Occurrence of artificial sweeteners in human liver and paired blood and urine samples from adults in Tianjin, China and their implications for human exposure

In this study, acesulfame (ACE), saccharin (SAC) and cyclamate (CYC) were found in all paired urine and blood samples collected from healthy adults, with mean values of 4070, 918 and 628 ng mL(-1), respectively, in urine and 9.03, 20.4 and 0.72 ng mL(-1), respectively, in blood. SAC (mean: 84.4 ng g(-1)) and CYC (4.29 ng g(-1)) were detectable in all liver samples collected from liver cancer patients, while ACE was less frequently detected. Aspartame (ASP) was not found in any analyzed human sample, which can be explained by the fact that this chemical metabolized rapidly in the human body. Among all adults, significantly positive correlations between SAC and CYC levels were observed (p < 0.001), regardless of human matrices. Nevertheless, no significant correlations between concentrations of SAC (or CYC) and ACE were found in any of the human matrices. Our results suggest that human exposure to SAC and CYC is related, whereas ACE originates from a discrete source. Females (or young adults) were exposed to higher levels of SAC and CYC than males (or elderly). The mean renal clearance of SAC was 730 mL per day per kg in adults, which was significantly (p < 0.001) lower than those for CYC (10 800 mL per day per kg) and ACE (10 300 mL per day per kg). The average total daily intake of SAC and ACE was 9.27 and 33.8 μg per kg bw per day, respectively.

Aspartame sensitivity? A double blind randomised crossover study

Background

Aspartame is a commonly used intense artificial sweetener, being approximately 200 times sweeter than sucrose. There have been concerns over aspartame since approval in the 1980s including a large anecdotal database reporting severe symptoms. The objective of this study was to compare the acute symptom effects of aspartame to a control preparation.

Methods

This was a double-blind randomized cross over study conducted in a clinical research unit in United Kingdom. Forty-eight individual who has self reported sensitivity to aspartame were compared to 48 age and gender matched aspartame non-sensitive individuals. They were given aspartame (100mg)-containing or control snack bars randomly at least 7 days apart. The main outcome measures were acute effects of aspartame measured using repeated ratings of 14 symptoms, biochemistry and metabonomics.

Results

Aspartame sensitive and non-sensitive participants differed psychologically at baseline in handling feelings and perceived stress. Sensitive participants had higher triglycerides (2.05 ± 1.44 vs. 1.26 ± 0.84mmol/L; p value 0.008) and lower HDL-C (1.16 ± 0.34 vs. 1.35 ± 0.54 mmol/L; p value 0.04), reflected in ¹H NMR serum analysis that showed differences in the baseline lipid content between the two groups. Urine metabonomic studies showed no significant differences. None of the rated symptoms differed between aspartame and control bars, or between sensitive and control participants. However, aspartame sensitive participants rated more symptoms particularly in the first test session, whether this was placebo or control. Aspartame and control bars affected GLP-1, GIP, tyrosine and phenylalanine levels equally in both aspartame sensitive and non-sensitive subjects.

Conclusion

Using a comprehensive battery of psychological tests, biochemistry and state of the art metabonomics there was no evidence of any acute adverse responses to aspartame. This independent study gives reassurance to both regulatory bodies and the public that acute ingestion of aspartame does not have any detectable psychological or metabolic effects in humans.

Trial Registration

ISRCTN Registry ISRCTN39650237

Aspartame: a safety evaluation based on current use levels, regulations, and toxicological and epidemiological studies

Aspartame is a methyl ester of a dipeptide used as a synthetic nonnutritive sweetener in over 90 countries worldwide in over 6000 products. The purpose of this investigation was to review the scientific literature on the absorption and metabolism, the current consumption levels worldwide, the toxicology, and recent epidemiological studies on aspartame. Current use levels of aspartame, even by high users in special subgroups, remains well below the U.S. Food and Drug Administration and European Food Safety Authority established acceptable daily intake levels of 50 and 40 mg/kg bw/day, respectively. Consumption of large doses of aspartame in a single bolus dose will have an effect on some biochemical parameters, including plasma amino acid levels and brain neurotransmitter levels. The rise in plasma levels of phenylalanine and aspartic acid following administration of aspartame at doses less than or equal to 50 mg/kg bw do not exceed those observed postprandially. Acute, subacute and chronic toxicity studies with aspartame, and its decomposition products, conducted in mice, rats, hamsters and dogs have consistently found no adverse effect of aspartame with doses up to at least 4000 mg/kg bw/day. Critical review of all carcinogenicity studies conducted on aspartame found no credible evidence that aspartame is carcinogenic. The data from the extensive investigations into the possibility of neurotoxic effects of aspartame, in general, do not support the hypothesis that aspartame in the human diet will affect nervous system function, learning or behavior. Epidemiological studies on aspartame include several case-control studies and one well-conducted prospective epidemiological study with a large cohort, in which the consumption of aspartame was measured. The studies provide no evidence to support an association between aspartame and cancer in any tissue. The weight of existing evidence is that aspartame is safe at current levels of consumption as a nonnutritive sweetener.

Formaldehyde-induced shrinkage of rat thymocytes

To test the possibility that micromolar formaldehyde, a metabolite of methanol derived from aspartame, exerts cytotoxicity, its effect on rat thymocytes was examined under the in vitro condition using a flow cytometer. Incubation of thymocytes with formaldehyde at 100 micro M or more for 24 h significantly increased the populations of shrunken cells and cells with hypodiploid DNA. The peak blood concentration of methanol in human subjects administered abuse doses of aspartame has been reported to exceed 2 mg/dL (625 micro M). It would increase the population of thymocytes undergoing apoptosis if formaldehyde at 100 micro M or more appears in the blood after administration of aspartame.

Pulmonary peptide delivery: effect of taste-masking excipients on leuprolide suspension metered-dose inhalers

The purpose of this study was to evaluate the effect of taste-masking excipients on in vitro and in vivo performance of a leuprolide metered-dose inhaler (MDI) suspension formulation. Taste-masking excipients (aspartame and menthol) were added to a leuprolide suspension MDI formulation. The leuprolide MDI formulation with the taste-masking excipients was characterized in terms of milling time, particle size distribution, dose delivery and uniformity, and drug absorption in dogs. The data were compared with a formula that did not contain taste-masking excipients. It was found that the longer milling time for the leuprolide suspension with the taste-masking excipients was required to obtain a similar particle size distribution compared with the formula without taste-masking excipients using a fluid energy mill. Although measurable differences in mass median aerodynamic diameter (MMAD) and geometric standard deviation (GSD) were not observed between the two formulations, the percent of particles < or = 5 microns and the actuator retention for the formula with the taste-masking excipients were significantly different from the formula without taste-masking excipients using the Marple-Miller cascade impactor. Taste-masking excipients did not show a significant effect on valve delivery and through-can dose uniformity. However, the mean ex-actuator dose was 150.4 mg for the formula with the taste-masking excipients and 162.2 mg for the reference formula, respectively, indicating a significant difference. In tracheostomized dogs, both formulations showed comparable pharmacokinetic parameters including Cmax, Tmax, AUC0-12 and bioavailability (F%), indicating that the taste-masking excipients do not have an effect on lung absorption of leuprolide acetate. Therefore, inclusion of taste-masking excipients in the leuprolide MDI suspension formulation showed a significant impact on drug micronization, exactuator dose, and particle deposition pattern. Mechanistically, the unfavorable performance of leuprolide MDI in the presence of taste-masking excipients could be due to modification of the properties of the suspension itself and alteration of propellant evaporation following actuation.

Genetic taste responses to 6-n-propylthiouracil among adults: a screening tool for epidemiological studies

Genetically mediated taste responsiveness to 6-n-propylthiouracil (PROP) has been linked to reduced acceptance of some bitter foods. In this community-based study male (n = 364) and female (n = 378) adults enrolled in a self-help dietary intervention trial were screened for PROP taster status. Respondents, aged 18--70 years, were mailed filter papers impregnated with PROP or with aspartame solutions. They received instructions to rate taste intensity and hedonic preference using nine point category scales. Women rated PROP as more bitter than did men. Both sweetness and bitterness ratings were lower for older adults. Taste responsiveness to PROP was unrelated to body mass index in women or men. Higher bitterness ratings for PROP were weakly associated with higher sweetness ratings for aspartame, but were unrelated to sweet taste preferences. Successful administration of PROP filter papers by mail suggests new avenues for the screening of taste phenotypes in epidemiological studies.

Aspartame pharmacokinetics - the effect of ageing

Aspartame is an intense sweetener which is increasingly used in the UK. It is registered at an acceptable daily intake (ADI) of 40 mg/kg, although there are no previous data relating to the metabolism of aspartame in older people. Twelve young and 12 elderly volunteers each received a single dose of approximately 40 mg/kg of aspartame. Baseline concentrations of phenylalanine (the main metabolite of aspartame) rose after ingestion with a significantly higher maximum concentration (Cmax) (81.3 vs. 63.3 micromol/1, p<0.01) and area under the plasma concentration-time curve extrapolated to infinity AUC 9(0-infinity)(518.7 vs. 353.5 micromol . h/l, p<0.01) in the elderly group. The higher concentrations reflected a significant fall in volume of distribution (V) from 2.03 to 1.59 1/kg (p <0.05) and clearance (CL) from 7.3 to 4.9 ml/min/kg (p <0.005) in the elderly group. The greater effect on CL than on V resulted in a small but non-significant rise in elimination half life (3.5 to 3.9 hours). The sizes of the differences were modest implying that there is no need on pharmacokinetic grounds for a change in the ADI for older people.

Determination of aspartame and its major decomposition products in foods

A liquid chromatographic procedure already evaluated in a preceding study for the analysis of acesulfam-K is also suitable for the determination of the intense sweetener aspartame in tabletop sweetener, candy, fruit beverage, fruit pulp, soft drink, yogurt, cream, cheese, and chocolate preparations. The method also allows the determination of aspartame's major decomposition products: diketopiperazine, aspartyl-phenylalanine, and phenylalanine. Samples are extracted or diluted with water and filtered. Complex matrixes are centrifuged or clarified with Carrez solutions. An aliquot of the extract is analyzed on a reversed-phase muBondapak C18 column using 0.0125M KH2PO4 (pH 3.5)-acetonitrile ([85 + 15] or [98 + 2]) as mobile phase. Detection is performed by UV absorbance at 214 nm. Recoveries ranged from 96.1 to 105.0%. Decomposition of the sweetener was observed in most food samples. However, the total aspartame values (measured aspartame + breakdown products) were within -10% and +5% of the declared levels. The repeatabilities and the repeatability coefficients of variation were, respectively, 1.00 mg/100 g and 1.34% for products containing less than 45 mg/100 g aspartame and 4.11 mg/100 g and 0.91% for other products. The technique is precise and sensitive. It enables the detection of many food additives or natural constituents, such as other intense sweeteners, organic acids, and alkaloids, in the same run without interfering with aspartame or its decomposition products. The method is consequently suitable for quality control or monitoring.

Bioavailability of phenylalanine and aspartate from aspartame (20 mg/kg) in capsules and solution

Aspartame (L-aspartyl-L-phenylalanine methyl ester) was given in capsules or solution to compare the bioavailability of its constituent amino acids, aspartate and phenylalanine. Twenty healthy subjects received a single 20 mg/kg dose of aspartame in capsules or solution in a randomized, crossover design. Plasma amino acid concentrations and the phenylalanine to large neutral amino acid ratios (Phe/LNAA) were determined. Plasma aspartate concentrations did not increase with either treatment. For plasma phenylalanine following capsule ingestion, there was a smaller peak plasma concentration (Cmax; 103.3 v 126.6 mumol/L), a longer time to peak concentration (tmax; 108.6 v 36.6 minutes), but no significant difference in the area under the plasma concentration-time curve (AUC) (7,656 v 7,200 mumol.min/L) when compared with solution ingestion. The maximum plasma Phe/LNAA ratio was smaller (0.16 v 0.19) with capsules. The changes for plasma tyrosine were similar to those seen with phenylalanine. There were no significant differences in the plasma concentrations of the other LNAAs between capsule and solution ingestion. Thus, given the small effect on phenylalanine Cmax and Phe/LNAA and no effect on the extent of absorption of phenylalanine, aspartame ingested in capsules at doses up to 20 mg/kg is a suitable dosage form for blinded clinical studies, provided that the slower rate of absorption of phenylalanine from capsules is taken into account.

Effect of sucrose on the metabolic disposition of aspartame

Twelve normal adult subjects ingested a beverage providing 0.136 mmol aspartame/kg body wt on 2 different days. On 1 study day the beverage provided only aspartame, on the other the beverage provided both aspartame and 3.51 mmol sucrose/kg body wt. The high mean plasma phenylalanine concentrations were similar after administration of aspartame alone (158 +/- 28.9 mumol/L, mean +/- SD) and administration of aspartame plus sucrose (134 +/- 44.1 mumol/L). Evaluation of the area under the plasma concentration-time curve (AUC) for phenylalanine also showed no significant difference between groups (197 +/- 49.1 vs 182 +/- 28.3 mumol.L-1.h for aspartame alone and aspartame plus sucrose, respectively). Similarly, the high mean ratio of phenylalanine to large neutral amino acids (Phe:LNAA) in plasma did not differ significantly (0.265 +/- 0.046 for aspartame alone, 0.275 +/- 0.107 for aspartame plus sucrose). However, there was a small but significant difference between groups for the 4-h AUC values for plasma Phe:LNAA. The simultaneous ingestion of sucrose with aspartame had only minor effects on aspartame's metabolic disposition.

Plasma and brain kinetics of large neutral amino acids and of striatum monoamines in rats given aspartame

Two doses (250 and 1000 mg/kg body weight) of aspartame were administered orally to male rats, and plasma and brain phenylalanine and tyrosine kinetic profiles were studied. In both plasma and brain the maximum increase in phenylalanine and tyrosine levels was reached 60 min after treatment. The changes in brain levels of phenylalanine or tyrosine 0, 60, 120 or 180 min after treatment with 1000 mg AMP/kg were directly correlated with the ratio of the plasma concentration of phenylalanine or tyrosine to the overall plasma concentration of the other large neutral amino acids. The time course of monoamine and metabolite concentrations, in the corpora striatum of the brain, was studied after an oral dose of 500 mg phenylalanine/kg. No significant modifications of monoamine levels were found at any of the times studied, up to 5 hr after dosing.

Oral aspartame and plasma phenylalanine: pharmacokinetic difference between rodents and man, and relevance to CNS effects of phenylalanine. Short note

The ingestion of aspartame, a phenylalanine-containing dipeptide, raises plasma phenylalanine levels. These increments are much greater in humans than rats, because the rat hydroxylates phenylalanine five times faster than man. Accordingly, dose comparisons of aspartame (or phenylalanine) between humans and rats have usually been corrected by a factor of five. Recently, a correction factor of sixty has been proposed (Wurtman and Maher, 1987); the rationale is based on a novel calculation of competitive phenylalanine transport into brain. An analysis of the logic behind this postulation reveals there to be no basis for accepting the higher dose conversion of 60 between rat and man.

Saccharin and aspartame. Are they safe to consume during pregnancy?

Saccharin and aspartame are commonly used artificial sweeteners. Some of the currently available information on their safety in pregnancy was reviewed, with recommendations formulated on their use in the periconceptional period and pregnancy.