Are high-protein diets harmful or safe for the kidneys: a review of studies. What could be the consequences of eating protein? Kidneys hurt from protein

Main building material for muscle cells are proteins. Contained in meat, fish or plant products Protein compounds include fats and carbohydrates, which is determined by the vital activity of the organism from which the food was obtained.

Protein used in sports nutrition, unlike plant and animal protein, is protein molecules purified from foreign impurities.

Due to the fact that people know about changes in the usual substance by chemical means, there is a belief that protein is harmful for male body. Influence at public opinion It was also influenced by the fact that purified protein can cause digestive disorders and allergic reactions.

Is the information about the dangers of protein true?

Technologies for the production of purified protein make it possible to include more essential protein in the diet without increasing the caloric content of a serving of food. High-protein mixtures are necessary for bodybuilding, weight loss and for healthy eating with reduced fat and sugar content.

Among the frequently encountered negative consequences for the body is called:

1. Allergic reactions.
2. Digestive disorders (diarrhea, constipation, flatulence).
3. Kidney pathologies.

Digestive disorders and protein allergies are a common natural reaction of the human body to foreign substances that enter it through food. The occurrence of these unpleasant phenomena is due only to the characteristics of each person; they cannot be called the consequences of taking purified protein. Almost everyone can encounter them even when consuming ordinary foods containing protein.

1. Allergies are based on individual intolerance to a substance. When it is contained in regular healthy foods, the body's reaction may be almost unnoticeable due to the presence of many other substances. They mask, reduce or even neutralize the effect of the allergen. But when it enters the body in concentrated form, this substance causes a characteristic reaction in the form of a rash, indigestion, and other things. Protein is a substance purified from carbohydrates and fats. Therefore, protein intolerance, unnoticeable during a normal diet, may well unexpectedly appear when taking a concentrated diet. This is how the myth about the allergic consequences of protein intake was born.
2. Digestive disorders can occur as a special case of allergies. In some cases, they can be caused by dysbiosis or deficiency of enzymes that are needed for the digestion and absorption of protein. In both cases, excess undigested protein accumulates in the intestines, which causes active activity of putrefactive bacteria. The process is accompanied by the release large quantity gases (indole, skatole, etc.). A similar situation occurs when the dose of protein concentrate is too high (250-300 g/day).

In order to prevent the unpleasant consequences of taking protein, it is enough to follow the recommended intake of the drug (15-20 g per dose) and take probiotics and digestive enzymes. Using enzymes will allow the body to digest protein faster and better absorb it. Increased intake of fluids and foods containing fiber will help avoid constipation.

How does protein affect the kidneys and potency?

Among the myths about the harmful effects of protein on the male body, the main place is occupied by concerns about decreased potency. These rumors stem from the fact that the nutrition previously produced for bodybuilders and athletes contained steroid additives. These substances are also capable of increasing muscle mass, but they are not related to the protein concentrates used in our time. To avoid intimate male problems, it is enough to buy high-quality sports nutrition, since cheap analogues may contain unwanted components in the form of steroids.

But even high-quality nutrition can have an impact on potency when consuming soy protein, which is usually used by vegetarians. Its effect lies in the high content of phytoestrogens in soy. These substances are plant analogues of female sex hormones. But, thanks to their relatively low content in ready-made food, we can talk about its practical safety for the male genital area. Those who still fear for their health should prefer whey or egg protein.

The truly dangerous consequences of consuming sports nutrition in a diet can only become if a man has undiagnosed kidney pathologies. Therefore, before including a protein drug in your diet, you should consult your doctor and undergo a medical examination. If kidney failure is detected, you will have to stop eating protein.

Due to the fact that the body spends a lot of fluid on protein processing, when using sports nutrition for weight loss or growth muscle mass It is recommended to ensure that the amount of liquid you drink per day is at least 2 liters.

Essential nutrients must be obtained from natural foods. Protein is no exception, and for a complete healthy diet, you should remember that protein concentrates should only be a food supplement.

Among builders of their own muscles, there is a widespread opinion - “the more protein, the better” and often such people, without making calculations, consume the maximum possible amount of protein products and supplements. What do scientists say about excessive amounts of protein in the body – can it be harmful?

Protein intake rate

To begin with, we should recall the official recommendations for protein consumption. For example, in the manual for sports nutrition NSCA for gaining lean muscle mass is recommended to consume in addition to a moderate excess of calories (10-15% above normal). 1.3-2 g/kg body weight per day.

And when active phase By reducing the percentage of fat, scientists even recommend increasing the rate of protein consumption - up to 1.8-2 grams / kg of body weight per day. Moreover, the lower the percentage of fat (for example, when preparing for competitions), the higher the requirements for protein consumption. If the goal is to reduce the percentage of fat to very low values, it is recommended to increase protein intake to 2.3-3.1 g of protein per 1 kg of body weight per day.

Let's now find out what happens to our body when we consume large amounts of protein.

Excess protein and kidneys

Don't ask this question if you have healthy kidneys, and control your protein intake if they are diseased. The smartest approach is to gradually increase protein intake to a higher level in the diet, rather than jumping in with both feet at the same time.

Usually, With increased protein intake, it is recommended to drink more water. One of the reasons is to reduce the risk of kidney stones. However, there is no clear scientific rationale for why this should be done, but it may be a reasonable approach.

Observations of active male athletes and measurements of the levels of urea, creatinine and albumin in urine showed that in the range of protein intake from 1.28 to 2.8 g/kg body weight (that is, at the level of the recommendations described above), no no significant changes were observed (1). However, this experiment lasted only 7 days.

Another study (2) also found no association between protein intake and kidney health (in postmenopausal women).

A study involving nurses (3) confirms these findings. But it does suggest that the protein safety data does not apply to cases of kidney failure and other kidney diseases, and that non-dairy animal proteins may be more harmful to the body than other proteins.

It has been suggested that protein intake leads to functional changes in the kidneys (4). Protein may affect kidney function (5,6), therefore, when using it, there is a possibility of damage to them. The most pronounced results were obtained during experiments on mice (protein ranged from 10-15% to 35-45% daily ration at a time) (7.8).

Also, one study (9) of healthy people found that doubling the amount of protein consumed (from 1.2 to 2.4 g/kg body weight) led to higher than normal levels of protein metabolism in the blood. There was a tendency for the body to adapt - an increase in the glomerular filtration rate, but this was not enough to bring uric acid and blood urea levels to normal within 7 days (9).

All these studies primarily suggest that too much protein leads to too rapid changes, and the process of gradually increasing volumes does not worsen renal function (10). This means that it makes more sense to gradually change your protein intake over a relatively long period of time.

People with kidney disease are advised to use protein-restricted diets, as this will slow down the seemingly inevitable deterioration of the condition (11,12). Failure to control protein intake in patients with kidney disease accelerates (or at least does not slow down) the decline in kidney function (3).

Excess protein and liver

There is no reason to believe that normal levels of protein intake as part of a normal diet would be harmful to the liver of healthy rats or humans. However, there is preliminary research suggesting that very large amounts of protein after a sufficiently long fast (more than 48 hours) can lead to acute liver injury.

During treatment liver diseases (cirrhosis) it is recommended to reduce protein intake, since it causes the accumulation of ammonia in the blood (13,14), which makes a negative contribution to the development of hepatic encephalopathy (15).

It has been shown in at least one animal model that liver injury occurs during cycling between 5-day periods of sufficient protein intake and periods of protein deficiency (16). A similar effect was observed when consuming a meal containing 40-50% casein after a 48-hour fast.(17). Animal studies (18,19) have provided preliminary evidence that increased protein intake (35–50%) at the time of refeeding after a 48-hour fast may cause liver harm. Shorter periods of fasting were not considered.

Amino acids are acids, right?

We remind you that proteins are complex organic compounds consisting of smaller “building blocks” - amino acids. Actually, proteins consumed in food are broken down into amino acids.

Theoretically, it is possible to prove the harm of amino acids due to their excess acidity. But this is not a clinical problem: their acidity is too low to cause any trouble.

Read how our body regulates the balance of acidity / alkaline content in the text “ “.

Excess Protein and Bone Mineral Density

Analysis of a large observational study shows no link between protein intake and the risk of bone fractures (an indicator of bone health). The exception is when, with increased dietary protein, total calcium intake falls below 400 mg/1000 kcal daily (although the hazard ratio was quite weak at 1.51 when compared with the highest quartile) (26). Other studies have failed to find a similar correlation, although this would logically be expected (27,28).

Soy protein itself appears to have an additional protective effect on bone tissue in postmenopausal women, which may be related to the isoflavone content of soy (30).

The Role of Strength Training

As funny as it may seem, there is a study on this topic in rats. The rodents were acutely exposed to large amounts of protein in their diet, causing their kidney function to deteriorate.

But “resistance training” (apparently, one of the groups of rats was “loaded” physically) reduced the negative effect in some of them and had a protective effect (8).

Research mentioned:

1. Poortmans JR, Dellalieux O Do regular high protein diets have potential health risks on kidney function in athletes. Int J Sport Nutr Exerc Metab. (2000)
2. Beasley JM, et al Higher biomarker-calibrated protein intake is not associated with impaired renal function in postmenopausal women. J Nutr. (2011)
3. Knight EL, et al The impact of protein intake on renal function decline in women with normal renal function or mild renal insufficiency. Ann Intern Med. (2003)
4. Brändle E, Sieberth HG, Hautmann RE Effect of chronic dietary protein intake on the renal function in healthy subjects. Eur J Clin Nutr. (1996)
5. King AJ, Levey AS Dietary protein and renal function. J Am Soc Nephrol. (1993)
6. Dietary protein intake and renal function
7. Wakefield AP, et al A diet with 35% of energy from protein leads to kidney damage in female Sprague-Dawley rats. Br J Nutr. (2011)
8. Aparicio VA, et al Effects of high-whey-protein intake and resistance training on renal, bone and metabolic parameters in rats. Br J Nutr. (2011)
9. Frank H, et al Effect of short-term high-protein compared with normal-protein diets on renal hemodynamics and associated variables in healthy young men. Am J Clin Nutr. (2009)
10. Wiegmann TB, et al Controlled changes in chronic dietary protein intake do not change glomerular filtration rate. Am J Kidney Dis. (1990)
11. Levey AS, et al Effects of dietary protein restriction on the progression of advanced renal disease in the Modification of Diet in Renal Disease Study. Am J Kidney Dis. (1996)
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