“BCAA” is the acronym for branched chain amino acids. They include three proteinogenic amino acids: valine, leucine, and isoleucine. Known for their energy supplying and muscle building properties, BCAA are especially popular with bodybuilders. But supplementation with leucine, isoleucine, and valine may also be recommended for endurance sports.

Branched chain amino acids are stored and further processed in muscle tissue. Most other amino acids are metabolized by the liver.

Building muscle

BCAAs are part of complex proteins and are ingested in a regular diet. Because of their presumed catabolic effects (inhibiting muscle breakdown) and anabolic benefits (promoting muscle building), taking branch chained amino acids has been thoroughly studied.

Leucine improves muscle building in athletes

Muscle building with BCAAIn an American study, the effects of leucine on muscle building in bodybuilders was researched. The study compared the muscle building effects of a standard protein drink with those of a protein drink enriched with leucine. The protein drink provided to athletes contained either a concentration of 1.87 g leucine, or 3.5 g leucine.

When the muscle building effects of the two drinks was compared, it was observed that the drink with the higher concentration of leucine could improve the muscle building effects over the standard amino acid formula by as much as 33% 1. However, with only 8 participants, this study did not have enough participants to validate its findings.

Similar results were obtained in a study conducted with extreme mountain climbers. But this study, too, with only 10 participants, was very small. But the evidence suggests that leucine can reduce muscle loss in the extreme conditions of high-elevation alpine climbing 2.

Leucine quickly elevates insulin levels following strength training. The muscle breakdown caused by the exertion of training (normal body reaction to obtain energy) can be stopped. At the same time, body-initiated muscle building is promoted after training 3.

Leucine Prevents Age-Related Muscle Atrophy

Leucine and BCAAOlder adults are more sedentary and have a slower metabolism. As a result, muscle mass is slowly reduced, which can also lead to joint problems. After osteoporosis and osteoarthritis, muscle wasting is the third major musculoskeletal problem for many seniors.

In a recent American study, it was found that supplementation with 12,000 mg leucine can improve protein synthesis in older adults 4.

In a follow-up study, these results were confirmed with a test pool of 20 seniors: taking whey protein combined with leucine stimulates protein synthesis in older adults 5.

A systematic review of a total of nine studies was conducted in 2014 (meta analysis). The result is clear: leucine can stop age-related muscle atrophy (read more here: leucine for the prevention of age-related muscle atrophy).


The usually recommended dose of BCAA is 5,000 mg per day. To attain the results observed in studies, amounts ranging between 9,000 mg and 14,000 mg are administered.

The body requires the following B vitamins to process BCAA: vitamin B5 (pantothenic acid), B6 (pyridoxine) and biotin (B7). Deficits in any one of these three B vitamins may inhibit the synthesis of leucine, valine, and isoleucine and thus limit muscle building benefits.

Side Effects

Doses of 10,000 mg a day or more may lead to light digestive problems. The dosage should thus be divided and spread across several intakes a day.


  1. Pasiakos SM, McClung HL, McClung JP, Margolis LM, Andersen NE, Cloutier GJ, Pikosky MA, Rood JC, Fielding RA, Young AJ. Leucine-enriched essential amino acid supplementation during moderate steady state exercise enhances postexercise muscle protein synthesis. American Journal of Clinical Nutrition. 94(3):809-818
  2. Leucine may help to burn fat but spare muscle wastage: Pilot study. Nutra Ingredients USA
  3. Van Loon LJ, Kruijshoop M, Verhagen H, Saris WH, Wagenmakers AJ. Ingestion of protein hydrolysate and amino acid-carbohydrate mixtures increases postexercise plasma insulin responses in men. The Journal of Nutrition. 2000. 130:2508-2513
  4. Casperson SL, Sheffield-Moore M, Hewlings SJ, Paddon-Jones D. Leucine supplementation chronically improves muscle protein synthesis in older adults consuming the RDA for protein. Clinical Nutrition. 2012. 31(4):512-519
  5. Luiking YC, Deutz NEP, Memelink RG, Verlaan S, Wolfe RR. Postprandial muscle protein synthesis is higher after a high whey protein, leucine-enriched supplement than after a dairy-like product in healthy older people: a randomized controlled trial. Nutrition Journal. 2014. 13:9
Share and help your friends!Share on Facebook
Tweet about this on Twitter
Email this to someone
Share on Tumblr