Is Aspartame Really Linked to Cancer?

Emily Oster

7 min Read Emily Oster

Emily Oster

Is Aspartame Really Linked to Cancer?

Panic headlines and the WHO's recent update

Emily Oster

7 min Read

A couple of weeks ago, the World Health Organization (WHO) weighed in on the possible link between aspartame and cancer. More specifically, the International Agency for Research on Cancer (IARC) discussed aspartame for the first time and judged it as “possibly carcinogenic to humans.” For those who haven’t been following this news, aspartame is an artificial sweetener most widely used in diet soda, including Diet Coke.

The subsequent discussion has been confusing. On one hand, the phrase “possibly carcinogenic” is very concerning. On the other hand, most of the language coming out of even this initial WHO document suggests that people shouldn’t be concerned about consuming “typical amounts” of aspartame. I think the discussion is well summarized by a paraphrase of this headline in Insider: “Aspartame is a ‘possible carcinogen’ but still safe to ingest.

Today I’m going to break down the context for this in the hopes of making it clear what is actually going on here. Because we all care about our health, but, as one reader told me, “I just want to enjoy my Diet Coke without thinking about my mortality.”

What actually happened?

The IARC is an agency within the WHO that is responsible for, among other things, classifying agents by their potential to cause cancer. Overall, they have classifications for over 1,000 cancer risks — from viruses to chemicals to lifestyle choices (note: they do not include genetic risk classifications). You can see the full list here.

When evaluating agents, the IARC uses four classifications:

  • Group 1: carcinogenic to humans
  • Group 2A: probably carcinogenic to humans
  • Group 2B: possibly carcinogenic to humans
  • Group 3: Not classifiable as carcinogenic

They note that group 3 doesn’t mean that something doesn’t cause cancer, just that they cannot classify it due to lack of evidence. The kind of evidence the IARC is looking for includes studies in people, studies in animals, and possible mechanistic pathways.

Group 1 here includes many things that are unsurprising: hepatitis C virus, HPV, tobacco, radiation, many industrial exposures. It also includes some situations in which the evidence is more nuanced — oral contraceptives, for example. People definitely take issue with the interpretation of some of the individual items on this list, but overall these are often accepted.

As we move into groups 2A and 2B, we encounter cases where the evidence is much weaker — unsurprising, given the classifications. But to give you a sense of some behaviors that are classified in group 2A (“probably carcinogenic”), we have:

  • Red meat consumption
  • Drinking very hot beverages
  • Working night shifts

For something like red meat consumption, the evidence here is largely based on correlations between red meat consumption and cancer risk. Those correlations are there, of course, but as I’ve talked about many times before, correlation isn’t the same as causation.

Aspartame has been classified in group 2B (“possibly carcinogenic”). Also in this group:

  • Aloe vera
  • Low-frequency magnetic fields (see my discussion here)
  • Pickled vegetables
  • A variety of food dyes

For something like low-frequency magnetic fields, where I know the data well, the claim for a causal link is quite weak. I don’t think the IARC disagrees with this — but the reality is that the classification “2B” doesn’t require strong evidence. Anything that whiffs or hints in the direction of a link can trigger it.

Aspartame

Studying the relationship between aspartame and health is hard. This is true for at least two reasons.

First: consumption of aspartame is associated with other demographic characteristics. Consumers of aspartame tend to have lower educational attainment and fewer income resources than non-consumers. These characteristics are associated with higher rates of cancer, due to other behaviors and also to differences in medical access. Separating out the aspartame effect is a challenge.

A second issue is that often people adopt diet soda when they are trying to improve their health. In particular, higher aspartame consumption is associated with a higher BMI — not because it is high in calories but because there is selection in who consumes it.

These issues crop up in the data the IARC used to make their assessment. The classification of aspartame as “possibly carcinogenic” is based on a possible link with a form of liver cancer. That, in turn, is based on studies like this one, which compared liver cancer diagnoses across groups with varying consumption of artificially sweetened sodas. The researchers find a small increase in risk for additional artificially sweetened soda consumption, but those higher-volume consumers also have more other health issues.

In addition to the possible bias, the effect sizes in these studies are extremely small (and this type of liver cancer is rare). This both makes these issues less important in terms of the need to change behavior and makes it more likely that other differences across groups play a role. Put simply: those differences wouldn’t have to be very large or important in order to eliminate this effect.

Looking at this together it seems clear that there is, as the WHO says, “limited” evidence that aspartame causes cancer in humans, certainly at the levels that it is typically consumed. The report discusses the possibility of more risks at very high consumption levels — say, if you drink 15 to 20 diet sodas a day — but this type of consumption is so rare that it’s even more difficult to imagine actually identifying impacts there.

The IARC has a hard job

Looking at the evidence on aspartame, from an individual standpoint, this falls very much into the “try not to think about it” category. There is little reason to think there is a relationship between aspartame and cancer. Could there be some tiny impact of aspartame on cancer? Of course. Very small effects are extremely difficult to rule out, especially with such limited data, and especially with a disease like cancer, which is so varied and can strike with such randomness.

Sometimes my read of the data on topics like this differs from official bodies, but this actually isn’t one of those times. By their own language, the IARC says there is limited risk here. Given this, a reasonable person might ask why they talk about this at all — why label it “possibly” a carcinogen?

The answer, I think, lies in why the IARC has a hard job. They could ignore aspartame. But once researchers start writing even not very high-quality papers on aspartame and cancer, it becomes hard to ignore. And once they start studying it, the standard they are holding these data to is fairly extreme. To put something in the category 2B, “possible carcinogen,” group requires only believing there is a possibility, not a probability. Ruling out the possibility of some relationship is a challenge.

If we had a large, long-term follow-up randomized trial of diet soda consumption over decades and we did not see any relationship with any kind of cancer, that would likely be enough to rule this out. In the absence of that, even a small, likely biased, observational relationship with a single kind of cancer does open up the “possibility” that there could be something — even if the probability that it is important enough to pay attention to is close to zero.

Bottom line

To the person who asked: please enjoy your Diet Coke without thinking about your mortality.

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With this in mind, it’s worth asking why this recommendation continues at all — or at least why the AAP doesn’t push it back to four months. They say decreased arousals from sleep are linked to SIDS, which could mean that babies sleeping in their own room is risky. But this link is extremely indirect, and they do not show direct evidence to support it.

According to the data we have, parents should sleep in the same room as a baby for as long as it works for them! Sharing a room with a child may have negative impacts on both child and adult sleep. We should give families more help in navigating these trade-offs and making the decisions that work best for them.

#emilyoster #parentdata #roomsharing #sids #parentingguide

The AAP’s guidelines recommend sleeping in the same room as your baby “ideally for the first six months.” However, the risk of SIDS is dramatically lower after four months, and the evidence in favor of the protective effect of room sharing is quite weak (both overall and even more so after four months). There is also growing evidence that infants who sleep in their own room by four months sleep better at four months, better at nine months, and even better at 30 months.

With this in mind, it’s worth asking why this recommendation continues at all — or at least why the AAP doesn’t push it back to four months. They say decreased arousals from sleep are linked to SIDS, which could mean that babies sleeping in their own room is risky. But this link is extremely indirect, and they do not show direct evidence to support it.

According to the data we have, parents should sleep in the same room as a baby for as long as it works for them! Sharing a room with a child may have negative impacts on both child and adult sleep. We should give families more help in navigating these trade-offs and making the decisions that work best for them.

#emilyoster #parentdata #roomsharing #sids #parentingguide
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Watch the full segment at the link in my bio 🔗

#tamronhall #tamronhallshow #emilyoster #parentingsupport #workingparents

It was an absolute pleasure to be featured on the @tamronhallshow! We talked about all things data-driven parenting and, in this clip, what I call the plague of secret parenting. To balance having a career and having a family, we can’t hide the fact that we’re parents. If mothers and fathers at the top can speak more openly about child-care obligations, it will help us all set a new precedent.

Watch the full segment at the link in my bio 🔗

#tamronhall #tamronhallshow #emilyoster #parentingsupport #workingparents
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My guest on this episode, @everodsky, has come up with a solution here, or at least a way for us to recognize the problem and make our own solutions. I’ve wanted to speak with Eve for ages, since I read her book Fair Play. We had a great conversation about the division of household labor, one I think you’ll get a lot out of!

Listen and subscribe to ParentData with Emily Oster in your favorite podcast app 🎧

#emilyoster #parentdata #parentdatapodcast #parentingpodcast #householdtips #fairplay #invisiblelabor

Invisible labor. It’s the work — in our households especially — that has to happen but that no one sees. It’s making the doctor’s appointment, ensuring birthday cards are purchased, remembering the milk.

My guest on this episode, @everodsky, has come up with a solution here, or at least a way for us to recognize the problem and make our own solutions. I’ve wanted to speak with Eve for ages, since I read her book Fair Play. We had a great conversation about the division of household labor, one I think you’ll get a lot out of!

Listen and subscribe to ParentData with Emily Oster in your favorite podcast app 🎧

#emilyoster #parentdata #parentdatapodcast #parentingpodcast #householdtips #fairplay #invisiblelabor
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Good news: fancier vitamins are not better.  Folic acid is the most important prenatal ingredient. Iron (with vitamin C) and DHA are also nice to have. Other included ingredients have only weak or no evidence to support their use. (If you do not consume animal products, add B12, plus a few others depending on your diet.)

Vitamins are just vitamins. Any prenatal vitamin that contains these is enough. 

Comment “Link” for a DM to an article with everything you need to know about prenatal vitamins.

#emilyoster #parentdata #prenatalvitamins #pregnancydiet #pregnancytips

Prenatal vitamins 💊 If there is any product that seems designed to prey on our fears, it’s this one. You’re newly pregnant and you want to do it right. Everyone agrees you need prenatal vitamins, so you get them. But do you want to be that person who just… buys the generic prenatal vitamins?

Good news: fancier vitamins are not better. Folic acid is the most important prenatal ingredient. Iron (with vitamin C) and DHA are also nice to have. Other included ingredients have only weak or no evidence to support their use. (If you do not consume animal products, add B12, plus a few others depending on your diet.)

Vitamins are just vitamins. Any prenatal vitamin that contains these is enough.

Comment “Link” for a DM to an article with everything you need to know about prenatal vitamins.

#emilyoster #parentdata #prenatalvitamins #pregnancydiet #pregnancytips
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#parentdata #emilyoster #newborncare #parentingadvice #parentingtips

When it comes to introducing your newborn to the world, timing matters. It’s a good idea to minimize germ exposure in the first 6-8 weeks; after that, it’s inevitable and, very likely, a good idea! This doesn’t mean you need to be trapped inside. The most significant exposure risks are from seeing other people at home — family, etc. These interactions are not infinitely risky, but they do pose more risk than a walk or a trip to the grocery store, since they involve closer interaction. Think simple and make sure everyone is washing their hands before holding the baby. 💛

#parentdata #emilyoster #newborncare #parentingadvice #parentingtips
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#emilyoster #parentdata #hotflash #perimenopause #womenshealth

The first edition of Hot Flash is out now! Comment “Link” for a DM to learn more about the late-reproductive stage.

There are times when we expect hormonal shifts. Our reproductive lives are bookended by puberty and menopause. We discuss those changes often because they are definitive and dramatic — a first period is something many of us remember clearly. But between ages 13 and 53, our hormones are changing in more subtle ways. During the late-reproductive stage (in your 40s), you can expect a lot of changes in your menstrual cycle, including the length and symptoms you experience throughout. It’s an important time in our lives that is often overlooked!

🔥 Hot Flash from ParentData is a weekly newsletter on navigating your health and hormones in the post-reproductive years. Written by Dr. Gillian Goddard, Hot Flash provides all of the information you need to have a productive, evidence-based conversation about hormonal health with your doctor.

#emilyoster #parentdata #hotflash #perimenopause #womenshealth
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Now tell me in the comments: what’s a parenting move you’ve made recently that feels right to you?

#parentingcommunity #parentingsupport #parentingquotes #emilyoster #parentdata

There are plenty of reels telling you how to parent. Plenty of panic headlines saying that “studies show” what’s best for your kid. Even good data, from a trusted source, can send us into a spiral of comparison. But I want you to remember that no one knows your kid better than you. It’s important to absorb the research, but only you will know the approach that works best for you and your child. 💙

Now tell me in the comments: what’s a parenting move you’ve made recently that feels right to you?

#parentingcommunity #parentingsupport #parentingquotes #emilyoster #parentdata
...

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Listen and subscribe to ParentData with Emily Oster in your favorite podcast app 🎧

#parentdata #parentdatapodcast #emilyoster #emilynagoski #comeasyouare #cometogether #longtermrelationship #intimacy #relationships

Let’s talk about sex (after) baby! Today on the podcast, I was lucky enough to speak with @enagoski about her new book on sexual connection in long-term relationships. Especially after having kids, this is something many people struggle with. Emily tells us to stop worrying about what’s “normal” and focus on pleasure in its many forms.

Listen and subscribe to ParentData with Emily Oster in your favorite podcast app 🎧

#parentdata #parentdatapodcast #emilyoster #emilynagoski #comeasyouare #cometogether #longtermrelationship #intimacy #relationships
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Comment “Link” for a DM to an article on another common formula question: should you throw away old formula powder?

#emilyoster #parentdata #babyformula #babyfeeding #parentingstruggles

Ever wondered if you can safely use leftover baby formula? 🍼 The CDC says to throw out unused formula immediately because of the risk of bacterial growth. However, research suggests that bacterial concentrations do not appreciably increase after 3, 12, or even 24 hours at refrigerator temperatures. Good news! This means there’s not a strong data-based reason to throw out formula right away if you store it in the fridge.

Comment “Link” for a DM to an article on another common formula question: should you throw away old formula powder?

#emilyoster #parentdata #babyformula #babyfeeding #parentingstruggles
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#emilyoster #parentdata #parentingtips #parentingadvice #newparents #parentingcommunity

What’s the most important piece of advice for new parents? Here’s one answer, but I want to hear from you! Share your suggestions in the comments ⬇️

#emilyoster #parentdata #parentingtips #parentingadvice #newparents #parentingcommunity
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What's in the bag of a Vagina Economist? 👀 Someone please tell me this looks familiar to you.

What`s in the bag of a Vagina Economist? 👀 Someone please tell me this looks familiar to you. ...

Comment ”link” for a DM to learn more about tongue ties 🔗

Breastfeeding is often difficult, especially at the start. For babies with tongue ties, many infants (and their moms) struggle to get the hang of a good latch. This can lead to painful nipples and to inefficient feeding, and then low weight gain.

So what does the data say about the increasingly common practice of cutting tongue-ties in infants to improve breastfeeding success? Several weeks ago, @nytimes published a long and quite scary article on this topic.

After diving into the data, here is what I found. There is limited evidence that frenotomy procedures improve breastfeeding efficacy and the harms of the procedure are minimal. Many women do report that it alleviates pain and helps them with breastfeeding. However, it should not be a first-line treatment for breastfeeding problems.

#parentdata #emilyoster #tonguetie #tonguetiebabies #breastfeedingsupport

Comment ”link” for a DM to learn more about tongue ties 🔗

Breastfeeding is often difficult, especially at the start. For babies with tongue ties, many infants (and their moms) struggle to get the hang of a good latch. This can lead to painful nipples and to inefficient feeding, and then low weight gain.

So what does the data say about the increasingly common practice of cutting tongue-ties in infants to improve breastfeeding success? Several weeks ago, @nytimes published a long and quite scary article on this topic.

After diving into the data, here is what I found. There is limited evidence that frenotomy procedures improve breastfeeding efficacy and the harms of the procedure are minimal. Many women do report that it alleviates pain and helps them with breastfeeding. However, it should not be a first-line treatment for breastfeeding problems.

#parentdata #emilyoster #tonguetie #tonguetiebabies #breastfeedingsupport
...

Tag a friend who needs to hear this 💛 For many choices in parenting, there is no one right answer. We can use research and data to make informed decisions, but ultimately, it won’t tell you what to do. Only you can decide what will be best for your kids and your family.

I’m here to remind you to take a deep breath and trust yourself. I’ll be here to support you along the way. 

Thank you to everyone who submitted videos, including:
@sarah.consoli
@jess_lynn627
@nicolevandenwills
@thedrblair
@ncbenedict29
@haleycimini
@iamkellysnodgrass
@calesse_smith
@garnet__gordon
@jencoopgaiser87
@danigirl18c
@jamielundergreen
@carly_comber
@thecelebratingmama
@emilyannbynum
@eeliz413

#emilyoster #parentdata #parentingadvice #parentingsupport #parentingquotes

Tag a friend who needs to hear this 💛 For many choices in parenting, there is no one right answer. We can use research and data to make informed decisions, but ultimately, it won’t tell you what to do. Only you can decide what will be best for your kids and your family.

I’m here to remind you to take a deep breath and trust yourself. I’ll be here to support you along the way.

Thank you to everyone who submitted videos, including:
@sarah.consoli
@jess_lynn627
@nicolevandenwills
@thedrblair
@ncbenedict29
@haleycimini
@iamkellysnodgrass
@calesse_smith
@garnet__gordon
@jencoopgaiser87
@danigirl18c
@jamielundergreen
@carly_comber
@thecelebratingmama
@emilyannbynum
@eeliz413

#emilyoster #parentdata #parentingadvice #parentingsupport #parentingquotes
...

Congratulations on making it through another year of panic headlines! We’ve had some doozies this year, like aspartame causing cancer and the perils of white noise, but these headlines are very often based on poor data. Correlation does not equal causation. There will certainly be more panic headlines in 2024, but ParentData is here to debunk them for you.

#emilyoster #parentdata #happynewyear2024 #panicheadline #datadriven

Congratulations on making it through another year of panic headlines! We’ve had some doozies this year, like aspartame causing cancer and the perils of white noise, but these headlines are very often based on poor data. Correlation does not equal causation. There will certainly be more panic headlines in 2024, but ParentData is here to debunk them for you.

#emilyoster #parentdata #happynewyear2024 #panicheadline #datadriven
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