Protein Myths Busted: Can You Only Digest 20-30 Grams of Protein at a Time?
We’ve all heard it: “Your body can only digest 20 to 30 grams of protein per meal. Anything extra goes to waste.” Sounds pretty straightforward, right? Unfortunately, like many fitness myths, this one is a little more fiction than fact.
The truth is that all protein you eat gets digested and absorbed. Your body won’t just say, “Sorry, you’ve hit your protein cap!” and ignore the rest of that delicious grilled chicken. But there’s more to this than just absorption. Let’s dive into what really happens when you chow down on more than 30 grams of protein, and why this myth probably got started in the first place.
What Actually Happens to Protein in Your Body?
First things first: your body is highly efficient when it comes to digesting and absorbing protein. When you eat a protein-rich meal, enzymes in your stomach and intestines get to work breaking down those proteins into amino acids, which then get absorbed into your bloodstream. For the average adult, the rate of amino acid absorption is about 8-10 grams per hour according to Boirie et al. (1997). So, yes, it might take a little longer for a large dose of protein to be processed, but all of it will ultimately get absorbed.
So why the confusion? This myth likely originates from studies on Muscle Protein Synthesis (MPS)—the process by which your body repairs and builds muscle tissue after a workout. For most people, eating around 20-30 grams of protein per meal is sufficient to maximize MPS, the process that helps you repair and build muscle. But here’s the twist: just because you don’t get extra muscle-building benefits from eating more protein doesn’t mean the extra protein vanishes into thin air.
The Reality: All Protein Is Absorbed, but Not All Is Used for Muscle
While protein is essential for muscle building, it’s also crucial for a ton of other bodily functions think hormone production, immune function, and even making enzymes. When you eat more than 30 grams of protein, the extra amino acids get redirected toward these other needs or stored as energy. In other words, your body puts all that protein to good use. So while you might not see extra gains from piling on more protein, the rest still contributes to your overall health.
This brings us to protein oxidation, the process where excess protein is broken down and used as energy. If you’re well fed and eating more protein than your body immediately needs, some of it will be converted into fuel. But this is only relevant in terms of maximising muscle growth; it’s not an indicator that your body has an absorption cap.
Busted: There’s No Hard Limit for Protein Absorption
While sticking to 20-30 grams of protein per meal is often ideal for muscle building, there’s no reason to worry if your meal sometimes includes more than that. It won’t be wasted it just won’t offer extra muscle-building benefits. You might see increased protein oxidation, but this is perfectly normal and doesn’t mean your body has a “protein waste line” above 30 grams.
So, if you’re craving that double chicken breast or extra scoop of protein powder, go for it! Just know that while the protein will all be absorbed, it may simply be used in different ways. In the end, all protein serves a purpose, even if it’s just keeping you full until the next meal.
The Bottom Line
This myth comes from a misunderstanding of the difference between absorption and muscle protein synthesis. Yes, 20-30 grams per meal can max out muscle protein synthesis for most people, but that doesn’t mean your body won’t make use of additional protein. So relax and enjoy your meal, your body has a plan for every bit of it.
References:
Boirie, Y., et al. (1997). "Slow and fast dietary proteins differently modulate postprandial protein accretion." Proceedings of the National Academy of Sciences, 94(26), 14930–14935.
