July 13th, 2023, the World Health Organization modified the classification of carcinogenic hazard to humans for the sugar substitute aspartame. This lands the substance into a new cancer risk category, indicating that it may possibly cause cancer in people. With all the news swirling around, let’s move past the headlines and get to the facts of what this means.
First, let’s explore what the new categorization indicates generally.
What are the IARC categories?
The World Health Organization’s (WHO) International Agency for Research on Cancer, or IARC, is an intergovernmental agency forming part of the WHO of the United Nations. Its role is to conduct and coordinate research into the causes of cancer, as well as to gather information worldwide on the occurrence of cancer. This group evaluates and categorizes many substances and evaluates their carcinogenic hazard to humans. It is important to note that the process of determining a substance’s classification does not take into account specific dosage/daily intake, but rather the agency utilizes already available studies to categorize the substance. The process scrutinizes the quality of the studies, their processes, and the strength of evidence. There have been four categories established.
- Group 1: The agent is carcinogenic to humans.
- This category is used when there is sufficient evidence of carcinogenicity in humans. In other words, there is convincing evidence that the agent causes cancer in humans. The evaluation is usually based on the results of epidemiological studies showing development of cancer in exposed humans. Agents can also be classified in Group 1 on the basis of sufficient evidence of carcinogenicity in experimental animals supported by strong evidence in exposed humans that the agent exhibits one or more of the recognized key characteristics of human carcinogens.
- Group 2: This category includes agents with a range of evidence for carcinogenicity in humans and in experimental animals.
- At one extreme of the range are agents with positive but not conclusive evidence in humans. At the other extreme are agents for which evidence in humans is not available but for which there is sufficient evidence of carcinogenicity in experimental animals. There are two subcategories, which indicate different levels of evidence.
- Group 2A: The agent is probably carcinogenic to humans.
- This category is used when there is limited evidence of carcinogenicity in humans and either sufficient evidence of carcinogenicity in experimental animals or strong mechanistic evidence, showing that the agent exhibits key characteristics of human carcinogens. Limited evidence of carcinogenicity means that a positive association has been observed between exposure to the agent and cancer but that other explanations for the observations (technically termed “chance”, “bias”, or “confounding”) could not be ruled out with reasonable confidence. This category may also be used when there is inadequate evidence regarding carcinogenicity in humans but both sufficient evidence of carcinogenicity in experimental animals and strong mechanistic evidence in human cells or tissues.
- Group 2B: The agent is possibly carcinogenic to humans.
- This category is generally used when only one of the following evaluations has been made:
- limited evidence of carcinogenicity in humans
- sufficient evidence of carcinogenicity in experimental animals
- strong mechanistic evidence, showing that the agent exhibits key characteristics of human carcinogens.
- Group 3: The agent is not classifiable as to its carcinogenicity to humans.
- This category is used most commonly when the evidence of carcinogenicity in humans is inadequate, the evidence of carcinogenicity in experimental animals is limited (or inadequate), and the mechanistic evidence is limited (or inadequate). Limited evidence of carcinogenicity in experimental animals means that the available information suggests a carcinogenic effect but is not conclusive.
You can read the WHO’s documentation in its entirety, including how the categories are determined and how their evaluations are carried out, here, along with the preamble to the document, here.
What does this mean when it comes to Aspartame?
The IARC categorized aspartame as part of Group 2B on the basis of “limited evidence for cancer in humans,” specifically for hepatocellular carcinoma, a type of liver cancer, according to a news release. The committee pursued the new evaluated after some recent studies pointed to the potential of an increased risk of liver cancer when study participants consumed aspartame.
A committee of 25 international experts has determined that aspartame may “possibly” cause cancer in people, according to a report released Thursday by the World Health Organization.
This new classification did not result in a change to the recommended daily intake of the artificial sweetener. To put the classification into perspective, there is a wide range of items in the same categorization, meaning the while the IARC believes there is some evidence that it can cause cancer in humans, the evidence is inconclusive. At the time this post was published, 323 other items, including aloe vera, gasoline exhaust, lead, carpentry, pickled vegetables, melamine, and working in the textile industry share the same category.
Sources share that the IARC found “limited” evidence that aspartame may cause liver cancer, based on a review of several studies that used intake of artificially sweetened beverages as a proxy for aspartame exposure. It also reviewed the evidence from a large French study, the NutriNet-Santé study, published in 2022, that found people who consumed the most aspartame had about a 15% increased risk of cancer, including breast and obesity-related cancers, compared with people who didn’t consume aspartame.
The research agency concluded that these were “high-quality” studies, as is a factor in their evaluation, however it could not rule out that the findings weren’t due to chance, bias, or “confounding variables”. This means that other factors could have been the cause behind any recorded cancer cases, including exposure to other carcinogens or lifestyle habits. “Thus, the evidence for cancer in humans was deemed “limited” for liver cancer and “inadequate” for other types of cancers, according to the analysis published in Lancet Oncology.
A second committee, the Joint Expert Committee on Food Additives, or JECFA, also reviewed the evidence and concluded that “the evidence of an association between aspartame consumption and cancer in humans is not convincing,” according to a summary released by the WHO. The group pointed to inconsistent evidence and determined the acceptable daily intake levels should remain in place.
The FDA disagrees with the WHO classification, “FDA scientists reviewed the scientific information included in the [International Agency for Research on Cancer’s] review in 2021 when it was first made available and identified significant shortcomings in the studies,” an FDA spokesperson wrote in an email. “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 ….”
Scientists have called for more long-term research, pointing out that it can take decades for cancer to develop after exposure to carcinogens. “I think there’s actually been very little long-term research, surprisingly,” says Dr. William Dahut, chief scientific officer at the American Cancer Society.
People want a simple yes or no answer on whether aspartame consumption can increase their cancer risk. “We don’t have the evidence yet,” he says. Several sources also highlight that despite the available studies being considered “high quality” in respect to their process, controls, etc., most of the studies in people have not actually tracked the amount of aspartame people consume over time, which could potentially shift results.
How much is too much?
The FDA established an acceptable daily intake (ADI) level, or amount of a substance considered safe to consume each day over the course of a person’s lifetime, for each of the six sweeteners approved as food additives. You can read more about aspartame and other sugar substitutes, here. For aspartame, the ADI is 50 milligrams per kilogram of body weight per day per the FDA’s ruling, and 40 milligrams per the U.N.’s guidance.
To put the intake level into perspective, a person who weighs 60 kilograms (about 130 pounds), could consume up to 2,400 milligrams per day, which is roughly equivalent to 12 cans of Diet Coke. This is much higher than most people consume.
“Our results do not indicate that occasional consumption should pose a risk to most consumers,” said Dr. Francesco Branca, director of the Department of Nutrition and Food Safety at the WHO, during a press conference in Geneva. He said the problem is for “high consumers” of diet soda or other foods that contain aspartame. “We have, in a sense, raised a flag here,” Branca said, and he called for more research.
“Our results do not indicate that occasional consumption should pose a risk to most consumers,” Branca added in a press briefing. “We’re not advising companies to withdraw products nor are we advising consumers to stop consuming altogether. We’re just advising a bit of moderation. . .”
Branca then added that if people consume aspartame as a way to avoid sugar and control weight, “the benefit is not there”. This supports a recent review (2022), which indicates sugar substitutes do not support long-term weight loss. You can read our post on that topic, here.
While there is yet to be a definitive answer as to whether aspartame is a carcinogen, what is clear is that long-term studies that consider intake levels must be done to thoroughly evaluate the risk to humans. Until then, as was our recommendation before, limit sugar and sugar substitutes as both can greatly impact your health- from inflammation, pain, headaches, harming your gut biome, weight gain, and more.
You can listen to a recent NPR segment on this new development below:
-https://www.cancer.gov/types
-https://www.thelancet.com/journals/lanonc/article/PIIS1470-2045(23)00341-8/fulltext
-https://pubmed.ncbi.nlm.nih.gov/35324894/
-https://www.thelancet.com/journals/lanonc/article/PIIS1470-2045(23)00341-8/fulltext
-https://pubmed.ncbi.nlm.nih.gov/35324894/
-https://apps.who.int/food-additives-contaminants-jecfa-database/Home/Chemical/62
-https://www.cancer.org/cancer/risk-prevention/chemicals/aspartame.html
-https://monographs.iarc.who.int/list-of-classifications
-https://apps.who.int/food-additives-contaminants-jecfa-database/Home/Chemical/62
-https://www.who.int/publications/i/item/9789240046429
-https://www.who.int/news/item/15-05-2023-who-advises-not-to-use-non-sugar-sweeteners-for-weight-control-in-newly-released-guideline#:~:text=%C2%A9-,WHO%20advises%20not%20to%20use%20non%2Dsugar%20sweeteners%20for,control%20in%20newly%20released%20guideline&text=The%20World%20Health%20Organization%20(WHO,of%20noncommunicable%20diseases%20(NCDs)
-https://www.cbsnews.com/news/aspartame-who-possibly-carcinogenic-artificial-sweetener/
-https://en.wikipedia.org/wiki/International_Agency_for_Research_on_Cancer