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Macronutrients: Protein

On today’s #ScienceFriday we are continuing with the series on macronutrients with protein. What is protein, what does it do for the body and why is it important for sport performance & recovery? If you have any questions or comments, please do not hesitate to contact us!

Protein & its role in the body

Protein, a vital constituent of our wellbeing that performs many varied functions in the body. Protein acts as a structural component of all cells and muscle tissues as well as hormones, immune cells and enzymes. This in turn supports muscle contraction and movement, the formation of haemoglobin to carry oxygen around the body, facilitates chemical reactions during digestion, supports the regulation and expression of genetic information and helps support immune function. All of which are highly important for endurance performance.

The process by which proteins are continually being repaired and replaced is known as protein synthesis. This process requires a consistent supply of molecules known as amino acids (the ‘building blocks’ of protein). Although the body can make and recycle its own supply of various amino acids (non-essential), it still relies on adequate dietary supplies of protein to provide the amino acids that can not be made by the body (essential). 

Protein requirements

The recommended protein intake of an average person is 0.8g per kg body weight per day. Athletes have a slightly higher demand for protein depending on their training volume and intensity. A sufficient amount of protein is needed to support the body through the daily demands of training as well as to preserve lean muscle mass (1)(2)(3). Daily requirements are dependent on an athlete’s training category (see below):

→ Recreational athletes: 1g/ kg BW daily

→ Moderately to well trained endurance athletes: 1.2-1.4g/ kg BW daily

→ Top endurance athletes: 1.4-1.8g/ kg BW daily

For the best results and to ensure the correct daily intake of protein, aim to eat 1-2 sources of protein with every meal throughout the day including snacks. This in turn helps to balance blood sugar levels to help with satiety and to regulate energy levels to avoid irritability and naughty cravings. Protein is also important in weight management, as it helps to reduce total daily calorie consumption (4).

Protein for recovery

Most commonly for athletes, protein is a key factor for post-exercise recovery. When consumed shortly after a training session, the body is then supplied the necessary amino acids it needs to repair damaged muscle tissue by maximising muscle protein synthesis (MPS) (2)(3). After intense exercise, about 20-40 g of high-quality protein should be consumed to optimize MPS (3). Research shows that taking 20g of protein four times every 2-3 hours after exercise is the most effective strategy for rapid recovery (5).

Sources of protein

One should not only be concerned with the amount of protein required but also the quality. High quality protein is essential and should come from a variety of foods with a good biological value (BV) (the amount of amino acids that is absorbed from a protein source). Animal products generally have a higher BV than plants, however, a balance of both sources is essential to provide a greater variety of nutrients to the body that only plants can supply.

Plant-based protein sources need extra consideration. Most plant-based protein sources are ‘incomplete’ proteins meaning they do not provide all essential amino acids. For example, legumes (e.g. chickpeas, lentils, beans) and grains (e.g. brown rice, quinoa, bulgar wheat) are complementary, as they provide a wider range of essential amino acids when combined. The combination of both sources in a meal will significantly improve the protein content.

Protein can be found in a variety of plant-based and animal sources. Below is a list of wholesome sources of protein with good BVs:

  • Dairy (full fat plain yoghurt, quark, cheese)
  • Free-range eggs
  • Organic chicken
  • Beef (grass-fed)
  • Fish (wild salmon, cod, tuna)
  • Grains (quinoa, brown rice, buckwheat, oats)
  • Vegetables (spinach, broccoli, mushrooms)
  • Legumes (green & black lentils, butter beans, chickpeas)
  • Nuts (walnuts, almonds, hazelnuts)
  • Seeds (chia, hemp, linseed, pumpkin, sunflower)

References

  1. Tarnopolsky, M. (2004). Protein requirements for endurance athletes. Nutrition, 20(7–8), 662–668. 
  2. Cintineo, H. P., Arent, M. A., Antonio, J., & Arent, S. M. (2018). Effects of Protein Supplementation on Performance and Recovery in Resistance and Endurance Training. Frontiers in Nutrition, 5, 83.
  3. Jäger, R., Kerksick, C. M., Campbell, B. I., Cribb, P. J., Wells, S. D., Skwiat, T. M., … Antonio, J. (2017). International Society of Sports Nutrition Position Stand: protein and exercise. Journal of the International Society of Sports Nutrition14(1), 20.
  4. Russell, W. R., Baka, A., Björck, I., Delzenne, N., Gao, D., Griffiths, H. R., … Weickert, M. O. (2016). Impact of Diet Composition on Blood Glucose Regulation. Critical Reviews in Food Science and Nutrition, 56(4), 541–590. 
  5. Areta, J. L., Burke, L. M., Ross, M. L., Camera, D. M., West, D. W. D., Broad, E. M., … Coffey, V. G. (2013). Timing and distribution of protein ingestion during prolonged recovery from resistance exercise alters myofibrillar protein synthesis. The Journal of Physiology, 591(9), 2319–2331.