- L-alpha-Aminoisocaproic acid
- Branched-chain amino acid (BCAA)
For Patients & Caregivers
Bottomline: Leucine is an essential amino acid required for muscle growth and maintenance.
Leucine is an amino acid that is not made in the human body and is required for muscle maintenance. Therefore it has to be obtained through dietary sources rich in protein such as dairy, soy, and meats. Studies done on leucine show that it improves muscle strength but is not useful in the treatment of sarcopenia (loss of skeletal muscle mass and strength). Leucine can also increase secretion of insulin but did not improve sugar levels in diabetic patients.
Leucine is available as a dietary supplement and it used to improve muscle strength and endurance.
- Muscle strength and endurance
Some studies show that leucine improves muscle strength and endurance.
In one study, leucine did not affect blood sugar level in diabetic men. Further research is needed.
Long term studies do not support use of leucine for the treatment of sarcopenia.
- You are taking Insulin and other antidiabetic medications (Leucine can stimulate insulin secretion and may further lower blood glucose levels).
- You are taking Vitamin B3 and vitamin B6 (Leucine can interfere with the production of these vitamins).
- You have Maple syrup urine disease (Leucine can accumulate in blood or urine resulting in dysfunction of nerve cells).
For Healthcare Professionals
Leucine is an essential amino acid that is not synthesized in human bodies and must be obtained from food consisting of plant or animal protein. Leucine is often used together with valine and isoleucine, which are branched-chain amino acids, in parenteral forms for nutritional support to maintain nitrogen balance, and to treat cirrhosis and hepatic encephalopathy. Purified leucine is marketed as a dietary supplement for body building. It is thought to stimulate protein synthesis by activating the mammalian target of rapamycin (mTOR) pathway (1)(2). Dietary supplementation with leucine can improve performance (3) and upper body strength in athletes (4). However, it does not prevent or treat sarcopenia (16) nor affect glycemic control in diabetic men (5).
Because leucine can enhance the proliferation of hematopoietic progenitors, there is current interest in developing it as a treatment for Diamond Blackfan Anemia (DBA) and for Myelodysplastic Syndrome (MDS) (6)(7).
Leucine from dietary sources is generally considered safe. However, excessive intake may result in hypoglycemia (8) and may also cause vitamin B3 and B6 deficiencies (9)(10). Amounts exceeding ∼39 g/d may pose a health risk (17).
Leucine stimulates protein synthesis by activating the mammalian target of rapamycin (mTOR) pathway (1). It is thought to enhance muscle anabolic signaling (11). In DBA patients, L-leucine modulates protein synthesis by enhancing translation leading to improvement in hemoglobin levels (7). In the presence of glucose, oral leucine ingestion can stimulate insulin secretion and lower blood glucose level (8).