Trust me, I have gone through so much reading on this subject and I'm still confused. I eat 2-3 times my recommended intake of protein and have been doing so every day for several months. Is there any evidence thus far on long-term, potentially negative, effects of too much protein? Fat storage? Is it insulinogenic? Something to do with the kidneys? And what the heck are uncoupling proteins? Or is there really no such thing as "too much protein?" I have a cornucopia of questions but I don't know where I want to begin and frankly, I don't know when it will end. I know there's not an end-all-be-all answer but any contribution backed by legitimate sources will help.
You might gain unsightly muscle, lose fat, and look hot. This would be tragic.
My understanding (always my opening caveat :P) is that excess protein in your diet simply gets excreted out in the urine; meaning hugely excessive intake can put more stress on the kidneys.
Having said that, the "RDA" for protein has nothing to do with what most human bodies are capable of utlising; it's probably more like the point below which you start losing bone density or something.
Anyway, as a ball-park figure, if you're eating below 200g a day, I'd say there's nothing to worry about (and even on paleo not many get close to even that).
However, if you're still concerned - just drink more water to oil the ol' kidneys :)
Aside from wasted money (as protein is generally the most expensive macronutrient from a supermarket-shelf point of view), I don't really see any downsides in taking a bit more than strictly necessary.
Well, there are folks that think too much protein can be problematic for longevity (Rosedale, Mercola, Ornish). I'm not sure if they are correct or not. My sense is that if you are in the range of 20-25% of calories as protein, you're probably okay.
Well if you consume too much lean protein, a condition called "rabbit starvation" or "protein poisoning" could occur. But really unlikely in a normal diet though. http://en.wikipedia.org/wiki/Rabbit_starvation
Many cite deamination or the conversion of amino acids into ammonia as the most notable danger in consuming protein in quantity.
Paul Jaminet, for example, claims that somewhere between 150 and 200 grams of protein depending on body/liver size, one will start to experience ammonia toxicity. This occurs because the body is no longer able to convert the ammonia to urea and the nitrogen and ammonia lingers in the body as a toxin.
Eat more fat. From what I've read, it's rather unlikely you could consume saturated fat in quantities that would be toxic to the body since it's utilized by such a vast number of organs/systems.
Dietary protein isn't directly related to uncoupling protein intake. This question has a pretty in-depth explanation of uncoupling proteins, but in a nutshell they allow your body to dissipate fat as heat when there is too much fat in the cell and you don't need to make any more energy (ATP)
edit: to make more sense
Just putting it out there that more protein than is beneficial (I'm not going to say more than "needed" because as has been pointed out, it's silly to base recommendations on what you absolutely need to avoid death) lowers testosterone levels in males. http://jap.physiology.org/content/82/1/49.long And I have seen a few others that show this.
So while there seem to be some benefits to a certain amount of protein, it may work against somebody trying to gain muscle if more than is needed for optimal muscle growth is consumed. Protein is essential for muscle growth but just how much is optimal is probably overestimated by nearly everyone.
This is open to debate if anyone has objections.
I think a lot of the negative consequences are actually about the lack of other nutrients when trying to subsist on only protein. And there's nothing conclusive enough to make official guidelines (and we all know how willing they are to jump to the wrong conclusions without evidence). And still that's 300g+ depending on your size for a high-protein diet, which I don't think you're eating!
i laughed when i read the RDA for protein. that's the minimal amount to prevent death. You know just like the RDA for Vitamin C will prevent death but not sub clinical survey diseases such as gingivitis and atherosclerosis and many more unknowns.i have no answer except that a healthy mind will tell a healthy body what to burn as fuel. All you have to do is relax and say to yourself, what sounds good to eat right now. you would be amazed that the mind can control food intake to the point that just overeating a single cucumber slice daily for twenty years will make you fat. By the way since switching to a paleo diet my protein intake has increased like eveybody elses. yet, i seem to get less dehydrated than before. So maby extra protein improves kidney function? who knows? i dont.
just one more comment i would like to make is most vegitarians like to argue this point with the paleo diet people because they can use numbers. As we all know paleo diet folk, never count calories because its pointless. i have never heard of a person getting fatter eating paleo yet i know plenty of vegitarians that eat so many carbohydrates they become diabetic. for instance, the country of india are mostly vegitarians ,yet suffer from diabetes at an alarming rate just as americans do.