How the Body Handles Protein
The problem with most absorption thresholds is there are many different numbers floating around, but the problem is a range of different factors not the least of which is your own genetics, your own lifestyle, and your own body composition, these factors will all dramatically influence your protein metabolism.
People have been saying for years that consuming large amounts of different types of protein 2 to 3 times a day will only result in deficiencies and result in farther "protein loss". When protein digestion starts when it gets absorbed into your stomach and is able to use the stomach acid and enzymes to breakdown the protein into building blocks called amino acids.
These molecules are then transported directly into your bloodstream by cells that line your small intestine, they are then delivered into the various parts circulating the body. The problem is, your small intestine has only so many transporter-cells available, which limits the amount of amino acids that can be infused into your blood every hour.
This is your maximum "protein absorption" dictation how quickly your small intestine is able to absorb amino-acids into your blood stream. This maximum protein absorbed happens at different types of speeds for the different types of protein available.
One review reflected that whey powder records 8 to 10 grams absorbed protein per hour, casein has 6.1 g/hr, soy has 3.9 g/hr, and a cooked egg will be 2.9 g/hr. It should be noted that because there are some difficulties in measuring protein absorption, these reports lend some insight nonetheless.
Certain proteins are found to absorb a lot slower than other proteins that are processed relatively quickly. It should also be noted that food substances will not move uniformly throughout your digestive tract, they also don't necessarily leave certain sections of your digestion in the same order that they first arrived in.
For example, when protein in your stomach gets stimulated the production of a hormone which is able to delay your "gastric emptying" (emptying food you're your stomach) gets activated.
Your body "buys the time" and slows down your intestinal contractions which is able to help your food to quickly move through your small intestines, where all your important nutrients get absorbed. Your carbohydrates and fats will move through your small-intestines and be then be fully absorbed while your protein is still getting worked on.
Your body is then able to regulate your rate that protein moves through your small intestines, ensuring that it will absorb all available amino acids. A study was done in France by the National Human Nutrition Research Center and they clearly showed that when testing 16 young women, all eating 79% of their protein in one meal with 54 grams of protein over 14 days.
Researchers found clearly no difference between those groups of women who had protein once a day or 4 meals a day, it did speed up protein metabolism. Another study done specifically on eating protein only in a 4-hour window, followed by 20 hours fasting after the protein. The study showed that fasting didn't did not impact the muscle preservation.