Journal Title (Medline/Pubmed accepted abbreviation): Br. J. Sports Med.
Page numbers: 454-456
Summary of the research article
This article summarizes the benefits, product availability, and recommended doses of protein and proline, an amino acid, as dietary supplements for enhancing sports performance. Protein
- Skeletal muscle protein turns over at a rate of about 1-2% per day. Therefore, in order to maintain (or increase) muscle, one must use diet and exercise to stimulate protein synthesis so that protein breakdown does not exceed it.
- It is recommended that athletes consume 1.2-1.7 g protein per kg body weight per day to maintain muscle mass.
- A serving of 20-25 g of protein, containing about 10 g essential amino acids, consumed post-workout has shown to maximize the rate of muscle protein synthesis. More than that does not appear to have further benefits.
- It is clear that the rate of protein synthesis has the potential to be maximal immediately after a workout, and amino acids must be in the blood to build protein. However, it is not clear if ingestion of protein before, during, or after the workout is best.
- Because muscle can be “stimulated” for at least a day after resistance training, it is recommended to consume protein frequently, about every 3-4 hrs to glean the most benefits from the workout.
- Protein that is highly digestible and that includes a ample high quality amino acids is recommended for maximal muscle protein synthesis. This includes protein from animals such as milk, eggs, and meat and soy protein. Whey protein, especially, is good due to its high amount of branched chain amino acids (BCAAs) including leucine.
- Proline is a non-essential amino acid, meaning that we can synthesize it from other compounds. In humans, it can be synthesized from ornithine and arginine or glutamine and glutamate (all other amino acids). It is also present in dairy, meat, eggs, and many plant proteins.
- In addition to building proteins, proline is important in sensing and signaling in the immune system.
- There have not been enough scientific studies done to recommend proline as a supplement to improve performance, prevent injury, or quicken recovery.
Key practice applications
Protein, in doses of about 20 g, is recommended immediately after a workout and through the rest of the 24 hour post-workout period in order to maximize the rate of muscle protein synthesis. Animal sources of protein (meat, eggs, and especially whey) and soy protein are high quality protein choices. It is debated as to whether protein before or during the workout is better than immediately after the workout, so, if it is more comfortable or feels better for you, consuming protein before or during the workout may also have equal benefit.
There have been very few studies on proline as a dietary supplement and cannot be recommended at this time.