A World Health Organization agency said Thursday that aspartame, an artificial sweetener commonly used in diet drinks and low-sugar foods, could potentially cause cancer.
However, a second WHO committee maintained its assessment of safe aspartame consumption. According to some calculations using the panel’s standard, a person weighing 150 pounds could avoid the risk of cancer and still drink about a dozen cans of diet soda a day.
A WHO agency’s statement on a cancer risk associated with aspartame is the first time the leading international organization has publicly commented on the effects of the nearly ubiquitous artificial sweetener. Aspartame has been a controversial ingredient for decades.
The International Agency for Research on Cancer (IARC) said it based its conclusion that aspartame is a possible carcinogen on limited evidence from three observational studies in people that the agency said linked consumption of artificially sweetened beverages to an increase in cases of liver cancer in compounded – in amounts well under a dozen doses a day. It warned that the results could potentially be skewed towards the profile of people who drink larger amounts of diet drinks and called for further research.
Still, people who consume large amounts of aspartame should consider switching to water or other unsweetened beverages, said Dr. Francesco Branca, Director of the WHO Division for Nutrition and Food Safety.
However, he added: “Our results do not suggest that casual use should pose a risk for most.”
Concerns about rising obesity and diabetes rates worldwide and changing consumer preferences have led to an explosion in sugar-free and low-sugar foods and beverages. Aspartame, one of six sweeteners approved by US regulators, is found in thousands of products from Equal packets to sugar-free chewing gum, diet sodas, teas, energy drinks and even yogurt. It is also used to sweeten various pharmaceutical products.
The US Food and Drug Administration, which approved aspartame decades ago, offered an unusual criticism of the global agency’s findings on Thursday, reiterating its long-standing position that the sweetener is safe. In a statement, the FDA said it “disagrees with IARC’s conclusion that these studies support the classification of aspartame as a possible human carcinogen.”
The FDA also said that “The WHO’s classification of aspartame as ‘possibly carcinogenic to humans’ does not mean that aspartame is actually associated with cancer.” The FDA declined to provide one of its experts for interview to discuss the agency’s specific concerns.
But his salvo against the international body would certainly spark more debate in Europe – where the sweetener is still considered safe – and renewed scrutiny in the United States. And the statements from the dueling global agencies are likely to cause confusion among consumers.
The WHO. has at times been at odds with other authorities regarding potential cancer risks like glyphosate, later leading to the finding that glyphosate is dangerous to human health. The international organization’s finding of a carcinogenic compound of this ingredient in Roundup, a herbicide, became the starting point for lawsuits against the herbicide’s manufacturers.
Around the world, the powerful beverage industry has fought long and hard against any regulatory or scientific evidence linking the use of artificial sweeteners to the risk of cancer or other health problems. Aspartame is just the latest battleground for multinational companies to fend off new studies or possible links to health risks.
“Aspartame is safe,” Kevin Keane, interim president of the American Beverage Association, said in a statement. Citing the contradicting announcements made by the WHO, he highlighted the second body, the Joint Expert Committee on Food Additives, which conducted a simultaneous review and left the recommended daily intake unchanged. According to a WHO summary, the evidence for human cancer is also “not convincing”.
“After rigorous review, the World Health Organization has concluded that aspartame is safe and there is insufficient reason to change the previously established acceptable daily intake,” Mr Keane said. “This compelling conclusion strengthens the position of the FDA and food safety authorities from more than 90 countries.”
Coca-Cola referred questions to the American Beverage Association and PepsiCo did not respond to requests for comment.
The safety of sugar substitutes, including the decades-long scientific controversy over the use of saccharin in the diet drink Tab, has been studied extensively. After being linked to bladder cancer in rats, Congress ordered another study of saccharin. Since then, according to the FDA, 30 studies have shown that the results in rodents did not translate to humans; US officials have removed saccharin from the list of potential carcinogens. More recently, other sweeteners have also been studied for their potential health risks.
At the heart of the aspartame controversy are rodent studies from 2005-2010 by Italian researchers that showed a link to cancer. The FDA has dismissed the long-discussed trials as “compromised.”
dr William Dahut, scientific director of the American Cancer Society, which led one of the key studies relied on by the WHO, said the findings should be considered along with the WHO’s report earlier this year, which indicated that artificial sweeteners do not aid in weight loss or protection from other chronic diseases.
He said there was currently little evidence that a daily Diet Coke would increase the risk of cancer, adding that “more research is needed”. Overall, the science is clearer on reducing the risk of cancer by avoiding tobacco, alcohol, processed meat and obesity.
IARC said it couldn’t rule out the possibility that the studies linking aspartame to liver cancer were due to chance or other factors associated with drinking diet soda.
The WHO Cancer Agency has four categories: carcinogenic, probably carcinogenic, possibly carcinogenic and no classification. These values reflect the strength of the science rather than the likelihood that the substance causes cancer.
The other WHO group on food additives recommended that daily consumption should be less than 40 milligrams of aspartame per kilogram of body weight – slightly below the US recommended level of 50 milligrams.
The FDA said it estimates that a person weighing 132 pounds would need to consume 75 packets of aspartame sweetener to meet the potential risk exposure threshold.
For the review of aspartame, IARC convened 25 cancer experts from 12 nations to Lyon, France, to conduct reviews of existing studies. They concluded that there was limited evidence of human cancer based on three studies linking artificially sweetened beverages to an increase in hepatocellular carcinoma, the most common type of liver cancer.
A 2016 study was led by WHO officials who looked at nearly 500,000 people in Europe who were followed for about 11 years. The study looked at participants’ juice and soft drink consumption and its association with liver and bile duct cancer. It looked at those who drank artificially sweetened soft drinks and found that each additional serving of diet soft drink per week was associated with a 6 percent increased risk of liver cancer.
A US study published last year by researchers from Harvard, Boston University and the National Cancer Institute looked at the consumption of sweetened beverages reported by people in questionnaires and cancer registries. Researchers found an increased risk of liver cancer in diabetics who reported consuming two or more artificially sweetened sodas per day. This study found no increase in liver cancer among diet soda drinkers who did not have diabetes.
A third study, led by the American Cancer Society, looked at the use of beverages sweetened with sugar and artificial sweeteners and data on cancer deaths. It found a 44 percent increase in liver cancer in men who never smoked and drank two or more artificially sweetened beverages a day. Even accounting for high body mass — itself a cancer risk factor — the men had a 22 percent increased risk, data in an addendum to the study shows.
The American Beverage Association, which represents Coca-Cola and PepsiCo, has been vocal in arguing that the WHO’s Food Additives Panel – and not the cancer experts – should be the lead authority in evaluating aspartame.
In recent weeks, the beverage industry trade group has funded a new coalition led by Alex Azar, a representative of former President Donald J. Trump, and Donna Shalala, a representative of former President Bill Clinton. Both Mr. Azar and Ms. Shalala were former secretaries of the Department of Health and Human Services. In an opinion piece in Newsweek earlier this month, the two applauded the FDA’s position on the safety of aspartame, calling the agency “the world’s gold standard for independent regulators.”
The trade group had previously challenged another review of aspartame’s possible links to cancer in California. In 2016, a state committee discussed reviewing aspartame, but went no further.
California officials said this week that the state could review the WHO’s recent decision.
In addition to aspartame, the WHO Cancer Agency has classified other possible carcinogens, ranging from seemingly harmless substances such as ginkgo biloba extract and aloe vera leaf extract to more worrisome substances such as gasoline exhaust fumes and perfluorooctanoic acid, the most commonly mentioned industrial chemicals, per- and polyfluoroalkyl -substances (PFAS) that have recently been the subject of billions of dollars in settlements for drinking water pollution.
With the classification of aspartame as a possible carcinogen, the IARC also took up one of the central controversies in aspartame research. It concluded that there was evidence of cancer in laboratory animals, based on studies by the Ramazzini Institute in Italy, citing the group’s finding that aspartame studies from the mid-2000s showed an increase in tumors. However, due to concerns about the group’s methods and interpretations, the results were deemed limited.
The Ramazzini Institute, in turn, said in 2021 that its work on aspartame was validated and that its previous findings “have been brutally attacked by the chemical industry and the food industry and their allies in the regulatory body.”
dr Responding to questions about the need for an IARC review during a press conference on Wednesday, the WHO’s Branca said 10 million people die from cancer every year. “So there is a societal concern that our organization had to respond to,” he said.
He said the results showed a clear need for more high-quality research.
“In a way, we have set a signal here that indicates that we still have much further to clarify the situation,” said Dr. branca “We cannot dismiss that at this point.”
Julie Creswell contributed to this article.