Buzz
Earlier this year, the World Health Organization made three distinct statements about aspartame. First, they advised against using sweeteners like aspartame for weight loss. Then, they classified aspartame, the sweetener in Diet Coke, as a 'possible' carcinogen. However, the agency’s food safety division has now confirmed that aspartame is indeed safe for use in foods. While these statements might seem contradictory at first glance, they actually reflect different aspects of the research and are not in conflict. Let’s break down what this really means.
To summarize the three key statements in simple terms, here’s what they actually convey, and all are in alignment:
Sugar substitutes, like aspartame, do not actively aid in weight loss, and a truly healthy diet involves cutting back on sweets rather than just replacing one ingredient with another. Simply switching to Diet Coke doesn’t constitute a strategy for improving your overall health.
There may be some connection between very large amounts of aspartame and certain types of cancer, based mostly on animal studies. However, there is no definitive proof of any cancer link in humans, nor is there any evidence linking typical aspartame consumption in food with cancer. Researchers should remain aware of the potential for future discoveries and continue their investigations.
The current levels of aspartame used in food are not likely to pose any significant health risks.
If you’re keeping score, it might seem like aspartame has two votes against it and one in favor. However, life isn’t a game of points, and science isn’t about tallying votes from either side. Both positive and negative aspects can exist simultaneously, and all can be valid.
What evidence exists linking aspartame to cancer?
As we’ve previously discussed, aspartame is classified as a 'possible carcinogen,' meaning there is no definitive proof of it being a carcinogen. Now that the official report is released, we can see how the International Agency for Research on Cancer (IARC), which is part of the WHO, evaluated the evidence for a potential cancer connection with aspartame. The conclusion: the evidence is far from convincing. (Emphasis theirs.)
Limited
evidence exists regarding cancer in humans
, particularly for liver cancer (specifically, hepatocellular carcinoma). Among the human studies available, only three investigated the link between artificial sweeteners and liver cancer. These studies, which involved four large cohorts, were conducted within the European Prospective Investigation of Cancer and Nutrition (EPIC) cohort, a pooled analysis of the National Institutes of Health (NIH)-American Association of Retired Persons (AARP) cohort, the Prostate, Lung, Colorectal, and Ovarian Cancer Screening (PLCO) cohort, and the Cancer Prevention Study (CPS)-II cohort. In these studies, artificially sweetened beverages were used as a proxy for aspartame exposure, supported by data on the country and time period of aspartame use in beverages. All three studies showed a positive link between the consumption of artificially sweetened beverages and liver cancer risk, either overall or in key subgroups of the population. However, the possibility of bias or confounding factors affecting these findings could not be excluded.
There was also
limited
evidence
for cancer in experimental animals. Increased incidences of malignant and benign neoplasms were observed in two species (mice and rats) of both sexes across three studies. However, the study design raised concerns, leading the working group to classify the evidence as limited. In particular, the two prenatal exposure studies did not account for litter effects (such as the number of litters or pups per treatment group), which could lead to false positives if pups from the same litter responded similarly due to genetic factors. Additionally, concerns were raised about the diagnoses of lymphomas (mainly those in the lungs) and unresolved issues with interpreting the histology of hepatocellular proliferations and bronchioloalveolar lesions.
To put it another way, it’s not as straightforward as saying “we gave aspartame to rats and they developed cancer.” In the animal studies, experts are still uncertain whether the lab rats actually developed more cancer when they were given aspartame. In the human studies, there was a slight increase in cancer rates among those who drank large amounts of diet soda compared to those who didn’t, but there are numerous factors (such as overall diet) that could explain this and cannot be ruled out.
If you’re interested in digging deeper, you can read the full report with the findings here. As for how to interpret this information, that responsibility lies with another group within the WHO, the Joint Expert Committee on Food Additives, or JEFCA.
Why did the WHO determine aspartame is safe?
The WHO’s recent announcement addresses aspartame’s “hazard and risk assessments,” which are two distinct evaluations. A health hazard refers to something known to have harmful effects on health. Aspartame was categorized as possibly being a health hazard.
Risk, however, is what truly matters when it comes to real-world implications. What is the risk we face from consuming aspartame? If there is any risk, it is minimal.
The WHO’s announcement states that JEFCA, their food additives committee, “reviewed the evidence on cancer risk from both animal and human studies, and concluded that there is no convincing evidence linking aspartame consumption to cancer in humans.”
The committee also clarified that when aspartame is consumed, it completely breaks down in the digestive system “into metabolites that are identical to those absorbed from common foods, and that no aspartame enters the bloodstream as such.” No matter how many Diet Cokes you drink, aspartame does not appear in your blood.
Based on these findings, the committee chose not to alter their previous guidance regarding aspartame. The established “acceptable daily intake” for aspartame is between 0 and 40 milligrams per kilogram of body weight.
How much aspartame is considered excessive?
According to this guideline, 40 mg/kg is the maximum recommended daily intake. (Just to be clear, consuming 41 mg/kg wouldn’t necessarily cause harm; this is simply the limit chosen for safety.)
A 12-ounce can of Diet Coke contains 184 milligrams of aspartame, according to several studies I found, such as this one. Other estimates for sodas in general place the typical amount between 200 and 300 milligrams.
Next, we should think about this in relation to our own body weight. (It’s common to calculate doses of medications or toxins based on body weight, since a larger person usually needs a higher dose for the same effect.) A kilogram equals 2.2 pounds. So if you weigh 220 pounds, that’s equivalent to 100 kilograms.
Let’s do the math. Personally, I weigh around 70 kilograms. I usually drink Diet Cokes from 16.9-ounce bottles. For me, each bottle provides a dose of 3.7 milligrams per kilogram. This means I could safely drink ten of these bottles a day, every day, and still stay within the WHO's acceptable range. (That’s more than a gallon—over twice the liquid you’d get from eight glasses of water a day. I don’t think anyone my size is at risk of unintentionally drinking ten 16.9-ounce bottles of anything.)
Aspartame isn’t just in Diet Coke, but it’s one of many artificial sweeteners. Many other products like drinks, yogurts, protein bars, and more use different sweeteners like acesulfame potassium (“ace-K”), sucralose, or “natural” non-sugar sweeteners such as stevia or monkfruit. There are also sugar alcohols, like erythritol. Personally, I avoid most of these, but not for health reasons—I simply don’t like the aftertaste. I’d rather go for the full-sugar versions of these products if I’m eating them at all. But we all have our quirks, and I’ll agree with my colleague Claire Lower: it’d be nice if we could just enjoy our damn Diet Cokes in peace.”
