This is also, of course, assuming that the protein you’re consuming either contains all the essential amino acids (like all animal derived proteins do) or you have eaten a protein rich meal within the past 4-6 hours that had all of the EAA’s present in abundant amounts. Just to give an example, whey protein (the KING of all proteins) has ~3g of leucine per 20g serving whereas brown rice protein has 3g of leucine per 40g serving. While these two doses are equivalent in their potential to drive muscle protein synthesis, they are not equivalent in calories, which may be a consideration you wish to make if you’re calorie restricted. (Note: many protein manufacturers have different leucine/serving ratios but this is a fairly accurate estimate based on most protein supplements).
2. You will optimize meal frequency. Somewhere along the line people started espousing the mantra “eat every two hours to stoke the metabolism” or “so you don’t become catabolic”, with catabolism meaning breaking down- in this case skeletal muscle- to use their constituents elsewhere in the body. Problem with these recommendations with respect to protein intake is that there is a known refractory period to muscle protein synthesis (MPS), which we can think about on a gross level as muscle growth/recovery/building. Every time a large enough dose of protein is ingested, i.e. one that provides enough leucine and EAA’s to push the MPS reaction over the edge, there’s a 3-5 hour refractory period that must transpire before another dose of protein (at a meal/shake/etc) will yield another bout of MPS. This means that if you ate a protein rich breakfast at 8am, then ate again at 10am, the meal at 10 am would contribute nothing to MPS and then, by definition- it would be stored away as energy -either glycogen or fat depending on other variables. Ultimately, we should be waiting longer between protein dosings to optimize our results. MPS is obviously important for the athlete, but it’s also important for the gen pop- particularly the aging population who is at risk for sarcopenia, decreased work capacity, and thus a host of other comorbidities (e.g. diabetes from decreased skeletal muscle buffering of blood glucose). The literature suggests that the aging population actually sees fantastic results with higher protein intakes and they even use whey protein shakes in many of their interventions.
3. You will determine optimal protein intake by taking rules 1 and 2 into consideration with total calorie intake, age, and gender. It intuits well, given rules 1 and 2, that the optimal protein intake per day is initially based on how much protein a person needs per meal to maximize MPS multiplied by the number of meals they will have per day. Other factors that are taken into consideration to increase or decrease the protein prescription for an individual includes the following modifiers: a)Gender- The more male someone becomes, the more sensitive to amino acids they are, in general. This would allow a male to need slightly less protein per pound than a weight and age-matched female. That being said, lean body mass weight also plays a role in the amount of leucine needed per meal to maximize MPS, but this is literally
- a- variation of 0.5-1g tops for a range of body weights between 100lbs-300lbs, so we don’t take it into consideration and 3-4g is very safe.
- b- Age- In general, the more someone ages the less sensitive they become to protein, so protein levels should go up over time slightly.
- c- Dietary Preferences- As the quality of protein increases (based on bio availability, protein digestibility amino acid corrected score, and amino acid profile) the total protein needed to optimize protein intake goes down. Similarly, the more vegan someone is, the more protein they require, i.e. the more calories from protein they require to get the same effect as their meat-eating, bone crushing, bacon frying counterparts. In short, the lower quality your protein sources are (lentils/rice/veggies/wheat/soy) the more protein you require for the same effect. This is an important consideration for those who are calorie restricted/limited.
4. You will not listen to bro’s who tell you that you only need x gram of protein/day. First off, we’re definitively NOT talking about protein needs here. Protein needs refers to what you NEED to not be deficient- not to optimize performance, aesthetics, or health but merely to survive. So yea, not what we’re talking about. Secondly, the amount of protein you actually need is a fairly complex answer based on everything we’ve discussed above. Do you really think the dude with the cut-off tee who maxes out on bench press every Monday and squats high (or more likely-leg presses) has taken all this into consideration before word vomiting his opinion to you while you foam roll?
5. You will not listen to the bros who tell you that you can only absorb x gram of protein/meal. The poor bro, he can’t catch a break. So this oft-repeated nonsense goes around and around and just will not die…until TODAY. Let me be crystal clear, you absorb and use virtually 100% of everything that enters your gastrointestinal tract from your mouth. If you don’t, you’ll not it because you’ll be having watery diarrhea post-prandial (after a meal) since the undigested and unabsorbed food will act osmotically to draw water into the large intestine and then well, you know what happens after that. Look, we’ve done the tracer studies and know that when you eat any amount of protein at a meal it all gets absorbed. All of it. Actually 110-120% of it. Yep, MORE THAN 100%. That’s because the cells the line the bowel, the enterocytes, make proteins themselves. These are called endogenous (made within the body) proteins and yep, they’re absorbed too. Yes Virginia, if you eat 100g of protein at a meal you’ll absorb it all. Yes, it will take longer than if you only ate 20g, but you’ll absorb the first 20g of protein from the 100g at the same rate as 20g on it’s own provided they have similar total fat content and fiber content within the entire meal. That being said, the time course to which a meal is absorbed matters little to anyone, unless they compete or train multiple times per day.
6. You will not fall into the trap of mega dosing protein, because gains? So far we’ve described why it’s hard to put a firm number on optimal protein intake based on numerous variables. That being said, there is definitely an upper limit- though not for the reason your doctor will try to justify. Most physicians, PA’s, nurses, etc. will all try to recite the urea cycle and scream stuff about ammonia at you whilst telling you that your kidneys and/or liver will fail with high levels of protein intake. I think every time they do this an angel gets its wings because it occurs too frequently and is so far removed from what actually happens in vivo (in the body) that I assume it’s just a religious ritual that all health care providers learn in school and pay homage to periodically. While I do not have time to layout the entire metabolic pathway for ammonia and urea, the two toxic byproducts of protein metabolism that supposedly build up an will harm your kidney and/or liver, I will briefly state that in a healthy person- there is no upper limit for protein intake, as the excretion (removal) rate of these toxins is massively unregulated in an adaptive way that is not harmful, but is a response to a hormetic stressor, i.e. something that disrupts our homeostasis. There is no evidence of any kidney or liver damage when the excretion pathways up regulate either. Similarly, in end stage renal disease, those who ate a “very low protein diet” had worse outcomes than those who ate either a “moderate protein” or “low protein” (but higher than very low) diet. This indicates, to me at least, that protein and its metabolism is not harmful to the kidney- even if it’s function is reduced. More data continues to accrue exposing other harmful factors to the kidney, namely elevated blood sugar in those patients who don’t deal with glucose very well….perhaps because they haven’t optimized their protein intake yet.
I say all this sort of tongue-in-cheek, as I do think there is an actual upper limit to useful protein intake, i.e. there is an inflection point where increased protein dosing does not yield improvements in performance, muscle protein synthesis, aesthetics, etc. This point is obviously different for many people, but I could make a pretty strong argument to avoid intakes in excess of 300g or so for anyone who is under 350lbs. Think about the 200lb bro- replete with cut off tank- who eats 400g of protein per day. While only a fraction (maybe half- depending on sources, age, etc.) will actually contribute to MPS, the other half is getting burnt (oxidized) or converted to carbohydrates and/or fat for storage. These processes are all controlled by enzymes, who will adapt (of course) to the stress imposed upon them. If/when these enzymes upregulate, i.e. increase in number and activity, the body becomes more efficient at using protein for fuel (oxidation to yield energy) and/or converting it to carbohydrates and fat. Similarly, such a robust protein intake concomitantly decreases intake of other substrates to a degree, i.e. carbohydrate and fat intake will be lower in a person who eats 400g of protein than if that same person only ate 200g of protein. This all sums to create a situation where a person is very good at breaking down protein as fuel and, God forbid, should his protein level ever significantly drop below 400g for an extended period of time- like if he were to spend a week at the Jersey Shore and only consume 100-150g of protein/day- then theoretically protein turnover would continue to be elevated since the body’s enzymatic ability to break down protein is so upregulated. Just some food for thought.