come fate a stare tranquilli con le diete?

[carnera]

La mia era un'introduzione. Se uno va a cercare consigli su un forum di BBing invece che da un dietologo significa che ha fatto i suoi conti sui costi\benefici e non possiamo giudicare la sua scelta. Qui nessuno chiede soldi per un consiglio, e ci mancherebbe altro.

[carnera]

Per quanto riguarda la prima parte posso risponderti dicendo che io ho sempre saputo, e nn perchè me lo sono inventato, che troppe proteine danneggiano i reni.

Lo hai sempre saputo perchè lo hai sentito al tg2 nella sezione "costume e società" seguendo il reportage: "attenzione alle diete fai da tè per la prova costume"?

E' appurato che 2g di proteine per kg di LBM per uno sportivo sano, senza problemi pregressi, non danneggino un bel niente.

High-Protein Weight Loss Diets and Purported Adverse Effects: Where is the Evidence?

Anssi H Manninen email

Department of Physiology, Faculty of Medicine, University of Oulu, Finland

author email corresponding author email

Journal of the International Society of Sports Nutrition 2004, 1:45-51doi:10.1186/1550-2783-1-1-45

The electronic version of this article is the complete one and can be found online at: http://www.jissn.com/content/1/1/45
Received: 1 March 2004
Accepted: 9 May 2004
Published: 10 May 2004

© 2004 A National Library of Congress Indexed Journal
Keywords: high-protein diets, adverse effects, American Heart Association

Abstract

Results of several recent studies show that high-protein, low-carbohydrate weight loss diets indeed have their benefits. However, agencies such as the American Heart Association (AHA) have some concerns about possible health risks. The purpose of this review is to evaluate the scientific validity of AHA Nutrition Committee's statement on dietary protein and weight reduction (St. Jeor ST et al. Circulation 2001;104:1869–1874), which states: "Individuals who follow these [high-protein] diets are risk for ... potential cardiac, renal, bone, and liver abnormalities overall. Simply stated, there is no scientific evidence whatsoever that high-protein intake has adverse effects on liver function. Relative to renal function, there are no data in the scientific literature demonstrating that healthy kidneys are damaged by the increased demands of protein consumed in quantities 2–3 times above the Recommended Dietary Allowance (RDA). In contrast with the earlier hypothesis that high-protein intake promotes osteoporosis, some epidemiological studies found a positive association between protein intake and bone mineral density. Further, recent studies studies suggest, at least in the short term, that RDA for protein (0.8 g/kg) does not support normal calcium homeostasis. Finally, a negative correlation has been shown between protein intake and systolic and diastolic blood pressures in several epidemiological surveys. In conclusion, there is little if any scientific evidence supporting above mentioned statement. Certainly, such public warnings should be based on a thorough analysis of the scientific literature, not unsubstantiated fears and misrepresentations. For individuals with normal renal function, the risks are minimal and must be balanced against the real and established risk of continued obesity.

Introduction

Certainly, living organisms thrive best in the milieu and on the diet to which they were evolutionarily adopted. From all indications, Homo sapiens sapiens (anatomically modern humans) has remained biologically unchanged during at least the last 50,000 years. [39] It was not until some 10,000 years ago that the transition from a roaming hunter and gatherer to a stationary farmer began. Consequently, our diet has become progressively more divergent from those of our ancient ancestors. The typical Paleolithic diet compared with the average modern American diet contained 3 to 4 times more protein.[40]

It is implausible that an animal that adapted to a high protein diet for 5 million years suddenly in 10,000 years becomes a predominant carbohydrate burner. Indeed, counter to the current US Dietary Guidelines which promotes diet high in complex carbohydrates, recent clinical investigations support the efficacy of high-protein diets for weight loss/fat loss, as well as for improved insulin sensitivity and blood lipid profiles. Thus, the popularity of high-protein diets for weigh loss is unquestionable. However, there are always some concerns about high-protein diets.

In 2001, the American Heart Association (AHA) Nutrition Committee published statement on dietary protein and weight reduction.[2] According to this statement, "Individuals who follow these [high-protein] diets are risk for ... potential cardiac, renal, bone, and liver abnormalities overall. However, it should be noted that there is little if any evidence supporting these contentions. Thus, this review deals with the relationship between protein intake and renal function, bone health, blood pressure, heart disease and liver function. Also, effects of very-low carbohydrate diet on lean body mass loss are discussed.

Protein Intake and Renal Function
Healthy individuals

Despite its role in nitrogen excretion, there are presently no data in the scientific literature demonstrating the healthy kidney will be damaged by the increased demands of protein consumed in quantities above the Recommended Dietary Allowance (RDA). Furthermore, real world examples support this contention since kidney problems are nonexistent in the bodybuilding community in which high-protein intake has been the norm for over half a century.[3] Recently, Walser published comprehensive review on protein intake and renal function, which states: "it is clear that protein restriction does not prevent decline in renal function with age, and, in fact, is the major cause of that decline. A better way to prevent the decline would be to increase protein intake. there is no reason to restrict protein intake in healthy individuals in order to protect the kidney."[4]

The study by Poortmans and Dellalieux investigated body-builders and other well-trained athletes with high- and medium-protein intake, respectively. [5] 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, bodybuilders had renal clearances of creatinine, urea, and albumin that were within the normal range. To conclude, it appears, at least in the short term, that protein intake under 2.8 g/kg does not impair renal function in well-trained athletes.

More recently, Knight et al. determined whether protein intake influences the rate of renal function change in women over an 11-year period.[32] 1624 women enrolled in the Nurses' HealthStudy who were 42 to 68 years of age in 1989 and gave bloodsamples in 1989 and 2000. Ninety-eight percent of women werewhite, and 1% were African American. In multivariate linear regression analyses, highproteinintake was not significantly associated with change in estimated glomerular filtration rate(GFR) in women with normal renal function (defined as an estimatedGFR ≥80 mL/min per 1.73 m2). Thus, the authors concluded that high protein intake does not seem tobe associated with renal function decline in women with normalrenal function. As pointed out by Lentine and Wrone[33], the generalizability of these findings is limited by sampling characteristics to white mid-adulthood, but this limitation is overshadowed by strong internal validity grounded in a large sample size, prospective outcomes ascertainment, and adjustment for multiple covariates.

Chronic Renal Failure

Historically, dietary protein restriction has been recommend as a therapeutic approach for delaying the progression of chronic renal failure (CRF). However, as pointed out by Ikizler,[6] it is important to reassess the applicability of this approach. Indeed, the results of the largest randomised clinical trial, The Modification of Diet in Renal Disease (MDRD), did not demonstrate a benefit of dietary protein restriction on progression of renal disease.[7] Further, CRF patients have been shown to require a protein intake of 1.4 g/kg/day to maintain a positive or neutral nitrogen balance during nondialysis days, and even this intake may not be adequate for dialysis days.[6]

Diabetics

According to American Diabetes Association (ADA), there is no evidence to suggest that usual protein intake (15–20% of total calories) should be modified if renal function is normal.[8] The long-term effects of consuming >20% of energy as protein on the development of nephropathy has not been determined, and therefore ADA nutritionists felt it may be prudent to avoid protein intakes >20% of total daily energy.[8] More recently, the metabolic effects of a high-protein diet were compared with those of the prototypical healthy (control) diet, which is currently recommended to persons with type 2 diabetes.[31] The ratio of protein to carbohydrate to fat was 30:40:30 in the high-protein diet and 15:55:30 in the control diet. The high-protein diet resulted in a 40% decrease in the mean 24-h integrated glucose area response. Further, glycated hemoglobin decreased 0.8% and 0.3% after 5 weeks of the high-protein and control diets, respectively. Finally, fasting triacylglycerol was significantly lower after the high-protein diet than after the control diet. The authors concluded that a high-protein diet lowers blood glucose postprandially in persons with type 2 diabetes and improves overall glucose control. Cleary, longer-term studies are necessary to determine the total magnitude of response and possible adverse effects.

Protein Intake and Bone Health

Increasing dietary protein increases urine calcium excretion such that for each 50 g increment of protein consumed, and extra 60 mg of urinary calcium is excreted. It follows that the higher the protein intake, the more urine calcium is lost and the more negative calcium balance becomes. Since 99% of the body's calcium is found in bone, one would hypothesize that high protein induced hypercalciuria would results in high bone resorption and increased prevalence of osteopenia or osteoporotic-related fractures.

However, the epidemiological and clinical data addressing this hypothesis are controversial. In fact, some epidemiological studies found a positive association between protein intake and bone mineral density (BMD).[9,37,38] Further, there is growing evidence that a low protein diet has a detrimental effect on bone. For example, Kerstetter et al. reported that in healthy young women, acute intakes of a low-protein diet (0.7 g protein/kg) decreased urinary calcium excretion with accompanied secondary hyperparathyroidism.[10] The etiology of the secondary hyperparathyroidism is due, in part, to a significant reduction in intestinal calcium absorption during a low protein diet.

In a recent short-term intervention trial, Kerstetter et al. evaluated the effects of graded levels of dietary protein (0.7, 0.8, 0.9, and 1.0 g protein/kg) on calcium homeostasis.[11] Secondary hyperparathyroidism developed by day 4 of the 0.7 and 0.8 g protein/kg diets (due to the decreased intestinal calcium absorption), but not during the 0.9 or 1.0 g protein/kg diets in eight young women. There were no significant differences in mean urinary calcium excretion over the relatively narrow range of dietary protein intakes studied, although the mean value with the 0.7-g/kg intake was lower than that with the 1.0 g/kg intake by 0.25 mmol (10 mg). According to authors of this study, the lack of change may be due to the small sample and the inherent variability in urinary calcium excretion. Similarly, when Giannini et al. restricted dietary protein to 0.8 g protein/kg, they observed an acute rise in serum parathyroid hormone (PTH) in 18 middle-aged hypercalciuric adults.[12] Taken together, both of studies suggest, at least in the short term, that the RDA for protein (0.8 g/kg) does not support normal calcium homeostasis.

Furthermore, dietary protein increases circulating IGF-1, a growth factor that is thought to play an important role in bone formation. Indeed, several studies have examined the impact of protein supplementation in patients with recent hip fractures. For example, Schurch et al. reported that supplementation with 20 g protein/day for 6 months increased blood IGF-levels and reduced the rate of bone loss in the contralateral hip during the year after the fracture.[28] More recently, the Cochrane-review assessed the effects of nutritional interventions in elderly people recovering from hip fracture.[41] Seventeen randomised trials involving 1266 participants were included. According to reviewers, the strongest evidence for the effectiveness of nutritional supplementation exists for oral protein and energy feeds, but the evidence is still weak.

Moreover, many of these early studies that demonstrated the calciuric effects of protein were limited by low subject numbers, methodological errors and the use of high doses of purified forms of protein.[35] Indeed, the recent study Dawson-Hughes et al. did not confirm the perception that increased dietary protein results in urinary calcium loss.[36] According to Dawson-Hughes et al., "Theconstellation of findings that meat supplements containing 55 g/d protein, when exchanged for carbohydrate did not significantlyincrease urinary calcium excretion and were associated withhigher levels of serum IGF-I and lower levels of the bone resorption marker, N-telopeptide, together with a lack of significant correlationof urinary N-telopeptide with urinary calcium excretion in thehigh protein group (in contrast to the low protein) point tothe possibility that higher meat intake may potentially improvebone mass in many older men and women."

Finally, the cross-cultural and population studies that showed a positive association between animal-protein intake and hip fracture risk did not consider other lifestyle or dietary factors that may protect or increase the risk of fracture.[35] It is of some interest that the author of the most cited paper favoring the earlier hypothesis that high-protein intake promotes osteoporosis no longer believes that protein is harmful to bone.[34] In fact, he concluded that the balance of the evidence seems to indicate the opposite.

Ringraziamo il nostro mod per aver postato lo studio.

[carnera]

Anche perchè non accetterebbe consigli su cosa mangiare.

[Perdij]

c'è da dire che i bber, per quanto sembri strano il loro modo di alimentarsi, di base mangiano leggero, e che il resto della popolazione (esclusi vegetariani e cose così) mangia molto ma molto pesante. maiale a tonnellate, fritti, zuccheri, grassi indigeribili, alcool. e poi si butta per un mese o due sul digiuno disperato per arrivare all'estate con l'aspetto di scampati all'olocausto perché "magrissimo=bellissimo" (anche per i maschi, ora, ho diversi amici che ne sono convinti e agiscono di conseguenza, mettendo a dura prova - bastano gli occhi per capirlo - il loro organismo).

e poi: quanto è iperproteica una dieta iperproteica, confrontata con l'alimentazione all'italiana di una famiglia? secondo me non molto. è dura arrivare ai 2g/kg se uno mangia pulito, ma se uno ama mangiare braciole, salsicce, salame etc. va tranquillo che li tocca comunque (e non son le proteine per me che fan male in questo caso, ma tutto quello che le accompagna). si fa una grigliata in compagnia? io vedo amici scofanarsi anche 7/8 salsicce come niente, vedo la gente riempirsi fino a quando non entra più nulla come se fosse la cosa più normale del mondo. sono stato a casa di uno che s'è divorato mezza caciotta dopo il pesce. e vedo donne mangiare dolci in quantità industriale (salvo poi bla bla bla).

e soprattutto noto una certa schizofrenia alimentare, digiuno/abbuffata, e noto un'assoluta ignoranza dei più basilari principi alimentari, tanto che la gente "comune" non ha la più pallida idea di come dovrebbe comporre un piano alimentare settimanale e va a tastoni, a voci, a caso (quante calorie pane e nutella? ma poi salto la cena, solo prima di andare a letto un pacco di biscotti).

quello che ho imparato sulla mia pelle è che chi modifica la propria alimentazione (rompendo le palle al mondo universo, questo sì) comincia ad avere una sorta di benefico autocontrollo che limita gli svarioni alimentari. a volte vado a cene in cui il mio fabbisogno viene tranquillamente soddisfatto, quando non superato, dall'antipasto.

francamente, per rispondere alla domanda del thread, sì mi fido e in ogni caso adatto ai miei gusti e alle situazioni della vita. non penso che mangiare 30 grammi di grana in più o due fette di coppa in meno possano provocare seri danni alla mia salute, specie perché da quando lo faccio mi sento molto meglio e ho un aspetto più sano e giovane. al limite potrei avere più dubbi su alcuni integratori in pillole, e volendoli eventualmente usare approfondirei di più la questione, ma sul cibo mi sento, a distanza di qualche anno, più che tranquillo.

[phoenix1927]

veramente la domanda è "come fai a stare tranquillo sulla tua dieta?" non "come fai a fidarti dei consigli altrui?" ma vabbè! xD

xanax e lexotan serviti in un calice di cristallo con del moet et chandon e passa l'ansia per la dieta! se la questioni ti agita proprio tanto vai col tavor

[Tetsujin]

su starbene di questo mese dicono a lettere cubitali che 50g di proteine al giorno sono la giusta quantità per i muscoli tonici. poi in piccolo, in un trafiletto, si parla di 0,8g / kg.

steewe ti faccio un esempino personale: io progetto impianti. il 90% degli impianti che vedo, una volta realizzati, sono fuori norma, ma il cliente finale (quello che paga, e pure salato) non se ne accorge mai (e dico MAI) e se lo tiene così, perchè non sapendo come dovrebbe essere un impianto fatto bene, non sa distinguerne uno fatto male. e le aziende su questo ci campano alla grande, tanto che è praticamente la normalità.

ora tu dimmi: come fai a esser certo che se vai da un dietologo, quello sia un bravo dietologo? perchè magari a te sembra bravo, ma visto che non ne capisci nulla (come noi), non hai gli strumenti necessari per valutarlo. per cui ti fidi (come tutti) e si spera che utilizzi quell'organo che ti hanno installato tra le orecchie (il cervello) per valutare con senso critico anche la dieta fatta dal dietologo. perchè non è che avere il titolo di dietologo (o di ingegnere, o di architetto) fa di te automaticamente un esperto. anzi più ti addentri nel mondo del lavoro, più ti accorgi che è pieno di caxxoni e di ciarlatani. quindi anche se ti rivolgi a un professionista, tieni sempre il cervello attivo e verifica quello che ti dice (per quanto possibile) con questo potente strumento di comunicazione che è internet