Last week we discussed the nutritional advantages of a higher protein intake for athletes, but most athletes actually use proteins to increase their muscle mass and strength and to speed up recovery after exercise.
In a recent publication, my colleagues and I had an in-depth look at this important aspect of protein intake by athletes.
Factors that determine muscle protein synthesis
According to Coleman, a dose of 8g of the 9 essential amino acids (lysine, threonine, methionine, phenylalanine, tryptophan, leucine, isoleucine, histidine and valine) has been found to produce maximum muscle protein synthesis. In terms of food intake, this represents 20g of high-quality protein, which can be obtained from 100g of red meat, or 3 eggs, or 2 ½ cups of skim milk.
Types of Protein
Research conducted to determine which types of protein maximise muscle protein synthesis – at rest and after exercise in untrained and trained subjects – showed that 20g of high-quality standard food proteins (skim milk, beefsteak, boiled eggs and a liquid meal supplement) produced excellent results.
Read: Protein and sports performance
It was interesting to note that liquid forms of protein achieved the highest amino acid concentrations twice as fast as solid protein-rich foods. Results obtained with proteins of plant origin such as soy milk were lower than those obtained with steak, eggs and a liquid meal replacement product.
Burke and her team concluded that the pattern of amino acid delivery into the blood after eating a protein-rich food depends on its amino acid composition and how quickly it is digested. Thanks to their research we can divide protein sources into “fast” or “slow” proteins.
These researchers aim to develop a protein classification system, similar to the glycaemic index or GI, which will measure the amino acid response of athletes after eating proteins. With this kind of protein classification system it should be possible to fine-tune diets for athletes even more accurately.
Timing of intake
The timing of protein intake in relation to exercise can also have a significant influence on the efficiency of protein synthesis in the athlete’s body. Research has indicated that getting 8g of essential amino acids from the abovementioned foods as soon as possible after a training session produces the most positive results. This method of protein intake not only enhances muscle protein synthesis, but also increases the percentage of lean muscle tissue in the body, and helps with muscle repair.
How to optimise protein intake
According to Coleman, athletes can optimise their protein intake with the following strategies:
- Eat more protein than the NRV (Nutrient Reference Value), in other words, 1,2 to 1,7g of protein per kg body weight per day.
- Concentrate on eating proteins derived from animal sources, such as red meat, dairy products and eggs.
- Make sure to eat 20-25g doses of high-quality protein that contains all 9 of the essential amino acids spread throughout the day (3 x meals + 2 x snacks).
- Make sure to also consume 20 to 25g of high-quality protein as soon as possible after exercise
- Your carbohydrate intake must be adequate and comprise at least 50-60% of your energy requirement, so that you don’t need to use protein for fuel. This is particularly important for strength and power athletes, who tend to believe that only endurance athletes need carbohydrates. This is not the case, and such athletes must also ensure that their carbohydrate intake is sufficient to compensate for fuel used during training sessions. It is important to keep in mind that adequate glycogen stores are “protein-sparing” ensuring that the protein is available for muscle growth and repair.
Timing of meals can have important effects on sport performance and endurance. In general, sports nutritionists recommend the following:
a) The pre-exercise meal:
The pre-exercise meal about 1 to 4 hours before exercise should be high in carbohydrates with a moderate protein content (e.g. pasta with a moderate portion of lean mince). Athletes should determine which foods they tolerate best before exercise during trial runs and not on the day of competition.
b) Protein intake after training:
To be able to refuel, rehydrate and repair damaged muscle tissue, athletes need to combine 15 to 20 g of high-quality protein with their carbohydrate intake as soon as possible after exercise. Lean red meat is a good choice to provide the essential amino acids required by athletes to repair damaged tissues. By combining the protein with carbohydrates, insulin hormone release will be stimulated, which will in turn stimulate the athlete’s muscles to take up amino acids.
Protein before Sleep
Recently a relatively new approach to boosting muscle protein synthesis rates was proposed by a researcher called Van Loon. He suggested that athletes should eat some protein just before going to sleep to increase the adaptive response of muscles to exercise training and to further improve exercise training efficiency.
Read: To train or not to train?
Van Loon pointed out that top athletes need more than their acute stage post-exercise protein intake to maximise overnight muscle conditioning. The finding that muscle protein synthesis is low during the night, has promoted research into delivering additional protein or amino acids to serious athletes by intake of liquid protein such as a milk drink before they go to sleep.
Examples of 20g protein portions
The following of portions of standard foods provide 20g of protein. These foods can be eaten throughout the day and especially after training sessions.
Standard food portions that provide 20g of protein:
- 70g cooked lean beef or lamb*
- 90g cooked lean mince*
- 1 large pure beef hamburger patty*
- 130g meat and vegetable stew
- 65g cooked chicken, without skin*
- 2 extra large eggs*
- 1 medium fish fillet*
- 80g drained, canned tuna*
- 450 ml skim milk*
- 430 ml low-fat unsweetened yoghurt*
- 160g low-fat cottage cheese*
- 1 cup of beans
- ¾ cup hummus
- 4 tablespoons of pumpkin seeds
- 4 cups of cooked rice or pasta
- 1 ¼ cup muesli with fruit and nuts
* High-quality protein providing all 9 essential amino acids
Keep in mind that sportsmen and women require a balanced, varied diet which includes a mixture of protein sources throughout the day and foods from the other food groups, such as carbohydrates and healthy fats.
Research is constantly discovering new things about the best possible diets for sportsmen and women and it is a good idea to keep up to date at all times so that you, as a competitive athlete, can maintain your edge.
Red meat for athletes – part I
Protein facts for vegetarians
- Beelen M et al ( 2010) Nutritional strategies to promote postexercise recovery. International Journal of Sport Nutrition & Exercise Metabolism, 20:515-532.
- Burke LM et al (2012). Effect of intake of different dietary protein sources on plasma amino acid profiles at rest and after exercise. International Journal of Sport Nutrition & Exercise Metabolism, 22:452-462.
- Coleman (2012). Protein requirements for athletes. Clinical Nutrition Insight, 38(9):1-3.
- Van Heerden IV, Hall N & Schönfeldt HC (2014). Red Meat & Sport. Red Meat in Nutrition & Health. Supplementary Chapter. Published by Lamb & Mutton SA.
- New Zealand Beef & Lamb (NZB&L). (2009). Food for Sport. Good Nutrition to Aid Performance. Eds. Nikki Hart & Christel Dunshea-Mooij. Published by New Zealand Beef & Lamb. July 2009.
- Van Loon LJC (2013). Protein ingestion prior to sleep: Potential for optimizing post-exercise recovery. Sports Science Exchange, 26(117):1-5.
Image: Young athletic woman from Shutterstock
Dr Ingrid van Heerden is a registered dietician and holds a doctoral degree in Nutrition and Biochemistry. She believes that "we are what we eat" and offers free nutrition and weight loss advice via her DietDoc service on Health24.com. Read more of her articles.