Protein-Stoffwechsel
Bill Phillips: Let's talk about something you mentioned in our last interview—cycling protein intake. How does this work, and why would someone want to do this? I was under the impression that you had to consume a high-protein diet every day to gain muscle. It sounds like a wild theory to be honest.
Torbjorn Akerfeldt: I realize that by introducing the concept of protein cycling, I might cause some of your readers to say, "That Swedish guy with the unpronounceable name has finally gone nuts..." I say this because I've found that bodybuilders hold three things sacred: heavy squats, steroids—or creatine for drug-free bodybuilders—and a high protein intake. As long as you don't touch these dogmas, many bodybuilders will listen and be prepared to do some of the most outrageous, unscientific, and often dangerous things, in an effort to become bigger and stronger. However, I have to challenge one of these fundamentals: namely, the high protein intake. I know some of your readers, after reviewing even this much of the text, will flip to the next article. I warn them that this is a big mistake. By "hearing me out," I promise they'll learn something new about protein metabolism and muscle growth that may change the way they view protein intake forever, allowing them to reach a new standard of muscle growth and fat loss.
BP: Should we cycle protein like calories—going two weeks on a high-protein diet and two weeks on a low-protein diet?
TA: No. I need to emphasize that my theory involves reducing protein intake only for a few days at a time. In order to understand why this is important—why it could allow bodybuilders to get better results from their workouts—I need to explain some of the basics about protein and its biochemistry, so please bear with me. I believe that if more bodybuilders understood the contemporary science behind the metabolic processes of muscle growth and fat loss, they would be able to spot a flawed theory before they had put a lot of their blood, sweat, and tears—not to mention money—into it. As I've explained in my previous interviews, it is important to understand that we all react and adapt to dietary changes; our bodies are constantly trying to outsmart us, you might say. I see this not only in the gym but also when reviewing statistics from scientific studies on nutrition. The body is amazing.
BP: What is it about protein metabolism that I, and other bodybuilders, really need to know?
TA: Let me start with the basics—as you know, protein is made up of "building blocks" called amino acids, which basically consist of one, two, or three nitrogen atoms bound together with a carbon skeleton. Amino acids can be attached to each other by peptide bonds, thus forming long chains of interconnected amino acids. These chains or peptides are named after the number of amino acids they contain; hence, they are called dipeptides, tripeptides, etc. If there are more than 10 amino acids present, the term polypeptide is used, and if the number exceeds 50, they are normally referred to simply as "proteins." These proteins have different properties, depending on the sequence of the amino acids which form them. Actually, more than 100 amino acids exist in nature, but only 20 of them can be used to build proteins in the human body.
Examples of amino acids which can't be part of the protein structure include gamma-aminobutyric acid [GABA] and L-dopa, both of which are known to be used and misused by bodybuilders. The body also has the ability to change the structure of certain amino acids that have already been incorporated into proteins, thus forming new amino acids such as hydroxyproline [which exists in connective tissue] and 3-methylhistidine [which exists in muscle].
Furthermore, the body can make non-protein amino acids, such as ornithine, and the nonessential, or dispensable, amino acids, which are necessary to synthesize proteins. The reason the body has developed this dynamic ability to create new amino acids is to fulfill the precise needs of the body despite protein intakes that vary widely in quality and quantity. However, the body cannot manufacture all amino acids—certain ones just cannot be synthesized. These are called essential, or indispensable, amino acids. They must consequently be provided in the foods you eat.
BP: I follow you—we covered these things in my Sports Supplement Review®, and I agree this basic science of protein should be understood by bodybuilders. What do you think is important to know about protein metabolism?
TA: Protein metabolism is very complex and is an area of science we're only beginning to really understand. However, there are some things which are relevant to my theory which bodybuilders should have a handle on. Basically, what you need to know is that all the amino acids we ingest in the form of proteins are broken down to free amino acids and used, for example, to build new proteins according to the metabolic state that exists at that moment in the body. What the body does with the various proteins once it disassembles them into these free amino acids depends on your previous food intake, your physical activity, your hormonal status, and a number of other things. These new proteins, depending on the type [e.g., muscle, gut, and liver proteins], have different rates of turnover. Since this area is quite complex, I have created an overview chart [below] that will hopefully offer some assistance. I think this chart includes some important information, especially for Muscle Media readers with a scientific background who are eager to learn more about protein metabolism. The numbers were chosen with a 200-lb bodybuilder in mind.
The free amino acid pool is mainly located inside cells and constitutes only about one percent of the body's total amino acid content in the form of proteins. Since the free amino acid pool is smaller than the daily incoming amount of amino acids from food, the consequence of one day of protein deprivation could be disastrous. Luckily, the body has solved this problem by having a very high rate of protein turnover [more than one pound daily], and by keeping a pool of labile [this means they can easily change] proteins which are readily available to be broken down without interrupting normal body functions.9,14,17 By having this high rate of protein turnover, the body can easily change the distribution of proteins, and this is of prime importance. During infection [a form of metabolic stress], for example, when the body needs to synthesize antibodies [which are proteins], the building blocks [amino acids] will be taken mostly from labile proteins, but unfortunately, during longer periods of sickness, starvation, or trauma, muscle protein will also be broken down to provide raw material for new proteins.
By studying the chart, you can see how I came to the conclusion that there are at least four areas we as bodybuilders must target: 1) decrease amino acid breakdown, 2) increase protein synthesis, 3) decrease protein breakdown, and 4) increase the proportion of newly synthesized muscle proteins. All the details about how to accomplish this are too complicated to get into in this article. However, in regard to protein intake, I can mention that degradation, or breakdown, is temporarily suppressed by an increased protein intake,8,16 and synthesis is promoted at intakes above 1.4 grams of protein per kilogram of bodyweight per day [g/kgBW/d].16,21 For a 200-lb lifter, that's about 130 grams of protein per day.
The size of the free amino acid pool is remarkably constant,24 and this, my friends, is bad news for bodybuilders since it has been shown that the amount of free amino acids both inside muscle cells and in the blood6 governs protein synthesis. This pool can be controlled very closely by a "safety valve" called "oxidation."4 By this process, the carbon skeletons from the excess amino acids are used to create energy. This can happen directly or via the synthesis of glucose [gluconeogenesis] or fat.
Another "safety valve" is the up-regulation of the enzymes in the urea cycle. This metabolic cycle takes place in the liver, and its purpose is to eliminate nitrogen [from protein] by converting it into a water-soluble form called urea, which can be excreted in the urine. The urea cycle and other liver enzymes also break down excess amino acids directly.
There are also other "safety valves" or systems the body uses to maintain a constant amino acid and protein balance, but the important thing to remember is that there are a number of systems that are altered for better or worse when you follow a high-protein diet. The consequence of this is that if you habitually consume a high-protein diet, you are setting off multiple "adaptations" and alterations in how your body metabolizes protein—it influences your protein requirement.18,19 In other words, the more protein you ingest, the more you need! This may not sound so bad for a protein lover, but think twice and you will see its downside. Eventually, you will need such a high protein intake in order to generate the positive effects that health problems could occur.
Another consideration is a large amount of protein supplements could be necessary to meet the extraordinary protein requirement you've built up.
And, perhaps most importantly, if you develop this need for a high amount of protein and you miss a meal or during your long overnight fast [the time you don't eat while you're sleeping], your body is quickly thrown into a protein catabolic state. You literally have to eat protein every few hours in order to not go "catabolic."
As we've discussed in previous articles, your body has the ability to adapt to almost anything you subject it to. For example, those individuals [probably not Muscle Media readers] who consume alcohol habitually experience an up-regulation in certain enzymes that metabolize alcohol; thus, the more frequently they drink, the more they need to consume to get intoxicated [drunk]. Follow me?
BP: I think so. What you're saying is if I consume 400 grams of protein every day, initially this might cause an anabolic effect, but eventually, if I keep doing this, I'll need 400 grams of protein a day just to maintain my current level of muscle mass. Is this what you're saying?
TA: Exactly. The body adapts by up-regulating enzymes and systems that break down amino acids.
BP: So how much protein should we consume?
TA: At first glance, a diet dominated by protein seems to be the logical choice for every bodybuilder. After all, there are reasons this macronutrient is called protein—it's Greek for "of prime importance."
In addition to carbon, hydrogen, and oxygen, protein contains nitrogen and some sulfur, which make it different from fats and carbohydrates.
Protein can be used to create carbohydrates, and with some difficulties, it can be converted to fat, but carbohydrates and fats can never be turned into proteins unless nitrogen is present, and as we've already discussed, nitrogen comes only from protein.
Strangely enough, the current United States Recommended Daily Allowance (RDA) does not include an additional amount of protein for those who regularly engage in physical exercise.15 Several recent studies, however, indicate that dietary protein intake in excess of the current RDA [.8 g/kgBW/d—that's only 72 grams a day for a 200-lb bodybuilder] is likely needed for optimal muscle growth. For example, in one study, heavy resistance-training young adult men consuming 3.3 g/kgBW/d [which is about 300 grams per day for a 200-lb guy] versus 1.3 [about 120 grams a day] gained 2.2 more pounds of bodyweight in just 14 days4!
Another study found protein synthesis in strength-training subjects went up when protein intake was increased from .9 to 2.4 g/kgBW/d.21 These studies concluded that 2.4 and 3.3 g/kgBW/d, respectively, were in excess of the amount needed for optimal muscle growth. For example, in the study using 3.3 g/kgBW/d, the "safety valve," called oxidation, increased by 159%.4 These and other researchers now think that the "optimal" protein intake for strength-training athletes might be 1.8 g/kgBW/d11,21 [about 160 grams of protein for a 200-lb lifter].
I strongly disagree with this theory. I do not believe the subjects who put on an additional 2.2 lbs of mass in 14 days by increasing their protein intake to 3.3 g/kgBW/d4 would have been equally successful if they had increased it only to 1.8 g/kgBW/d.
BP: So why would the researchers only recommend 1.8 g/kgBW/d?
TA: I think the answer lies in how we would define the word "optimal." For bodybuilders, it means maximum muscle growth, while for scientists, it means, more or less, the level at which "safety valves" are induced disproportionately to increased protein intake.25 This discrepancy can be explained within the anabolic drive theory, which was developed by a scientist named D.J. Millward, who has developed other interesting theories on muscle growth which we've discussed in earlier parts of this article series.
Dr. Millward believes dietary protein is a key active nutritional regulator. In short, his anabolic drive theory states that "excessive dietary indispensable [essential] amino acids, prior to their oxidation, exert an important transient regulatory influence on growth, development, and protein turnover, through their activation of various hormonal and metabolic responses, which collectively constitute the anabolic drive."12
The response he's referring to consists of an increase in anabolic hormones, including thyroid hormone [T3] which, in small amounts, is anabolic in muscle tissue. The metabolic response is a direct effect of enzymes stimulating protein synthesis and inhibiting protein degradation.
Notice that Millward mentioned this is a transient phenomenon, giving evidence that the anabolic drive theory is very much in line with my protein cycling theory.
Basically, what it all amounts to is that there are pros and cons associated with a high protein intake—the way to get the positive without the negative is to cycle protein intake.
