The Research Institute, The Hospital for Sick Children, Toronto, ON, Canada.
J Nutr. 2012 Dec;142(12):2220S-2224S. doi: 10.3945/jn.112.160259. Epub 2012 Oct 17.
Leucine is purported to improve athletic performance. Therefore, the BCAA, especially leucine, are popular as dietary supplements among strength-training athletes. There are, however, concerns regarding possible adverse effects of excessive leucine intake. The objective of the current study was to determine the metabolic and adverse effects of the acute ingestion of very high intakes of leucine supplements. Five healthy men (20-35 y) each received graded stepwise increases in leucine intakes of 50, 150, 250, 500, 750, 1000, and 1250 mg · kg(-1) · d(-1) corresponding to the Estimated Average Requirement, and Estimated Average Requirement ×3, ×5, ×10, ×15, ×20, and ×25 to a total of 29 studies. The graded stepwise approach was used rather than a randomization of leucine intake to minimize the possibility of severe adverse effects. Participants were given a maintenance diet for 2 d prior to each leucine level containing 1 g · kg(-1) · d(-1) of protein and 1.7× measured the resting metabolic rate. Leucine oxidation was determined using L-[1-13C]-leucine and the appearance of (13)CO(2) (calculated as F(13)CO(2)) in breath. A range of markers was used to monitor for adverse effects, including glucose, insulin, alanine aminotransferase, and ammonia. Plasma leucine concentrations significantly increased beyond an intake of 500 mg · kg(-1) · d(-1). The metabolic limit to oxidize leucine was between 550 and 700 mg · kg(-1) · d(-1). An increase in blood ammonia concentrations was observed at leucine intakes >500 mg · kg(-1) · d(-1). There were no changes in liver alanine aminotransferase. Glucose concentrations fell (P < 0.004) but remained within the normal range and without any change in insulin. This study is the first to our knowledge to directly estimate the safe upper limit of leucine intake in humans and raises concerns that intakes >550 mg · kg(-1) · d(-1) or ~39 g/d may be a risk to health. It is important to note that these are acute studies, where each participant was exposed to graded increases in leucine intake. Longer term adaptation was not studied.
亮氨酸据称可提高运动表现。因此，支链氨基酸（BCAA），尤其是亮氨酸，作为补充剂在力量训练运动员中很受欢迎。然而，人们对过量摄入亮氨酸可能产生的不良影响表示担忧。本研究旨在确定急性摄入高剂量亮氨酸补充剂的代谢和不良影响。5 名健康男性（20-35 岁）分别接受了 50、150、250、500、750、1000 和 1250mg·kg(-1)·d(-1)，相当于推荐摄入量（Estimated Average Requirement，EAR），以及推荐摄入量的 3、5、10、15、20 和 25 倍的逐步递增亮氨酸摄入量，共进行了 29 项研究。采用逐步递增而非随机化亮氨酸摄入的方法，以尽量减少出现严重不良影响的可能性。在每个亮氨酸水平前，参与者先接受为期 2 天的维持饮食，该饮食包含 1g·kg(-1)·d(-1)的蛋白质和 1.7×静息代谢率。通过使用 L-[1-13C]-亮氨酸和（13）CO2 在呼吸中的出现（计算为 F（13）CO2）来确定亮氨酸的氧化。使用一系列标志物来监测不良影响，包括葡萄糖、胰岛素、丙氨酸氨基转移酶和氨。血浆亮氨酸浓度在摄入量超过 500mg·kg(-1)·d(-1)后显著增加。氧化亮氨酸的代谢极限在 550 至 700mg·kg(-1)·d(-1)之间。在亮氨酸摄入量>500mg·kg(-1)·d(-1)时，血液氨浓度增加。丙氨酸氨基转移酶无变化。葡萄糖浓度下降（P<0.004），但仍在正常范围内，胰岛素无变化。本研究首次直接估计了亮氨酸在人体中的安全摄入量上限，并引起人们的关注，即摄入量>550mg·kg(-1)·d(-1)或~39g/d 可能对健康构成风险。需要注意的是，这些都是急性研究，每个参与者都暴露在亮氨酸摄入量的逐步增加中。未研究长期适应。
