Michael Hunter, MD on Medika Life

Sweet or Sinister: Unveiling the Real Story of Aspartame and Cancer

IS ONE OF THE WORLD’S MOST POPULAR SWEETENERS a potential cancer-causing agent? According to a new report from the World Health Organization (WHO), aspartame is a threat. Today, we explore whether aspartame is sweet or sinister, unveiling the real story of its relationship to cancer.

This essay will comprehensively analyze the available scientific evidence surrounding this topic.

By examining both sides of the argument and evaluating relevant studies, we can better understand the relationship between aspartame and cancer.

What is Aspartame

First, a bit about aspartame. The substance is all around us. Aspartame is a low-calorie artificial sweetener commonly used as a sugar substitute in various food and beverage products.

It comprises two amino acids, aspartic acid and phenylalanine, and a methyl ester.

Aspartame. https://en.wikipedia.org/wiki/Aspartame

Since its approval by regulatory agencies, such as the U.S. Food and Drug Administration (FDA), aspartame has undergone rigorous testing to assess its safety for human consumption.

Aspartame Safety Concerns

The safety of the popular artificial sweetener has long been debated.

Some argue that aspartame is carcinogenic; it causes cancer. Others have offered concerns about the following:

  • Behavioral and cognitive issues (including learning problems)
  • Seizures
  • Headaches
  • Irritability
  • Anxiety
  • Depression
  • Insomnia

A 2017 study in Nutritional Neuroscience cautioned that “aspartame consumption needs to be approached with caution due to the possible effects on neurobehavioral health.”

Aspartame and Cancer: Animal Studies

Concerns about the potential cancer-causing effects of aspartame arose shortly after its introduction.

Photo by Aleksandr Gusev on Unsplash

These concerns were fueled by anecdotal reports and animal studies that suggested a possible link between aspartame consumption and cancer development.

However, it is important to note that such studies often involved extremely high doses.

Aspartame and Cancer: Large-Scale Human Studies

Several large-scale human studies have been conducted to address aspartame and cancer concerns.

A comprehensive review published in Critical Reviews in Toxicology analyzed 500 scientific studies and concluded that aspartame is not associated with increased cancer risk.

More evidence that aspartame does not cause cancer comes from a cohort study published in the Journal of the National Cancer Institute involving over 500,000 participants.

The study found no significant association between aspartame consumption and the risk of various cancers.

Finally, the European Food Safety Authority (EFSA) conducted a comprehensive risk assessment and concluded that no consistent evidence supports an association between aspartame and cancer.

Aspartame and Cancer: New Study Raises Questions

In July 2023, the International Agency for Research on Cancer (IARC) — a branch of the World Health Organization — announced it had designated aspartame as “possibly carcinogenic [cancer-causing] to humans.”

As a cancer doctor, I received numerous inquiries about the new report. Fortunately, there is little about which to be concerned.

Here’s some context: In reviewing chemicals and other exposures suspected of having cancer-causing effects, the IARC evaluates the strength of scientific evidence and then classifies the agent in question as:

  • Carcinogenic to humans
  • Probably carcinogenic to humans
  • Possibly carcinogenic to humans
  • Not classifiable as to its carcinogenicity.

The World Health Organization placed aspartame in the second-to-lowest level of “possibly carcinogenic.” WHO admits that there is only limited evidence but suggests additional research.

Photo by Mikael Stenberg on Unsplash


Much of the concern regarding the aspartame: cancer connection is based on studies in rodents.

These investigations involved aspartame doses exceeding the U.S. Food and Drug Administration’s acceptable daily limit for humans of 50 milligrams per kilogram body weight.

To get the amount causing cancer in rodents, someone weighing 175 pounds must consume twenty 12-ounce cans of diet soda daily.

Furthermore, the classification of “possibly carcinogenic” does not account for the doses at which the cancer would occur or the risk level.

If aspartame causes cancer in one in 10 (or 100) million people, it could fall into this category.

Aspartame is Unlikely to Be Cancer-Causing

Dr. Peter Attia points out that there is no category for “unlikely to be carcinogenic.”

Dr. Attia continues, noting that the IARC evidence comes from that “seemingly inexhaustible fountain of bad science known as nutritional epidemiology.”

Fortunately, most evidence points to no association between aspartame and cancer.

Non-Cancer Aspartame Issues

I prefer to avoid artificial sweeteners, so I am not cheerleading for their use. I suspect the new headlines screaming “Aspartame Linked to Cancer” are sounding a false alarm. While artificial sweeteners may be linked to cancer, we have no high-level evidence to sound the alarm.

I worry more about the effects of artificial sweeteners such as aspartame on our metabolic health.

Photo by Jennifer Burk on Unsplash

In May 2023, the World Health Organization advised people not to consume non-sugar sweeteners (including aspartame) for weight loss.

The organization based its recommendation on a systematic review of the most current scientific evidence, which suggests that consumption of non-sugar sweeteners is associated with increased risks of the following:

  1. Type 2 diabetes
  2. Cardiovascular diseases
  3. Increased body weight
  4. All-cause mortality.

Phenylketonuria and Aspartame

Still, individuals with phenylketonuria, a rare genetic disorder, should avoid aspartame due to the presence of phenylalanine.

The U.S. Department of Health and Human Services observes that certain people with the genetic disease phenylketonuria (PKU), those with advanced liver disease, and pregnant women with hyperphenylalaninemia (high levels of phenylalanine in the blood) have a problem with aspartame.

They do not effectively break down the amino acid phenylalanine, one of aspartame’s components. High levels of this amino acid in body fluids can cause brain damage.

Overall, aspartame remains an approved and safe artificial sweetener for most people.

Aspartame Marketing Machine

From the start, G.D. Searle (later Monsanto and the NutraSweet Company) deployed aggressive public relations tactics to market aspartame as a safe product.

In October 1987, Gregory Gordon reported in UPI:

“The NutraSweet Co. also has paid up to $3 million a year for a 100-person public relations effort by the Chicago offices of Burson Marsteller. Burson Marsteller has hired numerous scientists and physicians, often at $1,000 a day, to defend the sweetener in media interviews and other public forums.”

The folks at the U.S. Right to Know organization add this disturbing coda:

Moreover, beverage companies such as Coca-Cola allegedly pay third-party messengers, including scientists and doctors, to promote their products and shift the blame when science ties them to serious health problems.


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Michael Hunter, MD
Michael Hunter, MD
I received an undergraduate degree from Harvard, a medical degree from Yale, and trained in radiation oncology at the University of Pennsylvania. I practice radiation oncology in the Seattle area.

Michael Hunter, MD

I received an undergraduate degree from Harvard, a medical degree from Yale, and trained in radiation oncology at the University of Pennsylvania. I practice radiation oncology in the Seattle area.

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