Amino Acid Supplementation May Alter Hormone Levels Without Improving Performance
Jan. 7, 2000 (Tuscaloosa, Ala.) -- A large oral dose of a mixture of amino
acids appears to have altered the hormonal balance of moderately conditioned
athletes, according to a preliminary study published in the December issue of
Medicine and Science in Sports and Exercise. However, experts who
reviewed the article for WebMD point out that it is unknown whether the
supplemental amino acids can improve athletic performance. They warn that the
study is not strong enough to support recommendations for supplemental dosing
of amino acids.
The study, by Luigi Di Luigi and colleagues at the Endocrine Research
Laboratory of the Sports Medicine Unit of the University Institute of Motor
Sciences in Rome and from the division of andrology at the University of Rome,
evaluated the effect of a mixture of amino acids on various hormones in 10
Ten male volunteers, aged 25-29, drank an orange-flavored mixture of several
amino acids, sugar, and water. Blood tests were taken at various times before
and after the mixture was consumed to measure various hormone levels in the
The researchers found that the amino acid mixture may have stimulated the
athletes' pituitary glands, increasing secretions of certain stress-and
sex-related hormones, including growth hormone. They believe the mixture of
amino acids, or possibly a single amino acid, "could be responsible"
for increases in cortisol and testosterone in the blood of the athletes.
However, the researchers emphasize that "further studies are required to
evaluate whether amino acid supplementations could also have a direct action at
testicular and adrenal levels in addition to the action we found at the
"I am surprised this study got published," says Melvin H. Williams,
PhD, who reviewed the article for WebMD. Williams, a professor emeritus of
exercise physiology at Old Dominion University in Norfolk, Va., is currently
revising the sixth edition of his classic McGraw Hill textbook, Nutrition
for Health, Fitness, and Sport. He says he will "probably not" be
mentioning this study in his book.
"This is only a small-scale, preliminary study," he tells WebMD.
"It did not include any data on performance. The only data that is
potentially important from the standpoint of athletic performance would be the
measurements of growth hormone."
And although the Italian researchers reported some increase in growth
hormone at various times during the test, by the end of the experiment no
significant increases in the absolute levels of growth hormone were found in
the bloodstreams of the volunteers, Williams notes.
"Since the absolute level of growth hormone did not increase, this study
has no clinical significance to practitioners or relevance to practicing
athletics," he concludes. "It is very weak data. No one should use
these results as a reason to go out and take amino acids."