Protein itself is not causing your issues but it could be due to your food choices. You're also OD'ing on your protein. To quote a nationally ranked powerlifting doctor:
6) You will not get lured into buying expensive protein with sub optimal amino acid profile. People, if you’re paying more than ~10 dollars/lb of protein you’re getting duped, as the manufacturer is preying on your ignorance. Whey is the king protein, period. It’s better than the 100 dollar fish protein from a certain manufacturer who is big in the land of shirtless dudes and vibram 5 finger clad women. Why? Because its amino acid profile is better, i.e. it has more BCAAs (leucine/isoleucine/valine) and a higher concentration of essential amino acids. Also, it’s cheaper…so that seems to be a good point in and of itself. Whey trumps casein on satiety, MPS rates, and time that it keeps plasma (blood) amino acid levels elevated. In other words, all the nonsense the bro at GNC regurgitates about casein being a slow digesting protein that is good to take at night because it slowly releases amino acids from the GI tract is BS. Well, to be fair to him (bro) or her (bra?), it [casein] does more slowly release amino acids into the blood stream from the gut, but it’s TOO SLOW to actually raise blood amino acid levels high enough to effectively drive muscle protein synthesis unless you dose it much higher than whey, which is the king of proteins. Also, whey keeps you fuller, longer (satiety) than casein, and it’s CHEAPER. Yep, whey is better than egg protein, beef protein, hemp protein (sucks), rice protein (sucks), pea protein (double sucks), and soy protein (double sucks). Whey protein concentrate, one of the cheapest options out there is where everyone should start for whey supplementation. If it doesn’t upset your GI tract, then stay there and never look back. If it does- and it will in some who are sensitive to an amino acid fraction (beta lactalbumin) – switch to whey protein isolate, which has this fraction removed. Whey protein concentrate (WPC) might actually be superior to whey protein isolate (WPI) because b-lactalbumin is a very concentrated source of leucine- so I prefer WPC in those who can tolerate it. No Virginia, WPI doesn’t always mean better and as you just learned- more expensive is not always better.
7) You will not fall into the trap of megadosing protein, because gainzZz? 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 upregulated 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 upregulate 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.
