Your Diet Coke is safe. Sort of.
After an extensive review of the data, the World Health Organization has concluded the sweetener aspartame can potentially cause liver cancer and maybe other health problems, but likely only when consumed in extremely high amounts.
The WHO left in place its previous recommendation that people drink no more than the equivalent of about nine to 14 cans of aspartame-sweetened soda a day or about 74 packets of sweeteners with aspartame, such as NutraSweet and Equal.
In a pair of reports released late Thursday, the WHO found that the occasional aspartame-sweetened drink, yogurt or stick of sugar-free gum is safe.
“Our results do not indicate that occasional consumption should pose a risk to most consumers,” said Francesco Branca, director of the department of nutrition and food safety at the WHO, in a Wednesday news conference.
But he recommended heavy users of aspartame cut down and that everyone drink water over soda and choose naturally sweet foods, like fruit, over items with added sugar or sugar substitutes when they want something sweet.
Earlier this year, the WHO concluded that calorie-free sweeteners in general do not help with weight loss and may increase the risk of type 2 diabetes and cardiovascular disease.
For aspartame, the organization recommends people consume no more than 40 milligrams per kilogram of body weight a day, or 2,800 milligrams a day for someone who weighs about 150 pounds. A typical can of soda has between 200 and 300 milligrams, Branca said, so the highest recommended amount would be nine to 14 cans per day.
(The Food and Drug Administration has set its recommended upper limit at 50 milligrams per kilogram per day, which works out to about 12 to 18 cans per day for the same 150-pound person. The average American drinks no more than about two cans a day, surveys have found.)
For people who now consume high levels of aspartame, Branca said, “the risk may be there if you’re approaching the limit, so why take the risk?”
Impact on products
Companies that make aspartame-sweetened products hailed the WHO’s decision not to change its recommendation.
“There is a broad consensus in the scientific and regulatory community that aspartame is safe. It’s a conclusion reached time and time again by food safety agencies around the world,” Kevin Keane, interim president and CEO of the American Beverage Association, a trade group, said in a prepared statement.
“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.
In a separate statement, Robert Rankin, president of the Calorie Control Council, which represents the low-calorie food and beverage industry, noted consuming above the daily limit “is not realistic, recommended, nor is it aligned with the intended use of these ingredients.”
But aspartame may still not be safe ‒ either in the literal sense or from consumer pressure.
Two independent WHO panels concluded there was no scientific proof the additive causes human disease when consumed at low or modest levels. But they also found that conclusive evidence is lacking.
Even with the current recommendations left in place, some will react to the negative attention created by the WHO review.
“This isn’t enough to exonerate (aspartame),” said Marion Nestle, an expert in molecular biology, nutrition and food science and emerita professor at New York University.
Recent concerns about the sweetener will probably drive some consumers to demand its removal, said Nestle, adding she’s already seen products proclaiming they are “aspartame-free.”
Branca suggested companies move away from all calorie-free additives.
“It’s about changing the formulation of products and changing the choice of ingredients, so you can still have tasty products without the need to use sweeteners,” he said.
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Lingering health concerns
So, if repeated studies and expert panels have determined it’s OK to use aspartame except in super-high quantities, why is aspartame safety still under discussion?
Despite the industry’s assertions, scientific evidence has not yet proven aspartame completely safe. All science can say is there isn’t clear evidence yet that it’s dangerous, which is an important distinction.
The WHO published two reports late Thursday, one from the International Agency for Research on Cancer and another from the Joint Expert Committee on Food Additives.
The IARC convened an independent body of experts to determine whether aspartame, consumed in any quantity, might cause cancer. And it did find limited evidence in both humans and animals, as well as a possible mechanism that might explain why high quantities of the chemical could lead to liver cancer in people.
People who began consuming aspartame in the 1980s when it first came on the market are just reaching the age when cancers are more common, so future studies may raise new concerns, said Mary Schubauer-Berigan, speaking Wednesday on behalf of the agency.
The JECFA’s own independent expert committee, all of whose members were also cleared of conflicts of interest, found the available evidence inconclusive. It suggested that people need to consume more than the already recommended amounts of aspartame to substantially increase their risk for liver cancer. So they left the current recommendation in place.
“We need better research,” Branca said.
Some studies have shown no increased risk of cancers, while other research has linked the use of aspartame to a slight increased risk of breast and colon cancer in addition to liver cancer, said Dr. Neil Iyengar, a medical oncologist who researches nutrition and exercise at Memorial Sloan Kettering Cancer Center in New York City.
Iyengar, who was not involved in the WHO studies, said he’s worried data shows that artificial sweeteners, including aspartame, disrupt the gut microbiome ‒ the bacteria, viruses, fungi and others that inhabit a healthy digestive system. Disrupting these microbes “can lower our defenses against cancer,” Iyengar said. “To me, as an oncologist, that’s concerning.”
If his patient’s No. 1 priority is avoiding cancer, then he’d tell them to avoid artificial sweeteners, including aspartame, he said. If, on the other hand, a patient was struggling with obesity, which increases the risk for 13 types of cancer, he might suggest they use artificial sweeteners in the short-term to help transition to a lower-calorie, lower glycemic index diet.
Iyengar also suggests people read labels to look for sweeteners. Although each sweetener is limited, many products include multiple sweeteners and one recent study suggests that combinations of sweeteners can increase cancer more than a single one alone.
Unrefined sugars, like those from monk fruit or dates, are generally considered healthier and have less impact on the gut microbiome, he noted, though he still recommends people keep under the FDA-recommended limit of 25 grams per day of added sugar.
“If there’s more effort into providing that kind of taste that people like but using ingredients that are less processed, that are potentially less harmful, then I think that will have a major public health benefit,” Iyengar said.
Bottom line for consumers
The mixed messages from industry and researchers is certain to create public confusion, said Nestle and George Kyriazis, who researches artificial sweeteners at the Ohio State University College of Medicine.
“Don’t panic, but also don’t ignore this,” Kyriazis advised.
An otherwise healthy person who puts one or two packages of Equal in their coffee or drinks a diet soda with a meal shouldn’t be alarmed by the data, he said. Someone with a lot of risk factors such as diabetes, a history of cancer and obesity who also drinks three to five aspartame-sweetened sodas a day, “probably that’s an individual who wants to consider cutting down,” Kyriazis said.
The reports should encourage everyone to examine their use of artificial sweeteners, including aspartame, he said. If someone is consuming a lot of sweeteners, “make an effort to cut it down. There’s no harm in that,” he said.
But there’s also no need to go overboard and cut sweeteners out entirely. That might lead to worse choices, like someone with diabetes increasing their sugar intake. “Let’s not go to the extreme,” he said.
Contact Karen Weintraub at kweintraub@usatoday.com.
Health and patient safety coverage at USA TODAY is made possible in part by a grant from the Masimo Foundation for Ethics, Innovation and Competition in Healthcare. The Masimo Foundation does not provide editorial input.
