This is a little something I wrote on 13 September 1995, and I am
resubmitting it for the benefit of those who insist that the sky is
falling.
Michel Margosis
----------------------------------------------------------------------
ASPARTAME

 A question arose through Internet as to whether the ingestion of
aspartame, the generic name for NUTRASWEET, has any effect on the
therapeutic efficacy of Sinemet in Parkinson patients.  One contributor
to Internet denounced aspartame for a multitude of ills and sins of the
world except for the Vet Nam, Korean, and World War II.

 Chemically, aspartame is the methyl ester of a dipeptide and has a
nutritive value of 4 calories per gram, but is about 160 times as sweet
as sucrose (table sugar). It was first approved by the FDA in 1974 as a
sugar substitute for table use, and as a sweetener in various products,
and later in carbonated beverages.  Formal objections based on safety
issues were evaluated thoroughly and at length, but the government
concluded that the proposed food additive use is safe under the proposed
usage.  It has become a major ingredient in diet sodas and many other
dietetic drinks and food preparations. The quantities of the substance
that can be consumed can be quite significant when compared to the
dosage amounts of Sinemet: for instance, one glass of soda contains
about 160 mg of aspartame.  However, 3 Oz or 100 Gm (1Gm=1,000mg) of
beef or other protein food is enormous in comparison.

 Aspartame is easily hydrolyzed (broken down) into two different amino
acids, aspartic acid  and phenylalanine.  This hydrolysis occurs in vivo
(in the body) as the substance is metabolized but can also be achieved
in vitro by boiling it in a liquid, which is why it is not to be used in
cooking, and likewise occurs in the early stage of metabolism.  Aspartic
acid and phenylalanine obtained from aspartame are identical to those
derived from any protein and likewise should compete with Sinemet for
the active receptor sites in the brain, if taken within at least one
half hour, the recommended interval, from dosing time. However, a brief
note in the Winter '93-'94 APDA Bulletin reported no adverse effect in a
double blind study with aspartame and L-dopa by Dr. P.J. Karsteadt and
J.H. Pincus of the Georgetown University Hospital  (Neurology,
43:611-613, 1993).

 It would be good to know there is no adverse effect from aspartame on
Sinemet, even at a high dietary level, no matter what the age of the
patient nor the elapsed time since the onset of Parkinson's disease.
However, this study does not give enough information to provide this
assurance.  The premise that ingestion of large neutral amino acids
within a specific time frame of dosing with Sinemet may affect the
response to the drug, and consequently, motor performance, is an
important one to examine.  This study  consisted of administering 600 mg
or 1200 mg of aspartame, intended to bracket a high, but larger amount
than ordinarily consumed to a group of 18 patients from 45 to 75 years,
a range of 30 years.  These patients had been ill from 4 to 30 years.
Various physico-chemical tests were used to measure disability,
dyskinesia, walking, and blood levels at various times after
administration.

   There is no way to know from this paper whether the patients were
assigned in a balanced way to the two groups, but the particular
measures of motor performance and disability could be expected to vary
by age and extent of illness.  Thus, if one group consisted of the
younger and also the less able patients, it could be that the group
would not show changes across the course of the study.  That would not,
however, account for differences or lack thereof in plasma
phenylalanine. It should be noted that the higher exposed group did show
differences in this measure.

 The authors' concluded that the aspartame has no adverse effects on
Parkinson patients even at high levels of consumption.  Yet, the study
does not include enough people, nor even enough in subgroups like the
aged or more disabled, to conclude that there is no effect at the lower
amount tested.  Further repeated intake (e.g., several diet sodas a day)
might produce a different motor performance profile and level of plasma
phenylalanine.  Therefore, it is suggested that it would be prudent to
treat aspartame like any protein and avoid it at least within half an
hour before and after a dose of Sinemet.