  • fuel demands of training and competition
  • balance between performance and training adaptation goals
  • total energy requirement of the athlete
  • body composition goals of the athlete

Table 5. Guidelines for Carbohydrate Intake by Athletes

Activity Level	Carbohydrate targets
Light (low-intensity exercise or skill-based training activities)	3 - 5 g/kg of athlete's BW/day
Moderate (moderate training/exercise for about an hour/day	5 - 7 g/kg of athlete's BW/day
High (endurance training programme, 1 to 3 hours/day, moderate to high-intensity exercise)	6 - 10 g/kg of athlete's BW/day
Very high (extreme training, more than 4 to 6 hours/day moderate to high-intensity exercise)	8 - 12 g/kg of athlete's BW/day

Timing and Glycemic Index of Carbohydrates

• More carbohydrates on game days and days of intense training
• Fewer carbohydrates on off days and recovery days
• Fewer carbohydrates means that the athlete eats more vegetables, leafy greens
• Lower glycaemic index carbohydrates on non-training days

Fat Intake and Needs for Athletes

• Healthy diets do include fat
• Fat provides energy
• Fat is an essential component of cell membranes
• Fat facilitates the absorption of fat-soluble vitamins
• Fat aids in recovery
  • Growth hormone
  • Testosterone levels in athletes
• Fat helps:
  • nervous system repair
  • cognitive function
  • decrease body inflammation
• Considerations with fat intake:
  • omega 6: omega 3 ratio
  • essential fatty acids
  • fish oil fats (omega-3s)
  • avoid trans fats

Amount of Fat Required

• Fat intake should not be less than 20% of an athlete's daily caloric intake
• Typically between 20% to 35% of total energy intake is acceptable
• Recommended: 0.5 to 1.0 g/kg of athlete's BW/day

Protein Intake and Needs for Athletes

• Athletes need more protein than the recommended daily allowance (RDA)
• Recommendations typically range from 1.2 to 2.0 g/kg of athlete's BW/day
  • Endurance athletes need 1.2 to 1.7 g/kg of athlete's BW/day
  • Strength training athletes need 1.6 - 2.2 g/kg of athlete's BW/day
• Vegetarians need more protein
• Benefits of protein intake at higher levels:
  • decreased blood triglyceride levels
  • improved body composition
  • enhanced weight loss
  • stabilised blood glucose levels
  • reduced risk of disease
  • improved bone health

Timing and Protein Intake

• Must have protein with every meal to help with muscle recovery and muscle protein synthesis
• Regular spacing of intakes of modest amounts of protein after exercise and throughout the day is recommended

Water

• Euhydrated = when an individual has normal body water content
• Hypohydrated = when an individual has lower than normal body water content

Hydration Goals for Athletes

• Begin exercise in a euhydrated state
• Prevent excessive hypohydration during exercise
• Replace fluid losses following exercise prior to the next training session/exercise bout
• Avoid exercise associated hyponatremia
  • Read more: Fluid Excess/Intoxication

Fluid needs for athletes are individual and depend on factors such as:

• sweat rate of the individual
• type of exercise
• exercise intensity
• environmental conditions
• duration of exercise

Dehydration has a negative impact on physical performance for activities that last more than 30 seconds, but it has no significant impact on performance for activities that last less than 15 seconds.

American College of Sports Medicine (ACSM) Current Recommendations on Hydration:

• Before exercise:
  • 5 - 10 ml/kg BW water, 2 - 4 hours before exercise

• During exercise:
  • 0.4 - 0.8 l/h during exercise
• After exercise:
  • 1.25 - 1.5 l for every kg BW lost

Post-Workout Nutrition

Athletes can apply different strategies for recovery after exercise. The amount, consumption and timing of nutritional strategies differ according to factors such as:

• the type of sport
• the time between training sessions
• the athlete's level of preparation
• the convenience of the specific nutritional strategy

The 4Rs is a useful mnemonic to consider:

• Rehydrate
  • enough water to compensate for weight loss during training (1.25 - 1.5 litres for every kg BW lost)
• Refuel
  • a combination of carbohydrates and protein is a good strategy for glycogen replenishment and tissue repair
• Repair
  • ingestion of high-quality protein can contribute to faster tissue growth and repair
• Rest
  • optimal sleeping time and good quality sleep are necessary for recovery

Resources

• Nutrition and Athletic Performance
• Ten things you need to know about sports nutrition
• The Athlete's Kitchen: Sports Nutrition Myths BUSTED!
• Australian Institute of Sport. Nutrition resources