In this article we will talk about excess protein in diet, which we could define as:
an assumption top al requirements individual, continued in chronic, of all le protein food (not only those of animal origin).
In detail, we will analyze the "possibility"that the dethetic excess of proteins can to compromise the state of health and "any" disorders related, both in the body sano, both in that sick.
Before going into detail, of course, it will still be necessary to make a brief overview of the information necessary for understanding the text.
We will not dwell on the chemical and nutritional bases, however indispensable for understanding the subject, and that kind readers will be able to find in a specifically dedicated article (see below).For further information: Proteins
Principle of protein turnover
Proteins also have a "life", which is short or long depending on the type, function, level of use, etc.
At the end of this period, the no longer functional proteins are broken down (proteolysis) into the individual amino acids (AA) and recycled as much as possible for the construction of new proteins (proteosynthesis).
The continuous process "replacement"of tissue proteins - an indispensable process to ensure the functioning of tissues, organs and systems - it is said turnover.
Note: not all amino acids can make up proteins, but only 20 proteosintetici (ordinary), which also include essential (EAA, from 9 to 14 in all, depending on the condition), which obviously also include the 3 branched (BCAA).
As can be deduced, a part of these AAs will be inexorably lost. This would be due to various factors such as: the impairment of the molecular structure, the use in neoglucogenesis or ketogenesis by the liver, direct oxidation for energy purposes in the muscles (of the branched ones) etc.
The loss of AA therefore defines the protein requirement, which however DON'T must respect alone a parameter quantity, but also qualitativo - given by the composition in AA, measurable with a parameter called biologic valueor (see below).
Principle of protein requirement
Il protein requirement mainly depends on the amount of amino acids lost during the turnover, which must therefore be replaced with the introduction of food proteins.
It is an extremely variable parameter, because it is influenced by numerous factors, several of which subjective (such as body composition, level and type of motor activity).
Among the most important factors:
- Anabolic demands (construction): growth, gestation, breastfeeding and stimulation of muscle growth due to strength training-hypertrophy;
- Compensation to the catabolic processes (demolition): calorie deficit induced by diet, calorie deficit induced by the practice of endurance sports, pathologies (severe burns, tumors, etc.);
- Digestive impairment: however, these are non-physiological situations, such as gastric, intestinal, pancreatic problems;
- Aging: for reduction of intestinal absorption capacity and anabolic resistance.
Translated into practical terms, the protein requirement depends above all on: age, body size, amount of muscle mass, any special physiological conditions, sport practice (type and training load), state of health.
How Much Protein in the Diet?
It is therefore logical to deduce that, for example, the protein requirement of a sedentary secretary with a small build is different (lower) than that of a robust worker who practices strength-lifting sports.
The guidelines on the general population, for reasons of practicality and applicability on large numbers, are rather restrictive and do not take into account many variables that we have mentioned above.
To maintain health, various sources recommend ∓ 1,0 g of protein per kilogram of body weight physiological (g / kg) - depending on the institution considered.
This increases slightly in the case of greater metabolic demands, such as during gestation, or more considerably, as in the case of a low-calorie diet or by practicing sports with a high strength training load (even> 2,0 g / kg).
What proteins in the diet?
Since not all amino acids are the same, it makes sense that one parameter must also be satisfied qualitativo.
We have said that ordinary amino acids are indispensable for proteosynthesis. However, some of them must necessarily be introduced with the diet and are defined essential (EAA). The others, on the other hand, can be synthesized within the organism starting from the previous ones.
Any deficiency of EAA can therefore become a condition limiting below your proteasynthesis.
It goes without saying that the AA composition of dietary proteins is "qualitatively" measurable based on the level of EAA; the closer it is to human peptides, the better. The parameter used for this estimate is called biological value (VB).
Foods containing proteins of greater biological value are: milk and derivatives, eggs, meat, fish, soy.
However, it is also possible to take different protein sources of lower biological value by compensating each other for the amino acid or the EAA limiting (deficient) - vegetarians for example, rotate cereals and legumes.
A protracted protein deficiency over time is therefore potentially responsible for a less effective protein turnover, to the disadvantage of tissue trophism (for example, reduced muscle growth or even loss of mass).
Fearing this circumstance, many subjects on a slimming diet and / or sportsmen tend to take higher protein quantities than the norm, often "decidedly" excessive compared to their needs.For further information: Protein Requirement
Absolute excess and relative excess
L'excess protein is defined as the intake of peptide quantities exceeding one's needs.
How is this excess established?
Analyzing the nitrogen balance, or measuring nitrogen ingested and that expelled - since nitrogen, an integral part of AA, when not bound to them (for example after conversion into glucose, ketone bodies or AcetylCoA) is eliminated as if it were a toxic residue.
nitrogen ingested - nitrogen eliminated = budget nitrogen
- One result positive indicates one expulsion of nitrogen lower compared to that ingested, due toutilization di AA in the anabolic pathways of proteosintesi;
- One result negative indicates a nitrogen expulsion top compared to that ingested, due to the catabolic pathways of proteolisi and use of AA in glocogenesis, ketogenesis and liposynthesis.
While it is true that, directly or indirectly, AAs can be used to produce kilocaloric energy (kcal), it is also possible to attribute an energy coefficient per gram (g) to dietary proteins.
The proteins (or rather, the AAs that compose them) provide 4 kcal / g.
Relative and absolute protein excess
However, measuring nitrogen balance is a difficult practice. This is why we tend to calculate the protein requirement thanks to the data provided by the scientific bibliography.
This estimate can be done in several ways. The simplest and most effective is the estimate of grams of dietary protein per kilogram of body weight per day (g / kg / the) - for subjects of normal weight or obviously muscular, the real body weight must be considered, while for overweight subjects it is more useful to use the theoretical physiological body weight (or, it is necessary to change the coefficient).
Alternatively, some use the percentage on total calories.
For example, a 90 kg subject who requires 2,0 g / kg of protein has a protein requirement of 180 g / day.
We have also said that proteins bring energy; the caloric fraction of these 180 g corresponds to 720 kcal.
But the use of AA (which affects the nitrogen balance) also depends on the metabolic condition - anabolism / catabolism, energy expenditure.
If the person in the example had a norm-calorie requirement of 2500 kcal, the remaining 1780 kcal would have to come from carbohydrates and fat.
- What if, on the other hand, fats and proteins were introduced in less quantities but we increased the proteins?
- What if instead fats and proteins were introduced in the right quantities but still increased the proteins?
Proteosynthetic amino acids resulting from digestion and absorption of dietary proteins are intended for different metabolism depending on condition of the organism.
As anticipated, in addition to to build new peptides, can be converted to acetyl-coenzyme A and then to fatty acidsin glucose (AA glucogenici) o in chetonic bodies (AA chetogenici).
This depends, in addition to the actual need proteosintetico (to build de-novo or re-build), also from the calorie demand total and not less from the amount of food carbohydrates - as glucose DON'T it can be replaced by fatty acids and ketone bodies; the only nutritional molecule other than carbohydrates from which it is possible to obtain it are glucogenic AAs.
- An energy deficiency and a reduced carbohydrate intake stimulate the use of AA in glucogenesis and ketogenesis.
- Conversely, the surpluse of AA associated with an enegetic surplus tends to increase the synthesis of Acetyl-CoA and then of fatty acids - which are deposited in the adipose tissue increasing fat mass.
- Or, bridging a possible deficit di Calories, especially of carbohydrates, with some dietary protein, some of the AAs would act as a substrate for neoglucogenesis e chetogenesis. If so, the excess protein would have a different impact on body weight based on the total energy balance, which may remain stable o alight, depending on whether the diet is normocaloric or hypocaloric.
Why did we make this distinction? Simply to better understand the mechanisms that may underlie any problems related to excess.
What Happens to Eating Too Much Protein?
Whether they need to be converted to Acetyl-CoA and then to fatty acids, ketone bodies or glucose, the AAs need to be private of nitrogen group which, once put into circulation, must then be disposed of.
The removal of nitrogen from the AA skeleton is a process that occurs in liver, while the expulsion with the urine - thanks to the consumption of water and minerals - is a process that occurs in Reindeer.
Furthermore, if the overall metabolic condition determines a backlog excessive of chetonic bodies (low-carb ketogenic diet), some of which is filtered by the kidneys and excreted in the urine.
Ultimately, any amino acid use other than proteosynthetic deposition results in increased hepatic and renal commitment.
Note: the only exception is the direct oxidation of BCAAs in the muscles.
How does physical activity affect all of this?
By stimulating the anabolic construction of contractile tissue and compensating for exercise-induced catabolism, it increases the protein requirement by participating in depositing higher levels of AA in turnover.
However, if continued with excessive training loads, and especially in the case of a low-calorie diet, even worse if hypoglucidic, it can increase both the work of the liver and that of the kidneys.
Nevertheless, movement leads to sweating, another important way of eliminating water and minerals.
So we come to the big question: is excess protein in the diet bad for you?For further information: High-protein diet
Liver and Kidneys
Too much protein: liver and kidney load or overload?
"Cutting the bull's head", in a healthy subject with average hepato-renal function, even if it involves an increase in hepatic processes and renal excretion, the excess of protein in the diet does not constitute a serious risk for the health.
This also applies to a possible increase in ketone bodies which, in the patient without pathologies, despite having adverse effects, never reach levels such as to induce a dangerous metabolic acidosis.
The liver and kidneys quickly adapt to greater effort, however high it may be.For further information: Ketogenic Diet
Calcium and Bones
Excess protein, calcium excretion and bone health
The increase in renal filtration due to protein excess requires a greater excretion of both water and minerals; among these (sodium, potassium, phosphorus, etc.), calcium expulsion is of major concern (urinary calcium).
However, this is unlikely to drop to critical levels in plasma, as the body reflexively increases intestinal absorption. To meet a deficiency, in addition to exaggerating with proteins, a chronic deficiency of the same would be indispensable.
Excess of proteins and tumors
Many have speculated, given a certain statistical trend, that excess protein in the diet may increase the risk of cancer.
In fact, it has been seen that such circumstances are going to manifest themselves in the population who consume more roasted or fried products, and cured meats.
This is due to the poisonous effect that carbonization residues, high in grilled, fried or grilled products, exert on the mucous membrane of the digestive tract.
Not only. Nitrites, molecules already present in nature but also used as preservatives in sausages, once in the stomach can react with amines forming the so-called nitrosamines. Cancer properties are attributable to high levels of these compounds, which always affect the mucous membrane of the digestive tract.
Who is at risk?
For whom can excess protein be dangerous?
Obviously, for the subjects already compromised!
Particularly vulnerable are people with imbalances area of functionality hepatic but especially kidney, therefore the insufficient properly called, cancer patients and mono-kidney.
Even subjects with a pathological past, albeit healed and apparently healthy, are to be considered "at risk".
Extreme caution is also recommended in type 2 diabetics, especially if severe or poorly compensated even with the use of drugs.
Benefits of Proteins
However we also remember that:
Carbohydrates, lipids and proteins also differ from each other for their specific dynamic action (TID). This parameter represents the energy expenditure that occurs following the ingestion of these macronutrients.
For proteins, the TID value is very high and ranges from 15 to 35%; this means that 15-35% of the calories supplied by proteins are spent on their digestion and absorption.
Example: assuming a protein intake equal to 100 calories 15-35 Kcal are spent to metabolize them so the actual calorie intake is reduced to 65-85 Kcal
A protein meal is able to stimulate the release of anabolic hormones such as testosterone and GH.
A diet rich in proteins reduces the sense of hunger, especially in the early periods, thanks to the duodenal release of a substance called cholecystokinin which regulates the sense of satiety.
In particular conditions such as growth, pregnancy, convalescence or muscle strengthening, protein synthesis increases and therefore a greater protein intake is necessary.
For a bodybuilder who trains seriously, the daily normocaloric protein intake should remain within the range of 1,6 - 2,4g of protein per kg of body weight, rising up to 3,1g / kg on a low calorie diet.
In light of the foregoing, it is evident that, in the healthy subject, the excess of protein in the diet does not constitute a problem for the liver and kidneys.
If not compensated by increasing water levels with food and drink, the protein excess inevitably tends to worsen the state of hydration.
It is evident that too many proteins favor a greater excretion of minerals with the urine, such as calcium; however, the resulting metabolic adaptation is capable of preventing its deficiency, provided that the nutritional intake is adequate.
Protein excess is not in itself responsible for the increase in carcinogenesis, while carbonization residues and nitrosamines are.
As for people at greater liver and kidney risk, it is not recommended to increase the protein intake in the diet until it reaches excessive levels.