Keep drinking your diet soda!

Naturally, you knew I was going to have to weigh in the latest artificial sweetener nonsense, it just took me a bit.  As with the last bad science on the matter, “Health Nerd” is all over it:

Also, a bunch of people are convinced that anything artificial is basically poison, and that diet soft drinks are probably killing us all.

This has hit the headlines recently, because apparently the International Agency for Research on Cancer (IARC), a World Health Organization body, is preparing to declare aspartame a class 2B carcinogen. This has caused a huge uproar, because aspartame is one of the most commonly-used artificial sweeteners in the world, and also because cancer is very scary.

Fortunately for people like me, who really like our diet drinks, the evidence really isn’t that compelling. Aspartame probably isn’t giving you cancer.

IARC Categories

The first point to consider in this discussion about aspartame is the way that the IARC classifies things that could potentially cause cancer in human beings. They have four categories:

1 — Causes cancer

2a — Probably causes cancer

2b — Possibly causes cancer

3 — Unclassifiable as a cancer risk

There are a few interesting points to make here off the bat. Firstly, the IARC doesn’t ever consider the magnitude of risk. There are class 1 carcinogens that cause cancer in every person exposed to them, and other class 1s that almost never cause cancer even in massive, lifelong doses. For example, both processed meat and plutonium are considered class 1 carcinogens, even though the risk from bacon is decidedly lower than that posed by nuclear explosions… [emphases mine]

Now, as the headlines state, the IARC is moving aspartame up to a class 2B carcinogen, which means it “possibly” causes cancer. For context, I downloaded the IARC database of human carcinogens, and the class 2B also includes:

1. Coconut oil soaps
2. Aloe vera
3. Pickled vegetables
4. Talcum powder
5. Working in the textiles industry
6. Nickel

And a whole host of other things as well. Class 2B does not mean that something definitely or even probably causes cancer — it means that there is some suggestion that the thing could plausibly cause cancer, and perhaps a small amount of evidence indicating that it does…

A recent systematic review of epidemiological studies, which also included a review of the toxicological literature, summarized this evidence — over more than a dozen large studies, there is very little evidence that aspartame and other sweeteners cause an increased risk of cancer. In fact, I could only find a single paper, which was published in 2022, that found a reasonably consistent correlation between aspartame intake and cancer, and even then it was not a strong connection…

Take the study I mentioned just before, which found an association between aspartame and cancer. In this paper, researchers looked at the Nutri-Net cohort of people, which includes over 100,000 individuals followed up between 2009–2021, and checked to see whether those who reported having more aspartame were more likely to get cancer than those who had none.

They found that, on average, people who ingested no aspartame got cancer at a rate of about 31 in 1,000 during this period. For people who had a ‘higher’ intake of the chemical, the risk of cancer was instead 33 in 1,000. In other words, going from having no aspartame at all, to drinking it regularly for a decade, increased the risk of cancer by 0.2%.

That’s a tiny risk by any measure. Ignoring all of the potential confounders here, and why it’s unlikely that this is a causal relationship, it’s still a bit of a meaningless risk for the average individual. It might be meaningful to population health workers, but even then possibly not.

And Amanda Mull:

Yesterday, Reuters reported that the World Health Organization’s International Agency for Research on Cancer will soon declare aspartame, the sweetener used in Diet Coke and many other no-calorie sodas, as “possibly carcinogenic to humans.” I probably should have felt vindicated. I may not feel better now, but many years down the road (knock on wood), I’ll be better off. I’d bet on the right horse! Instead, I felt nothing so much as irritation. Over the past few decades, a growing number of foods and behaviors have become the regular subject of vague, ever-changing health warnings—fake sweeteners, real sugar, wine, butter, milk (dairy and non), carbohydrates, coffee, fat, chocolate, eggs, meat, veganism, vegetarianism, weightlifting, drinking a lot of water, and scores of others. The more warnings there are, the less actionable any particular one of them feels. What, exactly, is anyone supposed to do with any of this information, except feel bad about the things they enjoy? …

The categories are not at all intended to communicate the degree of the risk involved—just how sure or unsure the organization is that there’s a risk associated with a thing or substance at all. And association can mean a lot of things. Hypothetically, regular consumption of food that may quadruple your risk of a highly deadly cancer would fall in the same category as something that may increase your risk of a cancer with a 95 percent survival rate by just a few percentage points, as long as the IARC felt similarly confident in the evidence for both of those effects…

Taken in aggregate, this morass of poor communication and confusing information has the very real potential to exhaust people’s ability to identify and respond to actual risk, or to confuse them into nihilism. The solution-free finger-wagging, so often about the exact things that many people experience as the little joys in everyday life, doesn’t help. When everything is an ambiguously urgent health risk, it very quickly begins to feel like nothing is. I still drink a few Diet Cokes a year, and I maintain that there’s no better beverage to pair with pizza. We’re all going to die someday.

If there’s actually compelling evidence I may reconsider my level of Diet Dr Pepper intake.  But based on what I’ve seen so far, there’s not nearly enough evidence to change artificial sweetener consumption.