neotame and Body-Weight

Safety studies done with neotame, a sweetener with intense taste, demonstrate that changes in bodyweight (BW) and BW gain (BWG) are due to reduced food consumption (FC) rather than toxicity. When offered a choice, rats preferred basal diet to diet with relatively low concentrations of neotame. When no choice was available, rats ate less as concentrations increased, demonstrating reduced palatability. Changes in dietary concentrations of neotame resulted in changes in FC. The maximum tolerable doses (MTDs) in rats, dogs, and mice were due to decreases in BWG secondary to poor palatability of diets when neotame concentrations exceeded approximately 35,000 ppm. Concentrations were increased as animals grew to maintain constant dosing on a "mg/kg bw/day" basis. Food conversion efficiency (FCE) was not changed in rats during periods of active growth. The only consistent findings across safety studies were reductions in BW, BWG, and FC with no dose-response in rats, mice, and dogs. In definitive safety studies, there were no adverse findings related to neotame treatment from clinical observations, physical examinations, water consumption, or clinical pathology evaluations; nor was there morbidity, mortality, organ toxicity, macroscopic or microscopic postmortem findings. Analysis of data from long-term studies in Sprague-Dawley rats support the conclusion that changes in FC alone can cause the observed changes in BWG in neotame studies when changes are scaled allometrically [Regul. Toxicol. Pharmacol. (2003)]. Consequently, BW parameters are not appropriate endpoints for setting no-observed-effect levels (NOELs) for neotame.

Topics: Administration, Oral; Animals; Body Weight; Carcinogenicity Tests; Diet; Dipeptides; Dogs; Dose-Response Relationship, Drug; Eating; Embryonic and Fetal Development; Female; Food Preferences; Male; Maternal-Fetal Exchange; Mice; Pregnancy; Rats; Rats, Sprague-Dawley; Sweetening Agents; Taste; Toxicity Tests, Chronic

In long-term safety studies with neotame, a new high-intensity sweetener 7000-13,000 times sweeter than sucrose, the percent changes (%Delta) in body weight gain (BWG) in Sprague-Dawley rats were several-fold greater than the %Delta in overall food consumption (FC). This study investigates the question of whether the changes in BWG were adverse or secondary to small, long-term decrements in FC. The hypothesis tested in Sprague-Dawley rats was that the relationship between long-term %Delta in FC and %Delta in BWG is linear and in a ratio of 1:1. The %Delta in FC were compared to %Delta in BWG after 52 weeks on study in one saccharin (825 rats), two sucralose (480 rats), two neotame (630 rats), and five dietary restriction (>1000 rats) studies. Non-transformed plotting of data points demonstrated an absence of linearity between %Delta in FC and %Delta in BWG; however, log-log evaluation demonstrated a robust (R2=0.97) linear relationship between %Delta in FC and %Delta in BWG. This relationship followed the well-known allometric equation, y=bxa where x is %DeltaFC, y is %DeltaBWG, b is %DeltaBWG when DeltaFC=1, and a is the log-log slope. Thus, in Sprague-Dawley rats at week 52, the long-term relationship between %Delta in FC and %Delta in BWG was determined to be: %DeltaBWG=3.45(%DeltaFC0.74) for males and %DeltaBWG=5.28(%DeltaFC0.68) for females. Sexes were statistically different but study types, i.e., the high-intensity sweeteners saccharin and sucralose versus dietary restriction, were not. The %Delta in BWG are allometrically consistent with the observed %Delta in FC for these high-intensity sweeteners, including neotame. BW parameters are not appropriate endpoints for setting no-observed-effect levels (NOELs) when materials with intense taste are admixed into food. An approach using objective criteria is proposed to delineate BW changes due to toxicity from those secondary to reduced FC.

Topics: Administration, Oral; Animals; Body Weight; Diet; Dipeptides; Drug Administration Schedule; Eating; Embryonic and Fetal Development; Female; Male; Maternal-Fetal Exchange; Pregnancy; Rats; Rats, Sprague-Dawley; Sweetening Agents; Taste; Time Factors; Toxicity Tests, Chronic