Brain tumors and artificial sweeteners? A lesson on not getting soured on epidemiology

Systematic review of the relationship between artificial sweetener consumption and cancer in humans: analysis of 599,741 participants

BACKGROUND

The effect of artificial sweetener consumption on cancer risk has been debated in animal models for over four decades. To further investigate this relationship, this study aims to synthesise results from several of the most recent studies in humans.

METHODS

An online literature search was performed in MEDLINE from 2003 to 2014 using Ovid, PubMed, Web of Science, and Scopus using keywords 'artificial', 'sweetener' and 'cancer'. Ninety-two results were then manually assessed for eligibility. Studies were included if the relationship between artificial sweeteners and cancer was their central hypothesis, and if they adjusted for age, gender, smoking status and body mass index. Extracted data included study design, patient characteristics, outcome measure and results.

RESULTS

In the five publications that satisfied the inclusion criteria, significant direct associations with artificial consumption were found for laryngeal (odds ratio, OR 2.34, 95% CI: 1.20-4.55), urinary tract tumours (OR 2.12, 95% CI: 1.22-3.89), non-Hodgkin lymphoma in men (RR 1.31, 95% CI: 1.01-1.72), multiple myeloma in men (RR 2.02, 95% CI: 1.20-3.40) and leukaemia (RR 1.42, 95% CI: 1.00-2.02). Inverse relationships were found in breast (OR 0.70, 95% CI: 0.54-0.91, p trend = 0.015) and ovarian (OR 0.56, 95% CI: 0.38-0.81, p trend < 0.001) cancers.

CONCLUSION

The statistical value of this review is limited by the heterogeneity and observational designs of the included studies. Although there is limited evidence to suggest that heavy consumption may increase the risk of certain cancers, overall the data presented are inconclusive as to any relationship between artificial sweeteners and cancer.

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.

Consumption of Aspartame-Containing Beverages and Incidence of Hematopoietic and Brain Malignancies

BACKGROUND

In a few animal experiments, aspartame has been linked to hematopoietic and brain cancers. Most animal studies have found no increase in the risk of these or other cancers. Data on humans are sparse for either cancer. Concern lingers regarding this widely used artificial sweetener.

OBJECTIVE

We investigated prospectively whether aspartame consumption is associated with the risk of hematopoietic cancers or gliomas (malignant brain cancer).

METHODS

We examined 285,079 men and 188,905 women ages 50 to 71 years in the NIH-AARP Diet and Health Study cohort. Daily aspartame intake was derived from responses to a baseline self-administered food frequency questionnaire that queried consumption of four aspartame-containing beverages (soda, fruit drinks, sweetened iced tea, and aspartame added to hot coffee and tea) during the past year. Histologically confirmed incident cancers were identified from eight state cancer registries. Multivariable-adjusted relative risks (RR) and 95% confidence intervals (CI) were estimated using Cox proportional hazards regression that adjusted for age, sex, ethnicity, body mass index, and history of diabetes.

RESULTS

During over 5 years of follow-up (1995-2000), 1,888 hematopoietic cancers and 315 malignant gliomas were ascertained. Higher levels of aspartame intake were not associated with the risk of overall hematopoietic cancer (RR for >/=600 mg/d, 0.98; 95% CI, 0.76-1.27), glioma (RR for >/=400 mg/d, 0.73; 95% CI, 0.46-1.15; P for inverse linear trend = 0.05), or their subtypes in men and women.

CONCLUSIONS

Our findings do not support the hypothesis that aspartame increases hematopoietic or brain cancer risk.

Artificial sweeteners--do they bear a carcinogenic risk?

Artificial sweeteners are added to a wide variety of food, drinks, drugs and hygiene products. Since their introduction, the mass media have reported about potential cancer risks, which has contributed to undermine the public's sense of security. It can be assumed that every citizen of Western countries uses artificial sweeteners, knowingly or not. A cancer-inducing activity of one of these substances would mean a health risk to an entire population. We performed several PubMed searches of the National Library of Medicine for articles in English about artificial sweeteners. These articles included 'first generation' sweeteners such as saccharin, cyclamate and aspartame, as well as 'new generation' sweeteners such as acesulfame-K, sucralose, alitame and neotame. Epidemiological studies in humans did not find the bladder cancer-inducing effects of saccharin and cyclamate that had been reported from animal studies in rats. Despite some rather unscientific assumptions, there is no evidence that aspartame is carcinogenic. Case-control studies showed an elevated relative risk of 1.3 for heavy artificial sweetener use (no specific substances specified) of >1.7 g/day. For new generation sweeteners, it is too early to establish any epidemiological evidence about possible carcinogenic risks. As many artificial sweeteners are combined in today's products, the carcinogenic risk of a single substance is difficult to assess. However, according to the current literature, the possible risk of artificial sweeteners to induce cancer seems to be negligible.

Aspartame: review of safety

Over 20 years have elapsed since aspartame was approved by regulatory agencies as a sweetener and flavor enhancer. The safety of aspartame and its metabolic constituents was established through extensive toxicology studies in laboratory animals, using much greater doses than people could possibly consume. Its safety was further confirmed through studies in several human subpopulations, including healthy infants, children, adolescents, and adults; obese individuals; diabetics; lactating women; and individuals heterozygous (PKUH) for the genetic disease phenylketonuria (PKU) who have a decreased ability to metabolize the essential amino acid, phenylalanine. Several scientific issues continued to be raised after approval, largely as a concern for theoretical toxicity from its metabolic components--the amino acids, aspartate and phenylalanine, and methanol--even though dietary exposure to these components is much greater than from aspartame. Nonetheless, additional research, including evaluations of possible associations between aspartame and headaches, seizures, behavior, cognition, and mood as well as allergic-type reactions and use by potentially sensitive subpopulations, has continued after approval. These findings are reviewed here. The safety testing of aspartame has gone well beyond that required to evaluate the safety of a food additive. When all the research on aspartame, including evaluations in both the premarketing and postmarketing periods, is examined as a whole, it is clear that aspartame is safe, and there are no unresolved questions regarding its safety under conditions of intended use.

Aspartame: scientific evaluation in the postmarketing period

Prior to marketing, the safety of the high-intensity sweetener aspartame for its intended uses as a sweetener and flavor enhancer was demonstrated by the results of over 100 scientific studies in animals and humans. In the postmarketing period, the safety of aspartame was further evaluated through extensive monitoring of intake, postmarketing surveillance of anecdotal reports of alleged health effects, and additional research to evaluate these anecdotal reports and other scientific issues. The results of the extensive intake evaluation in the United States, which was done over an 8-year period, and the results of studies done in other countries demonstrated intakes which were well below the acceptable daily intakes set by the FDA and regulatory bodies in other countries, as well as the Joint FAO/WHO Expert Committee on Food Additives. Evaluation of the anecdotal reports of adverse health effects, the first such system for a food additive, revealed that the reported effects were generally mild and also common in the general population and that there was no consistent or unique pattern of symptoms that could be causally linked to consumption of aspartame. Finally, the results of the extensive scientific research done to evaluate these allegations did not show a causal relationship between aspartame and adverse effects. Thus, the weight of scientific evidence confirms that, even in amounts many times what people typically consume, aspartame is safe for its intended uses as a sweetener and flavor enhancer.