EMORY UNIVERSITY SCHOOL OF MEDICINE
DEPARTMENT OF PEDIATRICS
2040 Ridgewood Drive, NE
Atlanta, Georgia 30322
Division of Medical Genetics
Statement for the Labor and Human Resources Committee, U.S. Senate
I have considerable concern for
the increased dissemination and consumption of the sweetener, aspartame
(1-methyl N-Laspartyl-L-phenylalanine) in our world food supply.
This artificial dipeptide is hydrolyzed by the intestinal tract to product
l-phenylalanine which in excess is a known neurotoxin. Normal humans
do not metabolize phenylalanine as efficiently as do lower species such
as rodents, and thus most of the previous studies in Aspartame effects
on rats are irrelevant to the question, "does phenylalanine excess occur
with Aspartame ingestion?" and if so "will it adversely affect human
Preliminary studies in my laboratory
provide tentative positive answers to both questions. Many studies
of both acute and chronic ingestion of 34 mg Aspartame/kg/day have demonstrated
a two to five fold increase in semi-fasting blood phenylalanine concentrations
(from approximately 50 to 250 pM) without concomitant increases in tyrosine
or other amino acids. The degree of increase by normal humans depends
on several variables including the efficiency of gut transport, liver utilization,
and growth rates. It was thought by many scientists and clinicians
that this degree of blood phenylalanine increases would not affect brain
However, currently available information indicates that this is not
In the developing fetus such a rise in maternal blood phenylalanine could
be magnified four to six fold by the concentrative efforts of the placenta
and fetal blood brain barrier. Thus a maternal phenylalanine of 150
pM could reach 900 pM in the developing fetal brain cell and this concentration
kills such cells in tissue culture. The effect of such an increased
fetal brain concentrations in vivo would probably be much more subtle and
expressed as mental retardation, microcephaly, or potential certain birth
In the rapidly growing post-natal brain (children of 9-12 months) irreversible
brain damage could occur by the same mechanism.
In the adult we have found that changes in blood phenylalanine in these
concentration ranges are associated with slowing of the electroencephalogram,
and prolongation of cognitive function tests.
Fortunately, these effects on the mature brain are reversible but
provide clear evidence for a negative effect on sensitive parameters of
In view of these new (and confirmation of old) research
findings, I suggest the following:
Louis J. Elsas, II, M.D.
Director, Division of Medical Genetics, Professor of Pediatrics
Immediate quantitative labeling of all aspartame-containing foods, so the
consumer will know how much phenylalanine he/she is ingesting.
Declare an immediate moratorium on addition of aspartame to more foods,
and remove it from all low-protein beverages, foods, and children's medications.
Provide funds not controlled by industry to:
Allow active surveillance for potential side-effects of aspartame on newborns
whose mothers dieted with NutraSweet (aspartame)-containing foods.
Allow active evaluation of other users whose complaints cannot be adequately
studied at present.
Clarify the dose relationship and mechanisms by which L-phenylalanine affects
human brain function..