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.

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.” 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.”

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).

Dutch researchers from Maastricht University found that older people supplementing 20 grams of protein immediately before or after weight training cannot increase muscle mass or strength beyond the effects of weight training alone (American Journal of Clinical Nutrition, vol 89: p 608-616, 2009). An article in ScienceDaily, April 2, 2018, said that eating protein may not benefit older men. The article stated, “A randomized, clinical trial conducted by Brigham and Women's Hospital investigator Shalender Bhasin, MD, and colleagues has found that higher protein intake did not increase lean body mass, muscle performance, physical function or other well-being measures among older men. The results of their study are published in the April issue of JAMA Internal Medicine.”

A most recent study has found that taking pure leucine supplements alone may be better for muscle protein synthesis and more anabolic than food! In a randomized crossover study (Nutrients, October 18, 2018) 10 healthy, young Japanese men underwent tests under different conditions: 2 grams of leucine alone, a mixed meal with 2.15 grams of leucine without any additional leucine supplementation; 2 grams of leucine right after a meal; and the final serving consisted of 2 grams of leucine, 180 minutes after a meal.

The study’s conclusion was, “based on the aforementioned discussions, the intake of free leucine alone markedly increased the plasma leucine concentration. However, the increase in leucine concentration after the intake of a mixed meal containing the same amount of leucine was significantly less than that of free leucine intake alone. Moreover, when free leucine was ingested after a mixed meal with the purpose of increasing the plasma leucine concentration, the maximum plasma concentration was attenuated when it was ingested immediately after the mixed meal, despite the fact that the total leucine content was doubled. These results suggest that when free amino acids are ingested with the purpose of increasing plasma amino acid concentrations, the timing in relation to the mixed meal intake needs to be considered.”

Evidence shows that anabolic resistance in older persons can be overcome with more leucine! In the elderly it has been reported that aging, decline of hormone levels, critical illness, obesity, lack of physical activity, poor nutrition, reactive oxygen species (ROS), systemic inflammation (“inflammaging”) and insulin resistance can contribute to anabolic resistance and sarcopenia. It has been suggested that leucine is effective for the prevention and treatment of anabolic resistance, sarcopenia, and type 2 diabetes. Studies in humans have shown that leucine supplementation can reverse the blunted response of muscle protein synthesis to amino acids/protein intake in the elderly (Nutrition Reviews, November 2011). Leucine is an effective nutritional strategy to improve postprandial muscle protein synthesis and counteract the anabolic resistance to feeding in insulin resistant muscle.

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. 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).

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

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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

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