Introduction to Sports Nutrition

Original Editor - Wanda van Niekerk

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

Basics of Nutrition[edit | edit source]

Macronutrients[edit | edit source]

Macronutrients provide calories or energy to the body.[1] 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[1]:

Table 1. Summary of macronutrients and their function
Carbohydrates Proteins Fats
  • Body's main fuel source[2]
  • Broken down into blood glucose
    • Red blood cells and the brain only use glucose for energy[3]
  • Types: sugars, starch, fibre[4]
  • Chemical foundation for all cells, antibodies, enzymes and hormones[5]
  • Amino acids are the building blocks of proteins[5]
  • Promotes wound healing[6]
    • 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[7]
  • An essential nutrient, necessary for the normal functioning of the body
  • Concentrated form of energy[8]
  • Help maintain body temperature and insulation of body organs[9]
  • Necessary for healthy skin and normal nerve function[10]
  • Carry the fat-soluble vitamins A, D, E, and K[11]

Micronutrients[edit | edit source]

Micronutrients are essential, but we need these in smaller amounts.[12] Micronutrients are necessary for cell growth and function. The human body cannot produce micronutrients, so they must be consumed.[12]

Table 2. Micronutrients in nutrition
Vitamins Minerals and their function
  • Fat-soluble - absorbed through intestines with fat (Vitamins A, D, E, K)[12]
  • Water soluble - dissolve in water (Vitamins B complex and C)[12]
  • Fluid and electrolyte balance (sodium, potassium)[13]
  • Bone health (calcium, magnesium)[13]
  • Oxygenation of blood (iron)[13]

Water[edit | edit source]

  • Water is best for hydration, but any calorie-free, non-caffeinated, non-alcoholic fluid can work
    • Caffeine and alcohol function as diuretics[14]

Food Groups[edit | edit source]

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[edit | edit source]

Energy Balance and Exercise[edit | edit source]

Some considerations with energy balance and exercise include[15]:

  • 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[15]:
    • daily living
    • their sport
    • building and repairing muscle tissue
  • Energy balance = Ein = Eout
    • Ein = energy consumed
    • Eout = 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.[15]
  • Factors that influence energy balance can be[15]:
    • internal
    • external
      • environmental
      • social
      • behavioural
Table 4. Influencing factors on energy intake and expenditure[15]
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[edit | edit source]

  • Increased risk of stress fractures[16]
  • Decreased athletic performance[17]
  • Slower phospocreatine recovery rates[18]
  • 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.[18]
  • Increased risk of injury[19]
  • Changes (decrease) in metabolic rate[20]
  • Breakdown of lean tissue[21]

How Many Calories Do Athletes Need?[edit | edit source]

  • TEE = REE x AL x TAE[18]
    • 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)[18]

Carbohydrate Intake and Needs for Athletes[edit | edit source]

Carbohydrates for athletes:

  • Provide energy[22]
  • They contribute:
    • dietary fibre
    • Vitamins, for example, vitamin B complex
    • Antioxidants in fruits and vegetables

Considerations when discussing carbohydrates with athletes[18]:

  • 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[edit | edit source]

  • Carbohydrate intake ranges from 3 to 10 g/kg BW/day (it may reach 12g/kg BW/day for extreme and prolonged activities)[23] - BW = body weight
  • Intake ranges are dependent on[23]:
    • 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[23]
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 g hours/day moderate to high-intensity exercise) 8 - 12 g/kg of athlete's BW/day

Timing and Glycemic Index of Carbohydrates[edit | edit source]

  • 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[edit | edit source]

  • Healthy diets do include fat
  • Fat provides energy[23]
  • Fat is an essential component of cell membranes
  • Fat facilitates the absorption of fat-soluble vitamins[11]
  • Fat aids in recovery
  • Fat helps[23]:
    • nervous system repair
    • cognitive function
    • decrease body inflammation
  • Considerations with fat intake[18]:
    • omega 6: omega 3 ratio
    • essential fatty acids
    • fish oil fats (omega-3s)
    • avoid trans fats

Amount of Fat Required[edit | edit source]

  • Fat intake should not be less than 20% of an athlete's daily caloric intake[23]
  • Typically between 20% to 35% of total energy intake is acceptable[23]
  • Recommended: 0.5 to 1.0 g/kg of athlete's BW/day[23]

Protein Intake and Needs for Athletes[edit | edit source]

  • 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[23]
    • 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:[23]
    • 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[edit | edit source]

  • Must have protein with every meal to help with muscle recovery and muscle protein synthesis[23]
  • Regular spacing of intakes of modest amounts of protein after exercise and throughout the day is recommended[23]

Water[edit | edit source]

  • Euhydrated = when an individual has normal body water content[24]
  • Hypohydrated = when an individual has lower than normal body water content[24]

Hydration Goals for Athletes[edit | edit source]

  • Begin exercise in a euhydrated state[25]
  • Prevent excessive hypohydration during exercise[25]
  • Replace fluid losses following exercise prior to the next training session/exercise bout[25]
  • Avoid exercise associated hyponatremia[26]

Fluid needs for athletes are individual and depend on factors such as[25]:

  • 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.[27]

American College of Sports Medicine (ACSM) Current Recommendations on Hydration[23]:

  • 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[edit | edit source]

Athletes can apply different strategies for recovery after exercise. The amount, consumption and timing of nutritional strategies differ according to factors such as[28]:

  • 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[28]:

  • 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[edit | edit source]

References[edit | edit source]

  1. ↑ 1.0 1.1 Costa-Pinto R, Gantner D. Macronutrients, minerals, vitamins and energy. Anaesthesia & Intensive Care Medicine. 2020 Mar 1;21(3):157-61.
  2. ↑ Slavin J, Carlson J. Carbohydrates. Advances in nutrition. 2014 Nov;5(6):760.
  3. ↑ Nimgampalle M, Chakravarthy H, Devanathan V. Glucose metabolism in the brain: An update. InRecent Developments in Applied Microbiology and Biochemistry 2021 Jan 1 (pp. 77-88). Academic Press.
  4. ↑ Blaak EE, Riccardi G, Cho L. Carbohydrates: Separating fact from fiction. Atherosclerosis. 2021 Jul 1;328:114-23.
  5. ↑ 5.0 5.1 Whitford D. Proteins: structure and function. John Wiley & Sons; 2013 Apr 25.
  6. ↑ Roefs MT, Sluijter JP, Vader P. Extracellular vesicle-associated proteins in tissue repair. Trends in cell biology. 2020 Dec 1;30(12):990-1013.
  7. ↑ Bellelli A, Tame JR. Hemoglobin allostery and pharmacology. Molecular Aspects of Medicine. 2022 Apr 1;84:101037.
  8. ↑ Muscella A, Stefàno E, Lunetti P, Capobianco L, Marsigliante S. The regulation of fat metabolism during aerobic exercise. Biomolecules. 2020 Dec 21;10(12):1699.
  9. ↑ Mohajan D, Mohajan HK. A Study on Body Fat Percentage for Physical Fitness and Prevention of Obesity: A Two Compartment Model. Journal of Innovations in Medical Research. 2023 Apr 21;2(4):1-0.
  10. ↑ Yildiran H, Macit MS, Özata Uyar G. New approach to peripheral nerve injury: nutritional therapy. Nutritional neuroscience. 2020 Oct 2;23(10):744-55.
  11. ↑ 11.0 11.1 Meijaard E, Abrams JF, Slavin JL, Sheil D. Dietary fats, human nutrition and the environment: Balance and sustainability. Frontiers in Nutrition. 2022 Apr 25;9:878644.
  12. ↑ 12.0 12.1 12.2 12.3 Beck KL, von Hurst PR, O'Brien WJ, Badenhorst CE. Micronutrients and athletic performance: A review. Food and Chemical Toxicology. 2021 Dec 1;158:112618.
  13. ↑ 13.0 13.1 13.2 Godswill AG, Somtochukwu IV, Ikechukwu AO, Kate EC. Health benefits of micronutrients (vitamins and minerals) and their associated deficiency diseases: A systematic review. International Journal of Food Sciences. 2020 Jan 7;3(1):1-32.
  14. ↑ Alwis US, Haddad R, Monaghan TF, Abrams P, Dmochowski R, Bower W, Wein AJ, Roggeman S, Weiss JP, Mourad S, Delanghe J. Impact of food and drinks on urine production: A systematic review. International Journal of Clinical Practice. 2020 Sep;74(9):e13539.
  15. ↑ 15.0 15.1 15.2 15.3 15.4 Manore, M. Chapter 5: Energy Requirements and Measurement of Energy Expenditure. In Burke, L, Deakin, V, Minehan M. Clinical Sports Nutrition. 6th Edition. Sydney. McGraw Hill. 2021
  16. ↑ Abbott A, Bird ML, Wild E, Brown SM, Stewart G, Mulcahey MK. Part I: epidemiology and risk factors for stress fractures in female athletes. The Physician and Sportsmedicine. 2020 Jan 2;48(1):17-24.
  17. ↑ Rupasinghe WA, Perera TS, Silva KD, Samita S, Wickramaratne MN. Nutritional intake of sport undergraduates in Sabaragamuwa University of Sri Lanka. BMC nutrition. 2023 Jan 2;9(1):2.
  18. ↑ 18.0 18.1 18.2 18.3 18.4 18.5 Mancini, L. Sports Nutrition. National Fellow Online Lecture Series. Available from https://www.youtube.com/watch?v=SGM1uLNATA8. (last accessed 06 July 2023)
  19. ↑ Logue DM, Madigan SM, Melin A, Delahunt E, Heinen M, Donnell SJ, Corish CA. Low energy availability in athletes 2020: an updated narrative review of prevalence, risk, within-day energy balance, knowledge, and impact on sports performance. Nutrients. 2020 Mar 20;12(3):835.
  20. ↑ Siedler MR, De Souza MJ, Albracht-Schulte K, Sekiguchi Y, Tinsley GM. The Influence of Energy Balance and Availability on Resting Metabolic Rate: Implications for Assessment and Future Research Directions. Sports Medicine. 2023 May 22:1-20.
  21. ↑ Benardot D. Nutritional concerns for the artistic athlete. Physical Medicine and Rehabilitation Clinics. 2021 Feb 1;32(1):51-64.
  22. ↑ Moore DR, Sygo J, Morton JP. Fuelling the female athlete: Carbohydrate and protein recommendations. European Journal of Sport Science. 2022 May 4;22(5):684-96.
  23. ↑ 23.00 23.01 23.02 23.03 23.04 23.05 23.06 23.07 23.08 23.09 23.10 23.11 23.12 23.13 Thomas DT, Erdman KA, Burke LM. Nutrition and athletic performance. Med Sci Sports Exerc. 2016 Mar;48(3):543-68.
  24. ↑ 24.0 24.1 Barley OR, Chapman DW, Abbiss CR. Reviewing the current methods of assessing hydration in athletes. Journal of the International Society of Sports Nutrition. 2020 Dec;17:1-3.
  25. ↑ 25.0 25.1 25.2 25.3 Belval LN, Hosokawa Y, Casa DJ, Adams WM, Armstrong LE, Baker LB, Burke L, Cheuvront S, Chiampas G, González-Alonso J, Huggins RA. Practical hydration solutions for sports. Nutrients. 2019 Jul 9;11(7):1550.
  26. ↑ Seal AD, Kavouras SA. A review of risk factors and prevention strategies for exercise-associated hyponatremia. Autonomic Neuroscience. 2022 Mar 1;238:102930.
  27. ↑ Carlton A, Orr RM. The effects of fluid loss on physical performance: A critical review. Journal of Sport and Health Science. 2015 Dec 1;4(4):357-63.
  28. ↑ 28.0 28.1 Bonilla DA, Pérez-Idárraga A, Odriozola-Martínez A, Kreider RB. The 4R’s framework of nutritional strategies for post-exercise recovery: A review with emphasis on new generation of carbohydrates. International journal of environmental research and public health. 2021 Jan;18(1):103.
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