Dialing in your nutrition plan isn’t easy, but the payoff is immense. But what if you’re overlooking something essential–like protein absorption? While it may sound simple, the way your body absorbs and uses protein is complex and fascinating. And protein absorption exact calories per gram of protein big implications for the way you structure your approach to nutrition.
In this article, you’ll learn what happens when you eat protein, how much protein you can absorb in a single meal or throughout the day, myths and facts, and practical takeaways about protein absorption. How Long Does Protein Take to Absorb? How Much Protein Can You Absorb Per Meal? How Much Protein Can You Absorb Per Day? The Science Behind Protein Absorption Although most people take the digestion and absorption of protein for granted, the process is far from simple. As soon as you start to drink a protein shake or chow down on a juicy steak, here’s what occurs.
Chewing and Digestion In your mouth, chewing breaks down food mechanically. And as you chew, the saliva in your mouth begins the process of protein digestion. Saliva contains proteolytic enzymes that help break whole proteins down into smaller parts. After you swallow, gastric fluids in your stomach further break down protein with a combination of hydrochloric acid and enzymes called proteases.
Next, the protein you ate reaches your small intestine. That’s also when your pancreas releases enzymes to break proteins down into shorter chains of protein and individual amino acids. And in the first part of the small intestine, your body also neutralizes the acidity of the protein, which is a necessary step for absorption. And as the protein you ate moves through your small intestine, extra enzymes from your intestinal cells continue to break proteins down. As the recently-shortened proteins and amino acids make their way through your small intestine, tiny hair-like structures called microvilli help your body absorb the protein meal into your intestinal bloodstream.
And when your liver uses amino acids for fuel, it creates ammonia as a byproduct. Because ammonia is toxic, your liver converts it to urea as a non-toxic way to eliminate excess nitrogen from your body. After that, your body transports the newly-created urea to your kidneys, which eventually discharge it as urine. Amino Acids and Protein Synthesis Your liver also controls the blood levels of amino acids for your entire body.
When your liver releases amino acids into circulation, your body can use them for protein synthesis, which is the process of building new proteins. And protein synthesis is an essential step in cell division, tissue repair, and building new muscle. Not only that, but your body can also recycle those same proteins and amino acids later on, even if you don’t supply it with new protein. The name for this process is protein turnover. Finally, your body also stores small amounts of amino acids inside and outside of cells. While researchers still aren’t entirely sure of the role of intracellular and extracellular amino acids, these stores appear to be vital for building and maintaining lean muscle.
Now that you’ve had a crash course in protein digestion, absorption, oxidation, and synthesis, we’re going to take a closer look at some vital protein absorption questions! The amount of time a protein meal takes to digest and absorb–in other words, how long it takes before your body can use it to build muscle–depends on several factors. And as we just covered, the gut absorption of proteins takes place after salivary, stomach, and pancreatic enzymes break them down into smaller components. First of all, protein must also pass from your stomach to your small intestine before your body can absorb it. And the type of protein you’ve eaten determines how long it sits in your stomach. For example, whey protein leaves your stomach about 4 times faster than casein protein. One study of lean, healthy young men found a gastric emptying rate of approximately 45 grams per hour after drinking whey protein.