Getting enough protein sounds simple on paper. Just eat your target grams per day, hit your macros, job done. But ask anyone who’s tried to boost their intake for training or fat loss and you’ll hear a different story. It’s not just about eating more chicken or shaking up another scoop of whey. It’s about what your body can actually break down and absorb. And that’s a bit trickier.
Protein digestion is a process. For people who train regularly, the demands on that process can be high. Recovery, muscle repair, growth, even appetite regulation, all of it hinges on amino acids getting to where they need to go. And if digestion is sluggish or impaired, you’re not getting the full return on the calories you’re investing. That’s where understanding protein digestion becomes more than just a gut issue, it’s a training one too.
This is exactly the kind of topic we explore in our nutrition coaching courses, helping fitness professionals bridge the gap between what’s eaten and what’s actually utilised by the body.
Protein Needs are More Than a Number
The science is clear, protein supports muscle repair, stimulates growth and plays a central role in metabolic health. People who train intensely may need anywhere from 1.4 to 2.0 grams of protein per kilogram of bodyweight per day. In some cases, such as during a fat loss phase, that number can climb even higher to help preserve lean mass. Athletes, older adults and anyone recovering from illness or injury also tend to need more.
But hitting that number isn’t always easy. Large servings of meat or dairy can be heavy, and protein shakes although convenient, can sometimes cause bloating or digestive discomfort. For some, appetite can even be the limiting factor. The catch is, if you can’t digest and absorb the protein properly, eating more doesn’t solve the problem. You just feel worse.
It’s why our nutrition courses also emphasise the importance of digestion and absorption, not just intake, when designing plans for real-world clients.
What Happens After You Eat Protein?
Once you eat protein, digestion begins in the stomach with the help of acid and an enzyme called pepsin. This process breaks down long protein chains into smaller peptides. From there, it moves into the small intestine, where more enzymes like trypsin and chymotrypsin take over. These cut those peptides into individual amino acids that are then absorbed into the bloodstream.
In an ideal world, this system works like clockwork. But plenty of things can slow it down or throw it off. This includes things like low stomach acid, poor enzyme output, inflammation, medications or age-related decline in digestive function. When that happens, not only do you absorb fewer amino acids, but you might also feel uncomfortable after eating, which can lead to reduced intake at the next meal.
This matters more than it sounds. The rise in blood amino acid levels after a meal, called postprandial aminoacidemia, is what drives processes like muscle protein synthesis. If digestion is inefficient, you may not reach the amino acid threshold needed to trigger those processes, even if you’re eating what looks like “enough”.
Can Enzymes Improve Protein Digestion?
A 2025 study led by Huang et al. looked at exactly this issue. Researchers tested the effect of a microbial enzyme blend (P3 HYDROLYZER®) taken alongside whey protein to see if it improved amino acid absorption and affected appetite. The study involved 24 healthy young adults who, across two visits, consumed 25 grams of whey protein with either the enzyme blend or a placebo.
The results showed that those who took the enzyme blend experienced a 14% greater increase in essential amino acids (EAA) and a 15% greater increase in branched-chain amino acids (BCAA) in the first 60 minutes after eating. That’s significant, especially for those looking to support recovery or muscle retention in a time-sensitive way, like after training or during intermittent fasting.
Interestingly, the enzyme blend didn’t change overall amino acid levels over the full 240-minute window. But the early spike could still be valuable. This “front-loaded” availability may support faster muscle protein synthesis or satiety signalling.
When we consider satiety, participants who consumed the enzyme blend reported feeling fuller and more satisfied in the hours after their meal. They also had lower ghrelin levels, that’s the hormone that stimulates hunger, compared to the placebo group. While total calorie intake at the next meal didn’t differ, the immediate post-meal sensations were improved. This could have practical value for clients trying to manage appetite without overeating, especially during fat loss phases.
What This Means for Our Clients
From a coaching perspective, this study highlights a few important ideas. First, digestion can be a bottleneck. You can prescribe the perfect protein target, but if your client struggles with digestion, they might not be getting the full benefit.
Second, there’s potential value in digestive enzymes, especially for clients who experience bloating or discomfort with high-protein diets, or for older adults who might not digest protein as efficiently. While whey protein is already considered a fast and complete source, the study suggests that adding enzymes may further improve early amino acid delivery, possibly helping with recovery and appetite regulation.
Third, there’s the psychological side. If clients feel better after eating, that is less bloated and/or more satisfied, they’re more likely to stick to the plan. And consistency is half the battle.
Understanding digestion as a key part of the nutrition puzzle, especially with protein, is essential, particularly for those looking to get the most out of what they eat, not just add supplements for the sake of it. For clients who struggle with appetite, bloating or hitting their targets, enzyme support might offer a helpful nudge.
It also reinforces a broader point: Nutrition goes beyond what you eat, it’s shaped by how well your body digests and uses what you consume. And as fitness professionals, knowing how to support that process can make all the difference.
Reference
- Huang Y, Bell ZW, Alhamwi A, et al. (2025). Acute effects of oral microbial protease co-ingestion with whey protein on postprandial plasma amino acid concentrations, appetite, and satiety in healthy adults: a randomized, double-blind, placebo-controlled, crossover clinical trial. The Journal of Nutrition. Click here to review the full research article.
- Paulussen KJM, Askow AT, Deutz MT, et al. (2024). Acute microbial protease supplementation increases net postprandial plasma amino acid concentrations after pea protein ingestion in healthy adults. Journal of Nutrition, 154(5), 1549–1560. Click here to review the full research article.
- Oben J, Kothari SC, Anderson ML. (2008). An open label study to determine the effects of an oral proteolytic enzyme system on whey protein concentrate metabolism in healthy males. Journal of the International Society of Sports Nutrition, 5(1), 10.Click here to review the full research article.
Get Qualified to Coach Nutrition From the Inside Out.
If you’re interested in offering nutritional advice to clients, the Level 4 Nutrition Coach course is designed for you, with no previous fitness qualification required. It’s ideal for those who want to understand not just what people eat, but how the body processes it. In a 2025 clinical trial, researchers found that when participants consumed whey protein with a microbial enzyme blend, their essential amino acid levels increased by 14% and BCAA levels rose by 15% in just 60 minutes. This shows how digestion can directly influence nutrient availability and satiety. On this course, you’ll explore evidence-based strategies like this to help clients improve dietary outcomes, support health goals and make smarter food choices that actually work in the real world.
Nutrition Coach Course – Distance Study
