A World Health Organization agency said Thursday that aspartame, an artificial sweetener widely used in diet drinks and low-sugar foods, may cause cancer.
A second WHO committee, however, firmly held to its assessment of a safe level of aspartame consumption. According to some calculations using the panel’s standard, a person weighing 150 pounds could avoid cancer risk but still drink about a dozen cans of diet soda a day.
The WHO body’s statement on cancer risk associated with aspartame reflects the first time the prominent international body has publicly weighed in on the effects of the near-ubiquitous artificial sweetener. Aspartame has been a controversial ingredient for decades.
The International Agency for Research on Cancer, or IARC, said it based its conclusion that aspartame is a possible carcinogen on limited evidence from three observational studies in humans, which the agency said linked consumption of artificially sweetened beverages to an increase in cases of liver cancer – at levels well below a dozen cans a day. It warned that the results could potentially be skewed towards the profile of people who drink higher amounts of diet drinks and called for further study.
However, people who consume high amounts of aspartame should consider switching to water or other unsweetened beverages, said Dr. Francesco Branca, director of the WHO’s Department of Nutrition and Food Safety.
But, he added: “Our results do not indicate that occasional consumption should pose a risk for the majority.”
Concerns about rising global rates of obesity and diabetes as well as changing consumer preferences have resulted in an explosion of sugar-free and low-sugar foods and beverages. Aspartame, one of six sweeteners approved by US regulators, is found in thousands of products, from packs of Equal to sugar-free gum, diet sodas, teas, energy drinks and even yogurts. It is also used to sweeten various pharmaceutical products.
The US Food and Drug Administration, which approved aspartame decades ago, on Thursday issued an unusual critique of the global agency’s findings and reiterated 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 classifying aspartame as a possible human carcinogen.”
The FDA also said that “aspartame being labeled by the WHO as ‘possibly carcinogenic to humans’ does not mean that aspartame is actually linked to cancer.” The FDA declined to make any of its experts available for interviews to discuss the agency’s specific concerns.
But its salvo against the international organization is sure to ignite further debate in Europe – where the sweetener is still considered safe – and renew a review in the US. And the dueling statements from global agencies are likely to fuel confusion among consumers.
World Health Organization. was sometimes out of step with other authorities on potential cancer risks, such as glyphosate, and later led the way in establishing that it was dangerous for man health The name of the international body of cancer link to that ingredient in Roundup, a weed killer, became the stepping stone for lawsuits against the producers of the herbicide.
Around the world, the powerful beverage industry has fought long and hard against any regulatory or scientific finding that linked artificial sweeteners to risks of cancer or other health problems. Aspartame is just the latest battleground for multinational companies to push back against new studies or possible links to health risks.
“Aspartame is safe,” Kevin Keane, interim president of the American Beverage Association, said in a statement. He cited the WHO’s dual announcements, bringing out the second panel, the Joint Expert Committee on Food Additives, which conducted a concurrent review and left its recommended daily intake amount unchanged. It also deemed the evidence for cancer in humans “not convincing”, a WHO summary shows.
“After a rigorous review, the World Health Organization finds that aspartame is safe and ‘not sufficient reason to change the previously established acceptable daily intake,'” Mr Keane said. “This strong conclusion strengthens the position of the FDA and food safety agencies of 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 year-long scientific controversy over the use of saccharin in the diet drink Tab, has come under heavy scrutiny. Once linked to bladder cancer in rats, Congress called for further study of saccharin. Since then, according to the FDA, 30 studies have shown that the rodent results do not apply to humans; US officials deleted saccharin from a list of possible carcinogens. More recently, other sweeteners have come under scrutiny for their links to potential health risks.
At the center of the aspartame controversy are rodent studies from 2005-2010 by Italian-based researchers that showed a link to cancer. The FDA dismissed the long-discussed studies as “compromised.”
Dr. William Dahut, chief scientific officer of the American Cancer Society, who led one of the key studies relied on by the WHO, said the findings should be considered alongside the WHO report earlier this year, which indicated that artificial sweeteners did not offer help in achieving weight loss. or protection from other chronic conditions.
He said there is little evidence now to suggest that a daily Diet Coke would raise the risk of cancer, adding that “more research is needed.” Overall, he said, the science was more definitive about reducing cancer risk by avoiding tobacco, alcohol, processed meat and excess body weight.
The IARC said it cannot rule out the possibility that the studies linking aspartame to liver cancer were the result of chance or other factors associated with drinking diet soda.
The WHO cancer agency has four categories: carcinogenic, probably carcinogenic, possibly carcinogenic and unclassified. Those levels reflect the strength of the science rather than how likely the substance is to cause cancer.
The WHO’s other group on food additives recommended that daily consumption be below 40 milligrams of aspartame per kilogram of a person’s weight – slightly lower than the proposed US level of 50 milligrams.
The FDA said it estimates that a person weighing 132 pounds would need to consume 75 packets of the aspartame sweetener for. reach the threshold of exposure to potential risk.
For its review of aspartame, the IARC brought together 25 cancer experts of 12 nations in Lyon, France, to review existing studies. It concluded that there was limited evidence for cancer in humans based on three studies linking artificially sweetened beverages to increases in hepatocellular carcinoma, the most common type of liver cancer.
One to study in 2016 was led by WHO officials who looked at nearly 500,000 people in Europe who were followed for about 11 years. The study tracked the participants’ juice and soft drink intake and the relationship to liver and bile ducts. It examined those who drank artificially sweetened soft drinks and found that each additional serving of a diet soft drink per week was associated with a 6 percent increased risk of liver cancer.
A American study published last year by researchers from Harvard, Boston University and the National Cancer Institute examined sweetened consumption reported by people in questionnaires and cancer registries. Researchers found a high risk of liver cancer in people with diabetes who said they consumed two or more artificially sweetened sodas a day. That 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, examined the use of beverages sweetened with sugar and artificial sweeteners and cancer death data. It found a 44 percent increase in liver cancer among men who never smoked and drank two or more artificially sweetened beverages a day. Even adjusting for high body mass — itself a cancer risk factor — the men had a 22 percent increase in risk, data in a supplement to the study show.
The American Beverage Association, which represents Coca-Cola and PepsiCo, said the WHO’s food additives panel – not the cancer experts – should be the primary authority on aspartame evaluation.
In recent weeks, the beverage industry trade group has funded a a new coalition led by Alex Azar, an appointee of former President Donald J. Trump, and Donna Shalala, an appointee 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 accepted the FDA’s position on the safety of aspartame, and called the agency “the world’s gold standard for independent regulatory bodies.”
The trade group previously opposed another review of aspartame’s possible links to cancer in California. In 2016, a state committee discussed reviewing aspartame, but it didn’t go any further.
California officials said this week that the state could review the latest WHO decision.
In addition to aspartame, the cancer agency of the WHO considered that other possible carcinogens range from the seemingly benign, such as Ginkgo biloba extract and aloe vera leaf extract, to the more worrisome, such as gasoline exhaust and perfluorooctanoic acid, the most common of the industrial chemicals known as. per- and polyfluoroalkyl substances, or PFAS, which has recently been subject to billion-dollar settlements over drinking water contamination.
In considering aspartame as a potential carcinogen, the IARC also dipped into one of the central controversies of aspartame research. It concluded that there was some evidence for cancer in laboratory animals based on studies conducted by the Ramazzini Institute in Italy, citing the group’s discovery of increased tumors in aspartame studies from the mid-2000s. Based on concerns about the group’s methods and interpretations, however, the results were deemed limited.
For its part, the Ramazzini Institute said in 2021 that its work on aspartame was confirmed and that its earlier findings were “savagely attacked by the chemical production and processed food industries and by their allies in regulatory agencies.”
Dr. Branca of the WHO responded to questions about the need for an IARC review during a press conference on Wednesday, saying that 10 million people die from cancer every year. “So there is a social concern that our organization had to respond to,” he said.
He said the results showed a clear need for further high-quality research.
“We kind of raised a flag here, indicating that we need to explain a lot more in the situation,” Dr. Branca said. “It’s not something we can dismiss at this point.”
Julie Creswell contributed reporting to this article.