Influência da dose e da distribuição da ingestão de proteínas, associadas ou não ao treino de força, sobre a taxa de síntese proteica muscular

Sabe-se que os principais estímulos anabólicos para o ganho de massa muscular são o exercício físico e a ingestão de proteínas e, durante décadas, os pesquisadores da área da nutrição esportiva, têm vindo estudando como potencializar o efeito destes dois estímulos para maximizar o ganho de massa muscular. Hoje, já existem diversos estudos demonstrando como alguns fatores da alimentação podem influenciar na resposta dos processos de síntese (SPM) e degradação proteica muscular (DPM), no ganho de massa muscular. Alguns deles, polémicos ainda, são a dose de proteínas e a distribuição proteica no decorrer do dia. Assim, o objetivo desta revisão narrativa foi sumarizar os estudos que investigaram a influência da dose e da distribuição proteica, associadas ou não ao treino de força, sobre a SPM. Uma busca de trabalhos na literatura científica foi realizada na base de dados PubMed. De um total de 16 artigos encontrados, dez foram selecionados para análise. Desses, sete artigos originais foram selecionados para discutir a influência da dose de proteínas sobre a SPM e outros três, foram analisados para discutir a influência da distribuição proteica ao longo do dia na síntese proteica. Apesar da existência de estudos interessantes sobre o assunto, ainda é precipitado concluir que manipular ambas as estratégias, - dose e distribuição -, garante um ganho de massa muscular superior na ausência delas, ao longo prazo. Porém, pareceria interessante que indivíduos jovens atingissem ao redor de 20 gramas de proteínas durante as principais refeições e respeitando um intervalo mínimo de 3 horas entre elas. ABSTRACT Influence of the dose and protein distribution on muscle protein synthesis, associated or not to resistance training sessionsIt is well known that the main stimuli for the gain of muscle mass are exercise and protein intake. For decades, researchers of the field of sports nutrition, have been studying how to get the most between these stimuli on the muscle mass gain. Nowadays, there are vast scientific works highlighting some nutritional factors which might influence the response of the muscle protein synthesis (MPS) as well as muscle protein degradation (MPD) on muscle gain. Among those factors, it is included the protein dose and the protein distribution along the day, yet controversial. Then, the aim of this narrative review was to summarize the studies that have investigated the influence of the dose and protein distribution, associated or not, to resistance training sessions, on MPS. A narrative literature review was performed using the PubMed database. Among 16 articles found, ten of them were selected for analysis. Between them, seven original articles were selected for discussing the influence of the protein dose on MPS and another three were analyzed for discussing the influence of protein distribution on protein synthesis. Despite of existing fascinating articles about this topic, it is still too soon to conclude that by manipulating these strategies – protein dose and protein distribution -, would guarantee a superior muscle gain in long term. However, it is still interesting that young men reach at least 20 grams of protein during their main meals at regular intervals, every three hoursÂ

A dieta cetogênica pode auxiliar no tratamento do câncer? Uma análise crítica

There is a growing interest in the therapeutic efficacy of the ketogenic diet, given the hypothesis that carbohydrate restriction (CHO) would favor a decreased tumor cell activity. Nevertheless, such diets continue to be a controversial topic in the oncology field. Thus, this manuscript aimed to summarize the studies that have already investigated the potential therapeutic effects of the ketogenic diet in the treatment of cancer in human patients. A narrative review was carried, considering the databases Latin American and Caribbean Literature databas (LILACS), the Scientific Electronic Library Online (SciELO), the Online System of Search and Analysis of Medical Literature (MEDLINE) and the Latin American and Caribbean Health Sciences Information (BIREME). The following keywords were applied alone or in combination: cancer, nutrition, carbohydrate restriction, cancer cells and ketogenic diet. Articles published between 2010 and 2018, both in the English and Portuguese languages were selected. No randomized clinical trial was found. Throughout the reviewed studies, which included mostly quasiexperimental designs and case reports, 221 patients were selected. Mixed results were observed, both supporting and refuting the therapeutic efficacy of the ketogenic diet in the treatment of cancer patients. Importantly, only 92 (42%) of these patients were submitted to ketogenic diets, of which only 41% had a good adherence to the diets. Randomized clinical trials investigating large patient segments over long periods with comparable dietary methodologies and protocols are still needed before such a diet can be recommended as a complementary treatment for cancer.Existe um crescente interesse na eficácia terapêutica da dieta cetogênica, dada a hipótese de que a restrição de carboidratos (CHO) favoreceria uma menor atividade de células tumorais. Mesmo assim, tais dietas continuam sendo um tema controverso na área de oncologia. Assim, este trabalho tem como objetivo sumarizar os estudos que já investigaram os potenciais efeitos terapêuticos da dieta cetogênica no tratamento do Câncer em pacientes humanos. Foi realizada uma revisão narrativa da literatura, nas bases de dados Literatura Latino- Americana e do Caribe (LILACS), Scientific Electronic Library Online (SciELO), Sistema Online de Busca e Análise de Literatura Médica (MEDLINE) e base Centro Latino Americano e do Caribe de Informação em Ciências da Saúde (BIREME). As seguintes palavras-chaves foram utilizadas isoladamente ou em associação: câncer, nutrição, restrição de carboidrato, células cancerígenas, e dieta cetogênica. Artigos publicados entre 2010 e 2018 e nos idiomas Inglês e Português foram selecionados. Nenhum estudo clínico randomizado foi encontrado. Ao longo dos estudos revisados, os quais se incluíam em sua maioria desenhos quasiexperimentais e estudos de caso, 221 pacientes foram selecionados. Resultados mistos foram observados, tanto apoiando quanto refutando a eficácia terapêutica da dieta cetogênica no tratamento de pacientes com câncer. Importantemente, apenas 92 (42%) desses pacientes foram submetidos à dieta cetogênica, dos quais somente 41% tiveram boa aderência à dieta. Estudos clínicos randomizados, investigando grandes segmentos de pacientes por longos períodos, com metodologias e protocolos dietéticos comparáveis, ainda são necessários antes que tal dieta possa ser recomendada como tratamento complementar do Câncer

Metabolismo de carnosina, suplementação de β-alanina e desempenho físico: uma atualização – PARTE II

Diversos são os fatores que podem levar à fadiga muscular durante os exercícios de alta intensidade e curta duração. Dentre eles, o acúmulo de íons H+, levando a uma queda do pH intramuscular, é apontado como uma das principais causas da fadiga durante este tipo de exercício. Sendo assim, as defesas tamponantes intramusculares representam a primeira linha de defesa contra o acúmulo destes íons. Estratégias nutricionais visando otimizar a ação de tais defesas tem recebido especial atenção no campo da nutrição esportiva. Nesse sentido, a suplementação de beta-alanina é a que mais tem se destacado em anos recentes. A suplementação com este aminoácido não essencial e não proteogênico induz um aumento das concentrações musculares de carnosina. A carnosina, por sua vez, é um dipeptídeo citoplasmático cuja função mais bem atribuída é a de tamponante. Com isso, diversos estudos têm se dedicado a investigar o potencial ergogênico da suplementação de beta-alanina sobre o desempenho em exercícios de alta intensidade. De fato, a eficácia ergogênica da beta-alanina tem sido investigada em diferentes populações (indivíduos sedentários, fisicamente ativos, idosos, atletas) e em diferentes protocolos de exercício (incrementais, anaeróbios contínuos, anaeróbios intermitentes, esporte-específico). Além disso, sua combinação com o treinamento físico e com outras estratégias consideradas ergogênicas também tem recebido especial foco de investigação. Em virtude do intenso e crescente interesse na suplementação de beta-alanina, esta revisão tem por objetivo descrever narrativamente tais estudos, ressaltando a implicação dos resultados encontrados para o campo da nutrição esportiva e fisiologia do exercício. ABSTRACTCarnosine metabolism, β-alanine supplementation and performance: an update - Part IIThere are several factors that can lead to muscle fatigue during high-intensity exercise. Among them, the accumulation of H+ ions, leading to a decrease in intramuscular pH, is considered a major cause of fatigue during this type of exercise. Thus, intramuscular buffering represents the first line of defense against the accumulation of these ions. Nutritional strategies aiming to optimize the action of such defenses have received considerable attention in the field of sports nutrition in recent times, with beta-alanine a particular focus in the last years. Supplementation with this non-essential, non-proteogenic amino acid induces an increase in muscle carnosine concentration. Carnosine is a cytoplasmic dipeptide whose most attributable function is acting as a buffer. Therefore, many studies have been devoted to investigate the effects of beta-alanine supplementation on high-intensity exercise performance and capacity; the ergogenic efficacy of beta-alanine has been investigated in different populations (sedentary, physically active, athletes and elderly) and in different exercise protocols (incremental, continuous anaerobic, intermittent anaerobic, sport-specific). Furthermore it is combination with physical training and other nutritional strategies to improve exercise has also received special focus of research. In light of the intense and growing interest in beta-alanine supplementation, this review aims to narratively describe such studies, emphasizing the implication of the findings for the areas of sports nutrition and exercise physiology

Metabolismo de carnosina, suplementação de β-alanina e desempenho físico: uma atualização – PARTE I

Os papéis fisiológicos da carnosina tem despertado interesse recente, apesar de já ser uma substância estudada há anos. É formada através de aminoácidos (β-alanil e L-histidina) e juntamente com seus análogos metilados (anserina e ofidina- balenina) fazem parte da classe dos dipeptídeos contendo histidina (HCDs, do inglês Histidine-Containing Dipeptides), os quais são abundantemente encontrados em uma ampla gama de animais terrestres e aquáticos. Maiores concentrações estão no musculo esquelético e bulbo olfatório, estando em menor quantidade em regiões do sistema nervoso central, fluido cerebroespinhal, rins e baço. Dentre os papéis fisiológicos atribuídos a ela estão: função tamponante especialmente nas fibras tipo II; ação antioxidante e melhora da liberação do cálcio do retículo sarcoplasmático, e na sensibilidade do aparato contrátil ao cálcio. A suplementação de β-alanina é a forma mais eficiente de aumentar a carnosina muscular, e vem recebendo demasiado destaque na área de nutrição esportiva em anos recentes. Esta estratégia nutricional apresenta um efeito “dose-resposta†com a ingestão aguda, além da parestesia como efeito colateral. Até hoje permanece incerto o tempo exato de washout da carnosina no músculo esquelético após a interrupção da suplementação de β-alanina. Estudos futuros devem ser realizados para avaliar outros possíveis mecanismos de ação da carnosina, e confirmar os já existentes. ABSTRACTCarnosine metabolism, β-alanine supplementation and performance: an update - Part IThe physiological role of carnosine has attracted recent interest, even though it is a substance studied for years. It is formed by amino acids (β-alanyl and L-histidine) and together with their methylated analogues (anserine and balenine) are part of the class of histidine-containing dipeptides (HCDs, English Histidine-containing dipeptides), which are abundantly found in a wide range of terrestrial and aquatic animals. Higher concentrations are in the olfactory bulb and skeletal muscle being a lesser extent in regions of the central nervous system, cerebrospinal fluid, kidney and spleen. The physiological roles attributed to it are: buffering function especially in type II fibers; antioxidant and improves the release of calcium from the sarcoplasmic reticulum, and the sensitivity of the contractile apparatus to calcium. Supplementation of β-alanine is the most efficient way to increase muscle carnosine, and has been receiving substantial highlight in the sports nutrition area in recent years. This nutritional strategy presents a "dose -response" effect from acute ingestion, as well as paresthesia as a side effect. Until these days the exactly washout period of carnosine in the skeletal muscle remains uncertain after β-alanine supplementation interruption. Future studies should be conducted to evaluate other possible mechanisms of action of carnosine and confirm existing ones

A systematic risk assessment and meta-analysis on the use of oral β-alanine supplementation.

β-Alanine supplementation is one of the world's most commonly used sports supplements, and its use as a nutritional strategy in other populations is ever-increasing, due to evidence of pleiotropic ergogenic and therapeutic benefits. Despite its widespread use, there is only limited understanding of potential adverse effects. To address this, a systematic risk assessment and meta-analysis was undertaken. Four databases were searched using keywords and Medical Subject Headings. All human and animal studies that investigated an isolated, oral, β-alanine supplementation strategy were included. Data were extracted according to 5 main outcomes, including 1) side effects reported during longitudinal trials, 2) side effects reported during acute trials, 3) effect of supplementation on circulating health-related biomarkers, 4) effect of supplementation on skeletal muscle taurine and histidine concentration, and 5) outcomes from animal trials. Quality of evidence for outcomes was ascertained using the Grading of Recommendations Assessment Development and Evaluation (GRADE) framework, and all quantitative data were meta-analyzed using multilevel models grounded in Bayesian principles. In total, 101 human and 50 animal studies were included. Paraesthesia was the only reported side effect and had an estimated OR of 8.9 [95% credible interval (CrI): 2.2, 32.6] with supplementation relative to placebo. Participants in active treatment groups experienced similar dropout rates to those receiving the placebo treatment. β-Alanine supplementation caused a small increase in circulating alanine aminotransferase concentration (effect size, ES: 0.274, CrI: 0.04, 0.527), although mean data remained well within clinical reference ranges. Meta-analysis of human data showed no main effect of β-alanine supplementation on skeletal muscle taurine (ES: 0.156; 95% CrI: −0.38, 0.72) or histidine (ES: −0.15; 95% CrI: −0.64, 0.33) concentration. A main effect of β-alanine supplementation on taurine concentration was reported for murine models, but only when the daily dose was ≥3% β-alanine in drinking water. The results of this review indicate that β-alanine supplementation within the doses used in the available research designs, does not adversely affect those consuming it

Carbohydrate Mouth Rinse Mitigates Mental Fatigue Effects on Maximal Incremental Test Performance, but Not in Cortical Alterations

Detrimental mental fatigue effects on exercise performance have been documented in constant workload and time trial exercises, but effects on a maximal incremental test (MIT) remain poorly investigated. Mental fatigue-reduced exercise performance is related to an increased effort sensation, likely due to a reduced prefrontal cortex (PFC) activation and inhibited spontaneous behavior. Interestingly, only a few studies verified if centrally active compounds may mitigate such effects. For example, carbohydrate (CHO) mouth rinse potentiates exercise performance and reduces effort sensation, likely through its effects on PFC activation. However, it is unknown if this centrally mediated effect of CHO mouth rinse may mitigate mental fatigue-reduced exercise performance. After a proof-of-principle study, showing a mental fatigue-reduced MIT performance, we observed that CHO mouth rinse mitigated MIT performance reductions in mentally fatigued cyclists, regardless of PFC alterations. When compared to placebo, mentally fatigued cyclists improved MIT performance by 2.24–2.33 when rinsing their mouth with CHO during MIT. However, PFC and motor cortex activation during MIT in both CHO and placebo mouth rinses were greater than in mental fatigue. Results showed that CHO mouth rinse mitigated the mental fatigue-reduced MIT performance, but challenged the role of CHO mouth rinse on PFC and motor cortex activation

The ergogenic effect of beta-alanine combined with sodium bicarbonate on high-intensity swimming performance

We investigated the effect of beta-alanine (BA) alone (study A) and in combination with sodium bicarbonate (SB) (study B) on 100- and 200-m swimming performance. In study A, 16 swimmers were assigned to receive either BA (3.2 g·day−1 for 1 week and 6.4 g·day−1 for 4 weeks) or placebo (PL; dextrose). At baseline and after 5 weeks of supplementation, 100- and 200-m races were completed. In study B, 14 were assigned to receive either BA (3.2 g·day−1 for 1 week and 6.4 g·day−1 for 3 weeks) or PL. Time trials were performed once before and twice after supplementation (with PL and SB), in a crossover fashion, providing 4 conditions: PL-PL, PL-SB, BA-PL, and BA-SB. In study A, BA supplementation improved 100- and 200-m time-trial performance by 2.1% (p = 0.029) and 2.0% (p = 0.0008), respectively. In study B, 200-m time-trial performance improved in all conditions, compared with presupplementation, except the PL-PL condition (PL-SB, +2.3%; BA-PL, +1.5%; BA-SB, +2.13% (p < 0.05)). BA-SB was not different from BA-PL (p = 0.21), but the probability of a positive effect was 78.5%. In the 100-m time-trial, only a within-group effect for SB was observed in the PL-SB (p = 0.022) and BA-SB (p = 0.051) conditions. However, 6 of 7 athletes swam faster after BA supplementation. The probability of BA having a positive effect was 65.2%; when SB was added to BA, the probability was 71.8%. BA and SB supplementation improved 100- and 200-m swimming performance. The coingestion of BA and SB induced a further nonsignificant improvement in performance

Does long-term creatine supplementation impair kidney function in resistance-trained individuals consuming a high-protein diet?

Abstract\ud \ud \ud \ud Background\ud \ud The aim of this study was to determine the effects of creatine supplementation on kidney function in resistance-trained individuals ingesting a high-protein diet.\ud \ud \ud \ud Methods\ud \ud A randomized, double-blind, placebo-controlled trial was performed. The participants were randomly allocated to receive either creatine (20 g/d for 5 d followed by 5 g/d throughout the trial) or placebo for 12 weeks. All of the participants were engaged in resistance training and consumed a high-protein diet (i.e., ≥ 1.2 g/Kg/d). Subjects were assessed at baseline (Pre) and after 12 weeks (Post). Glomerular filtration rate was measured by 51Cr-EDTA clearance. Additionally, blood samples and a 24-h urine collection were obtained for other kidney function assessments.\ud \ud \ud \ud Results\ud \ud No significant differences were observed for 51Cr-EDTA clearance throughout the trial (Creatine: Pre 101.42 ± 13.11, Post 108.78 ± 14.41 mL/min/1.73m2; Placebo: Pre 103.29 ± 17.64, Post 106.68 ± 16.05 mL/min/1.73m2; group x time interaction: F = 0.21, p = 0.64). Creatinine clearance, serum and urinary urea, electrolytes, proteinuria, and albuminuria remained virtually unchanged.\ud \ud \ud \ud Conclusions\ud \ud A 12-week creatine supplementation protocol did not affect kidney function in resistance-trained healthy individuals consuming a high-protein diet; thus reinforcing the safety of this dietary supplement.\ud \ud \ud \ud Trial registration\ud \ud ClinicalTrials.gov NCT01817673We are thankful to Fundação de Amparo à Pesquisa do Estado de São Paulo e Conselho Nacional de Desenvolvimento Científico e Tecnológico for the financial support

Dispelling the myth that habitual caffeine consumption influences the performance response to acute caffeine supplementation

Objective: To investigate the influence of habitual caffeine intake on aerobic exercise performance responses to acute caffeine supplementation. Methods: A double-blind, crossover, counterbalanced study was performed. Forty male endurance-trained cyclists were allocated into tertiles according to their daily caffeine intake: low (58 ± 29 mg.d-1), moderate (143 ± 25 mg.d-1), and high consumers (351 ± 139 mg.d-1). Participants completed three trials in which they performed simulated cycling time-trials in the fastest time possible following ingestion of: caffeine (CAF: 6 mg.kg-1 BM), placebo (PLA), and no supplement (CON). Results: Mixed-model analysis revealed time-trial performance was significantly improved in CAF compared to PLA and CON (29.92±2.18 min vs 30.81±2.67 and 31.14±2.71 min; P = 0.05). Blood lactate and ratings of perceived exertion were not different between trials and tertiles (P>0.05). Conclusion: Performance effects of acute caffeine supplementation during a ~30 min cycling TT performance were not influenced by the level of habitual caffeine consumption

Influence of training status on high-intensity intermittent performance in response to β-alanine supplementation

Recent investigations have suggested that highly trained athletes may be less responsive to the ergogenic effects of β-alanine (BA) supplementation than recreationally active individuals due to their elevated muscle buffering capacity. We investigated whether training status influences the effect of BA on repeated Wingate performance. Forty young males were divided into two groups according to their training status (trained: T, and non-trained: NT cyclists) and were randomly allocated to BA and a dextrose-based placebo (PL) groups, providing four experimental conditions: NTPL, NTBA, TPL, TBA. BA (6.4 g day-1 ) or PL was ingested for 4 weeks, with participants completing four 30-s lower-body Wingate bouts, separated by 3 min, before and after supplementation. Total work done was significantly increased following supplementation in both NTBA (p = 0.03) and TBA (p = 0.002), and it was significantly reduced in NTPL (p = 0.03) with no difference for TPL (p = 0.73). BA supplementation increased mean power output (MPO) in bout 4 for the NTBA group (p = 0.0004) and in bouts 1, 2 and 4 for the TBA group (p ≤ 0.05). No differences were observed in MPO for NTPL and TPL. BA supplementation was effective at improving repeated high-intensity cycling performance in both trained and non-trained individuals, highlighting the efficacy of BA as an ergogenic aid for high-intensity exercise regardless of the training status of the individual