Tyler Robbins Fitness

B.Sc. Biochemistry, Certified Strength and Conditioning Specialist (CSCS), Certified CrossFit Trainer (CCFT/CF-L3), USA Weightlifting Level 1

Filtering by Tag: Protein timing

How much protein can you eat at one time?

Recently, I wrote about the often talked about "anabolic window" and how overall protein consumption is more important than timing of protein consumption.

Today, we are going to discuss a similar topic of discussion, and by that, I mean a topic that I hear all the time from individuals who may just hear something from their local "fitness expert," either at the gym or in their online fitness circle. There are a myriad of "myths" or "mistruths" surrounding how much protein you can ingest at any given time.

To discuss this and understand the process behind nutrient digestion/absorption, let's first differentiate exactly what we are discussing here as well as give a sort of TL;DR for anyone who doesn't wish to proceed any further:

  1. How much protein can someone eat in a meal?
    Well, that is dependent on the individual, but I, myself, have polished off some rather large steaks in my life!
     
  2. How much protein can we absorb at any given time?
    It turns out, our small intestines can absorb about 5-10g of protein per hour. This is a rate-limiting step (explained later) but is also dependent on what you eat along with your protein.
     
  3. How much protein can the body utilize?
    Our bodies are like construction sites. Tissues are being broken down and replaced constantly. Exercise and resistance training can exacerbate this issue, causing muscle protein synthesis (MPS) to last from 24-36 hours. MPS will actually double in rate at the 24-hour mark, post-exercise, and then slowly return to normal levels at the 36 hour mark.

    So, if you were to resistance train even just 3-4 days per week, your body would be at an elevated level of MPS for much of your time through a week. This is why it is ideal to try and consume protein at all times of the day, although as we will discover, the amount of protein per meal should not be limited. Having said that, food takes an average of 6-8 hours to pass through your small intestines, so there is plenty of time for protein to be absorbed, even at a rate of 5-10g/hour.

How our bodies digest food

Humans eat food. It is required to live. We eat foods that consist of fats, proteins, carbohydrates, as well as a wide range of micronutrients such as minerals and vitamins. We put food in our mouths, chew them up (or drink them). Food reaches our stomach, where it bathes in acid and becomes an indistinguishable ball of stuff called "chyme."

At this point (in your stomach), your body doesn't care what you ate, the stomach has one job, to break everything down into a liquify paste to push out to the intestines where it is carried along (through a process called "peristalsis"), absorbing nutrients through the intestinal walls via microvilli.

As proteins are transported through the intestines, they must be absorbed and transported by, well, transporters. The transporters are the rate-limiting step in the absorption of protein. To make a simple analogy, there are only so many taxi cabs in the city of New York. If you have 50 people waiting for a taxi, but only 10 taxi cabs, only 10 people will get a taxi right away. The other people will eventually get a taxi, it will just take longer to transport them.

The rate of uptake fluctuates between 5-10g of protein per hour depending on the source. So, if you ingest 50g of protein in a meal, only 5-10g of that protein will be absorbed within the first hour, but that doesn't mean the 40-45g of remaining protein will be disposed of as waste.

How long does protein stay in the intestines?

Well, based on what we know so far, protein is absorbed through the intestine walls through a rate-limiting step of 5-10g/hour and the transit time through the small intestine is roughly 6-8 hours. So, assuming you don't eat and then immediately poop (don't let your friend spike your chocolate milk with laxative), then your food will take several hours to progress through your digestive system, absorbing as many nutrients as possible along the way.

Although it is not an ideal way to calculate the absorption rate, we can get a general range of how much protein the body can absorb from a single meal. We know that our bodies absorb 5-10g of protein per hour, and we know that food takes 6-8 hours to travel through the small intestine. That gives us a range anywhere from 30-80g of protein absorption from one meal.

What's fascinating is that the body releases a hormone called cholecystokinin (CCK), when dietary protein is present, that actually slows down peristalsis (the movement of food through your digestive system). This allows a greater amount of digestive time for the body to absorb as much protein as it can from the ingested food (90-95% yield). (Sources: here, here, here, and here)

There are other factors that slow or quicken the transit time of food from your mouth to your toilet bowl, such as what you ate, how much you ate, how hydrated you are, etc. etc.

So how much protein can I eat in a single sitting/meal?

So now we know that the body not only self-regulates protein digestion (through CCK), but it also self-regulates protein absorption (available transports). So how much protein can someone safely eat in one meal? Well, it should be noted that no study has ever been done to observe the maximum amount of protein someone could safely eat at any one time (pfft, ethics!).

There was a study done where women (average lean mass: 90 lbs.) consumed 54g of protein either in one meal, or spread out over 4 meals, with no observable differences in protein retention. (source) You could then speculate that even more protein could be consumed in one sitting for someone of a larger size.

Summary/Final Thoughts

If you skipped a lot of the reading above, or maybe misunderstood some of the science talk, let's summarize what we know quickly and efficiently:

The food we eat is digested and broken down into smaller "parts" in our stomach so that it can be absorbed and utilized by the body via the intestines. The speed at which the food passes through the intestines is slowed by the body itself so that as many of the macro and micro nutrients can be utilized as possible. The amount of protein you eat in one meal should not be a point of concern. Your body will not take anything over 30g and expel it as waste.

Eating food is enjoyable. If you wish to spread your meals out throughout the day, go for it! If, however, you lead a busy lifestyle and only have a small amount of time (eating window) to get your calories/macronutrients in, don't sweat it. Just because you eat a big dinner with lots of protein does not mean your body is going to miss out on a lot of those valuable nutrients.

I, myself, like to eat a big dinner. I can't sleep unless I have something in my belly. For that reason alone, I like to eat lots at dinner (including lots of protein) and then snack before bed. I can sleep soundly tonight knowing that that extra protein that I eat with dinner won't go to waste...at least not all of it.

Common questions or misconceptions:

Too much protein will be filtered by the liver and excreted

Wrong. The liver does not filter protein out of your blood. The liver may convert amino acids (digested proteins) into other usable forms of energy (such as glycogen) if more protein is available than needed for tissue repair. Amino acids have 3 potential uses:

  1. Used for tissue repair.
  2. Modified (via the liver) for glycogen synthesis.
  3. Modified (via the liver) for fat (adipose) synthesis.

Unused protein will be peed out

The kidneys take in blood solutes through a network of nephron tubules and capillaries called the glomerulus. The glomerulus has a glomerular capillary filtration barrier that allows less than 150 mg/L of protein to pass through over each 24 hour span. That may sound like a lot, but both kidneys combined produce an average of only 1.5L of urine per day; that means that non-pathological kidneys will only allow ~225mg (two tenths of a gram!) of protein to pass into the urine.

Moreover, typically the only proteins that are even small enough to pass through are albumins (blood plasma proteins), which are some of the smallest blood protein solutes. Proteinuria is almost a guarantee of either glomerular damage or renal tubule defects; in other words, kidney damage.

Protein is digested and either absorbed through the intestines for use or passed on to the colon to be fermented and excreted as waste (poop). The fermentation of protein stinks, leading to either smelly stools or those lovely "protein farts."

Check out a couple great scenes. The first involving Arnold and other bodybuilders ordering their meals during the filming of "Pumping Iron." Secondly, check out Arnold visiting the Epic Meal Time crew to make his Steak and Egger sandwich.






The Great Protein Timing Debacle

"You need to consume some protein within an hour after your workout!"

"There is something called an 'anabolic window' when your body is primed for protein intake!"

"Stay away from fats and casein protein, they slow digestion. You need the fastest-digesting whey protein you can find."

Etcetera, etcetera, etcetera.

If you exercise, have either looked into supplements before, have talked to a supplement store salesperson, or even carried on a conversation with someone about health and fitness then you have probably heard one of these statements, or least something along the same lines.

Basically, what we are lead to believe is that you will lose any and all of your potential gains if you don't ingest some protein within an hour after your workout. I think this sentiment has become something that is repeated so often that it must be true!

It just makes so much sense, right? You are working hard during your workout, your muscles are burning, your muscles are pumped, you feel fatigued, it must mean that your muscle tissue is damaged and ready to start rebuilding. Unless of course you don't eat some protein within an hour following your workout, in that case, your muscles are going to....shrivel up and decay!

That's ok, because all you need to do is invest in some of that fast-digesting whey protein. Oh, and definitely don't forget your BCAAs to take prior to your workout, especially when working out in a fasted state, you wouldn't want your muscles to shrivel up during your workout. Stack on this supplement, and that supplement, and the next thing you know, you are dropping hundreds of dollars a month just so your muscles don't waste away and you can build the biggest, most badass muscles around.

I have actually already written about why I think BCAAs are more hype than not, so head on over there to read about that.

Here are the 2 main problems I have with the current reasoning behind post-workout protein consumption:

  1. The theory is that consuming protein immediately following a workout is best for muscle protein synthesis (MPS) due to micro tears or trauma caused by resistance training. In actuality, MPS takes place over a longer period of time. In fact, the net intake of protein during a day is far more important than how much or when protein is taken in following a workout.

  2. Regardless of how fast your protein digests (whey vs. casein, for example), your muscles benefit more from readily-available amino acids in your bloodstream throughout the day rather than how quickly the protein can be absorbed.

So what can we learn and summarize from not only this article, but from the topic of nutrient timing?

  • If you are working out (resistance training) during a fasted state, it is beneficial for you to consume some protein as soon as you can following your workout. If, however, you have eaten some protein during the day and are working out in the evening, for example, then you have a greater "window" of opportunity (about 6 hours) in which it is beneficial for you to consume protein.
  • Protein intake should be spread out throughout your day. A "steady drip" of amino acids in your bloodstream give your body and muscle tissues the tools required to rebuild.
  • Having said that, regardless of how quickly protein digests and/or is absorbed into the bloodstream, muscle protein synthesis is a very slow process, generally lasting for a couple of days so the "speed" at which you can get your protein into your bloodstream is of little value. Your intestines absorb close to 95% of your ingested protein and can actually 'slow' the absorption rate in order to ensure your use as much as you can from the food you ate.
  • Ingesting protein following or even prior to a workout should not hinder your results by any means, in fact, it may hold some benefits. However one should not place too much emphasis on when they consume their protein nor should they listen to the hype about how fast a protein digests and/or absorbs.
  • Glycogen depletion is still a very relevant issue, and if you are an athlete who wishes to either perform for long periods of time, multiple times in the same day, or even perform on back-to-back days, then you should consider immediate glycogen replenishment after a training session or competition to perform at your very best.