Aspartame and other boogeymen

There is a persistent and common belief that artificial sweeteners and other food additives are “bad for you”. This belief is sometimes very vague, but sometimes in connection with specific concerns such as cancer. Googling “aspartame” and “cancer” unsurprisingly turns up dozens of pseudoscientific, alarmist websites proclaiming its toxicity, and a much smaller number of websites such as those run by the National Cancer Society in the US and the UK’s National Health Service, trying to assure the public that it is safe.

The confusion about aspartame and other specific food additives speaks to a serious problem in both epidemiological research and in scientific journalism. Observational studies in nutrition suffer from a really serious signal-to-noise issue – separating out particular dietary causes of cancer or heart disease among the huge variation in people’s broader diets, exercise habits, family histories and general life conditions is extremely challenging.

The epidemiologists who do this type of research are often appropriately circumspect and carefully state the limitations of their conclusions, but this doesn’t make for exciting headlines. The media jump on particular studies – especially those that report that something may be dangerous – remove all the caveats, and report a completely sensationalised and de-contextualised version of the research findings. And six months later, when another study finds the opposite, the very same newspaper might run a story to the opposite effect. See the coverage of research into the health benefits of chocolate and red wine for an example.

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This leaves the general public feeling like the scientific community is either constantly flip-flopping, since the media are perpetually reporting conflicting results about the same foods, or that we have decided something is definitely harmful because the only study that made the papers was the one reporting a link to cancer, while dozens of other studies showing no such association were ignored. In fact, the pace at which national dietary guidelines change is positively glacial, and most experts would be very guarded if you asked whether they thought this or that might be harmful, unless the evidence was absolutely overwhelming. (Most of us will unreservedly advise you not to drink lead paint, for example.)

Aspartame in particular is a frustrating example. Hysterical reporting on a couple of studies seems to have dominated the public perception of it, even though health authorities have been convinced by the weight of evidence that it’s safe for people without serious pre-existing kidney problems. Meanwhile, the additive that aspartame is supposed to replace – sugar – is the subject of far more damning evidence regarding its impact on obesity and type 2 diabetes.

In general, when you see newspaper articles about links between health and specific foods, you should assume they are overstating the case. Common sense – eat less junk food and more vegetables – doesn’t make for sexy headlines, even if that’s really what the public would benefit from hearing.

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