L-leucine 2018-02-14T14:17:47+00:00

What is L-leucine

BCAAL-leucine is an essential amino acid and makes up approximately eight percent of the body’s protein structures. One of the three branched-chain amino acids (BCAAs), leucine is involved in muscle repair and growth together with l-isoleucine and l-valine.

This amino acid helps to sustain nitrogen balance and energy supply during times of stress. These qualities make this amino acid particularly important for body builders and other athletes that require strength and stamina.

Click here to read our article on BCAAs

L-leucine is the most powerful BCAA for muscle building

L-leucine and other BCCAs for muscle buildingOf the three BCAAs, leucine is considered the most important because it has the most influence over muscle building. Leucine is quickly broken down by the body and converted into glucose as direct energy for muscles during workouts.

Furthermore, this amino acid induces the synthesis of muscle protein at a molecular level and simultaneously burn visceral fat deposits to ketone production1. This helps to support a leaner body mass with increased muscle; both important factors for athletes.

L-leucine and diabetes

Leucine plays a very important role in regulating blood sugar levels. When there isn’t enough of this amino acid in the body people will experience symptoms similar to hypoglycemia. This can include dizziness, headaches, depression, confusion, fatigue, and irritability.

Studies have shown that increases in dietary leucine can reduce diet-induced obesity, hyperglycemia, and cholesterol levels in animals2, 3. There is evidence to suggest that this amino acid may have a role to play in preventing diabetes4.

Scientists are also investigating the role l-leucine has in human diabetes. It is theorised that as leucine can help to improve protein synthesis people with insulin-dependent diabetes may benefit by increased intake of leucine to counteract protein degradation.

While there is some evidence that leucine can help to slow muscle wasting in people with diabetes and improve glucose homeostasis 5, 6, 7. This research is still under development and more in-depth longitudinal clinical studies are necessary.

L-leucine and sarcopenia

The term scarcopenia is used to describe the condition whereby skeletal muscle mass protein content declines and skeletal muscle fat levels increase. This occurs as the body ages and is believed to be associated with a reduction in the metabolic reaction to leucine protein synthesis8.

Scarcopenia makes people frail and more susceptible to injury. There is some evidence to suggest that by increasing dietary intake of leucine can help to improve muscle protein synthesis in the elderly9.

L-leucine and injury recovery

BACCs are important for helping the body to recovery following injury. Leucine helps to promote the healing of muscle tissue, skin, and bones following trauma.

Often people recovering from surgery are encouraged to take BACC supplements or eat a diet rich in these amino acids to accelerate healing.

Symptoms of a l-leucine deficiency or excess

As previously mentioned, symptoms of a leucine deficiency are similar to that of hyperglycemia, or elevated blood sugar levels. Excessive amount of leucine can impair liver and kidney function, plus predispose people to developing pellagra.

Natural sources of l-leucine

nuts with l-leucineL-leucine is found naturally in foods such as beans, brown rice, meat, nuts, whole wheat and soy flour. Most protein rich foods contain this essential amino acid. Supplements are often recommended to people who have a low protein diet and exercise a lot.

This amino acid needs to be taken together with isoleucine and valine for the body to utilise it effectively. There are many supplements formulated with the right BCAA ratio to support a healthy body.

As with any supplementation program, always consult a health physician before taking BCAA supplements to rule out any underlying adverse health effects.


  1. “Yeh Y (1984). Ketone body synthesis from leucine by adipose tissue from different sites in the rat. Archives of Biochemisty and Biophysics. Volume 233, Issue 1, pp. 10-8.”
  2. “Zhang Y, et al. (2007). Increasing Dietary Leucine Intake Reduces Diet-Induced Obesity and Improves Glucose and Cholesterol Metabolism in Mice via Multimechanisms. Diabetes. Volume 56, Issue 6, pp (1647-54)”
  3. “Escobar J, et al (2005). Physiological rise in plasma leucine stimulates muscle protein synthesis in neonatal pigs by enhancing translation initiation factor activation. The American Journal of Physiology. Volume 288, Issue 5, (pp. E914-E921).”
  4. “Gua, K. et al. (2010). Chronic leucine supplementation improves glycemic control in etiologically distinct mouse models of obesity and diabetes mellitus. Nutrition and Metabolism. Volume 7, Issue 57, doi: 10.1186/1743-7075-7-57.”
  5. “Godil, M. et al. (2005). Effect of Insulin with Concurrent Amino Acid Infusion on Protein Metabolism in Rapidly Growing Pubertal Children with Type 1 Diabetes. Pediatric Research. Volume 58, (pp. 229-34)”
  6. “Leenders, M. and van Loon, J. (2011). Leucine as a pharmaconutrient to prevent and treat sarcopenia and type 2 diabetes. Nutrition Reviews. Volume 69, Issue 11, (pp. 675-89).”
  7. “Pedroso, J. et al. (2015). Reviewing the Effects of l-Leucine Supplementation in the Regulation of Food Intake, Energy Balance, and Glucose Homeostasis. Nutrients. Volume 7, Issue 5. (p. 3914-37).”
  8. “Fujita S. and Volpi, E. (2006). Amino acids and muscle loss with aging. Journal of Nutrition. Volume 136, Issue 1, (pp. 2777S-80S).”
  9. “Katsanos, C. et al. (2006). A high proportion of leucine is required for optimal stimulation of the rate of muscle protein synthesis by essential amino acids in the elderly. American Journal of Physiology – Endocrinology and Metabolism. Volume 291, Issue 2, (pp. 384-7).”