The Smack Down On Protein
[ Q ] How much protein does a bodybuilder/athlete need on a day-to-day basis?
Here's where I always get into trouble. This is usually the first question I get asked and with my response, I usually piss everyone off. Oh well, here goes nothin'.
With respect to athletic needs, the work of Lemon, Tarnopolsky and colleagues has given some indication that athletes do require more protein (Lemon et al 1981, Tarnopolsky et al 1988, Tarmonpolsky et al 1992, Lemon et al 1997). This classic research indicates that during intensive training, strength and endurance athletes may need somewhere between 1.4 - 2.0 g of protein per kg of body mass to maintain nitrogen balance.
But what about all the athletes and weightlifters out there that consume fewer protein grams than the recommended 1.4 - 2.0 g of protein per kg of body mass? If they really needed those 1.4 - 2.0g/kg, wouldn't they be wasting away and dying? Since they're not, they must not need all that protein. What's the deal?
As Michael Rennie and colleagues have pointed out, there are several problems when trying to apply the Lemon and Tarnoposky data to habitual exercisers. First, the studies by Lemon and Tarnopolsky were done on athletes undergoing new training programs.
While they were recreationally active before the study began, the training stimulus (strength training in some studies, endurance training in others) was novel, most likely causing a short-term increase in protein need, an increase that would not persist in the long-term (Rennie et al 1999, 2000). In other words, Rennie argues that while a new exercise program (whether strength or endurance exercise) may increase protein need acutely, chronic exercise probably doesn't increase protein need at all.
[ Q ] Say what?
Hold on now, before you start hatin' on Rennie, it's important to understand that this guy is a protein research legend. Type his name into Medline and you'll get a couple hundred protein-related research publications. Beyond his excellent reputation, his ideas do have both theoretical and research support.
Specifically, the research of Butterfield and Calloway suggests that athletes may actually need less protein due to an increase in protein efficiency that may accompany chronic training (Butterfield and Calloway 1984).
What this means is that athletes may actually get more efficient in their protein use (i.e. increased anabolic efficiency) and therefore may need less protein than the 0.8g/kg required for sedentary individuals!
Actually, the Butterfield study suggests an exact number: 0.65 g/kg. In calculating the exact amount of protein they might recommend to maintain nitrogen balance, a 200lb athlete who trains consistently would find that they only need a measly 59g of protein to prevent nitrogen losses and protein malnutrition.
So, for those of you who staunchly believe that you're only required to eat enough protein to meet your needs, go right ahead and reduce your protein intake from 2.g/kg to 0.65g/kg. In the meantime, I'll be encouraging everyone else to actually increase his or her protein intake beyond the current 2.0g/kg recommendation.
Is this Rennie guy crazy? Butterfield? Me? Probably not! Then why do these comments fly in the face of what athletes and weight-lifters know; namely that a higher-protein diet helps pack on muscle mass and helps promote a favorable body composition? Well, actually, they don't! If you think so, you don't understand the difference between need with optimization.
An athlete may need less protein to stay alive but he/she should consume more protein to optimize performance and body composition. Therefore, when I'm asked how much protein an athlete needs, my best response is that it doesn't matter!
Asking "How much protein does an athlete need?" is much like asking the question "How much does a student need to study for an exam?" Since a student only needs to pass their exam to remain a student, the proper answer would be "however much it takes to score a 60%." However, very few students want to earn only a 60%. Therefore the best question would be "How much does a student need to study to get an A on their exam?"
[ Q ] Great, you hate my question - how about this one. How much protein should a bodybuilder/athlete consume to maximize muscle and strength gains?
Now that's better! I usually recommend that protein intake be in the neighborhood of 3-4g/kg. If this recommendation seems excessive and you think that you should stop this interview right now, hang on one second. Again, I'm not crazy.
Basically the reason someone might think this intake is excessive is because they have a narrow view of how protein fits into one's dietary strategy. They're looking at protein in the same narrow way that people used to look at vitamin C; essential at a specific dose but conferring no additional benefits with a higher intake.
With vitamin C, we all know it's important to consume enough of it (at least 10mg/day) to prevent scurvy. However, it's also commonly known there are a host of health benefits associated with much higher doses (200mg/day or more) including a reduced risk of cancer, increased HDL cholesterol, reduced risk of coronary artery disease, and a reduced duration of cold episodes and severity of symptoms.
Like vitamin C, instead of thinking of protein as a macronutrient that provides no benefit beyond preventing protein deficiency, we need to recognize the benefits of eating protein (at any dose).
Increased Thermic Effect Of Feeding - While all macronutrients require metabolic processing for digestion, absorption, and storage or oxidation, the thermic effect of protein is roughly double that of carbohydrates and fat. Therefore, eating protein is actually thermogenic and can lead to a higher metabolic rate. This means greater fat loss when dieting and less fat gain during overfeeding.
Increased Glucagon - Protein consumption increases plasma concentrations of the hormone glucagon. Glucagon is responsible for antagonizing the effects of insulin in adipose tissue, leading to greater fat mobilization. In addition, glucagon also decreases the amounts and activities of the enzymes responsible for making and storing fat in adipose and liver cells. Again, this leads to greater fat loss during dieting and less fat gain during overfeeding.
Increased IGF-1 - Protein and amino-acid supplementation has been shown to increase the IGF-1 response to both exercise and feeding. Since IGF-1 is an anabolic hormone that's related to muscle growth, another advantage associated with consuming more protein is more muscle growth when overfeeding and/or muscle sparing when dieting.
Reduction In Cardiovascular Risk - Several studies have shown that increasing the percentage of protein in the diet (from 11% to 23%) while decreasing the percentage of carbohydrate (from 63% to 48%) lowers LDL cholesterol and triglyceride concentrations with concomitant increases in HDL cholesterol concentrations.
Improved Weight - Loss Profile - New research by Layman and colleagues has demonstrated that reducing the carbohydrate ratio from 3.5 - 1 to 1.4 - 1 increases body fat loss, spares muscle mass, reduces triglyceride concentrations, improves satiety, and improves blood glucose management (Layman et al 2003 - If you're at all interested in protein intake, you've gotta go read the January and February issues of the Journal of Nutrition. Layman has three interesting articles in the two journals).
Increased Protein Turnover - All tissues of the body, including muscle, go through a regular program of turnover. Since the balance between protein breakdown and protein synthesis governs muscle protein turnover, you need to increase your protein turnover rates in order to best improve your muscle quality.
A high protein diet does just this. By increasing both protein synthesis and protein breakdown, a high protein diet helps you get rid of the old muscle more quickly and build up new, more functional muscle to take its place.
Increased Nitrogen Status - Earlier I indicated that a positive nitrogen status means that more protein is entering the body than is leaving the body. High protein diets cause a strong positive protein status and when this increased protein availability is coupled with an exercise program that increases the body's anabolic efficiency, the growth process may be accelerated.
Increased Provision Of Auxiliary Nutrients - Although the benefits mentioned above have related specifically to protein and amino acids, it's important to recognize that we don't just eat protein and amino acids - we eat food. Therefore, high protein diets often provide auxiliary nutrients that could enhance performance and/or muscle growth.
These nutrients include creatine, branched chain amino acids, conjugated linoleic acids, and/or additional nutrients that are important but remain to be discovered. This illustrates the need to get most of your protein from food, rather than supplements alone.
Looking over this list of benefits, isn't it clear that getting lots of protein would be advantageous to anyone's training goals? Since a high protein diet can lead to a better health profile, an increased metabolism, improved body composition, and an improved training response, why would anyone ever try to limit their protein intake to the bare minimum necessary to stave off malnutrition?
[ Q ] Ok then, how much protein is too much?
I can't answer that definitively.
[ Q ] But, but John, I thought you knew it all?
Well listen to this. Interestingly however, Dr. Loren Cordain (of Paleo Diet fame) shared with me some data suggesting an upper limit of protein intake in the 2.6g/kg - 3.6g/kg range. These data are based on studies by Rudman and colleagues (Journal of Clinical Investigation, 1973) in which urea synthesis (urea is a byproduct of protein metabolism) was compared against maximal urea excretion rates.
According to the logic presented here, if you eat so much protein (and make so much urea) that your body can't excrete all of the urea, a more chronic hyperaminoacidema and hyperammonemia can result. Therefore, for intakes higher than 3.6g/kg, one might not be able to all of the protein nitrogen from the body in a timely fashion.
[ Q ] Is this a bad thing?
Some scientists and doctors speculate so. Since nitrogen is a compound that is considered "toxic" (or at least "stressful") to the body, a chronic build-up of nitrogen can't be good. However, the human body is more adaptive than most of us give it credit for and since the Rudman studies were relatively short in duration, I wonder if maximal urea excretion rates might climb with habitual high protein consumption.
[ Q ] With those high intakes, I wonder how much protein the body can assimilate in one sitting?
[ Q ] Really? But I thought...
Ok, ok, I'm just kidding. Got your attention though, didn't I? Actually, my real answer is this. No one's done the studies to answer this question. So we can't know for sure. What we do know is this. Protein digestion depends on a number of factors including the protein source, how the protein source was prepared, whether or not you are on any drugs that affect the GI tract, and probably a host of other factors.
Let's tackle the digestion issue first. When a food is ingested the food first must undergo the digestive process. Since the larger the meal, the slower the GI transit time, it stands to reason that most (but not all) of the protein in any given protein meal (small or large) will be digested and absorbed across the intestinal mucosa eventually. You see, the enzymes for protein digestion aren't limiting so most of the protein thrown down your gullet will be digested and absorbed if it hangs out long enough. Let me say that in another way.
If you eat a meal containing 30g of protein and 95% of the protein is digested and absorbed through the intestinal mucosa, does that meal if you ate less protein, 100% would have been absorbed and if you ate more protein only 90% would be absorbed. Not at all.
If you ate less protein, the time this protein sits in the GI tract would be shorter and fewer enzymes would be released so you'd probably digest and absorb 95%. And if you ate more protein, the time that this protein sits in the GI tract would be longer and more enzymes would be released so you'd probably digest and absorb about 95% of the protein. So my speculation is that digestion is more contingent upon other factors (as discussed above) than protein meal size.
To this end, Gibson and colleagues published a study in 1976 (British Journal of Nutrition) showing that an increasing protein intake did not lead to increased fecal nitrogen loss. This means that higher protein diets did not lead to more un-digested protein in the gut.
These data are supported by further studies suggesting that most proteins have somewhere between 85% and 98% digestibility (meat and cheeses are around the 85-90% range while protein powders are closer to 95%). Interestingly, Pieter Evenepoel and colleagues published a nice study in the American Journal of Physiology showing that when subjects ate 25g of cooked egg protein, 93% of the protein was assimilated. However, when the eggs were not cooked, 65% of the eggs were assimilated. So it appears that food preparation is important; in the case of eggs, probably more important than meal size.
Evenpoel and colleagues also published a nice review of protein digestion and assimilation indicating, "Protein digestibility depends both on characteristics of the ingested meal and on the digestive and absorptive capacity of the upper gastrointestinal tract. The latter is significantly impaired in pancreatic disease but is also compromised by some drugs often used in clinical practice. We moreover confirmed that a substantial amount of even easily digestible dietary protein escapes assimilation in the small intestine."
So it's clear that protein type and preparation are critical to protein digestion. Unfortunately, I can't find any other studies comparing protein meals of different sizes. So the question as to how much protein can be digested in one sitting has to remain unanswered.
Beyond protein absorption through the intestinal mucosa, the protein (or, more appropriately, peptides and amino acids) must then pass through the liver en route to the blood. This is where things get can get even murkier. The liver can do a number of things with an influx of amino acids and peptides including letting them through unmolested, making glucose or glycogen out of them through deamination (gluconeogenesis), or oxidizing them. What the liver decides to do is probably dependent on the instantaneous load that it's faced with. This is probably why more protein is oxidized with a fast digesting whey than with slow digesting casein.
So, in the end, the question has to go unanswered. There's not enough data to draw definitive conclusions. Regardless, from real world experience, it's clear that weight-lifters eating even 3-4g/kg do very well. For a 100kg guy, that's an upper limit of 400g of protein. Assuming 6 - 8 meals per day, that's between 50 - 70g per meal. Assuming varied protein sources, proper preparation, and slower digesting proteins (like whole foods), at these intakes, I can't imagine any real assimilation problems.