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The WHO has declared aspartame, a food additive used frequently in diet soda and other low-calorie beverages, "possibly" carcinogenic to humans, to its recommendations for maximum daily aspartame consumption.

"It is very important to note that this was a hazard identification and not a risk assessment," Mary Schubauer-Berigan, PhD, acting head of the WHO's International Agency for Research on Cancer (IARC) monographs program, said Wednesday during an online briefing with reporters; she was discussing the conclusions of the agency's 25-member expert panel. "A hazard identification aims to identify the specific properties of the agent and its potential to cause harm -- that is, the potential of an agent to cause cancer. The classification reflects the strength of the scientific evidence as to whether an agent can cause cancer in humans, but it does not reflect the risk of developing cancer at a given exposure level."

"The working group classified aspartame as possibly carcinogenic to humans -- that is, Group 2B -- based on limited evidence for cancer in humans," Schubauer-Berigan continued. "This was specifically for hepatocellular carcinoma."

Joint Expert Committee on Food Additives Weighs In

In addition to the IARC's conclusion, the WHO also announced the results of an analysis by the WHO and Food and Agriculture Organization Joint Expert Committee on Food Additives (JECFA). "The main conclusion of the panel was that there is no convincing evidence from experimental or human data that aspartame has adverse effects after ingestion, within the limits established by previous committee [members]," said Francesco Branca, MD, PhD, director of the WHO's Department of Nutrition and Food Safety.

That limit, he said, is 40 mg/kg of body weight in aspartame per day, or the equivalent of 9 to 14 cans of soda, for an average-sized adult weighing 70 kg (154 lb); the number of cans varies depending on how much aspartame is in a particular beverage. For children, specifically a child who weighs about 20 kg (44 lb), the limit would be 800 mg of aspartame, or two to three cans of soda per day.

In analyzing both in vitro and in vivo genotoxicity studies, "these studies were giving conflicting results," said Branca. "It was not possible to demonstrate any general toxic effects ... It was also not possible to have any consistent or convincing evidence from the animal studies." In the 12 animal studies that JECFA analyzed, "the majority of them were giving negative results, and the panel also felt that the studies that were giving positive results were limited in the design and in the quality of the interpretation of the data."

The epidemiological studies in humans that JECFA analyzed identified some effects related to type 2 diabetes and to cancer, particularly liver cancer, breast cancer, and lymphoma, Branca said. He added, however, that limitations couldn't be ruled out, "particularly the estimate of exposure; the issue of not being able to identify specifically aspartame -- using exposure to all sweeteners as a proxy for aspartame -- and also issues around reverse causality, bias, and confounding."

Water is Still the Best Choice, Experts Say

The U.S. beverage industry, which uses aspartame in diet sodas and other products, framed the WHO statements as a victory. "Aspartame is safe," Kevin Keane, interim president and CEO of the American Beverage Association, said in a statement. "After a rigorous review, the World Health Organization finds aspartame is safe and [there is] 'no sufficient reason to change the previously established acceptable daily intake.' This strong conclusion reinforces the position of the FDA and food safety agencies from more than 90 countries. People all around the world can be confident in consuming food and beverages with aspartame."

"With more than 40 years of science and this definitive conclusion from the WHO, consumers can move forward with confidence that aspartame is a safe choice, especially for people looking to reduce sugar and calories in their diets," Keane said.

But others disagreed, including Thomas Galligan, PhD, principal scientist for food additives and supplements at the Center for Science in the Public Interest (CSPI), in Washington, D.C. "That's pretty much in line with what CSPI has been saying for years," Galligan said of IARC's classification of aspartame as a possible carcinogen. "It really reemphasizes the need for consumers to avoid aspartame."

However, Galligan said in a phone call, "it's very important that consumers don't go back and start drinking sugar-sweetened beverages," because that might contribute to weight gain and development of diseases such as diabetes. "Really your best bet is to avoid aspartame by choosing the best beverage: water, whether that's still, sparkling, or flavored. [Plain] coffee or tea are also good options, but water is the best bet."

George Kyriazis, PhD, who researches artificial sweeteners at the Ohio State University College of Medicine in Columbus, agreed. "If aspartame alone was an independent risk factor for the average prudent consumer, we would already know by now," he wrote in an email to 番茄社区app. "However, not every individual responds the same to any given dietary choice, so if one has other risk factors it would be reasonable to cut down or even eliminate aspartame and other artificial sweeteners from their diet."

How should clinicians advise their patients on this issue? "That depends!" Kyriazis said. "For those who wish to lose weight, aspartame and other artificial sweeteners are a better choice than sugar-containing sodas. However, water is the best alternative because it carries no risk. Individuals who are overweight or have metabolic or other diseases should always consult with their attending physician to tailor the recommendation based on the person's medical history and dietary objectives."

The WHO's announcement is a good opportunity for the FDA to revisit the aspartame issue, said CSPI's Galligan. He noted that the , a federal law passed by Congress in 1958, prohibits the use of cancer-causing additives in foods, and that the FDA has previously said that no amount of cancer risk is acceptable. "We would like to see the FDA protect consumers by banning aspartame," Galligan said. "We strongly hope that the FDA will take notice and re-evaluate, and even though they've said many times that aspartame is safe, we hope they'll take the WHO's evaluation very seriously."

The FDA, however, does not appear to agree. "The FDA disagrees with IARC's conclusion that these studies support classifying aspartame as a possible carcinogen to humans," the agency . "FDA scientists reviewed the scientific information included in IARC's review in 2021 when it was first made available and identified significant shortcomings in the studies on which IARC relied."

"We note that JECFA did not raise safety concerns for aspartame under the current levels of use and did not change the Acceptable Daily Intake (ADI)," the statement said. "Aspartame is one of the most studied food additives in the human food supply. FDA scientists do not have safety concerns when aspartame is used under the approved conditions."

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