Leucine supplement health benefit, amino acid used for muscle mass gain
August 25 2018 by Ray Sahelian, M.D.

Leucine is one of the building blocks of protein, particularly from animal foods, and it can be consumed through meat, dairy, soy, beans and other protein-rich sources. It's also widely sold as a dietary supplement. You can purchase a combination of leucine, isoleucine and valine branched chain amino acids by visiting BCAA supplement. BCAA also has glutamine amino acid. If you wish to increase muscle mass, consider creatine powder supplements or Creatine capsules.

Caution, risk
Amino Acids. 2015.  L-Leucine and NO-mediated cardiovascular function. Reduced availability of nitric oxide (NO) in the vasculature is a major factor contributing to the impaired action of insulin on blood flow and, therefore, insulin resistance in obese and diabetic subjects. Available evidence shows that vascular insulin resistance plays an important role in the pathogenesis of cardiovascular disease, the leading cause of death in developed nations. Interestingly, increased concentrations of L-leucine in the plasma occur in obese humans and other animals with vascular dysfunction. Among branched-chain amino acids, L-leucine is unique in inhibiting NO synthesis from L-arginine in endothelial cells and may modulate cardiovascular homeostasis in insulin resistance.

L Leucine and Muscle Tissue
L leucine is an essential amino acid, which means the body cannot manufacture it and it must be ingested through dietary protein. Along with other essential amino acids, leucine helps maintain muscle mass -- which has made leucine-containing supplements a favorite of bodybuilders and athletes. But, what do studies say? Human studies show conflicting results while an animal study shows leucine supplementation prevents muscle loss.

Leucine differentially regulates gene-specific translation in mouse skeletal muscle. Journal of Nutrition, 2017. Leucine stimulates muscle protein synthesis through its effects on translation of gene-specific targets. Existing data support the role of branched chain amino acids, primarily leucine, in stimulating muscle protein synthesis

Am J Clin Nutrition. 2015. A high whey protein-, leucine-, and vitamin D-enriched supplement preserves muscle mass during intentional weight loss in obese older adults: a double-blind randomized controlled trial. The objective was to examine the effect of a high whey protein-, leucine-, and vitamin D-enriched supplement on muscle mass preservation during intentional weight loss in obese older adults. A high whey protein-, leucine-, and vitamin D-enriched supplement compared with isocaloric control preserves appendicular muscle mass in obese older adults during a hypocaloric diet and resistance exercise program and might therefore reduce the risk of sarcopenia.

Long-term leucine supplementation does not increase muscle mass or strength in healthy elderly men.
Am J Clin Nutr, 2009. From the Department of Human Movement Sciences, Nutrition and Toxicology Research Institute, Maastricht, Maastricht University, Maastricht, Netherlands; the Department of Clinical Chemistry, Maastricht University Medical Center, Maastricht, Netherlands; and the Rehabilitation and Health Centre, Virga Jesse Hospital, Hasselt, Belgium. Leucine was provided by Ajinomoto Co, Inc.
It has been reported that the blunted muscle protein synthetic response to food intake in the elderly can be normalized by increasing the leucine content of a meal. The objective was to assess the effect of 3 months of leucine supplementation on muscle mass and strength in healthy elderly men. Thirty healthy elderly men with a mean age of 71 y were randomly assigned to either a placebo-supplemented or leucine-supplemented group. Leucine or placebo (2.5 g) was administered with each main meal during a 3-mo intervention period. Whole-body insulin sensitivity, muscle strength (one-repetition maximum), muscle mass (measured by computed tomography and dual-energy X-ray absorptiometry), myosin heavy chain isoform distribution, and plasma amino acid and lipid profiles were assessed before, during, and/or after the intervention period.: No changes in skeletal muscle mass or strength were observed over time in either the leucine- or placebo-supplemented group. No improvements in indexes of whole-body insulin sensitivity (oral glucose insulin sensitivity index and the homeostasis model assessment of insulin resistance), blood glycated hemoglobin content, or the plasma lipid profile were observed. Long-term leucine supplementation (7.5 g/d) does not augment skeletal muscle mass or strength and does not improve glycemic control or the blood lipid profile in healthy elderly men.

A diet rich in the amino acid leucine might help prevent the muscle loss that typically comes with aging. French researchers found that a leucine supplemented diet restored a more youthful pattern of muscle-protein breakdown and synthesis to elderly rats. The older animals had shown a tendency toward excessive protein breakdown before going on the leucine rich diet, but the amino acid appeared to erase that imbalance. It's well known that after the age of 40 or so, people gradually lose muscle mass, and it's thought that an imbalance in muscle-protein synthesis and breakdown is involved. In younger people, this process is typically in balance. For example, research shows that after a meal, muscle-protein breakdown slows, whereas synthesis ramps up in response to the influx of amino acids from food. But in the new study, older rats did not show this post-meal dip in protein breakdown, whereas their younger counterparts did. A short time on the leucine supplemented diet, however, restored a youthful pattern of protein breakdown in the elder rats. December, 2005 issue of the Journal of Physiology.

Advances in Nutrition, 2018. Perspective: Protein Requirements and Optimal Intakes in Aging. The Dietary Reference Intakes set the protein RDA for persons >19 y of age at 0.8 g protein per kg body. We propose that it should be recommended that older individuals consume ≥1.2 g protein per kg per day, and that there should be an emphasis on the intake of the amino acid leucine, which plays a central role in stimulating skeletal muscle anabolism.

Cystic fibrosis influence
J Cystic Fibrosis. 2013. Dietary essential amino acids are highly anabolic in pediatric patients with cystic fibrosis. Current nutritional approaches have been partially successful in Cystic Fibrosis (CF). Essential amino acids mixtures with high Leucine levels (EAA) have anabolic properties in catabolic conditions, however data in CF are lacking. On two days according a randomized crossover design, 15 pediatric CF patients ingested 6.7 g EAA versus mixture of total amino acids as present in whey. Whole body protein and Arginine metabolism (as EAA lack Arginine) were assessed by stable isotope methodology. Protein synthesis but not protein breakdown was higher after EAA and 70% higher values for net anabolism were found both in patients with and without nutritional failure. Arginine turnover was lower and de novo Arginine synthesis tended lower after EAA. Nitric oxide synthesis was not different. CF patients are highly responsive to EAA intake independent of their nutritional status. Addition of Arginine to the EAA mixture may be warranted in CF.

Q. Does a leucine supplement help with muscle mass as good as creatine does?
     A. I doubt if a l leucine supplement is as effective as creatine. Creatine is one of the most important supplements for muscle growth that I know of and would far surpass the effectiveness of leucine supplement.

Q. My friend gave me a bottle of leucine powder. What would this be used for?
     A. I don't really know why anyone would need to take a leucine powder supplement since I think all the amino acids are helpful for health and I don't see the need to take a leucine supplement by itself. However, having said this, I realize that there has been a study that a leucine supplement given to older rats was helpful for muscle tissue. But I think creatine or a general protein supplement would be preferable.