Aspartame does not cause cancer

The non-nutritive sweetener is rapidly broken into amino acid byproducts

Aspartame does not pose a health risk to humans, cancer or otherwise, especially at levels we would consume.

Unfortunately, misinterpretation of information, clickbait headlines, and bad actors have continued to spread fear and exploit the risk perception gap and lack of basic chemistry knowledge.

Aspartame is a chemical made of the two natural amino acids: L-aspartic acid and L-phenylalanine with a methyl ester at the end.

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Aspartame is a non-nutritive sweetener, which means that it provides no functional calories when we consume it.

This is unlike nutritive sweeteners such as sucrose (table sugar), honey, maple syrup, etc., but it is not because we don’t extract calories from it, but because we only ever use tiny amounts of it.

Chemically, aspartame does contain the same 4 Calories per gram as carbohydrates (nutritive sweeteners), but we never consume more than negligible amounts of aspartame. Aspartame is roughly 200 times sweeter to us than sucrose (table sugar). As a result, we only need very small amounts are needed to achieve desired sweetness. This means that the amount of aspartame used in foods and drinks is so minimal that it contributes virtually no significant caloric value to the diet.

For context, one teaspoon of table sugar is about 16 calories of sugar (4 grams). For similar sweetness, you would use 0.02 grams (20 milligrams) of aspartame. At 4 Calories per gram, that means you’d be consuming 0.08 Calories of aspartame.

You might be asking, well what about those packets of Equal? Those are definitely bigger than 0.02 grams. That’s because this amount of aspartame is so tiny, it is mixed with fillers in order to ensure filling and dispensing is accurate. Typically, fillers are often other carbohydrates, but, in combination, still add far fewer calories than nutritive sweeteners.

A packet of Equal has the same sweetness as 2 teaspoons of table sugar (sucrose), contains 35 milligrams of aspartame, and has 4 calories compared to 32 calories of the same volume of sugar. For this brand, they use dextrose and maltodextrin to add bulk.

Similarly, if you’re drinking a diet soda, you are only consuming milligrams of aspartame, which equates to a fraction of a calorie.

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Aspartame is rapidly metabolized into amino acids as byproducts.

When we consume aspartame, it is rapidly broken down into those amino acids: L-aspartic acid and L-phenylalanine, plus methanol - all of which are utilized by our bodies for various cellular processes. Remember: amino acids are the building blocks of proteins, and they are essential for life.

There is no biological plausibility or human evidence that consuming aspartame would cause harm to human health. Many people have demonized aspartame along with other non-nutritive sweeteners as they are “artificial”, but this is not based on science and is based solely on the appeal to nature fallacy.

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Misinformation about aspartame has circulated for decades.

Last July, the WHO’s International Agency for Cancer Research (IARC) classified aspartame in category 2B “possibly carcinogenic”, which triggered a flood of clickbait media headlines.

But remember, the IARC and their carcinogenicity assessments are based on hazard assessments. IARC is a working group that assesses ‘hazards’ for carcinogenicity of an array of exposures. This means they make statements about theoretical potentials, without considering dosage, exposure, or even the likelihood of the potential exposure.

IARC classification 2B of “possibly carcinogenic” to humans means there is NO robust evidence that the substance is linked to cancer. This is the category IARC put aspartame in, the same one as aloe vera & pickled vegetables.

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Does this mean aspartame causes cancer in humans? Absolutely not.

In fact, there is no evidence that aspartame poses a human health risk, cancer or otherwise. The classification of “possibly carcinogenic” is the lowest of the risk tiers, and the rating of aspartame is based on limited evidence from animal studies that suggested an increased risk of cancer in some organs, but no evidence from human data.

The IARC noted that levels of aspartame used in animal studies were much higher than the levels that people consume. Remember, just because something may cause harm in animals does not mean it translates to humans. Further, the levels of aspartame these animals were fed is exponentially higher than the amount of aspartame humans would ever realistically consume. Even the IARC stated that the classification ‘possibly carcinogenic’ does not mean that aspartame is actually linked to cancer. It is not.

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Headlines spreading fear about aspartame completely ignored conclusions from more relevant expert agencies that do perform risk assessments.

Numerous scientific agencies have concluded that aspartame is safe for human consumption at levels we would be exposed to. The FDA-acceptable daily intake (ADI) for aspartame is 50 milligrams per kilogram of body weight. ADI levels are conservative, and this threshold is far lower than what could pose a health risk.

Last July, that same week the IARC released their monograph, the Joint FAO/WHO Expert Committee of Food Additives (JECFA), released their newest risk assessment on aspartame. The JECFA is a scientific expert committee managed jointly by the FAO (Food and Agriculture Organization) of the UN, and the WHO. This organization actually assesses food safety, particularly of food additives.

JECFA reaffirmed on July 13, 2023 that aspartame is safe for human consumption. They also reaffirmed the previously set levels for acceptable daily intake (ADI) of 40 mg/kg, which aligns with the FDA’s ADI of 50 mg/kg.

These levels means the average adult would have to consume over 90 packets of aspartame (which contain 35 mg of aspartame), or drink 16-50 cans of soda PER DAY to even reach the ADI, which is a conservative level.

This conclusion is aligned with other experts, including European Food Safety Authority (EFSA) and leading cancer research organizations such as the National Cancer Institute, the American Cancer Society, and Cancer Research UK.

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So, should you worry about aspartame? No.

Decades of research has evaluated potential links between aspartame consumption and cancers. While some animal studies claimed links between aspartame and cancer, findings were found to be flawed, dosages were not realistic, and none of these findings have been mirrored in humans.

For an individual, something being listed as “possibly carcinogenic” by the IARC should not impact day-to-day choices (in this case, whether or not to consume aspartame). That is especially true when you contrast IARC conclusions with other global regulatory agencies that do assess likelihood of harm based on dosage.

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If you like your Diet Coke, continue to drink it without fear or anxiety.

If it wasn’t clear: there is no evidence that aspartame causes cancer or is even remotely linked to cancer in humans.

The IARC classification has been taken out of context and is being used to sow doubt among people who consume aspartame – many of whom use it as a sugar substitute to reduce calorie consumption, control blood sugar levels, or reduce risk of tooth decay.

Unfortunately, ineffective communication, misinterpretation of information, and lack of understanding of the roles different organizations play is already leading to the spread of misinformation, clickbait headlines, and fearmongering. All of this will ultimately undermine public health and science literacy. Please don’t fall prey and instead, look to the actual data and conclusions from agencies and experts who consider likelihoods, not just hypotheticals.

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Thanks for joining in the fight for science! 

Thank you for supporting evidence-based science communication. With outbreaks of preventable diseases, refusal of evidence-based medical interventions, propagation of pseudoscience by prominent public “personalities”, it’s needed now more than ever. 

Your local immunologist,

Andrea