EMORY UNIVERSITY SCHOOL OF MEDICINE
DEPARTMENT OF PEDIATRICS
2040 Ridgewood Drive, N.E. Atlanta, Georgia 30322
MEDICAL GENETICS (404) 727-5840
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-L-a-aspartyl-L-
phenylalanine) in our world food supply. This artificial dipeptide is
hydrolyzed by the intestinal tract to produce 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?”.
Preliminary studies in my laboratory provide tentative positive answers
to both questions. Many studies of both acute and chronic ingestion of 34mg
Aspartame/kg/day have demonstrated a two to five fold increase in semi-
fasting blood phenylalanine concentrations (from approximately 50 to 250 �M)
without concomitant increases in tyrosine or other aminoacids. The degree
of increase by normal humans depends on several variables including the
efficiency of tut transport, liver utilization, and growth rates. It was
thought by many scientists and clinicians that this degree of phenylalanine
increase would not affect brain function. However, currently available
information indicates that this is not true.
1. In the developing fetus such a rise in material 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 �M could reach 900 �M 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 defects.
2. In the rapidly growing post-natal bran (children of 0-
12 months) irreversible brain damage could occur by the
3. 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 negative
effect on sensitive parameters of brain function.
In view of these new (and confirmation of old) research
findings I suggest the following:
1) Immediate labeling of all aspartame-containing foods,
so the consumer will know how much phenylalanine
he/she is ingesting.
2) Declare an immediate moratorium on addition of
aspartame to more foods and remove it from all low-
protein beverages, foods, and children’s medications.
3) Provide funds not controlled by industry to:
a. Allow active surveillance for potential side-effects
of aspartame on newborns whose mothers dieted with
Nutrasweet (aspartame) -containing foods.
b. Allow active evaluation of other users whose
complaints cannot be adequately studied at present.
c. Clarify the dose relationship and mechanisms by
which L-phenylalanine affects human brain function.
Louis J. Elsas, II, M.D.
Director, Division of Medical Genetics
Professor of Pediatrics
The above statement was before the Committee of Labor and Human Resources
on the subject “Nutrasweet: Health and safety concerns”, and dated November