When it comes to protein, how much is too much?

Published: May, 2018

You’ve probably heard the claims by now: Here’s a diet that’s delicious, easy to stick with, and guaranteed to help you lose weight effortlessly. Or, perhaps it’s supposed to build muscle, protect your joints or prevent Alzheimer’s. Whatever the diet and whatever the claim, there’s a good chance that it is, indeed, too good to be true.

In recent years, high protein diets are among the most popular, whether the protein is consumed as a supplement (protein shakes for body builders!) or simply a larger than usual portion of a balanced diet (such as The Zone, Atkins or Paleo Diets).

Perhaps you’re curious about one of these diets or have already tried them – did you ever wonder whether too much protein might be a problem?

How much protein do you need?

Protein is essential for life – it’s a building block of every human cell and is involved in the vital biochemical functions of the human body. It’s particularly important in growth, development, and tissue repair. Protein is one of the three major “macronutrients” (along with carbohydrates and fat).

So, consuming enough protein is required to stave off malnutrition; it may also be important to preserve muscle mass and strength as we age. And, in recent years, some have advocated a higher protein diet to rev up metabolism to make it easier to lose excess weight, though success in this regard is highly variable.

  • The ideal amount of protein you should consume each day is a bit uncertain. Commonly quoted recommendations are 56 grams/day for men, 46 grams/day for women. You could get 46 grams/day of protein in 1 serving of low-fat greek yogurt, a 4 oz. serving of lean chicken breast and a bowl of cereal with skim milk.
  • A weight-based recommended daily allowance (RDA) of 0.8 grams per kilogram of body weight. For a 140 pound person, that comes to 51 grams of protein each day. (You can convert your body weight from pounds to kilograms by dividing by 2.2; so, 140 pounds is 64 kg; multiplying this by 0.8 equals 51). Active people – especially those who are trying to build muscle mass – may need more.
  • Based on percent of calories – for an active adult, about 10% of calories should come from protein
  • To pay more attention to the type of protein in your diet rather than the amount; for example, moderating consumption of red meat and increasing healthier protein sources, such as salmon, yogurt or beans.

But, some experts suggest that these recommendations are all wrong and that we should be consuming more protein, up to twice the standard recommendations. Still others claim that the average American diet already contains too much protein. (Read more about the thinking of experts on this subject in this summary of two “Protein Summits” in 2007 and 2013 organized “to discuss the role of protein in human health and to explore the misperception that Americans overconsume protein.” Note, these meetings were sponsored in part by animal-based food industry groups.)

Can too much protein be harmful?

The short answer is yes. As with most things in life, there can be too much of a good thing and if you eat too much protein, there may be a price to pay. Among the conditions linked to high protein diets are:

  • High cholesterol and a higher risk of cardiovascular disease
  • Increased cancer risk
  • Kidney disease and kidney stones
  • Weight gain (yes, this seems odd for a proposed weight loss strategy)
  • Constipation or diarrhea

However, keep in mind these are only associations – that is, some studies have noted these conditions among people on high protein diets; but that doesn’t mean the protein actually caused the condition. Also, some of these are not necessarily due to the protein itself but rather due to how the protein is consumed or what the protein replaces – for example, a high protein diet that contains lots of red meat and high fat dairy products might lead to higher cholesterol, and a higher risk of heart disease and colon cancer while another high protein diet rich in plant-based proteins may not carry similar risks. And one study found weight gain was more likely when protein replaced carbohydrates in the diet but not when it replaced fat.

So, when it comes to protein, how much is too much?

It’s hard to provide a specific answer since so much is still uncertain and the experts themselves don’t agree. However, for the average person (who is not an elite athlete or heavily involved in body building) it’s probably best to avoid more than 2 gm/kg; that would be about 125 grams/day for a 140 pound person. New information could change our thinking about the maximum safe amount, but until we know more about the safety, risks and benefits of high protein diets, this seems like a reasonable recommendation.

What’s a protein lover to do?

If you want to maintain a high protein diet, the details matter:

  • Find out from your doctor if you have any health conditions (such as kidney disease) that might make such a diet risky
  • Get your protein from healthy sources such as low-fat dairy products, fish, nuts and beans, lean chicken and turkey; avoid proteins sources that contain highly process carbohydrates and saturated fat
  • Spread your protein consumption across all of your meals throughout the day
  • Choose a well-balanced diet that includes lots of vegetables, fruits, and fiber; the Mediterranean diet or the DASH diet are good starting points.

Image: © Tatjana Baibakova | Dreamstime

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Is There Really a Limit to How Much Protein You Can Absorb in One Sitting?

Ever cooked up a solid pound of steak only to have someone tut tut and say, “You can only absorb 30 grams of protein at once. You’re wasting that meat.”

Don’t slide the rest of that beef into the trash. The body, believe it or not, can handle medium-sized amounts of protein—and more.

Why Do We Think There Are Limits on How Much Protein We Can Eat in One Sitting?

The whole idea started with very smart people who measured pee.

Protein is the only macronutrient that contains nitrogen, and some studies found that when you consume more than 30 grams of protein, the amount of nitrogen in test subjects’ urine increased significantly. It was concluded that this means you’re excreting the excess protein and you should stick to 30 grams per meal. (This means if you’re shooting for 150 grams per day, you need five separate doses of protein.)

It sounds nice in theory, but the thing is that this doesn’t mean the carbon is wasted.

“If you if you eat sixty grams of chicken breast, do you poop half of it out? Looking exactly like chewed chicken breast?” asks Trevor Kashey, a nutrition scientist and consultant. “No. The protein wastage thing was based off nitrogen measurements, but nitrogen doesn’t contain calories. Carbon compounds do.”

More nitrogen leaving our bodies doesn’t mean you’re peeing out your gainz with it. Protein also contains carbon, hydrogen, and oxygen, along with other elements that still get digested.

Does Eating More Frequently Increase How Much Protein Your Body Absorbs?

It gets a little trickier here, and questions like this stir up old questions of whether or not you can eat one big meal or many small meals. This is a debate that’s been raging between intermittent fasters and frequent feeders since the dawn of nutrition science, and it’s harder to answer than you might think.

Does frequent feeding stimulate greater protein synthesis? It might, but in Kashey’s words, “Protein synthesis doesn’t tell you shit.”

“It tells you genes are turned on, but just because genes are turned on doesn’t mean there is a measurable or practical difference,” he says. “That’s why the ‘anabolic window’ thing is such a pain in the ass. People tend to forget that protein synthesis is for other protein besides muscles, and it doesn’t account for protein turnover. That refers to the fact that we’re constantly losing muscle mass, so just because synthesis is elevated doesn’t mean you are netting any muscle mass. You could be losing as fast as you are gaining. That’s called turnover.”

So, it’s not as simple as eating more often—bigger meals just get digested more slowly. (And let’s not forget that going without food for a time can also have benefits for anabolic hormones, further complicating things.)

But while health-wise, you’ll be fine if you have a couple of big meals versus several smaller ones, things could be different with regards to workout performance. For a lot of people, they perform well if they have a meal of protein, carbs, and healthy fats in the hours leading up to a workout and they recover better with another, larger meal afterward.

Is Performance More Important Than Meal Timing?

Anecdotally, a lot of coaches say people who have multiple, high-protein meals throughout the day have more muscle. But that doesn’t mean much.

“Practically speaking, when the rate of muscle gain is considered, performance and adherence will trump the ‘perfect plan’ every time,” Kashey says.

Are you reaching your daily protein goal? Are you reaching your daily calories? Are you doing your workouts? And do you feel like the frequency and size of your meals is letting you perform at your best? If the answer is yes, then that’s far, far more important than how often and how much you’re eating.

This doesn’t mean it isn’t worth experimenting with larger or smaller meals. Some studies show greater muscle gain with a couple of big, high-protein meals in a short timeframe, others don’t.

We’re not trying to oversimplify things, since biochemistry is an enormously complex topic. But the best way to answer “How often should I eat protein?” really does appear to be “As often and as much as makes you feel comfortable and perform well.” So experiment and see what works for you.

Read This Next: ‘Real’ Athletes Eat Raw Eggs

This article first appeared on Barbend.

Ask The Macro Manager: How Much Protein Is Too Much?

Traditional bodybuilding dogma has always held that more protein is better. While this is true to a point, it can sometimes be more beneficial to decrease your protein intake and get those nutrients from other sources.

Too Much Protein

If you’re eating more than 30-35 percent of your daily calories from protein, that’s too much. This amount will maximize hypertrophy (muscle building) while leaving room in your diet for optimal levels of other essential nutrients.

30-35 percent of your daily calories is still a lot of protein, and essentially double the RDA, but it falls within the National Academies of Medicine’s acceptable macronutrient distribution range, so you don’t need to worry about any adverse effects.

Protein consumed above this level will start to be oxidized for energy rather than being used to create muscle mass.

Dietary Displacement

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Think about your diet as a pie chart: x percent of that pie will be made up of protein, y percent fat, and the remainder carbohydrates. Regardless of the percentages you pick, they will always add up to 100 percent. You can never eat above 100 percent, so increasing one nutrient source will always decrease your intake of another.

If you continue to drive your protein intake upward, chowing down on more dry chicken breasts, then the protein percent of your pie will get bigger and bigger. This shrinks the fat and carbohydrate pie slices, thereby reducing your intake of essential fats, fiber, fruits, vegetables, and grains—all of which play important roles in a muscle-building diet. Depending on your fitness goals, there are actually ideal ranges for each macronutrient.

What Happens to Excess Protein

We typically oversimplify protein, thinking it will always go toward growth. It actually does more than drive protein synthesis and provide amino acids for building muscle. Once those needs have been met, your body will actually break down and oxidize protein for energy.

You don’t necessarily want to be a protein oxidizer. You don’t want to train your body to break down protein (dietary or muscle) and use it for energy.

We typically oversimplify protein, thinking it will always go toward growth.

Just as switching from a high- to low-carbohydrate diet causes your body to increase the enzymes that burn fat as fuel, eating protein far beyond your body’s ability to build muscle with it will cause increases in the enzymes that oxidize protein (both dietary and muscular) for energy.

Maximizing Protein Synthesis

Instead of offering your body excess protein to oxidize for energy, your goal should be to maximize protein synthesis by eating the proper amount of protein at the right times.

We now know that there is both a protein threshold and timing component to protein’s muscle-building ability. For whatever reason, people have long assumed that you can only digest 30 grams of protein at a time. But your body can certainly digest much more than that in one sitting.

However, 30 grams may be the proper amount of protein needed to get blood amino-acid levels high enough to flip the muscle-building switch. Like a light switch, once you flip the protein threshold and initiate protein synthesis, you can’t turn it “more” on. Your body will digest protein above that level, but it will be used as fuel, not for additional muscle building.

The other component to protein synthesis is flux. Giving yourself a constant infusion of amino acids throughout the day via protein shakes, eggs, steaks, and chicken isn’t actually maximizing protein synthesis. Instead, you need a change in your blood amino-acid levels.

To reboost protein synthesis, blood amino acids need to drop and then spike. This occurs naturally when you eat 4-5 meals per day, but not if you’re drinking a protein shake at every turn. I know it seems counterintuitive, but skip the constant protein-shake sip and you’ll actually maximize synthesis.

It would seem logical that the more protein you pack away during a meal, the bigger your muscles grow. More is always better, right?

Well, your body doesn’t necessarily work that way. There’s only a certain amount of protein that your muscles can absorb in one sitting.

“Skeletal muscle protein synthesis is maximized by 25 to 35 grams of high-quality protein during a meal,” says Doug Paddon-Jones, Ph.D., a professor of nutrition and metabolism at the University of Texas Medical Branch.

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“Protein synthesis” is basically a fancy way of saying “building and repairing muscle.” Exercise creates micro-tears in your muscles. The harder you work, the more of these tears occur. Protein helps to repair these tears, which then causes your muscles to grow bigger and stronger.

If your muscles receive fewer than 25 grams of protein in a sitting, however, muscle tears brought on by exercise persist due to a lack of building materials.

But if your muscles receive more than 35 grams of protein, they have all the building materials they need and the protein goes to other parts of your body—or into the toilet.

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The magic amount of protein your muscles are capable of absorbing during a meal seems to be about 25 to 35 grams.

What does that amount look like? Here are a few examples…

  • 1 cup cottage cheese (28 grams protein)
  • 1 cup Greek yogurt plus a handful of nuts (25g)
  • A palm size portion of steak, fish and/or poultry (28g)
  • 3 whole eggs + 3 egg whites (27g)
  • 1 scoop of whey protein (25 g)

So chewing through an entire side of beef may not benefit your muscles any more than taking down a smaller portion of tenderloin.

Alexandre MOREAU

In fact, if you’re piling your plate with too much protein, you might be pushing other vital nutrients out of your diet from foods such as vegetables, fruits, healthy fats, and whole grains, all of which can help with muscle recovery and weight loss.

And you don’t have to down a huge shake or omelet after a workout. Studies on protein timing show muscles’ elevated sensitivity to protein lasts at least 24 hours.

In fact, one 2012 review study by McMaster University showed that muscle protein synthesis may continue for 24 to 48 hours post-workout.

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What matters most is your total protein intake throughout the day.

Reframe how you think about protein, especially if you’re trying to build muscle. Instead of eating 60 grams of protein during three meals a day, trying eating 25 to 35 grams of protein four or more times a day.

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Consume one of these meals within one to two hours pre- and post-workout so you cover your bases.

Additional research by Jessica Girdwain

Chris Mohr, Ph.D., R.D. Chris Mohr, PhD, RD is the co-owner of Mohr Results, Inc (MohrResults.com) a well-being consulting company

How much protein can you eat in one sitting?

Quickly and easy calculate your optimal daily intake with our protein intake calculator.

Digestion

When you consume food, it must pass through the stomach and into the intestines before it is absorbed into the body. The process of muscle contractions that push food along the esophagus and into the stomach and then through the intestines is called ‘peristalsis’. Its speed can vary.

Food ingested loses its form in the acid bath known as the stomach, and turns into an indistinguishable mass called ‘chyme’. Chyme is pushed through the intestines by peristalsis, and the outer layer gets ‘eaten’ (or taken up) by the walls of the intestine into the body. This is the process of nutrient absorption.

So basically, there may not be much difference between your breakfast and your morning snack, as the morning snack could just meet up with and fuse with the hunk of chyme that your breakfast has become. The chyme does not stay in the intestines for a set time – it varies.

Getting amino acids into the intestines

Transportation into the intestines

Dietary protein (or amino acids) that lay around in the gut will be absorbed into the intestines, and later into the body, by amino acid transporters.

There are many different transporters that take up amino acids. The most common are sodium (Na) dependent transporters that can take up neutral or charged amino acids and then there are some chloride (Cl) dependent transports as well. The general idea is that some transports are assisted by ions and are catered to different amino acids. Some transporters also exist for small di-(two) or tri-(three)peptides, which are groups of amino acids, usually by a transport known as PEPT-1. Collectively, the assortment of transporters in the intestines determines the bulk amount of amino acids that can be transported into the intestines and is the rate-limiting step.

The overall amount of absorption can be determined by measuring fecal amino acids (if not absorbed, nitrogen’s only other significant route is rectal excretion). The oro-ileal digestibility (a measure of overall protein usage) tends to be around 91-95% depending on source and assuming a reasonable acute dose (10-50g at once), with animal sources a bit higher than plant.

The rate of uptake on an hourly basis fluctuates between 5-10g per hour, depending on source.

Can I eat too much at once?

Amino acids and some peptides are able to self-regulate their time in the intestines. An example of this is the digestive hormone CCK which, in addition to regulating appetite and satiety in response to food can also slow down intestinal contractions and speed in response to protein. CCK is released when dietary protein is present, and demonstrates a way in which the body can slow down digestion in order to absorb all present protein.

Protein storage and release

Small intestines be saving my muscles?

The small intestine is where, under standard conditions, 95% or so of dietary protein is absorbed with the unabsorbed fragment going to the colon to be fermented by bacteria.

The small intestines are also an organ, and they need nutrients to survive as well. The small intestines will absorb a lot of amino acids, but may eat some to survive and proliferate. Almost half of eaten amino acids are used by the gut and related tissues, with the gut consuming more of the amino acids found normally in animal products. Specifically Glutamate, Glutamine, Branched Chain Amino Acids, Threonine, Cysteine, and Arginine.

Due to this high demand, the small intestines are able to absorb and hold onto a large amount of amino acids; waiting to release them until the body needs them, and can recycle some amino acids.

Free amino acid pool?

Due to the aforementioned ability of the small intestines to ‘hold’ onto protein, they are considered a ‘free amino acid pool’ that the body can draw amino acids from on an as-needed basis. Its not wholly an ‘out’ storage though, as the intestines may partake in some ‘recycling’ and bring up amino acids to turn into glutamine (their main fuel source).

During periods of protein deprivation, the gut may reduce its need to use amino acids as fuel though.

Learn how to select the best whey protein powder for you

Whey protein is far more complex than you’d think – supplement companies are always trying to pull a fast one over you with legal loopholes and proprietary blends.

Our Definitive Guide to Whey Protein breaks down everything you need to know about whey protein so you can buy the best whey protein for you.

I’m ready to learn and save money on protein

Putting it All Together

If we assume the final goal is health, you can consume a fair amount per sitting as the gut will tend to slow down absorption and feast happily on the amino acids. No study has looked at the ‘maximal’ amount that can be consumed though, as ‘health’ is hard to define accurately. The same notion applies to building muscle and losing fat, which want amino acids floating around in the blood (systemic circulation) rather than hopping between the intestines and liver (portal circulation). The body will tend to slow down absorption in response to how much you eat, as the presence of amino acids can self-regulate their own digestion. The body likes to adapt in response to stresses, and is pretty good at it. There isn’t a single number which is the answer here, as the body tends to try and preserve all amino acids. How effective it is at this is individual. In a study done on women, consumption of more than 54g of protein in a single meal versus across four meals resulted in no differences. As these women had on average 90 lb of lean mass, it is highly plausible that more protein could be efficiently processed. The same researchers found that a single high protein meal was actually more effective in a population of elderly women. Research done on Intermittent Fasting supports the theory that your body can cope with far more protein than most people think, with two studies showing that the consumption of an average of 80-100g of protein in 4 hours yielded no differences in lean mass That being said, since fecal losses of protein and short-chain peptides tend to smell incredibly bad one can use a ‘sniff-test’ after bowel movements to assess if protein is being lost in the feces and thus not taken up by either the intestines or the muscle.

30g of protein?

There really is no literature to indicate this number as a ‘holy grail’ of protein absorption. It may have arisen from looking at the rate of amino acid transporters, assuming 10g/hour as a standard, and applying that to the typical mini-meal approach to bodybuilder nutrition (with a meal every three hours). You can also refer to our page on how much protein you need per day to figure out the exact amount of protein you should be eating (in one or multiple sittings). Quickly and easy calculate your optimal daily intake with our protein intake calculator.

How Much Protein Can You Absorb In One Sitting?

Is there a maximum amount of protein you can eat in one meal before it gets “wasted”?

There are a whole lot of myths in the fitness industry, and some of the most pervasive myths revolve around protein intake – how much protein is optimal for muscle growth, which protein sources are highest in quality, how often protein should be consumed, etc.

One of these myths is the idea that your body can only consume 30 grams of protein in one sitting, and that anything beyond that level is just wasted and left unutilized.

According to this kind of old-school bodybuilder advice, you need to consume protein every 2-3 hours in order to maximize protein synthesis, and that if you DON’T eat your protein with such frequency, then your muscles will be left in a state of slow decay until you manage to salvage what’s left of them with another quick protein injection.

This is why the more obsessive types would set their alarms for 3AM every night just so that they could wake up, stumble to the kitchen in a fog, and throw down a thick, goopy protein shake in an attempt to save their protein-starved muscles from shriveling away overnight.

But is there actually any truth to this idea, that you have to consume protein every 2-3 hours to stave off muscle loss?

And where did this myth come from, anyway?

The Boire Study On Fast Vs. Slow Proteins

From what I can gather, it seems like this myth started up soon after the Boire study on protein absorption was published, titled “Slow and fast dietary proteins differently modulate postprandial protein accretion.”

The Boire study examined the speed of absorption of two different types of protein – specifically, whey and casein.

The results of the Boire study showed that 30 grams of whey protein was fully digested by the body in about 3-4 hours, whereas casein protein took over 7 hours.

The High Protein Cheat Sheet

If you want to build muscle and strength, getting enough protein is key. The High Protein Cheat Sheet is a handy reference guide that shows you which foods are highest in protein, so you can easily add more protein to your diet!

This is why whey protein has its reputation as a fast-absorbing protein, and casein as a slow-absorbing protein.

In the following chart, you can see that whey protein quickly spikes blood levels of amino acids, and then quickly returns to baseline levels within 3-4 hours. Casein, on the other hand, has a less dramatic entrance into the bloodstream, but delivers a longer-lasting, steady supply of amino acids.

It’s very important to note that under this study’s conditions, the subjects were given the protein after a morning fast and the protein was consumed by itself without any other food. If the protein had been administered with whole foods, absorption rates would have slowed down considerably.

In any case, somehow the bodybuilding community interpreted the results of this study to mean that it was necessary to consume protein every 3 hours or so to maintain protein synthesis and prevent the body from going “catabolic”, or in other words, breaking down muscle tissue.

To be honest, I’m not exactly sure how this logical jump would have occurred, because it doesn’t make much sense, but as I know very well by now, the biggest fitness myths are usually started by the stubborn guys who shout the loudest – not the guys who take their time to read and understand the research.

Based on this study, whey’s absorption rates were about 8-10 grams per hour, which is why 30 grams of whey was absorbed in 3-4 hours. But if the subjects had taken DOUBLE the protein, then it would have taken longer to absorb the whey, likely 6-8 hours.

The casein results alone show that even 30 grams of protein has the potential to be absorbed over longer periods of time – without ANY food – so I’m not really certain when the 2-3 hour panic set in, but I do believe it was from some false, knee-jerk reaction to this study.

So What’s The Truth?

The human body is smart and it’s extremely adaptable. The fact of the matter is that the body will take its time to fully digest and absorb all the nutrients in any given meal.

When you eat a meal, the food is broken down in your stomach via acids and enzymes, and then proceeds to make its way into the small intestine. The body then directly absorbs the nutrients through the walls of the small intestine into the bloodstream.

This process can take as long as it needs for all the nutrients to be fully absorbed. The body has auto-regulatory processes in place to slow down the speed of digestion and give it the time it needs to fully absorb all the nutrients.

A small meal will have a short digestion time, whereas a large meal will have a longer digestion time.

(Not rocket science here.)

Now getting back to protein, if you’re consuming a large amount of protein in a single meal, all this means is that it will take a longer time for the body to fully digest the meal and utilize all the protein.

This concept is supported by several studies.

In one study conducted on women, a group of subjects was given over 54 grams of protein in a single meal, and the other group was given the same amount of protein but spread out over 4 smaller meals. After 14 days of the experiment, the results showed NO differences between the two groups.

Taking a look at intermittent fasting studies further discredits the “2-3 hour window” nonsense.

In the study “Intermittent fasting does not affect whole-body glucose, lipid, or protein metabolism”, Soeters and colleagues compared the diets of two groups: one which was doing a 20 hour fast every other day and consuming all calories within a 4 hour window, and another following a more standard diet with multiple meals per day.

Even though the intermittent fasting group consumed all of their protein (80-100 grams) within a 4 hour window, the results of the study showed that there was no difference in the preservation of fat-free mass between the groups.

Furthermore, if we just take a look at anecdotal evidence from our Caliber Fitness online personal training clients, we see the same conclusion being played out over and over again.

Despite the fact that many of our training clients follow some sort of intermittent fasting protocol and consume upwards of 100 grams of protein in a single meal, this has never been shown to impede muscle growth results whatsoever.

Conclusion

Here’s the TL;DR version of this article:

Don’t worry about how much protein your body can absorb in a given meal, because there’s no evidence to show that there is such a maximum, and plenty of evidence to support the fact that your body can absorb whatever nutrients you give to it.

The biggest difference between large and small portions effectively comes down to how long it takes to digest the meal, and that’s it.

So you can safely file away this fear of eating too much protein in a single meal, and get back to the fundamentals of training and nutrition that actually matter to get results.

Questions or comments? Just comment in the section below!

Scientific American presents Nutrition Diva by Quick & Dirty Tips. Scientific American and Quick & Dirty Tips are both Macmillan companies.

Nutrition Diva reader Thomas writes:
“Some people claim that the body can’t absorb more than 20-30 grams of protein at a time. Others insist that your body utilizes all the protein you take in. Who is right? Is a post-workout shake with 50 grams of protein a waste?”
This idea that the body can only utilize a certain amount of protein at one sitting has become widely accepted nutrition lore. But is there any validity to the claim? It all comes down to what exactly you mean by “utilizing” protein.
This notion about protein seems to have gotten started on body-building forums – and this may be the main source of some of the confusion. Body-builders are particularly interested in protein’s ability to build and repair muscles. And there does seem to be a limit to how much protein the body can use for muscle synthesis at a given time.

> Continue reading on QuickAndDirtyTips.com

More episodes of the Nutrition Diva available on QuickAndDirtyTips.com

How Many Grams of Protein Can Your Body Absorb in One Sitting?

  • American Journal of Clinical Nutrition: Rapid Aminoacidemia Enhances Myofibrillar Protein Synthesis and Anabolic Intramuscular Signaling Responses After Resistance Exercise
  • Institute of Medicine: Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids
  • European Food Information Council: Nutrient Bioavailability — Getting the Most Out of Food
  • International Journal of Sport Nutrition and Exercise Metabolism: A Review of Issues of Dietary Protein Intake in Humans
  • American Journal of Clinical Nutrition: Ingestion of a Protein Hydrolysate Is Accompanied by an Accelerated In Vivo Digestion and Absorption Rate When Compared With Its Intact Protein
  • Journal of the International Society of Sports Nutrition: International Society of Sports Nutrition Position Stand: Protein and Exercise
  • Journal of the American Dietetic Association: Moderating the Portion Size of a Protein-Rich Meal Improves Anabolic Efficiency in Young and Elderly
  • Academy of Nutrition and Dietetics: Protein and the Athlete: How Much Do You Need?
  • Journal of Nutrition: Dietary Protein Distribution Positively Influences 24-Hour Muscle Protein Synthesis in Healthy Adults
  • American Journal of Physiology: Endocrinology and Metabolism: Amino Acid Absorption and Subsequent Muscle Protein Accretion Following Graded Intakes of Whey Protein in Elderly Men

Protein supplements: Is protein absorption the problem?

For ages the great debate over protein has been how much protein do I need? There have been many knock-down, drag-out fights over how much is enough and how much is too much.

In the blue corner: the fitness experts who recommend 1-2g/lb (2.2 to 4.4 g/kg)!

Ding! Ding!

Now I’m going to be the one who leaps into the ring unexpectedly with the folding chair.

Forget how much you’re eating. How much are you absorbing?

What if you aren’t absorbing all – or even half – of the protein you’re eating?

Whoa, now that’s a knockout idea!

Eating versus absorbing

You may be smugly thinking, “Helen, this isn’t news. Everybody know that most people have low stomach acid and can’t absorb all the protein from a steak.” But what about whey protein? You should be able to absorb that pretty easily, right? Figure you could absorb pretty close to 100% of a whey protein shake, right? You feeling lucky, protein punk?

Well, you’re wrong. We only digest a small amount of whey protein in liquid form. Are you surprised? If not, I’m not ashamed to admit that I was.

Surprise aside, the research is pretty clear. Indeed, a recent study examined how much whey protein we can absorb in one sitting. And let me just say that it looks like a lot of whey is literally going down the toilet.

Forget the spider – Little Miss Muffet has other problems

Turns out that it takes 1.5 hours for viscous liquids (e.g. a whey protein shake) to pass through the section of the gut that can actually absorb it. But that’s not the breaking news. Here’s the big story. The maximum rate that whey protein can be absorbed is about 8-10 grams per hour.

WARNING! Math ahead!

Little Miss Muffet drank a 50 gram whey protein shake. Since Miss Muffet can absorb only 10 grams every hour. How long does it take for Miss Muffet to absorb all the protein?

50 grams / 10 grams per hour = 5 hours

So, it would take 5 hours to digest all that protein. But remember, we have only 1.5 hours to get ‘er done. Therefore Miss Muffet has no chance of absorbing all of it. She’ll absorb – at most – 15 grams. And the other 35 grams? Well, they’re wasted. Unless…

Research question

As mentioned above, a recent article looked at one possible way of boosting whey protein absorption – and, by extension, amino acid delivery and muscle growth. Here’s the reference:

Oben J, Kothari SC & Anderson; ML. An open label study to determine the effects of an oral proteolytic enzyme on whey protein concentrate metabolism in healthy males JISSN 2008 5(10).

In this study the researchers asked the question: what can people do to increase whey absorption?

(Well, actually, they asked whether “digestive proteases would increase the absorption rate of WPC.” But the question above just sounds better…that’s why we translated the academese for you.)

Methods

In this study, forty-one participants volunteered to have their blood and urine analysed. They were healthy men that were lean (with BMI between 20 and 24), and relatively younger – between 19-35 years old.

These participants were given a plain vanilla flavoured whey protein concentrate powder that was 85% protein, 6% fat, 3% ash, and 6% lactose – no solublizers, emulsifiers or “fillers”. (By the way, it turns out that 50 grams of whey protein powder is actually 42.5 grams protein.)

What next?

Well, first, the researchers looked at what happens when these guys drank a 50g serving of whey protein alone (known as the control sample). And after the supplement, they tested two things: serum amino acid levels (the amount of amino acids circulating in the bloodstream) and total nitrogen excreted.

They measured serum amino acid levels before drinking the whey and at various points afterwards (30 minutes, 1 hour, 2 hours, 3 hours, 3.5 hours and 4 hours after drinking the whey protein).

To measure total nitrogen excreted, researchers also collected participants’ urine for 24 hours after drinking the whey. Knowing how much protein in ingested (the whey) and how much nitrogen is excreted (urine) you get a sense of the overall nitrogen balance. It’s important to note that there are are more sensitive methods for determining overall nitrogen balance using blood analysis.

Geek alert!
More in-depth scientific explanation!

Nitrogen balance is when nitrogen intake (food with protein) = nitrogen excretion.

If nitrogen intake is more than nitrogen excretion then you have an anabolic state in the body that allows for growth (good if you want to gain or maintain muscle).

If nitrogen is less than nitrogen excretion then you have a catabolic state in the body that allows for tissue breakdown (not good if you want to gain or maintain muscle).

Since the amount of whey ingested is the same in all cases a decrease in nitrogen excretion means a more positive nitrogen balance. So, in this case less nitrogen excretion means a situation for more muscle growth!

Results

It turns out that when participants drank whey alone, it took 4 hours to reach maximum total serum amino acids levels, which increased about 30% from baseline (from 1.71mg/L to 2.22mg/L). So, with straight unadulterated whey you get a 30% increase in total amino acid levels after 4 hours. Now what?

Maybe Little Miss Muffet should get off her tuffet and try digestive enzymes.

While the findings about whey alone are interesting, the real purpose of this study was to test whether proteolytic enzymes helped increase protein absorption. Proteolytic enzymes (in this case, Aspergillus niger and Aspergillus oryzae) are simply digestive enzymes that help digest protein.

After the entire group took whey without any enzymes, researchers split the group up. One group drank whey along with 2.5 grams of enzymes; the second group drank the same amount of whey, but with 5 grams of enzymes.

As with drinking whey on its own, both groups had peak serum amino acid levels 4 hours afterwards. Nothing exciting there. We’ve already learned that it takes time for whey to be absorbed.

But whey and enzymes together had much higher amino acid levels after 4 hours. Remember that without any enzymes there was only a paltry 30% increase in amino acid levels. With 2.5 grams of enzymes, amino acid levels were 110% higher after 4 hours. With 5 grams of enzymes, even better: 127% higher.

Holy curds! 127% versus 30% in the same time frame – that’s impressive!

As it happens, the researchers also looked at individual amino acids. You know, alanine, valine and a bunch of other ‘ines. The group taking in 5 grams of enzymes also had higher individual amino acid levels than when drinking whey alone, with the exception of serine and methionine. So all branched chain amino acids (BCAAs) were higher with 5 grams of enzymes.

Another interesting finding was that less nitrogen was excreted when the whey also had enzymes. Again, remember: less nitrogen excreted means a more positive nitrogen balance, which means a more anabolic environment in the body.

Conclusions

First, it’s pretty clear that you probably aren’t absorbing all the protein in your whey if you’re drinking it plain and in viscous (liquid) form. From this study (and others), it seems that under normal conditions, liquids rush through the GI tract too quickly and that only a small amount of protein can be absorbed during normal transit time.

From this study it’s also evident that higher doses of whey protein are better absorbed if you take digestive enzymes at the same time. When you do this, you get higher amino acid levels in your blood, so that you have more available to your muscles and other tissues, which is pretty much the whole point of drinking whey – to make amino acids available to your body.

Second, it got me thinking: what other things help us absorb whey protein? My questions:

  1. If I sip my whey protein drink, or drink small amounts every 15 minutes or so, therefore spreading the whey drink out over an hour or two, is the absorption better?
  2. If I find some way to slow down transit time, by making a Super Shake, by adding the protein to oatmeal, or by using a milk blend containing casein, would that slow transit time enough to make a difference in absorption?

My suspicions are yes – both would help increase absorption. Although not as much as seen with enzyme supplementation. So the best of both worlds, if you’re looking for increased absorption, would probably be to slow down transit time AND supplement with proteolytic enzymes.

Now, on a side not, I do have to mention that this study was sponsored by the company that makes whey protein powder with these enzymes. Of course, I’m not saying the study isn’t accurate. However, I always, always look at where the money comes from for studies. Why? Because to some degree, funding will influence the interpretation, design, or outcome of the research.

But back to the physiology. It appears that in the end, we should all be more concerned about how much of whatever we are eating is actually being absorbed. What you eat doesn’t necessarily mean what you absorb and have available to you.

In the case of whey protein supplementation, thanks to the science, the days of slamming 50g protein shakes straight are gone. If you don’t find ways to slow transit time and/or increase the rate of whey absorption, you’ll be spending your hard earned cash on boosting fecal and urinary nitrogen vs. increasing muscle protein.

Eat, move, and live…better.©

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Too much protein at once

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