More protein: What's in it for me?
These past eight weeks highlight the most time I've ever spent reading research. Unsurprisingly I have learned a great deal and even less of a surprise...I found how little I know. That's OK with me, I'm happy to open doors that sometimes just lead to more doors. We all have a certain amount of thresholds we're willing to cross before we decide "that's plenty". Still not satisfied with how much I know about protein, how it's metabolized, what tissues need it most and what effects consuming various amounts has on our physiology.
That's the boring version. The fun version is "if I eat more protein, does it help me get more jacked and lean"? It certainly isn't going to help my tan but that's cool.
It's quite common to think training equals muscle damage equals needing protein for our muscles equals getting bigger muscles. That's reductive but it's what I have believed for a long time. The problem is, muscle tissue accounts for less than half of the lean tissue on our body so it isn't the main draw on the protein we eat. All of our organs (skin, heart, brain, liver, kidneys, gut) are highly metabolically active and turn over protein at higher rates than muscle. In fact, if you compare the amount of calories burned per kilogram of weight, muscle tissue comes out lower than all other organs. If you compare the percentage of amino acid (protein) utilization by organ, muscle comes last again.
Professor Don Layman has mentioned that we typically turn over about 300g of protein per day. Naturally this isn't all from our diet as most people don't consume nearly this much (I'm close though) as the amino acids we use for repairing and building tissue come from the protein we eat plus the protein in our organs. This all enters the intracellular matrix and bloodstream to form what's called the "amino acid pool". Think of this as a circulating amount of amino acids being fed from diet and broken down organ protein, which all organs (muscle included) then pull from for repair and growth.
Naturally, if you consume more protein there is more available for all the body's processes. Unlike carbohydrates or fat, we don't really store protein. The gut pulls about half of the amino acids in one meal for later use but aside from that we aren't stocking extra protein like we can with fat tissue and glycogen. You're probably thinking that if we eat the amount we need, more doesn't do anything since we can't save it to use later on. Since we cannot store protein most of it is oxidized (burned off) for energy or turned into other usable substrate like glucose or ketones.
So something happens with eating extra protein but does all this steak I'm eating actually have a benefit? C'mon man!
More protein isn't better, but can it help?
It’s long been wishful thinking that simply eating more protein leads to better performance, recovery and muscle mass in a linear fashion. Charles Poliquin touted eating 2g per lb to break through plateaus and Arnold’s Encyclopedia highlighted favoring protein, especially red meat and eggs, over carbohydrates for muscle mass gains.
Naturally, every young new trainee who begins lifting will see some of their best growth in muscle mass in a short amount of time. Anecdotally this happens with a concomitant increase in protein influenced by bodybuilding magazines, gym culture and of course, the internet.
However, beyond meeting new protein turnover needs, is all the extra protein worth it? Does consuming more than what’s necessary for increased muscle protein synthesis demands actually yield better results? We can open the interpretation of results to factors beyond simply getting bigger biceps; faster recovery times, less soreness, better blood sugar control, decreased hunger and overall anabolic drive certainly contribute to the success of a nutrition approach.
This question leads us to ideas concerning protein intake and the effects we see at varying intakes.
What we use protein for
This facet, in my opinion, is something most people interested in protein don’t quite understand. Until the past couple of years, I didn’t realize how much more protein was needed for than simply growing muscles. Taken in the context of what percentage of protein intake reaches the muscles, we can see that whole body protein needs go way beyond the gym. Some basic tenets that elucidated this for me were:
- Up to 50% of ingested protein is stored in the gut as well as the majority of ingested glutamine. This storage acts as a buffer for time between meals
- The remaining amino acids reach the liver for synthesis and oxidation – up to 75% of these are metabolized with only a small amount (mostly BCAAs) going to muscle tissue
- Amino acids are used for the production of hormones, energy, synthesis of new substrate and turnover in whole body protein needs
What happens if we eat more protein than we need?
The RDA for protein is 0.8g/kg whereas the ISSN position stand on protein intake recommends 1.4-2.0 g/kg for active individuals. Dr Jose Antonio recommends 1.8 g/kg as the minimum for weight-training individuals (Antonio et al May 2014).
In an article by Schoenfeld and Aragon (JISSN Feb 2018), the authors cite research conducted in Stu Phillips lab that muscle protein synthesis is maximized with 20-25g dietary protein per meal. Many studies, including the high-protein studies conducted by Antonio, use whey protein taken alone which does bring into question the efficacy of such findings. I've also come across some data from Wolfe et al 2015, that gave subjects either 40g or 70g protein from beef. Protein at 40g in one meal had a max out effect on muscle protein synthesis but 70g increased TOTAL body protein synthesis. Remember all that other tissue that needs protein? Yeah, just measuring protein synthesis in muscle ignores over half of your protein-using organs.
Whey and hydrolysates can bypass slow digestion processes leading to a sharp spike in blood amino acid levels and an increase in amino acid oxidation in the liver. Furthermore, increased protein intake correlates with increased protein storage (in the gut) during the day, greater amino acid oxidation in the liver and increased protein breakdown at night. Even if you infuse amino acids directly into the bloodstream the majority are used by the small intestines and liver. A study conducted on diabetes patients found that even 3g/kg of protein intake saw a doubling of BCAA concentrations but only a 30% increase in blood amino acids (Wahren et al 1976).
Excess amino acid ingestion, beyond what is needed for muscle protein synthesis, results in a correlative increase in amino acid oxidation or conversion to other substrate. This seemed to drive the nail in the coffin initially to me that more protein offers zero benefit. However, the theory that increased amino acid oxidation contributes to the anabolic drive of the body paired with positive body composition changes as shown by Antonio et al 2015 holds some promise. When we start to look at other research as pointed out by Wolfe above, we can eat more protein than what maxes out protein synthesis in muscle because we have other tissues that factor in.
In Antonio’s study, subjects consuming a high protein diet (3.4g/kg) saw a decrease in body fat and increase in fat free mass while following the protocol. By the way, if you weight 150lbs that's 68kg and you'd be eating 231g protein per day. Nothing to sneeze at. Despite consuming more calories than the normal protein group, they experience improved body composition changes. This research was based off client reporting so of course it is possible that the data is not extremely accurate but does point us in the right direction. Even if increases of protein result in spontaneous calorie restriction, it still leads to positive body composition changes.
Contemplating what this might mean for me
Whether this improved body composition change from increased protein intake is simply from physiological processes such as the thermogenic effect of feeding (TEF) or spontaneous calorie restriction may not be entirely relevant from a practical standpoint. Positive changes are all that matter to most clients and coaches, especially when risks are low and benefits are high.
In all honesty, I am still digging into this stuff. I have a hunch that we can see improved fat loss by consuming more protein as it increases the amount of calories used for digestion and this is a win. We either get to eat more without gaining fat or use the added calorie burn from increased protein to lean out a bit faster. Especially if protein is satiating and filling, eating more will also dampen the hunger you'd feel on a calorie deficit. Likewise, if overeating in an attempt to gain muscle mass sees LESS fat gain when subject eat more protein, a high-protein mass gain might potentially limit your fat gain on that protocol.
There's still a lot to consider when making these hypothesis but I do have some cool research from Webb and Annis 1983 that shows when over-feeding subjects 1000 calories per day, they didn't see the predicted fat gain from the calories consumed.
Predicted average fat gain (at 6 kcal/g) should be 5kg of fat.
Mixed American Diet gained 2.68 kg of fat, 46% less than expected with a
7% increase adaptive thermogenesis
High Protein Diet gained 1.75 kg of fat, 65% less than expected with a
greater than anticipated adaptive thermogenesis 14%
What's interesting is that even in the lower-protein group, there was still an adaptive component to eating more. At 1000 calories per day over daily needs, these subjects should've gained 5kg of fat and yet then didn't; the high protein group gained even less. In Jose Antonio's 2017 narrative review, all the studies cited on high-protein overfeeding showed a protective benefit from consuming more protein. Essentially, eating more protein when overeating calories limits the amount of fat you gain. Back to my practical assumption, even if this doesn't pan out significantly in a physiological way, it has profound behavior changing effects that can still lead to losing body fat.
From a client perspective, consuming more protein might help them lean out faster/gain less fat from a metabolic standpoint. And more powerfully, consuming more protein usually leads to subconscious energy restriction which is awesome for fat loss. So a guy looking to gain a ton of mass might not want to waste his time eating tons of extra protein if it's only going to make him more full. For the rest of us, there's certainly a practical benefit from eating more than then JISSN position stand of 1.4g/kg - 2.0g/kg daily for active individuals.