ANÁLISIS DE LA SENTENCIA:

aspartame and high phenylalanine on behavior relates to the competition of phenylalanine with tryptophan and other large neutral amino acids for a common carrier across blood brain barriers (Groff and Gropper, 2000). Phenylalanine has higher

affinity for the carrier (lowerKm) as compared to tryptophan, so

increased concentrations of phenylalanine hypothetically could cause a reduction in brain tryptophan, leading to lower serotonin levels and behavioral effects.

6.9.2.3.1. Studies in Children. Mental retardation result-

ing from hyperphenylalaninemia in PKU is observed in chil- dren having plasma concentrations in the range of 1200–

6000µmol/L, and the plasma threshold is considered to be near

1000µmol/L (Groff and Gropper, 2000). Seizures and other

neurological abnormalities are also symptoms of PKU. Whether adverse effects occur in the lower range concentrations of hy- perphenylalaninemia is less clear. Children with classic PKU who maintain chronic levels of serum phenylalanine levels in

the range of 240 to 480µmol/L do not experience mental retar-

dation. Therefore, most investigators believe that some elevation of serum phenylalanine above normal levels, even if chronic, is without adverse effect (Yost, 1989).

Eleven hyperactive boys with attention deficit disorder (ages 6–12 years) were evaluated by parents and teachers for changes in behavior and cognitive measures during 2 weeks of consum- ing phenylalanine (20 mg/kg bw/day) or a placebo (Zametkin et al., 1987). Plasma phenylalanine levels were increased dur- ing the phenylalanine-dosing phase, but no difference was found in urinary phenylethylamine. The authors concluded that their findings support the safety of aspartame, but do not support the hypothesis that precursor loading will affect hyperactivity.

Kruesi et al. (1987) evaluated the effect of sugar and aspar- tame on aggression and activity in preschool boys (ages 2 to 6 years) who were identified as sensitive to sugar or “sugar re- sponders”. The study was a double-blind cross-over challenge with aspartame (30 mg/kg bw), sucrose (1.75 g/kg bw), sac- charin (amount not specified) and glucose (1.75 g/kg bw) to

sugar-responsive (n =14) and age-matched control boys (n =

10). The sweeteners were given in a lemon-flavored drink once in a laboratory setting, and once 4 days later in a home setting. Children were scored for activity and aggression by researchers during the laboratory playroom challenge and by their parents in the days following to detect any delayed reaction, and during the home challenge. Washout periods of 5–7 days occurred between

challenges. There was no significant difference in scores of ag- gression among sweeteners, and lower activity scores during the aspartame challenges (Kruesi et al., 1987). Therefore, this study does not support the hypothesis that aspartame is associated with disruptive behavior in children.

Similar negative results were reported by Roshen and Hagen (1989) and Sarvais et al. (1990) in studies evaluating the effect of aspartame on the learning, behavior and mood of children.

A double-blind controlled trial of 48 preschool children fed diets containing a daily intake of 38 mg/kg bw/day aspartame for 3 weeks showed no adverse effects attributable to aspartame or dietary sucrose on children’s behavior or cognitive function (Wolraich et al., 1994). Shaywitz et al. (1994b) assessed the ef- fect of aspartame on behavior and cognitive function of children with attention deficit disorder using a randomized, double blind, and placebo-controlled crossover study design. The dose of as-

partame was 34 mg/kg bw/day. Children (n =15, 11 males,

4 females, ages 5 to 13 years) were given capsules of either aspartame or placebo (microcrystalline cellulose) each morn- ing for a 2-week period. Parents were instructed to provide an aspartame-free diet during the study. No effect was found on cognitive, attentive or behavioral testing or on urinary levels of neurotransmitters (norepinephrine, epinephrine, dopamine, HVA, and 5HIAA), although plasma tyrosine and phenylalanine levels were higher 2 h after the aspartame treatment. Plasma phenylalanine levels were reported graphically, and increased

from approximately 6µmol/dl at baseline to about 8.5µmol/dl

2 h after aspartame dosing. Plasma tryosine level values were not provided (Shaywitz et al., 1994b). Krohn (1994) criticized this study for the small number of participants, stating that such as study does not demonstrate that all children with ADD would be insensitive to aspartame.

Several studies have used aspartame as a negative control compound in investigations into the effect of sucrose on behav- ior. For example, no differences were found in behavior of 16 hyperactive boys following challenges with a single oral dose of sucrose (57 g) and aspartame (197 mg) in two studies con- ducted by Wolraich et al. (1985). The problem with these studies is that both dietary sucrose and aspartame have been reported to affect behavior, so it is difficult to use one or the other as a nega- tive control. Wolraich et al. (1994) subsequently addressed this concern in a very well controlled study to assess the behavioral effects of sucrose and aspartame using saccharin as a negative control. This was a 9-week study with all food being provided to families of participants throughout the study to control for other dietary components that may impact behavior. Participants were

preschool children (n =25) described as normal and school age

children (n=23) described as sensitive to sugar. Experimental

diets were provided during 3-week periods in a Latin-square de- sign. The diets provided participants with sucrose (4500–5600 mg/kg bw/day), aspartame (32–38 mg/kg bw/day), or saccharin (10–12 mg/kg bw/day) as the sweetener. Behavior and cogni- tive measures were assessed weekly. This study also included measures of diet compliance using biochemical tests. No effect

of sucrose or aspartame on behavior or cognitive function was observed in either age group of children (Wolraich et al., 1994). However, the use of glucose or sucrose as a placebo needs to be viewed with caution as other studies have shown improvement of memory and cognitive function following their administration (Sunram-Lea et al., 2001; Sunram-Lea et al., 2002; 2004).

6.9.2.3.2. Studies in Adults. A double-blind randomized

crossover trial with 10 healthy volunteers (6 men, 4 women, ages 21–36 years) evaluated the effect of a single dose of aspartame (15 mg/kg bw) or placebo capsules on mood, cognitive function, and reaction time. No effect was observed on hunger, headache, memory, reaction time, or cognition during the study despite elevation of plasma phenylalanine levels following consumption (data values not reported). The percentage of total LNAA that was phenylalanine increased from approximately 11% to a peak of about 18 at the 2-h time point after dosing, but dropped to normal after 8 h (Lapierre et al., 1990).

A single dose of aspartame had no effect on food consump- tion, mood or alertness in healthy males ages 20 to 35 years. Sub-

jects (n=13/group) were given capsules containing placebo or

aspartame (5 or 10 g) in a randomized crossover design (Ryan- Harshman et al., 1987). Blood phenylalanine levels increased

from a mean of 7.1µmol/dl at baseline, by 5.5 and 19.3µmol/dl

at 90 min after consumption of 5 and 10 g aspartame, respec-

tively. Blood tyrosine levels increased by 2.5 and 4.7µmol/dl,

from a baseline of 7.7 µmol/dl at 90 min after consumption

of 5 and 10 g aspartame, respectively. These differences were statistically significant, but no behavioral effects were observed. Pivonka and Grunewald (1990) compared the effect of water, and aspartame- and sugar-containing beverages on mood in 120 young women and found no effect on self-reported surveys of mood.

A highly publicized case report of adverse effects of aspar- tame consumption in a military pilot led to two controlled studies on the effect of acute (Stokes et al., 1991) and chronic (Stokes et al., 1994) aspartame ingestion on cognitive performance in pi- lots. The first study involved 12 healthy certified pilots (4 females and 8 males). The study was double-blinded with each subject being tested 5 times, with at least 1 week between treatments given in random order among the 12 participants. Participants were pretested for baseline values, then given placebo capsules, aspartame (50 mg/kg bw), or ethyl alcohol (positive control, es- timated dose to raise blood alcohol 0.1%), followed by a posttest with no treatment. For all treatments, participants consumed or- ange juice with either a trace or the test dose of alcohol, and capsules with either placebo (dextrose) or aspartame. Cognitive performance was tested using the SPARTANS cognitive test bat- tery, which is a sensitive test to detect changes in performance of complex tasks required for aircraft operations. As has been discussed previously, concerns have been voiced regarding the possible potentiation of the effects of aspartame by consump- tion concurrently with carbohydrates. Therefore, all participants consumed a small carbohydrate meal prior to treatments. Con-

sumption of other foods, aspartame, and alcohol was controlled prior to testing. Blood levels of amino acids were not measured. Cognitive impairment was detected in several tasks following consumption of the low dose of alcohol but not aspartame or placebo treatments (Stokes et al., 1991).

A follow-up study employed a more complex battery of tests (SPARTANS Version 2), chronic exposure to aspartame and measurement of blood phenylalanine (Stokes et al., 1994). Twelve subjects (college students, sex not defined) received placebo capsules or aspartame capsules (50 mg/kg bw/day) for 9 days, or an acute dose of ethyl alcohol to achieve 0.1% blood ethanol levels as described earlier. All participants received the placebo and ethanol treatments once and the aspartame treatment twice with a 7-day interval. Blood phenylalanine and breath alco- hol levels were measured. On the last day of treatment periods, when subjects completed the cognitive testing, blood alcohol levels were 0.0% during all treatments except following the al- cohol treatment when it averaged 0.09%. Plasma phenylalanine

levels averaged 59.08µmol following placebo treatments and

121.5µmol following aspartame consumption. Forty-seven task

variables were measured and significant differences between pre- and post-test results and aspartame treatment were detected for three tasks. However, unexpectedly, an improvement, rather than impairment, of function was observed in participants fol- lowing the aspartame treatments. Following ethanol treatments, participants scored lower on 14 tasks. The authors attribute the finding of enhanced performance following aspartame treatment to chance, and conclude that although aspartame given at high doses (50 mg/kg bw/day) approximately doubled plasma pheny- lalanine levels, there is no evidence of impaired cognitive per- formance (Stokes et al., 1994).

Cognitive, neurophysiologic and behavioral effects of con- suming aspartame for 20 days were evaluated by Spiers et al. (1998) in a group of 48 healthy volunteers (24 men, 24 women, ages 18–34 years). This was a three-way crossover double- blind study with treatments consisting of aspartame, sucrose and placebo. Twenty-four participants received a high dose of aspar- tame (45 mg/kg bw/day) and the remaining received 15 mg/kg bw/day. Acute effects were evaluated on day 10 of each treatment arm, with testing starting 90 min after consumption of test ma- terial. Chronic effects were evaluated on day 20. Plasma pheny- lalanine levels increased dose-dependently with aspartame consumption, but no other effects were observed.

Concerns exist that the only studies done that show no ef- fect of aspartame are those which use healthy adults and people used to high intakes of aspartame such as diabetics and people on weight-loss regimes (Tsakiris et al., 2006). However, the effect of acute high-dose aspartame was also evaluated in a double- blinded study of 18 patients with Parkinson’s disease, as this was considered a susceptible target population for adverse ef- fects (Karstaedt and Pincus, 1993). Ten patients received a dose of 600 mg, and eight received 1200 mg aspartame in capsules or placebo capsules in random order. Motor scores and plasma lev- els of phenylalanine were measured every hour for 4 h. Although

plasma phenylalanine levels were significantly increased follow- ing aspartame consumption, there was no significant difference in motor or disability scores following aspartame as compared to following placebo ingestion (Karstaedt and Pincus, 1993).

Another group considered possibly vulnerable to aspartame were patients suffering from depression (Walton et al., 1993). Participants were adults (ages 24–60 years) undergoing treat-

ment for depression (n=8, 3M, 5F) or nondepressed volunteer

controls (n =5, 3M, 2F) of which three considered themselves

susceptible to adverse effects of aspartame. Subjects received aspartame (30 mg/kg bw/day) or placebo (sucrose) in capsules for a period of 7 days. Subjects were asked to self-monitor and score the severity of a list of symptoms, which included headache, nervousness, dizziness, nausea, feeling blue or de- pressed, temper outbursts, and others. One patient experienced pain in his eye, which was followed by retinal detachment. This occurred during the placebo phase, but the authors speculated that consumption of aspartame prior to placebo might have been responsible. Another patient experienced a conjunctival hemor- rhage during the aspartame phase. These events lead to a halt of the study. Only 11 participants completed the study, but total points for adverse effects were compared for all 13 participants. Higher point values were recorded by depressed patients during

consumption of aspartame (mean=40) as compared to during

consumption of placebo (mean=10), but nondepressed partic-

ipants recorded similar points during aspartame (mean=13)

and placebo (mean=15) phases. The authors concluded that

individuals with mood disorders should be discouraged from consuming aspartame (Walton et al., 1993). The limitations of this study include the small number of participants, the provision of a suggested list of adverse effects that may have influenced self-diagnosis, and the lack of control of other dietary factors during the study. The statistics used were also questionable as

multiplet-tests were used to compare nonparametric measures.

The effect of aspartame on behavior and cognitive function has been studied extensively in animals, and in healthy children, hyperactive children, sugar-sensitive children, healthy adults, individuals with Parkinson’s disease, and individuals suffering from depression. The only study to suggest that aspartame may be associated with behavior was the study in depression patients. The limitations of this study were discussed above. Overall, the weight of the evidence indicates that aspartame has no effect on behavior or cognitive function.

6.9.2.4. Effect of Aspartame on Seizures. Children who