science nutrition blog

By Steve Blechman

Sarcopenia is the loss of muscle mass caused by the natural aging process. Muscle loss is a serious problem in older adults, leading to decreased quality of life, diabetes and premature death. Dietary protein is an important stimulator of muscle protein synthesis. Older adults can stimulate muscle protein by consuming supplements containing protein and leucine (Clinical Nutrition 2013, 32: 412-419; Journal of Physiology 2012, 590: 2751-2765).

Peak muscle mass occurs between ages 20 and 35, declining gradually at age 40. Typically, men lose 20% of their muscle mass between ages 40 and 60. The problem becomes progressively worse with age. So, leucine, the anabolic trigger, might be valuable for preventing age-related muscle wasting. Leucine muscle building can be particularly beneficial for maintaining muscle mass as we age. Incorporating leucine for muscle growth can help in retaining strength and vitality.

Unfortunately, older adults show a blunted muscle protein synthesis (MPS) and anabolic resistance compared to younger adults. Recent research has suggested that the anabolic resistance can be overcome by consuming greater quantities of leucine. In a recent study, published in the Journal of Nutrition on July 1, 2018, it is confirmed that leucine and not total protein content of a "… supplement is the primary determinant of muscle protein anabolic responses in healthy older women." This highlights the importance of leucine for muscle growth. The study showed that "lower protein (10 compared with 25 g/dose) leucine-matched beverage induced similar increases in acute and integrated myoPS in healthy older women. Lower-protein supplements with added leucine may represent an advantageous approach in older adults to maintain skeletal muscle anabolic sensitivity and attenuate muscle loss; however, further work is needed using longer-term interventions." This raises the question, does leucine build muscle effectively? The evidence suggests it does, particularly when integrated into a balanced diet and exercise regimen.

Older muscle (in people over 40) is less responsive to protein to build lean body mass. Adequate and frequent protein intake is important for maintaining muscle mass in older adults. Providing weight training and ensuring protein and leucine availability during recovery is the best way to promote muscle growth and prevent muscle atrophy (breakdown) in people of any age (Applied Physiology, Nutrition, and Metabolism, 2009, 34:403-410). For those wondering, does leucine build muscle effectively? The answer is yes, especially when combined with proper training and nutrition.

To use leucine as an anabolic trigger, and overcome the anabolic resistance in older people, take 5 grams of leucine (on an empty stomach) 30 minutes before a post-workout meal, or protein shake. This approach answers the question, does leucine help build muscle? A meta-analysis (Nutrition, 2017) that combined the results of seven studies showed that BCAA supplements are best taken after exercise, not before or during exercise (intra-workout). The role of leucine muscle building is evident as it helps enhance recovery and muscle synthesis post-exercise.

Increase in muscle protein synthesis is dependent on leucine concentration. Research has shown that leucine stimulates the anabolic effect of muscle protein synthesis on its own (Wilkinson et al., J Physiol 2013). When leucine is taken on an empty stomach, it has a powerful anabolic switch that turns on protein synthesis.

By taking pure leucine on an empty stomach, you will get a better spike in blood levels than if you take leucine with food, because food can slow leucine's absorption. The addition of isoleucine and valine may hinder the benefits of leucine due to competition for transport into muscle cells. Leucine increases mTOR activity for several hours after training. When leucine is taken after resistance exercise and before a post-workout, protein-containing meal rich in essential amino acids, it triggers greater protein synthesis for improved recovery and greater gains.

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References:

Wall, Benjamin T et al. Leucine co-ingestion improves post-prandial muscle protein accretion in elderly men. Clinical Nutrition, Volume 32, Issue 3, 412-419.

Churchward-Venne TA, Burd NA, Mitchell CJ, West DW, Philp A, Marcotte GR, Baker SK, Baar K, Phillips SM (2012). Supplementation of a suboptimal protein dose with leucine or essential amino acids: effects on myofibrillar protein synthesis at rest and following resistance exercise in men. The Journal of physiology, 590(11), 2751-65.

Devries MC, Philips SM, Baker SK et al. Leucine, Not Total Protein, Content of a Supplement Is the Primary Determinant of Muscle Protein Anabolic Responses in Healthy Older Women. The Journal of Nutrition, July 1, 2018.

Phillips SM. Physiologic and molecular bases of muscle hypertrophy and atrophy: impact of resistance exercise on human skeletal muscle (protein and exercise dose effects). Applied Physiology, Nutrition, and Metabolism, 2009, 34:403-410,https://doi.org/10.1139/H09-042

Lex B Verdijk, Luc JC van Loon et al. Protein supplementation before and after exercise does not further augment skeletal muscle hypertrophy after resistance training in elderly men, The American Journal of Clinical Nutrition, Volume 89, Issue 2, 1 February 2009, Pages 608-616, https://doi.org/10.3945/ajcn.2008.26626

Brigham and Women's Hospital. "Eating more protein may not benefit older men." ScienceDaily. ScienceDaily, 2 April 2018. www.sciencedaily.com/releases/2018/04/180402123241.htm

Bhasin S, Apovian CM, Travison TG, et al. Effect of Protein Intake on Lean Body Mass in Functionally Limited Older Men. A Randomized Clinical Trial. JAMA Intern Med 2018;178(4):530-541. doi:10.1001/jamainternmed.2018.0008

10. Yoshii et al. Nutrients 2018, October 18, 2018 (10), 1543; https://doi.org/10.3390/nu10101543Effect of Mixed Meal and Leucine Intake on Plasma Amino Acid Concentrations in Young Men.

Cholewa JM et al. Dietary proteins and amino acids in the control of muscle mass during immobilization and aging: Role of MPS Response. Amino Acids 2017.

Morton RW et al. Defining Anabolic Resistance: Implications for Delivery of Critical Care. Nutrition 2018, Curr Opinion Critical Care.

Phillips SM, Baker SK et al. A randomized controlled trial of the impact of protein supplementation on leg lean mass and integrated muscle protein synthesis during inactivity and energy restriction in older persons, The American Journal of Clinical Nutrition, Volume 108, Issue 5, 1 November 2018, Pages 1060-1068, https://doi.org/10.1093/ajcn/nqy193

Marika Leenders, Luc JC van Loon. Leucine as a pharmaconutrient to prevent and treat sarcopenia and type 2 diabetes, Nutrition Reviews, Volume 69, Issue 11, 1 November 2011, Pages 675-689, https://doi.org/10.1111/j.1753-4887.2011.00443.x

Rahimi MH, Shab-Bidar S et al. Branched-chain amino acid supplementation and exercise-induced muscle damage in exercise recovery: A meta-analysis of randomized clinical trials. Nutrition 2017.

Wilkinson DJ et al. Effects of leucine and its metabolite beta-hydroxy-beta-methylbutyrate on human skeletal muscle protein metabolism. J Physiol 2013,591,2911-2923.

Macotela Y, Emanuelli B, Bang AM et al. (2011) Dietary leucine - an environmental modifier of insulin resistance acting on multiple levels of metabolism. PLoS One 6, e21187.

Li H, Xu M, Lee J, He C and Xie Z. (2012). Leucine supplementation increases SIRT1 expression and prevents mitochondrial dysfunction and metabolic disorders in high-fat diet-induced obese mice. American Journal of Physiology - Endocrinology and Metabolism, 303(10), E1234-E1244. http://doi.org/10.1152/ajpendo.00198.2012

Chunzi Liang, Benjamin J Curry, Patricia L Brown and Michael B. Zemel. "Leucine Modulates Mitochondrial Biogenesis and SIRT1-AMPK Signaling in C2C12 Myotubes." Journal of Nutrition and Metabolism, vol. 2014, Article ID 239750, 11 pages, 2014. https://doi.org/10.1155/2014/239750.

Binder E, Bermúdez-Silva FJ, André C, Elie M, Romero-Zerbo SY, et al. Leucine Supplementation Protects from Insulin Resistance by Regulating Adiposity Levels (2013). Leucine Supplementation Protects from Insulin Resistance by Regulating Adiposity Levels. PLOS ONE 8(9): e74705. https://doi.org/10.1371/journal.pone.0074705

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