Is Your Protein Going to Waste?
In the world of fitness, protein has become quite synonymous with building muscle. Yet, you've probably heard of this common theory of a 30g limit for protein intake. If you want to find out the truth about how much protein the body can really absorb, you want to read this article...
The one thing everybody knows about building muscle, right from the very first day as a novice weight trainer, is that if you’re not getting enough protein in your diet, then you’re already falling behind. Although, there is a lot of variation in advice in how much protein you should be taking. Some old-school dieticians out there still believe that the average diet already has too much protein. This concept was based on the recommended daily allowance of 0.8 g/kg, which, for the greater part of two decades now, has been repeatedly shown to be inadequate for muscle building. Hopefully this misinformation will cease as the science keeps spreading. Accepting the fact that the muscles require extra protein to maximize muscle growth, the question commonly asked is: “How much protein can be absorbed all at once?”
This is a common question that sparks a lot of discussion, even around the RADLAB™. 30 g of protein seems to be a popularized limitation, but why? Can the body really absorb more than 30 g of protein? The short answer is undoubtedly yes, but really, that is the wrong question to ask. Just because a nutrient is being absorbed doesn’t always means it’s being put to the use you want it to.
Protein Digestion and Absorption is Not Limiting
Due to the quantity, specificity and efficiency of the multiple types of enzymes involved with protein digestion, there is no evidence to suggest that digestion is a limiting step in the effectiveness for protein supplementation. Most of protein digestion occurs in the stomach while any remainder can still be further digested in the small intestine. Furthermore, more than half of all the protein in a normal diet is absorbed in the first 1/6 of the small intestine alone, which presumes a large reserve of absorptive capacity. The capacity of amino acid absorption is estimated to be upwards of 700 g, which is a fairly high capacity for protein absorption. Again, this is actually less important than you may think.
Amino Acids are More than Just Building Blocks
Amino acids really have at least two independent functions that are difficult sometimes to distinguish. On one hand, amino acids are literally the materials that are used when creating new tissue such as muscle. This means that the protein you consume, after being digested into amino acids, is literally becoming the new muscle you are eager to grow. This occurs as the amino acids enter the muscle cell and becomes incorporated into intact and functioning muscle proteins, in a process called protein synthesis.
However, it is important to understand that this process does not occur without regulation. Muscle cells require a signal to determine when to incorporate new amino acids to build muscle and when to stop building muscle. It is the regulation of protein synthesis that should be the focus of what governs muscle growth. Protein synthesis is sensitive to mechanical stimulation such as exercise, and hormonal stimulation such as insulin. Coincidentally, amino acids also have this capability as well. Specifically the essential amino acids, and of greatest importance, leucine, actively communicates with the muscle cells to initiate the assembly of the cellular machinery required to activate protein synthesis. This is an enzymatic process where leucine and other essential amino acids are not being used for their structural properties but rather their biochemical properties to initiate protein synthesis. Once protein synthesis has been activated, the amino acids are then physically used by the process of protein synthesis for the construction of muscle protein.
To reiterate this distinction, amino acids function duly to, first, activate the protein synthesis pathway, and then second, contribute the actual material used for protein synthesis. This distinction is important when understanding the limitations of protein supplementation and why you shouldn’t be worried too much about how much protein you can absorb. This is because once protein synthesis is turned off, it will not matter how many amino acids are still left circulating in the blood stream. The limiting factor of how much protein can be incorporated into muscle is related to the ceiling effect of stimulating protein synthesis.
There absolutely is a ceiling effect where protein synthesis will reach a maximum rate despite higher levels of protein ingestion. Several studies have focused on determining the optimal protein dose for maximal results, however it’s nearly impossible for a single study to analyze all possible doses and plot out response curve to determine where the plateau really occurs. Despite of this, the clearest example of the ceiling effect is from a 2011 study where 30 g of protein was shown to stimulate a similar response of protein synthesis compared 90 g of protein. This data suggests that as a high as 30 g of protein is already at a saturable protein dose for maximum protein synthesis. Other studies comparing the effects of 20 g or 40 g have inconsistent results. Some show that 40 g may be only slightly better than 20 g (~10%) and others indicate that there is no significant difference in protein synthesis following 20 g or 40 g of protein ingestion. This data suggests that although 20 g may or may not quite be the saturating dose, it is pretty close to it. In reality, somewhere between 20 and 30 grams of protein is most likely where the ceiling effects lays, but just to be sure, taking at least 30 g should have most people covered.
Maximizing Protein Synthesis Efficiency
Just because 30 g is the maximum dose to stimulate protein synthesis at one time, doesn’t mean all the rest of it needs to go to waste. To maximize protein efficiency taking 30 g doses of protein throughout the day can repeatedly maximize protein synthesis in succession as long as there is sufficient time between doses. The notion that you can continue to sip on amino acids throughout the day to keep protein synthesis always at a maximum level is a falsehood. A 2001 study showed that even during a constant infusion of amino acids, protein synthesis rapidly increases within the first hour but then rapidly declines back to basal levels between 2-3 hours despite high levels of amino acids still circulating around the bloodstream. It is therefore evident that a refractory period is necessary to re-stimulate protein synthesis again. Because of this, it is speculated that protein synthesis can be maximally stimulated no more than 5-6 times daily.
Is Too Much Protein Bad?
If there was a finite amount of protein made available, then yes equally distributing protein consumption throughout the day would serve as a benefit, but there is nothing terribly wrong with eating a giant steak for dinner or consuming well above 30 g of protein in one sitting. Research shows much of the extra protein not being used in protein synthesis actually becomes oxidized for energy. Excess protein beyond that can also be converted to other fuel sources such as carbohydrates and fats. Therefore, when in a bulking phase high levels of protein will not only ensure maximum protein synthesis, but the remaining amino acids can be used to improve glycogen stores in the liver and any excess beyond that will be stored as fat. Unfortunately, extra protein isn’t stored anywhere other than in muscle. Muscle is the storage unit for protein, so once the amino acids are converted to another fuel source, it is irreversible. None of the other fuel sources can be converted back to protein due to its loss of nitrogen. So, when your muscles are ready for another dose of protein, this can only come from the diet again. Therefore, to keep your muscles at their maximum, it’s best to focus on protein frequency rather than protein quantity. Adding a couple doses of protein in the morning is where most people can see the best improvements.
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