Oral Branched-Chain Amino Acids

Oral Branched-Chain Amino Acids

PEP Topic 

Branched-chain amino acids are essential amino acids in which the chemical configuration has a branched shape. Tryptophan, an amino acid precursor of serotonin, is thought to play a role in the pathogenesis of cancer anorexia. Uptake of tryptophan into the brain is regulated by a specific transport system, which is competitively shared with the other amino acids, branched-chain amino acids. By administering oral branched-chain amino acids, the desired result would be a reduced level of tryptophan concentrations in the brain, limiting its anorexic effects. Branched-chain amino acids include leucine, isoleucine, and valine. These are available without a prescription as dietary supplements. Effects have been examined related to anorexia.

Effectiveness Not Established

Research Evidence Summaries

Cangiano, C., Laviano, A., Meguid, M.M., Mulieri, M., Conversano, L., Preziosa, I., & Rossi-Fanelli, F. (1996). Effects of administration of oral branched-chain amino acids on anorexia and caloric intake in cancer patients. Journal of the National Cancer Institute, 88, 550–552.

doi: 10.1093/jnci/88.8.550

Study Purpose:

To evaluate the efficacy of oral branched-chain amino acids versus placebo on anorexia and food intake in patients with cancer

Intervention Characteristics/Basic Study Process:

A mixture of 4.8 g branched-chain amino acids was administered three times daily versus placebo powder three times daily for 60 minutes before each meal for seven consecutive days.

Sample Characteristics:

  • The initial sample included 28 patients; attrition of 3 patients occurred secondary to early surgery not related to study (treatment arm = 13,  placebo arm = 12).
  • Groups were equivalent in sex, age, and tumor origin.
  • Patients were included in the study if they were newly diagnosed with cancer, undergoing surgical resection, experiencing anorexia, and not losing weight.
  • None of the patients received radiotherapy or chemotherapy during the study or four weeks prior.


Multiple institutions in Italy that were not listed or further described

Study Design:

A double-blinded, placebo-controlled, randomized trial design was used.

Measurement Instruments/Methods:

  • Nutritional status prior to and at end of study using biochemical indices
  • Daily caloric intake measured by weighing food before and after each meal
  • Presence of anorexia measured using questionnaire not described in the article
  • Blood tests on days 0, 3, and 7 to measure levels of plasma amino acids and tryptophan


Nutritional status was within normal limits for both groups prior to and at the end of study. Daily caloric intake was significantly increased in the treatment arm. There was no change in the placebo group. Incidence of anorexia was significantly decreased in the treatment arm (100% prior to and 45% at the end of study). There was no significant change in the placebo arm (100% prior to and 84% at the end of study). Blood tests showed a significant increase in plasma amino acid levels and a decrease in free tryptophan levels in the treatment arm and no change in levels noted in the placebo arm.


  • The study had a small sample size.
  • Inclusion criteria was fairly narrow, including newly diagnosed, resectable patients who were not losing weight. Whether results can be applied to patients with cancer not meeting these criteria is questionable.
  • The study had a short treatment time of seven days, leading to questions regarding long-term effects.
  • The measurement tool used for anorexia was a questionnaire not described in this paper but rather referenced from a previous article.
  • Anorexia was not defined.
  • The study sites were not listed or described.