Miti sulle proteine

[Eagle]

Fa piacere leggere un bel pò di studi, però:

Nessuno poi sulla tanto temuta iperfiltrazione.....

E' ovvio che un pò come un'auto più la facciamo camminare più motore, gomme ecc si consumano, allora ha ragione chi dice che dovremmo mangiare ed in generale agire poco per conservarci più a lungo?

Che i modelli animali siano adatti a studiare il funzionamento renale, non lo metto in dubbio, non ho le competenze per farlo, però non sono predettivi per quanto riguarda il metabolismo energetico e la fisiologia muscolare e del tessuto adiposo, e lo dico avendoci lavorato su, continuo a non condividere il tuo approccio di considerare a se stante l'apporto proteico rispetto all'uso che il nostro organismo ne fa.....ma anche qui non abbiamo dati chiari ed inequivocabili alla mano....

Sulla iperfiltrazione sono un pochino perplesso.
Concetto che mi sembra decisamente semplice da capire in base alle nozioni di fisiologia renale che possediamo: le sostanze più importanti da eliminare sono i residui azotati ed acidi, che sono, guarda a caso, il prodotto finale degli aminoacidi non utilizzati.

Viene citato sempre negli articoli su proteine e reni, è dato per scontato da tutti gli specialisti, nessuno lo mette mai in dubbio, però vuoi delle "dimostrazioni"?

Boh ...

Sul metabolismo diverso nell'atleta rispetto al non atleta, non capisco il punto.

Partiamo dal fatto che il numero di nefroni è fisso dopo la pubertà.
Non se ne possono formare di nuovi, anche se da sedentario diventi atleta di elite.
Se ne perdono comunque col tempo, l'unica strategia "salutistica" possibile è quella di limitarne le perdite.

Detto questo, facciamo i conti della serva.

Soggetto di 70 kg, che da sedentario introduce 70-100 g di proteine die, ed è in bilancio calorico ed azotato neutro.

Le elimina TUTTE, perchè bilancio neutro significa che azoto che introduci = azoto che elimini.
Tutto quello che ci sta in mezzo, quante "sostituzioni" proteiche avvengono, non ha alcun impatto sul rene.

Questo soggetto si mette ad allenarsi, cambia dieta, dopo 3 anni pesa 85 kg e sta a 2 grammi proteine / kg = 170 g.

Se anche fosse in costante bilancio azotato positivo, e riuscisse (fortunello!) a costruire 1 kg di muscoli ogni 3 mesi, significa che ha, a bilancio, 200 g di proteine trattenute in 90 giorni.

200 g in 90 giorni = 2,2 grammi al giorno.

Questo soggetto quindi introduce 170 grammi di proteine e ne elimina (reni) 167,8 grammi, ogni giorno (170 - 2,2 che trattiene).

In altre parole, i reni di questo soggetto, che sono sempre esattamente quelli di quando pesava 70 kg ed eliminavano 70-100 g di proteine die, si trovano adesso a filtrare ed eliminare 167,8 g di proteine die.

Questo comporta un aumento circa doppio della necesità di filtrazione, che rientra nel concetto di iperfiltrazione.
Infatti questi reni si ipertrofizzano = nefroni prima di riserva, quiescienti, si attivano, e se misuri i reni anche solo con un ecografia, sono più grossi.

Questo aumento di lavoro renale sarà dannoso?
NON LO SO.

Gli studi non riportano danni misurabili nel breve periodo, ma studi sul lungo e lunghissimo periodo non ce ne sono, e mai ce ne saranno penso.

Considerando che la riserva renale nel sano è molto abbondante, e chi segue diete iperproteiche è in genere giovane, quindi con riserva renale intatta, penso che sia comunque non corretto pensare che CON CERTEZZA non ci siano dei rischi.

Tutto quì.


Eagle

[brosgym]

Sembra comunuqe che più proteine introdotte = più lavoro per i reni, senza danni misurabili.

Consideriamo però che i reni, come tutte le parti del nostro corpo, sono destinate a consumarsi col tempo. La riserva renale, abbondante alla nascita, via via si riduce. Questo vale per tutti, ovviamente in misura diversa.

Consideriamo ad esempio chi perde un rene.
Questi va incontro a ipertrofia compensatoria del rene superstite, in cui la riserva viene messa in campo… e dopo 30 anni circa va in insufficienza renale.

Chi li ha entrambi, se non li danneggia con cose note (pressione, diabete, colesterolo, etc etc etc), dura di più, e spesso arriva a fine vita senza insufficienza renale.

Ci sono poi dei modelli animali.
Modelli animali ritenuti particolarmente adatti a studiare il funzionamento del rene sano e malato dell’uomo (sorry brosgym, ma pare proprio sia così), come il maiale e il ratto, con diete iperproteiche (35% delle calorie da pro) sembra che si scassano i reni per benino.

J Nutr. 2010 Sep;140(9):1646-52. Epub 2010 Jul 28.
Long-term high intake of whole proteins results in renal damage in pigs.

Jia Y, Hwang SY, House JD, Ogborn MR, Weiler HA, O K, Aukema HM.
Source

Department of Human Nutritional Sciences, University of Manitoba, Winnipeg, MB, Canada.
Abstract

Despite evidence of potential antiobesity effects of high-protein (HP) diets, the impact of consuming diets with protein levels at the upper limit of the acceptable macronutrient distribution range (AMDR) on kidney health is unknown. To test whether HP diets affect renal health, whole plant and animal proteins in proportions that mimicked human diets were given to pigs, because their kidneys have a similar anatomy and function to those of humans. Adult female pigs received either normal-protein (NP) or HP (15 or 35% of energy from protein, respectively) isocaloric diets for either 4 or 8 mo. The higher protein in the HP diet was achieved by increasing egg and dairy proteins. Although there were initial differences in body weight and composition, after 8 mo these were similar in pigs consuming the NP and HP diets. The HP compared with NP diet, however, resulted in enlarged kidneys at both 4 and 8 mo. Renal and glomerular volumes were 60-70% higher by the end of the study. These enlarged kidneys had greater evidence of histological damage, with 55% more fibrosis and 30% more glomerulosclerosis. Renal monocyte chemoattractant protein-1 levels also were 22% higher in pigs given the HP diet. Plasma homocysteine levels were higher in the HP pigs at 4 mo and continued to be elevated by 35% at 8 mo of feeding. These findings suggest that long-term intakes of protein at the upper limit of the AMDR from whole protein sources may compromise renal health.
Testo completo: http://jn.nutrition.org/content/140/9/1646.long






A diet with 35% of energy from protein leads to kidney damage in female Sprague-Dawley rats.

Wakefield AP, House JD, Ogborn MR, Weiler HA, Aukema HM.
Source

Department of Human Nutritional Sciences, R2033-1 St Boniface Research Centre, University of Manitoba, 351 Tache Avenue, Winnipeg, MB, Canada.
Abstract

High-protein (HP) diets for weight loss remain popular despite questions surrounding overall safety. In a recent study using the pig model, we showed that long-term intakes from whole proteins at 35 % energy (en %) cause moderate renal histological damage. To examine whether this observation may be species specific or more generalisable, the effect of this diet in rats was examined. Using plant and animal whole proteins, 70-d-old female Sprague-Dawley rats were randomised to either a normal-protein (NP; 15 en %) or a HP (35 en %) diet for 4, 8, 12 and 17 months. Renal function was assessed by creatinine clearance and urinary protein levels, and pathology was assessed by examination of glomerular hypertrophy, glomerulosclerosis and tubulointerstitial fibrosis. Rats consuming the HP diet had 17 % higher kidney weights (P < 0·0001), three times higher proteinuria (P < 0·0001) and 27 % higher creatinine clearance (P = 0·0012) compared with those consuming the NP diet. Consistent with this, HP-fed rats had larger glomeruli (P < 0·0001) and more glomerulosclerosis (P = 0·0003) compared with NP-fed rats. The HP diet also resulted in altered levels of free monocyte chemoattractant protein-1 (P < 0·0001). The histological changes are consistent with those observed in the pig model. In contrast to the pig model, the elevated proteinuria and creatinine clearance observed in the rat model are also usually observed with HP consumption in human subjects. These results indicate that the rat is a useful model for HP effects on the kidney and, along with previous results using the pig model, suggest that long-term intake of high levels of protein may be detrimental to renal health.


Prog Pediatr Surg. 1989;23:18-41.
Renal function in single-kidney rats.

Provoost AP, De Keijzer MH, Wessel JN, Molenaar JC.
Source

Department of Pediatric Surgery, Erasmus University, Rotterdam, The Netherlands.
Abstract

Can a single kidney survive for a normal life span? This is the type of question frequently asked by patients and especially by parents of children who lose one kidney in early childhood. Based on our wide experience with single-kidney rats, we will try to give an answer to this question. After the removal of its counterpart, the single remaining kidney will rapidly adapt to the new situation by a compensatory increase in the glomerular filtration rate (GFR) and renal mass. This is true not only for intact kidneys but also for damaged ones. The GFR level obtained by damaged kidneys will be less than that of intact single kidneys, however, depending on the degree of initial damage. The GFR is stable for a certain period of time, which is longer for intact single kidneys than for damaged kidneys and also depends on the daily protein intake; after that renal function will deteriorate. This decline in GFR is preceded by a marked increase in urinary protein excretion. Although the follow-up period is not completed yet, the survival time of single intact kidneys in rats on a normal diet is expected to be 15%-20% less than the normal rat life span. In rats on a lifelong high protein intake thekidney survival time drops to 40% below the normal rat life span. In rats on a moderately reduced protein intake, however, single intact kidneys may survive for a normal life span. The situation is worse for single damaged kidneys. Depending on the severity of the initial damage, kidney survival time will be much less than a normal life span. We studied rats with an initial recovery to 75% of renal function. Despite this initial recovery, the animals died of renal failure within 50% of the expected life span. A low-protein diet prolonged the renal survival by about 12%, a high-protein diet shortened it by the same percentage.

t;c�:6�σ h?� der:none windowtext 0cm;padding: 0cm;mso-ansi-language:FR'>Dellalieux O.
Source

Department of Physiological Chemistry, Institute of Physical Education and Kinesiotherapy, Free University of Brussels, Belgium.

Abstract

Excess protein and amino acid intake have been recognized as hazardous potential implications for kidney function, leading to progressive impairment of this organ. It has been suggested in the literature, without clear evidence, that high protein intake by athletes has no harmful consequences on renal function. This study investigated body-builders (BB) and other well-trained athletes (OA) with high and medium protein intake, respectively, in order to shed light on this issue. The athletes underwent a 7-day nutrition record analysis as well as blood sample and urine collection to determine the potential renal consequences of a high protein intake. The data revealed that despite higher plasma concentration of uric acid and calcium, Group BB had renal clearances of creatinine, urea, and albumin that were within the normal range. The nitrogen balance for both groups became positive when daily protein intake exceeded 1.26 g.kg but there were no correlations between protein intake and creatinine clearance, albumin excretion rate, and calcium excretion rate. To conclude, it appears that protein intake under 2. 8 g.kg does not impair renal function in well-trained athletes as indicated by the measures of renal function used in this study

Fa piacere leggere un bel pò di studi, però:

Nessuno poi sulla tanto temuta iperfiltrazione.....

E' ovvio che un pò come un'auto più la facciamo camminare più motore, gomme ecc si consumano, allora ha ragione chi dice che dovremmo mangiare ed in generale agire poco per conservarci più a lungo?

Che i modelli animali siano adatti a studiare il funzionamento renale, non lo metto in dubbio, non ho le competenze per farlo, però non sono predettivi per quanto riguarda il metabolismo energetico e la fisiologia muscolare e del tessuto adiposo, e lo dico avendoci lavorato su, continuo a non condividere il tuo approccio di considerare a se stante l'apporto proteico rispetto all'uso che il nostro organismo ne fa.....ma anche qui non abbiamo dati chiari ed inequivocabili alla mano....

[Eagle]

Curioso poi che non tutte le proteine diano lo stesso effetto sui reni. Alla faccia di Giovanni Cianti (perdonatemi la battuta) pare che le proteine dei latticini, albumi e soia “impattino” i reni in modo meno hard della carne.



J Am Diet Assoc. 2007 Apr;107(4):644-50.
Are high-protein, vegetable-based diets safe for kidney function? A review of the literature.

Bernstein AM, Treyzon L, Li Z.
Source

Department of Nutrition, Harvard School of Public Health, 665 Huntington Ave, Boston, MA 02115, USA.
Abstract

In individuals with chronic kidney disease, high-protein diets have been shown to accelerate renal deterioration, whereas low-protein diets increase the risk of protein malnutrition. Vegetarian diets have been promoted as a way to halt progression of kidney disease while maintaining adequate nutrition. We review the literature to date comparing the effects of animal and vegetable protein on kidney function in health and disease. Diets with conventional amounts of protein, as well as high-protein diets, are reviewed. The literature shows that in short-term clinical trials, animal protein causes dynamic effects on renal function, whereas egg white, dairy, and soy do not. These differences are seen both in diets with conventional amounts of protein and those with high amounts of protein. The long-term effects of animal protein on normal kidney function are not known. Although data on persons with chronic kidney disease are limited, it appears that high intake of animal and vegetable proteins accelerates the underlying disease process not only in physiologic studies but also in short-term interventional trials. The long-term effects of high protein intake on chronic kidney disease are still poorly understood. Several mechanisms have been suggested to explain the different effects of animal and vegetable proteins on normal kidney function, including differences in postprandial circulating hormones, sites of protein metabolism, and interaction with accompanying micronutrients.


I’iperfiltrazione, concetto vago (ma che ben si capisce se uno vuole) è quello che succede mangiando tante proteine. Non è uno stato “definito”, adesso sono in iperfiltrazione, tra un’ora non più. E’ una misura di quanto faccio lavorare i miei reni IN RAPPORTO a quanto possono lavorare al 100%.

E’ come fare 50 kg in panca con il massimale di 120 piuttosto che di 70. Per qualcuno 200 g di proteine metteranno i reni a duro lavoro, per altri no.
Sarà variabile da persona a persona.

In tutti però, se raddoppio le proteine introdotte, raddioppio (più o meno) la filtrazione, ovvero raddoppio il “lavoro dei reni”.
Ripeto e sottolineo che questo non significa necessariamente danno.

Am J Kidney Dis. 2004 Dec;44(6):950-62.
High-protein diets: potential effects on the kidney in renal health and disease.

Friedman AN.
Source

Division of Nephrology, Indiana University School of Medicine, Indianapolis, IN 46202, USA. allfried@iupui.edu
Abstract

High-protein (HP) weight-loss diets have existed in the United States for decades, although their popularity has recently surged as obesity has become more common. Despite their widespread use, valid concerns exist that HP diets may induce clinically important alterations in renal function and health. HP consumption has been found, under various conditions, to lead to glomerular hyperfiltration and hyperemia; acceleration of chronic kidney disease (CKD); increased proteinuria; diuresis, natriuresis, and kaliuresis with associated blood pressure changes; increased risk for nephrolithiasis; and various metabolic alterations. Unfortunately, a comprehensive understanding of the implications of HP diets is limited by the lack of a universally accepted definition for HP intake, a paucity of rigorous long-term human interventional studies that necessitate relying on short-term or fairly circumstantial evidence, and sparse data on the effects of HP consumption in obese individuals. In addition, matters are further complicated because the renal impact HP diets for limited periods is most likely different than that for more chronic consumption. Nevertheless, although there are no clear renal-related contraindications to HP diets in individuals with healthy kidney function, the theoretical risks should be reviewed carefully with the patient. In contrast, HP diets have the potential for significant harm in individuals with CKD and should be avoided if possible. Because CKD is often a silent disease, all individuals should undergo a screening serum creatinine measurement and urinary dipstick test for proteinuria before the initiation of such a diet.


A complicare le cose ci sono poi segnalazioni che anche le calorie siano in gioco nei possibili danni renali … e probabilmente ci saranno altre cose che non pensiamo…


Am J Nephrol. 1999;19(3):433-40.
A low-calorie unrestricted protein diet attenuates kidney damage in uninephrectomized spontaneously hypertensive rats.

Reisin E, Harris KY, Azar S, DeBoisblanc B, Thakur V, Liuzza GF.
Source

Department of Medicine, Louisiana State University, New Orleans, LA 70112-2822, USA.
Abstract

BACKGROUND/AIMS:

Uninephrectomized, spontaneously hypertensive rats (UNX-SHR) develop glomerular hyperfiltration, hyperfusion, and interstitial infiltrate of the remnant kidney. Consequently, UNX-SHR is a useful animal model to investigate mechanisms involved in the progression of hypertensive renal disease.
METHODS:

Body weight; tail systolic blood pressure (SBP); urine excretion of protein, urea, and electrolytes; and serum biochemistry were determined in UNX-SHR at 2 months of age prior to uninephrectomy (week 0), prior to treatment (week 8) with a low-calorie (LC) or control diet, and one month after diet treatment (week 12). The LC diet was modified to allow equal intake of protein, sodium phosphorus, and other nutrients in both groups.
RESULTS:

UNX-SHR treated with the LC diet had significantly lower body weights and SBP at the end of the experiment than did the controls (p < 0.0001). Changes in serum biochemistry and 24-hour urinary excretion of protein, sodium, potassium, and urea nitrogen in both groups were not statistically significant. The final glomerular filtration rate and renal plasma flow were similar in both groups, but the LC diet significantly reduced the glomerular damage index (0.0007), mesangial expansion index (p < 0.002), volume of interstitium per cortex (p < 0.0003), tubular interstitium volume fraction (p < 0.0008), glomerular volume (p < 0.02), and remnant kidney weight (p < 0.01).
CONCLUSION:

We demonstrated that in UNX-SHR, the prevention of renal damage by LC diet may involve diminished glomerular growth and interstitial infiltrate without changes in renal hemodynamics. Consequently, LC diet, regardless of protein ingestion, may be an important tool in the prevention of renal damage in hypertension. Additional studies of obese-hypertensive rats may confirm the beneficial effect of a LC diet and weight reduction on the renal damage of obesity-hypertension.



Personalmente anche dopo questa rinfrescata rimango con le mie conclusioni di prima.

Eagle

[Eagle]

Sembra comunuqe che più proteine introdotte = più lavoro per i reni, senza danni misurabili.

Consideriamo però che i reni, come tutte le parti del nostro corpo, sono destinate a consumarsi col tempo. La riserva renale, abbondante alla nascita, via via si riduce. Questo vale per tutti, ovviamente in misura diversa.

Consideriamo ad esempio chi perde un rene.
Questi va incontro a ipertrofia compensatoria del rene superstite, in cui la riserva viene messa in campo… e dopo 30 anni circa va in insufficienza renale.

Chi li ha entrambi, se non li danneggia con cose note (pressione, diabete, colesterolo, etc etc etc), dura di più, e spesso arriva a fine vita senza insufficienza renale.

Ci sono poi dei modelli animali.
Modelli animali ritenuti particolarmente adatti a studiare il funzionamento del rene sano e malato dell’uomo (sorry brosgym, ma pare proprio sia così), come il maiale e il ratto, con diete iperproteiche (35% delle calorie da pro) sembra che si scassano i reni per benino.

J Nutr. 2010 Sep;140(9):1646-52. Epub 2010 Jul 28.
Long-term high intake of whole proteins results in renal damage in pigs.

Jia Y, Hwang SY, House JD, Ogborn MR, Weiler HA, O K, Aukema HM.
Source

Department of Human Nutritional Sciences, University of Manitoba, Winnipeg, MB, Canada.
Abstract

Despite evidence of potential antiobesity effects of high-protein (HP) diets, the impact of consuming diets with protein levels at the upper limit of the acceptable macronutrient distribution range (AMDR) on kidney health is unknown. To test whether HP diets affect renal health, whole plant and animal proteins in proportions that mimicked human diets were given to pigs, because their kidneys have a similar anatomy and function to those of humans. Adult female pigs received either normal-protein (NP) or HP (15 or 35% of energy from protein, respectively) isocaloric diets for either 4 or 8 mo. The higher protein in the HP diet was achieved by increasing egg and dairy proteins. Although there were initial differences in body weight and composition, after 8 mo these were similar in pigs consuming the NP and HP diets. The HP compared with NP diet, however, resulted in enlarged kidneys at both 4 and 8 mo. Renal and glomerular volumes were 60-70% higher by the end of the study. These enlarged kidneys had greater evidence of histological damage, with 55% more fibrosis and 30% more glomerulosclerosis. Renal monocyte chemoattractant protein-1 levels also were 22% higher in pigs given the HP diet. Plasma homocysteine levels were higher in the HP pigs at 4 mo and continued to be elevated by 35% at 8 mo of feeding. These findings suggest that long-term intakes of protein at the upper limit of the AMDR from whole protein sources may compromise renal health.
Testo completo: http://jn.nutrition.org/content/140/9/1646.long






A diet with 35% of energy from protein leads to kidney damage in female Sprague-Dawley rats.

Wakefield AP, House JD, Ogborn MR, Weiler HA, Aukema HM.
Source

Department of Human Nutritional Sciences, R2033-1 St Boniface Research Centre, University of Manitoba, 351 Tache Avenue, Winnipeg, MB, Canada.
Abstract

High-protein (HP) diets for weight loss remain popular despite questions surrounding overall safety. In a recent study using the pig model, we showed that long-term intakes from whole proteins at 35 % energy (en %) cause moderate renal histological damage. To examine whether this observation may be species specific or more generalisable, the effect of this diet in rats was examined. Using plant and animal whole proteins, 70-d-old female Sprague-Dawley rats were randomised to either a normal-protein (NP; 15 en %) or a HP (35 en %) diet for 4, 8, 12 and 17 months. Renal function was assessed by creatinine clearance and urinary protein levels, and pathology was assessed by examination of glomerular hypertrophy, glomerulosclerosis and tubulointerstitial fibrosis. Rats consuming the HP diet had 17 % higher kidney weights (P < 0·0001), three times higher proteinuria (P < 0·0001) and 27 % higher creatinine clearance (P = 0·0012) compared with those consuming the NP diet. Consistent with this, HP-fed rats had larger glomeruli (P < 0·0001) and more glomerulosclerosis (P = 0·0003) compared with NP-fed rats. The HP diet also resulted in altered levels of free monocyte chemoattractant protein-1 (P < 0·0001). The histological changes are consistent with those observed in the pig model. In contrast to the pig model, the elevated proteinuria and creatinine clearance observed in the rat model are also usually observed with HP consumption in human subjects. These results indicate that the rat is a useful model for HP effects on the kidney and, along with previous results using the pig model, suggest that long-term intake of high levels of protein may be detrimental to renal health.


Prog Pediatr Surg. 1989;23:18-41.
Renal function in single-kidney rats.

Provoost AP, De Keijzer MH, Wessel JN, Molenaar JC.
Source

Department of Pediatric Surgery, Erasmus University, Rotterdam, The Netherlands.
Abstract

Can a single kidney survive for a normal life span? This is the type of question frequently asked by patients and especially by parents of children who lose one kidney in early childhood. Based on our wide experience with single-kidney rats, we will try to give an answer to this question. After the removal of its counterpart, the single remaining kidney will rapidly adapt to the new situation by a compensatory increase in the glomerular filtration rate (GFR) and renal mass. This is true not only for intact kidneys but also for damaged ones. The GFR level obtained by damaged kidneys will be less than that of intact single kidneys, however, depending on the degree of initial damage. The GFR is stable for a certain period of time, which is longer for intact single kidneys than for damaged kidneys and also depends on the daily protein intake; after that renal function will deteriorate. This decline in GFR is preceded by a marked increase in urinary protein excretion. Although the follow-up period is not completed yet, the survival time of single intact kidneys in rats on a normal diet is expected to be 15%-20% less than the normal rat life span. In rats on a lifelong high protein intake thekidney survival time drops to 40% below the normal rat life span. In rats on a moderately reduced protein intake, however, single intact kidneys may survive for a normal life span. The situation is worse for single damaged kidneys. Depending on the severity of the initial damage, kidney survival time will be much less than a normal life span. We studied rats with an initial recovery to 75% of renal function. Despite this initial recovery, the animals died of renal failure within 50% of the expected life span. A low-protein diet prolonged the renal survival by about 12%, a high-protein diet shortened it by the same percentage.

t;c�:6�σ h?� der:none windowtext 0cm;padding: 0cm;mso-ansi-language:FR'>Dellalieux O.
Source

Department of Physiological Chemistry, Institute of Physical Education and Kinesiotherapy, Free University of Brussels, Belgium.

Abstract

Excess protein and amino acid intake have been recognized as hazardous potential implications for kidney function, leading to progressive impairment of this organ. It has been suggested in the literature, without clear evidence, that high protein intake by athletes has no harmful consequences on renal function. This study investigated body-builders (BB) and other well-trained athletes (OA) with high and medium protein intake, respectively, in order to shed light on this issue. The athletes underwent a 7-day nutrition record analysis as well as blood sample and urine collection to determine the potential renal consequences of a high protein intake. The data revealed that despite higher plasma concentration of uric acid and calcium, Group BB had renal clearances of creatinine, urea, and albumin that were within the normal range. The nitrogen balance for both groups became positive when daily protein intake exceeded 1.26 g.kg but there were no correlations between protein intake and creatinine clearance, albumin excretion rate, and calcium excretion rate. To conclude, it appears that protein intake under 2. 8 g.kg does not impair renal function in well-trained athletes as indicated by the measures of renal function used in this study

[Eagle]

Riprendendo il discorso
Ho letto un po’, chiacchierato e discusso con qualche nefrologo.

Abbiate pazienza, non so se riuscirò ad essere breve.
Riporto anche alcuni studi che ho letto.
Tenete presente comunque che leggere qualche studio è sempre rischiso, a ben guardare si trova sempre anche uno studio che dice il contrario. Bisognerebbe leggerli tutti, sapere come e chi li ha fatti, controllare la correttezza di alcuni metodi e test statistici, insomma un lavoro immane. Per fortuna ci sono le “linee guida” delle società scientifiche che in genere fanno questo lavoro per noi. La mia prendetela quindi come una carrellata molto personale, e che non ha alcuna pretesa di “fare chiarezza” su un argomento su cui non c’è chiarezza nel mondo degli scienziati che se ne occupano sul serio.

Fatemi anche fare un’altra premessa.
Io non sono contro le diete iperproteiche, io stesso mangio tante proteine (mangio tanto in generale a dire il vero). Mi piace però cercare di capire le cose evitando pregiudizi.


Studi sull’uomo pare non abbiano evidenziato che reni sani vengano danneggiati da diete anche fortemene iperproteiche, ma le durate sono sempre limitate. Dato che ci vogliono decenni, se uno non ha altri fattori di danno, per consumare le riserva renale, il discorso, nella misura in cui si parla di tante proteine per decenni, secondo me, rimane aperto.

Dietary protein intake and renal function

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1262767/

Am J Clin Nutr. 2009 Dec;90(6):1509-16. Epub 2009 Oct 7.
Effect of short-term high-protein compared with normal-protein diets on renal hemodynamics and associated variables in healthy young men.

Frank H, Graf J, Amann-Gassner U, Bratke R, Daniel H, Heemann U, Hauner H.
Source

Klinikum rechts der Isar, Technical University Munich, Munich, Germany. helga.frank@lrz.tum.de
Erratum in

· Am J Clin Nutr. 2010 Feb;91(2):494. Graf, Juliane [corrected to Graf, Julia].
Abstract

BACKGROUND:

High-protein diets are effective for weight reduction; however, little is known about the potential adverse renal effects of such diets.
OBJECTIVE:

The aim of our study was to compare the effect of a high-protein (HP) with a normal-protein (NP) diet on renal hemodynamics and selected clinical-chemical factors.
DESIGN:

We prospectively studied the effect of an HP diet (2.4 g x kg(-1) x d(-1)) with that of an NP diet (1.2 g x kg(-1) x d(-1)) on the glomerular filtration rate (assessed on the basis of sinistrin-an inulin analog-clearance) and renal plasma flow (para-aminohippuric acid clearance) by using the constant infusion technique. Filtration fraction and renal vascular resistance were calculated. Twenty-four healthy young men followed the 2 diet protocols for 7 d each in a crossover design. They were individually advised by a dietitian to achieve the planned protein intake by selecting normal foods under isocaloric conditions. Serum and urinary variables and renal hemodynamics were measured on day 7 of both diets.
RESULTS:

The glomerular filtration rate (NP: 125 +/- 5 mL/min; HP: 141 +/- 8 mL/min; P < 0.001) and filtration fraction (NP: 23 +/- 5%; HP: 28 +/- 5%; P < 0.05) increased significantly with the HP diet. Renal plasma flow was not significantly different between the HP (496 +/- 25 mL/min) and NP (507 +/- 18 mL/min) phases. Renal vascular resistance was not significantly different between the NP (94 +/- 6 mm Hg x mL(-1) x min(-1)) and HP (99 +/- 8 mm Hg x mL(-1) x min(-1)) phases. Blood urea nitrogen, serum uric acid, glucagon, natriuresis, urinary albumin, and urea excretion increased significantly with the HP diet.
CONCLUSIONS:

A short-term HP diet alters renal hemodynamics and renal excretion of uric acid, sodium, and albumin. More attention should be paid to the potential adverse renal effects of HP diets.

Testo completo: http://ajcn.nutrition.org/content/90/6/1509.long



Eur J Clin Nutr. 1996 Nov;50(11):734-40.
Effect of chronic dietary protein intake on the renal function in healthy subjects.

Brändle E, Sieberth HG, Hautmann RE.
Source

Department of Urology, University of Ulm, Germany.
Abstract

OBJECTIVE:

Relatively little is known about the influence of chronic oral protein intake on the kidney function. In most studies only the effect of a short-term change in protein intake [6-28 days] or the effect of an acute protein load on the glomerular filtration rate was studied. The purpose of this study was to investigate the effect of chronic oral protein intake on endogenous creatinine clearance and on the albumin excretion rate.
DESIGN AND SUBJECTS:

In a prospective study 88 healthy volunteers with normal renal function (32 vegetarians, 12 body-builders with no supplementary protein concentrates, 28 body-builders with supplementary protein concentrates and 16 subjects with no special diet) were examined. In order to investigate the effect of chronic oral protein intake, the participants were on their diet for at least 4 months.
RESULTS:

Endogenous creatinine clearance as a measure for glomerular filtration rate varied between 32 ml/min and 197 ml/min or 34 and 186 ml/min x 1.73 m2, respectively. Nitrogen excretion rate was used as a measure for the daily protein intake, since it is known to correlate linearly with the daily protein intake. Nitrogen excretion rates ranged between 2.66 g/d and 33.93 g/d reflecting a daily protein consumption between 17 and 212 g/d or 0.29 g/kg bw/d and 2.6 g/kg bw/day, respectively. Between nitrogen excretion rate and endogenous creatinine clearance a non linear, highly significant correlation was found showing a saturation with a maximum endogenous creatinine clearance of 181.7 ml/min (dose response curve). A similar correlation was observed between urea excretion rate and endogenous creatinine clearance. Using a model for multiple regression analysis the dependence of the albumin excretion rate on nitrogen excretion rate and endogenous creatinine clearance was examined. Only a significant correlation was found between albumin excretion rate and endogenous creatinine clearance, while the correlation between albumin excretion rate and nitrogen excretion rate was not significant.
CONCLUSION:

This investigation shows that chronic oral protein intake of widely varying amounts of protein is a crucial control variable for the glomerular filtration rate in subjects with healthy kidneys. It is suggested that these changes reflect in part structural changes of the glomerulus and tubules due to chronic protein intake.

Int J Sport Nutr Exerc Metab. 2000 Mar;10(1):28-38.
Do regular high protein diets have potential health risks on kidney function in athletes?

Poortmans JR, Dellalieux O.


Source

Department of Physiological Chemistry, Institute of Physical Education and Kinesiotherapy, Free University of Brussels, Belgium.

Abstract

Excess protein and amino acid intake have been recognized as hazardous potential implications for kidney function, leading to progressive impairment of this organ. It has been suggested in the literature, without clear evidence, that high protein intake by athletes has no harmful consequences on renal function. This study investigated body-builders (BB) and other well-trained athletes (OA) with high and medium protein intake, respectively, in order to shed light on this issue. The athletes underwent a 7-day nutrition record analysis as well as blood sample and urine collection to determine the potential renal consequences of a high protein intake. The data revealed that despite higher plasma concentration of uric acid and calcium, Group BB had renal clearances of creatinine, urea, and albumin that were within the normal range. The nitrogen balance for both groups became positive when daily protein intake exceeded 1.26 g.kg but there were no correlations between protein intake and creatinine clearance, albumin excretion rate, and calcium excretion rate. To conclude, it appears that protein intake under 2. 8 g.kg does not impair renal function in well-trained athletes as indicated by the measures of renal function used in this study

[spot86]

Lo studio è interessante, il top sarebbe su soggetti normali (non obesi)...

[WhiteTyson]

Poi il mio parere è che se c'è iperfiltrazione in risposta ad un pasto questo deve contenere un quantitativo di proteine molto consistente tipo 50-60g, altrimenti si starebbe sempre in iperfiltrazione, dunque raramente saremo in iperfiltrazione.

Io direi che non si può che quotare, se non si stabilisce un valore massimo è inutile dire che pasti iperproteici aumentino l'iperfiltrazione, iper infatti rispetto a cosa?

[brosgym]

Sì, capisco, chiedo scusa, intendevo solo che in medium stat virtus, ecco una cosa del genere insomma

In regge l'ablativo quindi: in medio stat virtus

Comunque è una discussione abbastanza tecnica, quindi gradiremmo consigli e post di conseguenza.

[LastNatural]

Sì, capisco, chiedo scusa, intendevo solo che in medium stat virtus, ecco una cosa del genere insomma

[brosgym]

questo studio potrebbe essere interessante per la discussione, riporta dati su obesi senza patologie renali dopo un anno di dieta iperproteica:


http://www.ncbi.nlm.nih.gov/pubmed/20338292

Si, ho dato un occhio all'abs, certo si parla di 124g di pro al giorno che per i soggetti, non sarà molto più di 1gxKg visto che hanno un BMI oltre 30, però al breve termine da un'indicazione.

[blindevil7]

questo studio potrebbe essere interessante per la discussione, riporta dati su obesi senza patologie renali dopo un anno di dieta iperproteica:


http://www.ncbi.nlm.nih.gov/pubmed/20338292

interessante, anche se il campione non mi sembra poi così significante dal punto di vista statistico... attendiamo le voci dei Big

[brosgym]

Scusate se mi intrometto. Sono un principiante assoluto.
Ho letto incuriosito tutta la dscussione e gli studi recenti.
Sapete dirmi per caso cosa è la gotta^ Gli studi moderni cosa dicono a riguardo? Una volta si chiamava la malattia dei re perchè erano gli unici a potersi permettere una alimentazione iperproteica mentre gli altri potevano permettersi solo farinacei e si ammalavano di pellagra.
Credo che a volte la storia ci insegna tante cose, senza bisogno di ricorrere agli studi recenti

Dai un occhio più serio, la gotta è legata al metabolismo delle purine che provengono principalmente dagli acidi nucleici ovvero DNA ed RNA, quindi le carni ne contengono alcune più di altre, ma molti vegetali come piselli, asparagi o arachidi ne sono ricchissimi, anche l'alcol pur non essendo legato al metabolismo delle purine peggiora molto le cose, comunque con le proteine in se non c'entra.

Quindi la storia ci insegna, ma prima di proporre qualcosa cerchiamo di farlo a ragion veduta

[LastNatural]

Scusate se mi intrometto. Sono un principiante assoluto.
Ho letto incuriosito tutta la dscussione e gli studi recenti.
Sapete dirmi per caso cosa è la gotta^ Gli studi moderni cosa dicono a riguardo? Una volta si chiamava la malattia dei re perchè erano gli unici a potersi permettere una alimentazione iperproteica mentre gli altri potevano permettersi solo farinacei e si ammalavano di pellagra.
Credo che a volte la storia ci insegna tante cose, senza bisogno di ricorrere agli studi recenti

[jinx]

questo studio potrebbe essere interessante per la discussione, riporta dati su obesi senza patologie renali dopo un anno di dieta iperproteica:

http://www.ncbi.nlm.nih.gov/pubmed/20338292

[brosgym]

Mi modero se si parla sullo stesso piano, altrimenti per far sentire la mia voce ai piani superiori occorre necessariamente urlare.

Tu hai fatto questa domanda: "E poi si parla di singolo pasto ad alte proteine non di dieta iperproteica in generale, e che significa pasto iperproteico 30g, 40, 50g non so, e si si fanno tanti pasti da 20g?"

Come puoi trovare risposta in un abstract? Probabilmente la trovi nel testo intregrale.



Questo era il senso del mio intervento.

Certo, ma visto che sei stato moderatore anche tu, dovresti ricordare che scrivere in maiuscolo, per giunta con punti esclamativi equivale a gridare.

E nessuno ti stava relegando in posti di minor rilievo o attenzione.

Torniamo IT, la risposta non la trovi nell'abs, ma neanche nel full visto che si tratta di una review che sicuramente non parlerà così nello specifico di ogni lavoro analizzato, non solo questa era una domanda rivolta più ad Eagle visto che quello che anche l'autore scrive nell'abs sembra qualcosa di consolidato in medicina e nefrologia in particolare, quindi sicuramente non verrà analizzato nella review.

Poi il mio parere è che se c'è iperfiltrazione in risposta ad un pasto questo deve contenere un quantitativo di proteine molto consistente tipo 50-60g, altrimenti si starebbe sempre in iperfiltrazione, dunque raramente saremo in iperfiltrazione.