Protein Absorption & Timing: How much protein can your body absorb in each meal?

Every athlete or gym buff has to go through the ‘bro-science’ phase before they eventually learn to distinguish the myths from the facts. It’s almost like a coming of age passage ritual for anyone who ever steps into a gym.

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    We are pretty sure that you too have been privy to some real juicy ones.

    But what surprises us, is that some of these myths refuse to die down. They have been floating around on the internet for years. Time and again, we see rehashed versions of these being rehashed and circulated.

    Some of the most appalling ones that we’ve seen are about protein absorption and nutrient timing.

    Have you ever heard or read about the ‘anabolic window’ myth?

    The Anabolic Window is supposedly a short period of time, typically 15-45 minutes post workout, where your body is primed to absorb the nutrients you consume. Picture your muscles like a sponge dropped in a bucket of water.

    In a nutshell, it means that you have 45-minutes at best to gulp down that protein shake after you step out of the gym.

    But what happens if you do not consume the nutrients within that time frame?

    Do your muscles starve? Do you lose a couple of inches on your biceps overnight? Will you make fewer gains in the long run?

    Unfortunately, there aren’t too many discussions about this.

    That’s not all. Another myth that pops up every now and then is about the maximum amount of protein that you can absorb in one meal or sitting.

    There are tons of theories about this too. But an arbitrary number that’s loosely thrown around is 30 grams. Ever wonder what happens to the additional protein that you might consume unknowingly? Does your body spit it out? Excrete it?

    We figured that it was time to dispel these myths once and for all and shine some light on these perpetual debates.

    Nutrient Timing - The Origin

    Nutrient Timing, or consuming nutrients at specific times during the day has been a topic of research (and debate) for years. Its applications are not limited to sports performance either.

    Carbohydrate timing has been researched as a potential adjuvant to primary therapies in blood sugar management. But we’ll limit our scope of discussion to its significance in fitness and sports performance.

    One of the earliest studies on the rates of protein synthesis and its subsequent degradation was conducted in 1955 on untrained volunteers. Since then, there have been numerous studies that have tried to establish the importance of consuming macronutrients around the time of exercise (Also called The Performance Zone).

    In 1997, exercise scientists and researchers, Dr. John Ivy and Dr. Robert Portman published their findings in a book called ‘Nutrient Timing: The Future of Sports Nutrition’. This book was considered to be a landmark study in sports nutrition research back then and for many years after.  

    It can also be largely credited (held guilty?) of establishing the significance of the ‘when’ over the ‘what’ in nutrition. But to be fair to the authors, the research that was available at their disposal at that time was somewhat limited and a little flawed. We’ll talk about this in a bit.

    However, with the book, the idea of the ‘performance zone’ and consuming macronutrients around it, was born and it has stuck around since.

    The Generally accepted theories surrounding Nutrient Timing

    There are three primary theories that you might hear or read while researching nutrient timing. Here’s debunking all three with some facts.

    Myth #1 – The Post Workout Meal aka ‘The Anabolic Window’ 

    The Post Workout meal is also sometimes called ‘The Most Important meal of the day’ if you are an athlete or a fitness buff. The theory is that any resistance exercise or anaerobic exercise will deplete your stored glycogen stores, which is true. Your Muscle protein synthesis is increased for a brief period, which again, is true. Consuming a fast-digesting carbohydrate such as glucose and a certain amount of protein within 45-minutes, replenishes the depleted glycogen stores and prevents a negative protein balance. This will stimulate muscle repair and renewal. In other words, the efficiency of the consumed nutrients is enhanced somewhat.

    Fact – Most studies that supported nutrient timing were short term ones that lasted a few weeks or months. Further studies revealed that the ‘Anabolic Window’ might in fact extend for up to 46-hours. Also, nutrient timing makes little difference to your skeletal muscle tissue and lipolysis in the long run. Sure, there might be short term benefits to consuming a high protein meal post workout, as pointed out by this 2006 study & this one. But it might be limited to that. Short term. It means that can stop getting hung up over consuming your macros within a stipulated time frame. Be it 15-minutes or 45-minutes. Just don’t sweat over it. There’s ample time to feed your body. What’s more important is your overall protein intake in a day.

    Myth #2 – Eat 6-Meals a day to lose weight

    It’s hard to find the origin of the 6-meals a day theory. But it’s been around for a fair bit of time and has been supported by a number of studies. The proponents claimed that by eating 6 short meals at regular intervals, you increase energy expenditure. This leads to a faster metabolism and subsequently, weight loss.

    Fact – There have been at least 8 studies after the Meta Analysis that’s posted above, that have concluded that there’s no difference in energy expenditure and fat oxidation regardless of the number of meals you eat in day. In fact, there’s more recent research that reveals that eating two meals a day might be a healthier option for patients with Type-II diabetes. So, it’s back to the tried and tested, ‘Calories in vs. Calories out’ if you are looking for an improvement in body composition.

    Myth #3 – Eating macronutrients at specific times

    Macronutrient timing at specific times of the day, to achieve a particular fitness goal is the third, most widely supported theory. It was believed for the longest time that carbohydrates were a no-no post lunch if you were looking to maintain a slim waistline. Most calories and carbs were to be consumed in the first two meals of the day. Then came the newer studies that supported the intake of carbohydrates and calories at dinner time, for improved metabolic stability, and body composition.

    Fact – These theories are contradictory, with no clear consensus as to which one’s better than the other.  The fact may lie somewhere in the middle. Is it better to consume most of your calories at breakfast? Sure. If that’s what’s working for you, do it. But if you feel that your energy levels wane by the end of the day, and you exercise during the evening, you might want to consider rethinking that. There’s no one-size-fits-all in nutrition.

    Protein Absorption – The science behind it

    Let’s talk about the second most popular fitness myth, protein absorption.

    Athlete, bodybuilder, fitness buff, the average Joe, no matter what best describes you, you need protein. It’s simple. Protein builds muscle. It is also associated with numerous other biological functions, which are beyond the scope of this article.

    But what happens exactly when you bite into that juicy ribeye, or gulp down that sludgy goop post workout?

    How exactly does protein get absorbed into your body and how does it go about enhancing muscle renewal and repair?

    The protein you ingest is broken down in several stages before it is made available to fulfill the plethora of biological functions it is tasked with.   

    • The first stage of digestion is mechanical breakdown, which begins in your mouth as you chew food. The process is aided by the saliva, which allows the protein source to be swallowed easily.
    • It passes the esophagus and enters the stomach where chemical breakdown Hydrochloric acid denatures the protein revealing the polypeptide bonds, which are then broken down by an enzyme called Pepsin.
    • The stomach contracts and turns this partially digested protein into a compound called Chyme, which moves into the small intestine.
    • A majority of the protein digestion occurs in the small intestine. A blend of pancreatic enzymes & some enzymes released by the small intestinal cells break the chyme down into individual types of amino acids.
    • Amino acids make their way into the blood stream. Then into the liver. A little bit of it is broken down here (oxidation) and the rest is sent to their respective destinations.

    That of course, is a very dumbed-down version of the process. But it gives you a rough idea without getting overly technical.

    How much protein can your body absorb in one meal?

    The big question. Can your body only absorb a certain amount of protein in a meal?

    No. There is no protein ceiling as it was previous believed. Here’s why.

    Most of the studies that established the ‘protein ceiling’ theory were based on just one function of protein, ‘Muscle Protein Synthesis’. But there are a bevy of other functions that protein accomplishes, which the studies fail to take into account. The other scientific reasoning that’s often presented to support the supposed ‘protein ceiling,’ is based on a 1959 study by the US Department of Agriculture. There are more supportive studies. But that’s the one that’s most often cited.

    The study shows that when you ingest more than 30 grams of protein, there seems to be a subsequent increase in urinary nitrogen levels.

    Proteins are nitrogenous molecules. The correlation was established that ingesting more than 30 grams of protein in a meal might cause the excessive protein to be excreted via the kidneys.

    The fact though, is that protein is rarely wasted. A wee bit maybe. But most of it is absorbed by the body and utilized for various purposes.

    • Protein is first broken down into amino acids which are then absorbed into the blood stream to serve a variety of biological & cellular functions. One of these functions as we all know, is muscle protein synthesis. Other than this, amino acids are also used to replace the body’s oxidized protein, making macromolecules such as DNA, synthesizing numerous hormones, enzymes, and neurotransmitters & making other compounds that are rich in Nitrogen.
    • Your body can absorb and store amino acids for future use in its amino acid pool.

    What explains the increase in urinary nitrogen then? That’s because of an increased protein breakdown. In simple terms, that’s the body flushing out the damaged and oxidized protein that’s being replaced with healthy amino acids.

    All said and done, there is no definitive answer to the exact amount of protein your body can ingest in one meal. It differs from one protein source to the other, and there are a multitude of variables that come into play.

    What you do need to know, is that it’s not limited to 30 grams. For instance, if you are consuming 1.5-2 grams of protein per kilogram of your body weight, but only eating two meals a day, you can very well divide your total protein intake between these two meals.

    Be rest assured that your body will utilize the protein eventually.

    What affects protein absorption?

    Protein absorption is dependent on a variety of factors.

    #1 – The amino acid composition – Some types of amino acids are easier to break down and subsequently get absorbed sooner.

    #2 – The amino acid chain – Proteins are broken down into long-chain amino acid peptides and short-chain peptides. As implied by the name, long-chain peptides take more time to be broken down. Short-chain peptides are broken down much sooner.

    #2 – The absorption rate in the small intestines – The small intestine can be divided into three parts. The duodenum, the jejunum, and the ileum. Each part has a different absorption rate for different protein types. For instance, the duodenum rapidly absorbs Whey Protein Concentrates, while Egg protein takes a longer time to break down and is absorbed only in the jejunum.

    The ingestion of other macronutrients will also affect the rate at which your body absorbs protein. But the takeaway is that irrespective of whether you consume a fast-absorbing protein, or a slow-digesting one, the difference to the outcome might be minimal.

    On that note, here’s a look at some of the commonly consumed protein sources, rated on a scale of 0-100 according to their absorption rates in an hour.  

    • Whey Protein Isolate – 8-10 grams
    • Casein Protein – 6-7 grams
    • Soy Isolate – 3.9 grams
    • Milk Isolate – 3.5 grams
    • Egg Protein Cooked – 2.8 grams
    • Egg Protein Raw – 1.3 grams

    Wrapping Up

    Don’t get hung up over numbers and these myths originating from redundant scientific journals. Instead, focus on the overall fitness goal that you are aiming for. Are you looking to build muscle? Aim for 1.5-2 grams of protein per kilogram of your body weight.

    Calculate your net calorific intake and start off by getting at least 25% of that from protein. Fill out the rest of the gaps and you’ll be good to go.


    About The Author

    Michael Collins

    Michael Collins

    Michael is a gym enthusiast with experience that spans more than 20 years. He started his exhilarating journey of keeping fit in his late teens, and over the years, he has immensely grown to become a resourceful gem in matters of fitness.

    He has been writing for many years, focusing on answering all the questions you may have on nutrition, muscle building and fitness. Keeping fit and staying healthy is his main passion, and this is evidenced in the articles he writes in a simple and understandable language out of intensive reading and real-life experiences.