Fizzy soft drinks can being opened

While recent news about aspartame might have been difficult to follow, beneath the headlines there was extremely good news for consumers and the science of food safety.

Despite some confusing and, at times, frightening headlines, the clear takeaway is that the WHO and UN Food & Agriculture Organization’s Joint Expert Committee on Food Additives (JECFA) reaffirmed aspartame is safe. The committee, in fact, found “no convincing evidence” of any health risk, including cancer, from consuming aspartame at or below an amount far greater than what is commonly consumed.

If this sounds surprising, it may be because the WHO’s sub-agency on cancer research (IARC) simultaneously formalised its opinion classifying aspartame as a “possible carcinogen”. The word “carcinogen” dominated media headlines and caused concern, but having participated as an observer in the IARC review meeting, I can attest that the evidence on which this opinion is based was exactly as IARC describes it: “limited” and “insufficient”.

IARC’s opinion is, therefore, much less alarming than it may seem. In addition to acknowledging its opinion is based on limited and insufficient evidence, IARC’s process for determining cancer hazard is much more limited than JECFA’s more comprehensive review.

IARC looks only at hazard (“does aspartame cause cancer under any conditions?”). JECFA, on the other hand, assesses both hazard and real-world risk (“is aspartame likely to cause cancer under real-world conditions?”).

To put this in layperson’s terms: there is a hazard that a meteor falling from space could hit people. But there is little or no risk that walking outside makes a person likely to be harmed by a falling meteor.

Since IARC’s review does not assess any context such as consumption data or magnitude of effects, it does not give a complete picture of actual impacts on human health. IARC also frequently relies on research considered to be low-quality, including animal studies that have been previously discredited by regulatory authorities, as well as on observational studies that cannot prove causation. Furthermore, IARC excludes some very important analysis and expert assessments, such as meta-reviews, unless they provide “original data”.

It’s unfortunate that the IARC opinion was leaked prior to its formal announcement, violating the confidentiality code agreed and causing a great deal of needless public confusion. Nevertheless, the real news is that aspartame has, once again, been proven safe. JECFA’s determination is consistent with the overwhelming weight of evidence from more than 100 high-quality human, animal, and mechanistic studies conducted over several decades.

There’s further good news. Since the IARC opinion was first leaked in June, many countries’ regulators have stood by their own robust positive safety findings, as well as the comprehensive JECFA review. Health and food safety authorities in more than 90 countries around the world have repeatedly found aspartame to be safe at common consumption levels, and the JECFA finding further strengthens confidence in these robust regulatory reviews.