When we refer to high protein diets, we do not refer to the slightly higher protein intake that all of us more or less have.
We refer to way higher protein intakes, over often 3 grams and even 4 grams of daily proteins per kilogram of body weight.
There are mainly two segments of the population that may have such high protein intakes.
One is weight loss dieters.
Many popular weight loss diets are high protein diets.
These diets make you lose weight fast, although most of the initial weight loss is not fat, water, to flush out the extra nitrogen.
The other segment is athletes and especially bodybuilders.
We already know that you need a little bit more protein to build new muscle, but the protein you get from an average diet is in general already more than enough.
There is a physiological limit to how much muscle you can build in a day, and to cover that, 10 to 20 extra grams of daily protein will be enough even for the most motivated of the bodybuilders.
Protein requirement for bodybuilders
The DRI say that “no additional dietary protein is suggested for healthy adults undertaking resistance or endurance exercise”, so their need for protein is the same as every other healthy adult.
Other institutions agree that athletes need more protein, some say 0.9 grams per kilo, some 1.2 grams per kilo, some 1.5 grams per kilo.
But anything above that is wasted.
So when we get all that extra protein, what do we really do with it?
We know that our body cannot store excess protein for later use, so one of these two things will happen.
If we need energy, then we will use the extra protein for energy production.
This is the case of athletes on high-protein diets, they get all these extra proteins, they need a tiny little bit for muscle growth, and the rest, they just end up using it for energy.
The other possibility, if we do NOT need extra energy because we are sedentary, then we will have nothing else to do with these proteins other than converting them to fat and store them in our adipose tissue.
This is what often happens to athletes when for one reason or another they stop exercising, but they keep eating the same way they were eating before, and so all the excess protein that before they were burning, now just get converted to fat which will show up in their bellies within a couple of months.
Many of them will blame the lack of exercise, but really, the problem is not just that they stopped exercising, but that they kept eating as if they were still exercising, and now all those extra proteins they are not burning anymore.
High protein diet effect on kidney and liver
One concern that is very often brought up is that excess protein overburdens the liver and kidneys because of the work they have to do to catabolize them.
The liver has to remove the toxic ammonia, turn it to urea, and send it to the kidneys for prompt clearance.
Early nutrition scientists concluded from this biochemical fact that somehow your liver and kidney get tired or even damaged from doing this extra work over the long term.
But the truth of the matter is they don’t, we have studies done with athletes eating insanely high amounts of proteins for extended periods of time, and their liver and kidneys don’t really care.
Our liver and kidneys are perfectly equipped to deal with protein catabolism without any problem, as long as they are healthy.
If they are not, so if you have liver disease or kidney disease, then protein intake needs to be more controlled.
You may be getting excess calories from high protein diet
Like we said, if we get extra proteins and we don’t need them for anything else, we will just turn them to fat and accumulate into our adipose tissue.
But it is not a concern for athletes, since they are burning their proteins for energy, and while they get more calories from proteins, they generally get less from fats and carbs.
It may be a problem of excess animal products.
For most people, going on a high protein diet generally means just eating more meat and animal products which is bad, not for the proteins but for everything else, you’re likely getting a lot of saturated fat, have a diet that’s low in fiber, your gut microbiota will change in a way that’s less favorable, increasing the risk for colon cancer, and so on.
Again, this is not generally a problem for athletes since they mostly use isolated proteins, the typical protein shake.
But for normal people, going on a high protein diet, they’ll just eat a lot of animal food.
Does high protein diet cause dehydration?
Dehydration is another possible concern, remember that high proteins induce water loss, so if you are not drinking enough, that may become a problem.
It is, however, a minor concern since generally, we drink enough water.
The most significant concern associated with high protein diets is that they increase urinary excretion of calcium.
When you go on a high protein diet you start flushing out a lot of calcium, and we are not exactly sure why this happens, but very likely it is because to catabolize amino acids and especially the sulfur-containing ones, methionine and cysteine, we generate acids that need to be buffered to maintain the right blood pH.
The kidneys normally do that, but if we have a lot then the kidneys alone can’t do it, and so we use calcium to buffer these acids, make salts and flush them out.
The first consequence of this is an increased risk for kidney stones formation, although this only happens in genetically predisposed individuals.
The other concern is bone mineral loss and risk of osteoporosis and bone fractures.
Indeed, if we are not getting enough of this calcium from the diet, we will need to steal it from our bones to buffer the protein-generated acids.
And if this happens over and over again, we’ll deplete our bones of their precious calcium.
Once again, for athletes, this is a minor concern because resistance training is so good at increasing bone strength that it more than compensates any possible issue with calcium.
Do you need too much protein?
So in conclusion, exceeding protein needs is unnecessary because we already get enough from our normal diet, but for athletes, it is not a major concern, they’ll just use the excess protein for energy.
However, for sedentary individuals long-term excess protein can be detrimental: it’s a lot of excess calories, it’s a lot of animal products, and it will increase calcium excretion and therefore the risk of kidney stones and loss of bone mineral density.
On top of their function as a part of proteins, individual amino acids may directly intervene in some metabolic pathways on their own or as starting material to build other important non-protein regulatory molecules.
The branched-chain amino acids, leucine, isoleucine and valine, are so named because they have a branched carbon skeleton.
These are the three amino acids that are preferentially used by our muscle as an energy source when glycogen stores are depleted.
For this reason, they are often sold as supplements and marketed as “amino acids for sport”, but you’ll likely not need them because you get enough from food.