Obviously this is an extremely broad topic and there is way too much to ever cover in just one post, but I want to touch on the importance of protein consumption and why we need to consume it for optimal health. What I would like to talk about is what happens to protein during digestion and absorption. What happens when we consume too little or too much? And how much we need in order to maximize our protein consumption for optimal muscle protein synthesis.
Protein is composed of 21 amino acids, 9 of which are essential, formed in a complex globular shape that when consumed, gets broken down first in the stomach due to the high pH which causes the protein to become denatured and unfold. This is important because it allows pepsin, a protein-degrading enzyme to cleave the bonds between the amino acids into smaller proteins called peptides. Once the protein moves through to the small intestine where the environment is a more neutral pH, enzymes released from the pancreas can further facilitate the degradation into individual amino acids. The small intestine contains small villi, which are folds that increase the surface area and where the pool of amino acids becomes absorbed through facilitated diffusion and enters the bloodstream. Now, once all this protein is broken down into amino acids and enters the bloodstream, where does it go and what does it get used for? The body will then take these amino acids and distribute them via the bloodstream, which first goes through the liver and takes what it needs for its own purposes such as albumin and then releases the rest which go to various other areas of the body to build new proteins as needed. Protein is essential not only for the construction of skeletal muscle, but also blood, connective tissue and eye lens, which are composed of the highest amounts of protein in our body! Protein is also essential for forming regulatory proteins and transport proteins for various metabolic processes.
Protein requirements vary with different life stages and higher requirements are needed for infants, children, teenagers, pregnant women, elderly and of course athletes or individuals who wish to gain muscle mass. What we do know is that the total daily protein intake for the average individual to sustain their muscle mass and for proper physiologic function is around 08.g/kg of body weight and for individuals wishing in increase their muscle mass or have a higher intensity lifestyle for exercise, around 1.2g/kg-1.7g/kg of body weight is recommended. What isn’t completely known and has a lot of controversial studies is around how to maximize this protein consumption through either various meals throughout the day or 1 large amount in one meal. We also know that a healthy individual has virtually an unlimited capacity to absorb protein and amino acids, but how much of that is actually utilized for muscle mass synthesis isn’t entirely known. One study by Moore et al., found that after an intense leg-exercise, consumption of 20g of whole egg protein vs. 40g yielded no statistical difference between the two groups, suggesting that consuming 20g gave the individuals all they needed for muscle protein synthesis. This was also proved in another study that compared a group that consumed 30g of beef protein with a group that consumed 90g of beef protein where there was no evidence to show that the 90g meal enhanced the stimulation of muscle protein synthesis. These studies showed that after consuming more than 20g of protein that urea production and oxidation were increased meaning that amino acids were being used for energy rather than production of protein synthesis. Now on the other hand, there was a study conducted on intermittent fasting and consuming all 101g of protein in a 4 hour window compared with a more conventional diet with the meals spaced out between four different meals throughout the day which showed no difference between muscle mass preservation. So this just makes everything much more complicated in terms of how and when to consume your daily protein. There is also a lot to look from these studies, like the size of the individual and their individual requirements as well as long term effects.
But to kind of tie everything together and come to a sound conclusion, I think the most important message is to ensure you are consuming your proper total daily protein intake that is suitable for your size and physical activity requirements. 1g/lb of body weight is plenty of protein for the average healthy individual and depending on your own personal goals and lifestyle it is really up to you about how you choose to consume your protein throughout the day.