Aspartame is a sweetener commonly used in food products for the diet or low calorie market, including soft drinks and chewing gums. It was approved for use in foods in the US and EU member states since the early 1980s.
However suspicions have been raised about whether it is entirely safe, and two studies by the Italian Ramazzini group reignited debate after concluding that there was a link between the ingredient and cancer in rats.
Although the European Food Safety Authority (EFSA) and the US Food and Drug Administration (FDA) assessed the first study and said they saw no grounds to reevaluate safety of the ingredient or change intake advice, the affair placed a new question mark over aspartame. Such marks, accompanied as they are media attention, fade only over time and with concerted communication efforts by industry.
The second study, published this summer, is being reviewed by EFSA and FDA but is not expected to bring about a big change in opinion. Indeed Europe's food regulator itself carried out a review of all the original and more recent data on aspartame in 2002.
The new review, published in Critical Reviews in Toxicology (Informa Healthcase) was conduced by a panel of eight experts over an 11 month period. It considered over 500 studies, articles and reports conducted over the last 25 years - including work that was not published, but that was submitted to government bodies as part of the regulatory approvals process.
The studies and assessments variously looked at aspartame's potential effect on behaviour, reproductive health, neurological function, cancer, and tumour development. They also covered a broad spectrum of population subgroups, including Parkinson's disease and diabetes sufferers, children with various sensitivities, people with allergies and those suffering from depression.
The reviews concluded: "The weight of existing evidence s that aspartame is safe at current levels of consumption… No credible evidence was found that aspartame is carcinogenic, neurotoxic, or has any other adverse effect on health when consumed even at quantities many times the established ADI [acceptable daily intake] levels."
The reviewers took into consideration modern consumption levels, which were estimated using data from a recent food consumption survey conducted in the United States. This is crucial given changing consumption patterns over the past 30 years, and penetration of aspartame in the food industry.
However average intake was still found to be low amongst aspartame users - just 4.9 mg/kg of body weight. The US government-approved upper-limit is 50mg/kg per day
Given the furore sparked by the Ramazzini studies, the reviews paid particular attention to the methodology and conclusions drawn. They said they found "numerous flaws". Moreover, the authors speculated that the carcinogenicity was caused by a methyl group in aspartame metabolising into formaldehyde.
The reviewers, however, pointed out that the body metabolises methyl groups from other sources without issue; and moreover, reevaluation of epidemiological studies have led to questions over whether formaldehyde can be considered a carcinogen at all.
The new review was sponsored by aspartame supplier Ajinomoto. However Informa Healthcare took precautions to avoid allegations of underhand influence. It says the panellists were unware who was footing the bill throughout the review process, and up until submission and peer review of the manuscript.
Likewise, the sponsor as not made aware of the panelists' identities.
"There were no known conflicts of interest with the sponsor or potential biases of the authors," said Informa.
Journal: Critical Reviews in Toxicology (Informa Healthcare). Volume 37, Issue 8, pp 629-727
Title: "Aspartame: A safety evaluation based on current use levels, regulations, and toxicological and epidemiological studies".