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Protein Intake and Muscle Protein Synthesis

The usefulness and the effect of dietary supplementation, especially in concern of protein supplements, is a highly discussed topic. I would like to try to give you an overview over the current knowledge available about exercise and nutrition and its effect on muscle growth. As this is my first article in my career as a blogger, I hope you won’t get to hard on me. It is meant to be a small introduction into protein intake in this very interesting field of how our nutrition effects training results and to show that it does matter what you eat. Just anything isn’t good enough.

Fact is, that our muscle tissue is built of proteins. Every time you have a training bout, either resistance training or endurance training, those proteins are working and are getting used up and damaged. As a response, your body performs two essential tasks in your recovery phase.

The Two Major Tasks Your Body Deals with in the Recovery Phase

The first one is muscle protein breakdown (MPB). Your organism is breaking down damaged proteins, so they might be used for rebuilding new muscular tissue or used elsewhere. The second task is muscle protein synthesis (MPS), which includes the repairing and rebuilding mechanism of new muscle. Those two, MPB and MPS, are usually balanced. If this so called net muscle protein balance (NPB) is disrupted, the consequences are a reduction or a growth in muscle mass. In that concern it is important to know, that every time you perform resistance training the MPB rate is elevated for about 24 hours, whereas the MPS rate is heightened for 24 to 48 hours. To achieve the best training effects, it now is all about the recovery period and what kind of nutrients you provide for your body in this window of heightened muscle protein synthesis.

Recommended Daily Protein Intake and the Definition of “Athlete”

In general, the recommended daily intake of protein for healthy adults (19 y+) is 0.8 g per kg body weight and it fits for 98% of healthy adults. In this recommendation they considered reduced availability/digestibility and so on, but what wasn’t considered are the high training yields of athletes. When it comes to the definition of an athlete it ranges from a person who is trained or skilled in exercises, sports, or games requiring physical strength, agility, or stamina (ct. Merriam-Webster) to a person who is very good at sports or physical exercise, especially one who competes in organized events (ct. Cambridge Dictionary) and ends with a person who is proficient in sports and other forms of physical exercise (ct. Oxford Dictionary). So basically, everyone can be called an athlete who is involved in regular and intense training sessions within a certain sport. There was a study conducted in 1992 with strength trained athletes. The first group got 0.86 g of protein per kg body mass and day, the second received 1.4 g protein per kg body mass and day and the last group was provided with 2.4 g protein per kg body mass. Not surprisingly the first group suffered from a reduced whole-body protein synthesis compared with the other two groups. Interestingly there was no difference between the other two groups in concern of protein synthesis but rather the latter group oxidised the protein. This doesn’t mean anything else but that they started to use the excess in available protein to gain energy. This study result doesn’t mean, that 1.4 g protein per kg body mass a day is ideal or enough, it just clearly shows that the recommendation of 0.8 grams is not enough for this kind of athletes to keep up their training’s effects with the necessary training bouts… So, what is enough? Well, depending on your training state it might range between 1.2 and 1.7 g per kg body mass per day following the American College of Sports Medicine, for endurance and resistance trained people respectively. In another more recent study from 2009 the results showed that a single dose of 20 g of high-quality protein ingested post-exercise is ideal for an 85 kg man to obtain the maximal MPS, which equals to around 10 g of essential amino acids. Interestingly you’ll have the same effect when consuming 3 to 4 g of the amino acid Leucin, following studies already published in the 1970s.

Based on the literature it is unclear if there is an ideal moment of intake with respect to before/during/after training. If the protein intake is within 1 hour before starting and 1 hour after finishing the training, the effects on muscle metabolism have shown to be greatest. More important than the pre/post training protein intake is the protein quality and if it was combined with carbohydrates or not. Apparently, there is a synergetic effect between protein supplements and carbohydrates compared with proteins alone. Several studies treat this topic. One explanation given is that the insulin triggers muscle growth accordingly to its role as an anabolic hormone.

I must stress at this point that most of those studies are on resistance not on endurance training as well as with untrained and trained persons, mostly men.

To eventually come to an end, a study, published this year in March in the Journal of the International Society of Sports Nutrition on the amount of protein a human body can use in a single meal for muscle building, comes to the finding that an athlete should ideally consume 0.4 g protein per kg body weight a meal, 4 times a day, to reach 1.6 g per kg body mass to maximize the MPS. Intermitted fasting resulted in a too little energy and nutrient intake of the test subjects, whereas time-restricted feeding protocols seemed to have a greater effect on fat-loss while maintaining lean body mass compared with a normal diet.

Stay healthy! 😊

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