Aspartame is possibly linked to cancer in humans, says the WHO
A World Health Organization agency declared Thursday that aspartame, an artificial sweetener widely used in diet drinks and low-sugar foods, may possibly cause cancer.
However, another WHO committee stuck to its assessment of a safe level of aspartame consumption. By some calculations using the panel’s standard, a person weighing 150 pounds could avoid a risk of cancer but still drink about a dozen cans of diet soda a day.
The declaration by a WHO agency about a 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 was a possible carcinogen on limited evidence from three observational human studies that the agency said linked consumption of artificially sweetened beverages to an increase in cases of liver cancer — at levels well under a dozen cans a day. It warned that the results could potentially be biased towards the profile of people who drink larger amounts of diet drinks and called for further studies.
Still, people who consume large amounts of aspartame should consider switching to water or other unsweetened beverages, said Dr. Francesco Branca, director of WHO’s Department of Nutrition and Food Safety.
But, he added, “Our results do not indicate that occasional consumption should pose a risk to most people.”
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 drinks. Aspartame, one of six sweeteners approved by US regulators, is found in thousands of products, from packets of Equal to sugar-free gum, diet soda, tea, 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, on Thursday issued an unusual criticism of the global agency’s findings and reiterated its longstanding 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 “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 body was sure to ignite further debate in Europe – where the sweetener is still considered safe – and renew its assessment in the US. And the statements of the global agencies in the duel are likely to cause confusion among consumers.
WHO. has occasionally been out of step with other authorities about potential cancer risks, such as glyphosate, and later led the way in determining that it was dangerous to human health. The international body’s designation of a cancer link to that ingredient in Roundup, a weed killer, became a springboard for lawsuits against the herbicide’s manufacturers.
Around the world, the powerful beverage industry has fought long and hard against any regulatory or scientific findings 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 push back against new studies or potential links to health risks.
“Aspartame is safe,” Kevin Keane, interim president of the American Beverage Association, said in a statement. He cited the WHO announcements dueling, and singled out the other panel, the Joint Expert Committee on Food Additives, which conducted a concurrent review and left the recommended daily intake unchanged. It also considered the evidence for cancer in humans to be “not convincing”, according to a WHO summary.
“After a thorough review, the World Health Organization finds aspartame to be safe and ‘no sufficient reason to change the previously established acceptable daily intake,'” Keane said. “This strong conclusion reinforces the position of the FDA and food safety agencies 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-old scientific controversy over the use of saccharin in the diet drink Tab, has been extensively scrutinized. Once linked to bladder cancer in rats, Congress mandated further study of saccharin. Since then, according to the FDA, 30 studies showed that the rodent results did not apply to humans; US officials removed saccharin from a list of potential carcinogens. Recently, other sweeteners have been investigated for their ties to possible health risks.
At the center of the aspartame controversy are rodent studies from 2005-2010 by Italian researchers that showed a link to cancer. The FDA has rejected the long-debated studies as “compromised”.
Dr William Dahut, chief scientific officer of the American Cancer Society, who led one of the key studies the WHO relied on, said the findings should be considered alongside a WHO report earlier this year that indicated artificial sweeteners did not help achieve weight loss. or protection against other chronic conditions.
He said there was little evidence now to suggest a daily Diet Coke would increase the risk of cancer, adding that “more research is needed.” Overall, he said, the science was more definitive on reducing cancer risk by avoiding tobacco, alcohol, processed meats and excess body weight.
The IARC said it could not 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 no classification. These levels reflect the strength of the science rather than how likely the substance is to cause cancer.
The second WHO group on food additives recommended that daily intake should 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 estimated that a person weighing 132 pounds would need to consume 75 packets of the aspartame sweetener to reach the threshold of exposure for a potential risk.
For its review of aspartame, the IARC convened 25 cancer experts from 12 nations in Lyon, France, to conduct the review of 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.
A 2016 study led by WHO officials looked at nearly 500,000 people in Europe who were followed for about 11 years. The study tracked the participants’ intake of juice and soft drinks and the relationship with liver and biliary tract cancer. It examined those who drank artificially sweetened soda and found that each additional serving of diet soda 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 examined consumption of sweetened beverages as reported by people on questionnaires and cancer registries. Researchers found an elevated 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 drinks 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, has said the WHO’s Food Additives Panel – not the cancer experts – should be the lead authority reviewing aspartame.
In recent weeks, the beverage industry trade group has funded 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 was the former secretary of the Department of Health and Human Services. In an opinion piece in Newsweek earlier this month, the two embraced the FDA’s stance on the safety of aspartame, calling the agency “the world’s gold standard for independent regulatory agencies.”
The trade group had previously contested a new review of aspartame’s potential links to cancer in California. In 2016, a government committee discussed reviewing aspartame, but it went no further.
California officials said this week that the state could review the latest WHO decision.
Besides aspartame, the WHO’s cancer agency has assessed other possible carcinogens to 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 have recently been the subject of billion-dollar settlements for the contamination of drinking water.
By considering aspartame a possible carcinogen, the IARC also delved into one of the central controversies in aspartame research. It concluded that there was some evidence of cancer in laboratory animals based on studies conducted by the Ramazzini Institute in Italy, citing the group’s findings of increased tumors in aspartame studies from the mid-2000s. Based on concerns over the group’s methods and interpretations, the findings were considered limited.
For its part, the Ramazzini Institute said in 2021 that the work on aspartame was validated and that its earlier findings were “fiercely attacked by the chemical manufacturing and processed food industries and by their allies in regulatory agencies.”
Responding to questions about the need for an IARC review during a press conference on Wednesday, WHO’s Dr. Branca said 10 million people die from cancer each year. “So that’s a societal concern that our organization needed to respond to,” he said.
He said the results show a clear need for further high-quality research.
“We’ve kind of raised a flag here, indicating that we need to clarify a lot more about the situation,” Dr. Branca said. “It’s not something we can dismiss at the moment.”
Julie Creswell contributed reporting to this article.
