The statement by the Food and Drug Administration (FDA) earlier this week comes after the EU's food safety regulator discredited scientific studies by the Italy-based European Ramazzini Foundation (ERF) that claimed the artificial sweetener caused cancer.
A regulatory rejection of the study means food and beverage makers will not have to reformulate their products and find a substitute.
The FDA said that on learning of the study results, it requested the study data from Ramazzini so as to evaluate the findings. On February 28, 2006, the agency received a portion of the data requested.
In 2005, ERF published new findings of a long-term feeding study on aspartame conducted on rats. Scientists from ERF concluded from their study that aspartame causes cancer and that current uses and consumption of the sweetener should be re-evaluated.
"We are actively reviewing the data provided by ERF and will complete our review of those data as soon as possible," the FDA stated. "When FDA completes its review of the ERF study data, it will announce its conclusion."
The FDA approved aspartame for use in the US in 1981. Since then the safety of aspartame has been questioned by some scientists, the FDA stated.
"To date, however, the agency has not been presented with scientific information that would support a change in our conclusions about the safety of aspartame," the FDA stated. "Those conclusions are based on a detailed review of a large body of information, including more than 100 toxicological and clinical studies regarding the sweetener's safety."
A recent study in the US sponsored by the National Cancer Institute (NCI) found no statistically significant link between aspartame consumption and leukemias, lymphomas or brain tumors. The study involved 340,045 men and 226,945 women, ages 50 to 69.
The FDA statement follows the release of a review of the study last Friday by the European Food Safety Authority (EFSA), which reviewed the data.
EFSA said its evaluation of the Ramazzini long-term study concluded that "there is no need to further review the safety of aspartame nor to revise the previously established Acceptable Daily Intake (ADI)."
The current ADI for aspartame is 40 mg/kg body weight. Current average intakes of aspartame in Europe, including levels up to 10 mg/kg body weight per day, are well below the ADI, EFSA noted.
The EFSA review was sparked off last year after researchers at Ramazzini's cancer research centre in Italy caused a stir by claiming that their study indicated that aspartame consumption by rats leads to increase in lymphomas and leukaemias in females at dose levels "very near those to which humans can be exposed".
The study led to heightened public concerns over the artificial sweetener. Since the study's publication last year, some suppliers have exited the market and some food and beverage companies have stopped using it for their diet products. About 6,000 different foods and drinks currently contain aspartame.
A more recent study by the foundation, published last month in Environmental Health Perspectives, found a link between life-long aspartame consumption in the rats and cancer of the kidney and peripheral nerves.
The EHP report concluded: "The results of this mega-experiment indicate that APM (aspartame) is a multipotential carcinogenic agent, even at a daily dose of 20 mg/kg body weight, much less than the current acceptable daily intake. On the basis of these results, a reevaluation of the present guidelines on the use and consumption of APM is urgent and cannot be delayed."
Today scientists taking part in the EFSA review of the Ramazzini study found the conclusions full of flaws. Iona Pratt, chair of a group of scientists who reviewed the Ramazzini study for EFSA, said that it did not reveal any evidence that would point to aspartame as a cancer causing agent.
EFSA stands by its previous recommendations that even at high consumption levels aspartame does not lead to an increased incidence of cancers.
In a press conference Pratt said there were other "plausible" explanations for the high incidents of cancers found in the Ramazzini study.
In the main, she said the rats in the study had a high rate of chronic respiratory diseases, which may have "predisposed" them to cancer. More importantly, there was no correlation between the incidence of cancers and the variations in low to high dosage rates of aspartame given to the rats.
One would have expected that in the doses from five to 5,000 mg cancers would have increased with the level of aspartame given to the rats, she said.
"We concluded that the lymphomas and leukaemias were not related to aspartame treatment because the rats had a predisposition due to the high rate of inflamatory diseases," she said.
The panel also concluded that the study did not show that aspartame was a "multipotential carcinogenic agent" as claimed. The cancers found in the control rats, ones not fed aspartame, were "unusually" low. Some of the rats fed aspartame and found to have cancer in the kidneys, bladder and ureter were not relevant to the study as this was linked to a "rat-specific" disease.
Once the statistical analysis was adjusted the EFSA panel found the study did not prove that aspartame was carcinogenic.
There was also no evidence that aspartame was genotoxic, meaning it had the ability to cause changes to DNA.
Since its discovery in 1965 aspartame has be the source of controversy within the scientific community and industry over whether it causes health problems. Some studies have indicated a health risk, some have indicated that it does not cause harm to humans. Industry has consistently denied that the artificial sweetener poses a health risk, claiming that the numerous scientific studies were faulty.
They also point to four previous long term studies sponsored by G.D. Searle, a chemical company that held the patent to aspartame, which were the basis for regulatory acceptance worldwide. Searle was later bought by Monsanto and became NutraSweet Co.. The US Food and Drug Administration approved aspartame for consumption in 1981.
"The overwhelming body of scientific evidence clearly demonstrates that aspartame, even in amounts many times what people typically consume, is safe and not associated with adverse health effects," claims the Aspartame Information Center, an industry funded body.
The organisation cited 200 studies showing the sweetener's safety, including the recent large scale one sponsored by the National Cancer Institute.
However Knowles noted that the Ramazzini study was the first long term independent study relating to cancer. The results of the seven-year study into the long-term effects of eating aspartame in rats were released in July 2005.
Knowles said the study should be a valuable lesson for industry, which can learn from the experience, no matter if it turns out to be painful.
"There should be a quality assurance partnership between researchers and the food additive industry," she said. "There should be independent evaluations using long term studies."
Since the study, Holland Sweetener Co., the largest supplier of aspartame in the European market, said it will stop production of the sweetener by the fourth quarter of 2006.
"The global aspartame markets are facing structural oversupply, which has caused worldwide strong price erosion over the last five years," the Netherlands-based company stated in announcing the decision.
The US patent on aspartame expired in 1992. NutraSweet, Ajinomoto, Merisant and Holland Sweetener were the main players in the market. Holland Sweetener is a joint venture between Royal DSM of the Netherlands and Tosoh Corporation in Japan.
After saccharin, aspartame is the second most used artificial sweetener in the world. In terms of world consumption, the artificial sweetener represents
62 per cent of the value of the intense sweetener market.
Aspartame is found in about 6,000 products worldwide, including carbonated and powdered soft drinks, hot chocolate, chewing gum, candy, desserts,
yogurt, tabletop sweeteners, and some pharmaceutical products, such as vitamins and sugarfree cough drops. The Aspartame Information Center estimates the sweetener is consumed by about 200 million people a year worldwide.
Aspartame was first authorised for use by several EU member states in the 1980s. European legislation harmonising its use in foodstuffs was introduced in 1994 following safety evaluations in 1984, 1987, 1988. A further review of all the original and more recent data on aspartame was carried out in 2002 by the bloc's food regulator.
Both published and unpublished data, including all the information on genotoxicity and carcinogenicity in animals and humans, were considered at that time and the SCF re-confirmed the previously established ADI for aspartame.
Various food associations have dismissed the Ramazzini study, saying it did not follow established scientific procedures.
According to market analysts Freedonia, the sweetener market is set to grow at around 8.3 per cent year on year until 2008: considerably higher than growth in the ingredients industry currently at about three to four per cent.