Aspartame - Undeserved Reputation

Last week, Pepsi announced they will be removing aspartame, the artificial sweetener, from Diet Pepsi (in the US), and replacing it with another artificial sweetener, sucralose. This reignited the discussion on aspartame, probably one of the most maligned substances in fizzy drinks – but what does the science say on its safety? This graphic looks at the evidence behind aspartame’s bad reputation, and whether it makes sense to remove it from drinks.

There’s no shortage of material when it comes to aspartame research – the FDA has described it as one of the most studied food additives currently approved. We’re talking a huge number of studies, more than 500, so you’d justifiably think that this is an issue that the research can weigh in on pretty heavily, and with good authority. Even if we cast an overly suspicious eye, and exclude studies funded by soft drinks manufacturers and the like, there are still hundreds of studies that have been carried out on aspartame.

You could be forgiven for thinking that, if Pepsi are removing it from their drinks, there must be some pretty damning evidence behind their decision. That, sadly, is where you’d be wrong. In fact, Pepsi have admitted as much: they state that their decision is a ‘response to consumer preferences’, and cite aspartame as the number one reason customers aren’t buying diet sodas.

In the public sphere, there isn’t much that aspartame hasn’t been accused of – opponents of its use have linked it with cancers, seizures, neurotoxicity, and more besides. Despite this, it’s still present in a number of soft drinks, and if you examine the wide body of evidence, the reasons for this become clear.

Firstly, let’s consider what happens when aspartame is ingested. Your body breaks down aspartame into three different components: two amino acids, aspartic acid and phenylalanine, and methanol. Most people have heard of methanol – also known as wood alcohol, it’s a substance that’s poisonous to humans in sufficient quantity. However, as regular readers of the blog will appreciate, the dose makes the poison, and methanol is no exception.

Of course, the idea that aspartame is broken down into a product that is toxic is initially an alarming one, but let’s pause and think about this in more detail. Firstly, not all of the aspartame in a soft drink will be converted into methanol. In fact, it’s only about 10%, which translates to around 55 milligrams of methanol produced per litre of fizzy drink. 55 milligrams isn’t a lot, but any amount of methanol is bad, right?

Well, as it turns out, aspartame isn’t the only thing in your diet that contributes to your methanol intake. In fact, a lot of substances you might not initially expect contain methanol in small amounts. Most alcoholic drinks will contain a degree of methanol – for example, red wine can contain anywhere between 99 and 271 milligrams per litre. In fact, fruits have higher levels of methanol than even the most aspartame-loaded drink could produce; for example, tomato juice contains up to 218 milligrams per litre. Whether you drink aspartame-containing beverages or not, you’re being exposed to methanol on a daily basis.

Generally, then, aspartame is a pretty measly contributor to our daily methanol exposure. Though methanol is also metabolised in the body, into formaldehyde and then formate, much higher levels of these chemicals than produced by aspartame have been shown to have no negative health effects. The same is true for its other breakdown products, phenylalanine and aspartic acid, amino acids that are present in other foods we eat on a daily basis, and in higher levels. With that said, one of these isn’t completely without its dangers. Phenylalanine intake can pose risks, but only for a specific subsection of the population: those suffering from phenylketonuria.

Phenylketonuria is a rare genetic condition, that affects only 1 in every 10,000 people. People with this condition are unable to break down the amino acid phenylalanine, and as a result it can build up in their bodies to toxic levels. Obviously, for sufferers, aspartame-containing drinks pose a very real risk, as high levels can lead to brain damage, which is why any beverage containing aspartame must be clearly labeled as such. However, it must be emphasised that for the normal population, this isn’t a concern, as they can break down phenylalanine well before it reaches these levels.

The spectre of cancer is often one that looms over food additives. Aspartame has been studied for decades concerning whether or not it can have carcinogenic effects, and the vast majority of studies have found no causal link. In the mid-2000s, an Italian institute did claim to have provided evidence linking aspartame with cancers. However, the methods of these studies were criticised for a number of reasons, including using dosages that didn’t reflect normal human exposure levels, the presence of infection in the test animals prior to the tests with aspartame, and other issues.

Of course, the study was greeted with concern when published – however, in trying to ascertain the quality of the data produced, the FDA asked to be supplied with aspects of the data. The institute in question was unwilling to release the majority of the data, and other agencies later further criticised their methods, further devaluing their ‘results’. It’s now widely accepted that the data they collected on aspartame and cancer is highly unreliable, and has not been replicated.

So, it seems that the evidence supporting serious health effects from aspartame is largely spurious. But how about milder unpleasant effects? A lot of people claim that aspartame-containing drinks give them headaches. Surely all of these people can’t be wrong?

Whilst the science hasn’t conclusively ruled out a link, it’s been noted that headaches are one of the most commonly reported placebo symptoms. Some studies have suggested that those who identify as sensitive to aspartame do experience more headaches with aspartame under controlled conditions, compared to a placebo. It’s worth noting, however, that aspects of this study were criticised.

Others, meanwhile, have found no correlation between aspartame and headaches. A study in the 1980s found a group with self-reported sensitivity to aspartame experienced headaches 100% of the time when they knew they were ingesting aspartame, compared to only 35% of the time when they didn’t know. Additionally, they experienced headaches 45% of the time with a placebo, with the study ultimately finding aspartame to be no better at inducing headaches than a placebo. In other more general studies,the reactions of subjects who identified as sensitive to aspartame have not been reproducible.

So, with all of this evidence backing up the safety of aspartame, why is Pepsi removing it? The answer brings us back full circle: it’s aspartame’s reputation. There are other, less maligned artificial sweeteners out there, and Pepsi’s move is little more than a marketing one – and one that’s got them no small amount of publicity, to boot. Regardless of the evidence, the tide of public opinion affects sales, and Pepsi has clearly judged that kicking aspartame into touch will be good for business.

Of course, this isn’t to say that people shouldn’t be free to choose not to consume aspartame, or other artificial sweeteners, for that matter. But we should be honest about the reasons for its gradual disappearance from the products on shop shelves, which has little to do with health, and more to do with money.

Note: the original version of this article didn’t clarify that Pepsi themselves have stated their removal of aspartame is a purely commercial decision, and unrelated to health concerns. The text has since been amended to reflect this.

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References & Further Reading

41 CommentsClose Comments


  • Lerkero
    Posted April 28, 2015 at 10:47 pm 0Likes

    It’s funny how ‘evidence’ rarely has to do with something’s reputation. There are all sorts of artificial substances in food and people are always looking for a ‘bad guy’

    • Edd Black
      Posted April 29, 2015 at 12:40 am 0Likes

      We are not looking for a bad guy, we are just looking for real food.

      • Compound Interest
        Posted April 29, 2015 at 6:57 am 0Likes

        Without the artificial preservatives in many foods, there wouldn’t be enough ‘real’ food though!

        • Edd Black
          Posted April 29, 2015 at 7:14 am 0Likes

          For you to think this, you do not know enough about food…

          • Compound Interest
            Posted April 29, 2015 at 7:18 am 0Likes

            Well, this is a lack of argument if I’ve ever seen one.

          • Larrian
            Posted June 9, 2015 at 8:49 pm 0Likes

            I did research on the metabolism of foods high in the biogenic amines for people with interstitial cystitis. The issue is about metabolism and the presence of sufficient pyridoxal-5- phosphate to prevent the alternate pathway of xanthurenic and kynurenic acid production, which are highly charged and affect the glycosaminoglycans layer of cells, causing a membrane leak. Published in the British Journal of Urology

            Metabolic Appraisal of the Effects of Dietary Modification on Hypersensitive Bladder Symptoms

            Volume 72, Issue 3, pages 293–297, September 1993
            Red heads and others with deficiency of P5P tend to break down the biogenic amines differently than people with adequate metabolism, making them subject to the symptoms described. Its an interesting way to explain the observation.

          • Compound Interest
            Posted June 9, 2015 at 8:57 pm 0Likes

            Interesting stuff! Do you know of any further research carried out on the subject? Would be interesting to read around.

          • Larrian
            Posted June 9, 2015 at 9:10 pm 0Likes

            No my metabolic studies were the only ones documenting this problem in both blood and urine of people with painful bladder syndrome, who often times had high blood ammonia levels as well contributing to their headaches and bladder pain, amongst many other things.

  • crocodilechuck
    Posted April 28, 2015 at 11:50 pm 0Likes

    I have always avoided these aspartame sweetened beverages [since Don Rumsfeld got the FDA to approve its use when he headed up G.D. Searle]; they make me feel jittery & unsettled.

    Last, QANTAS still forbids its pilots from drinking one < 90 minutes before flight take-off.

    • Compound Interest
      Posted April 29, 2015 at 6:58 am 0Likes

      I doubt that has anything to do with aspartame. If you can link me anything that specifically states that that regulation is due to aspartame, I’ll take a look at it, but I’d be surprised – I’m not familiar with that guidance, but does it apply to all sodas?

      • crocodilechuck
        Posted April 29, 2015 at 7:21 am 0Likes

        Andy, see the para on airline pilots and methanol ingestion @ altitude in this FDA circular: Whether there’s something to this, is another thing.

        I’m friends with a few qantas pilots & have heard about this 90″ ban anecdotally (but, there’s nothing about it on the ‘Net)

        There’s also some less credible stuff on the ‘Net concerning aspartame & pilots, but its sufficiently ‘suss’ that I wouldn’t link to it here/bring to your attention.

        All I know is how I feel after consuming it, which is significantly more intense when on an empty stomach. Try it this way & see for yourself…

        btw, am an ex-chemist and really enjoy your blog. Looking forward to the book!

        • Compound Interest
          Posted April 29, 2015 at 5:16 pm 0Likes

          Thanks for the link! I’ll certainly dig deeper on some of the studies mentioned therein – though, as a cautionary note, I see that the link is merely a docket submitted to the FDA by Mark D Gold of the ‘Aspartame Toxicity Information Center’… I get the sense he may not be completely impartial on the issue!

          I’m guessing it’s hosted on the FDA site in the interests of transparency, but I still find it odd that they’d keep it there when Mark Gold isn’t an FDA employee, and it being hosting there makes it appear to be an official document.

          Anyway, glad you’re enjoying the blog! I’m looking forward to the book too – it’s been pushed back a few times, but hopefully the wait will be worth it!

          • crocodilechuck
            Posted April 30, 2015 at 4:05 am 0Likes

            Try it: have an aspartame sweetened [ugh] cola after fasting [say, no breakfast] @ 10:00 am

            See how you feel at 11:30

            Interested in your reaction!

  • SNPMaster
    Posted April 29, 2015 at 12:41 am 0Likes


    Could you please compose a similar blog for sucralose? Is it potentially more dangerous than aspartame based on structure / biochemistry?

    • Compound Interest
      Posted April 29, 2015 at 6:59 am 0Likes

      Could certainly look into it when I get the time!

  • Mahesh
    Posted April 29, 2015 at 9:19 am 0Likes

    An interesting and demystifying posting.

    I remember at some point earlier this year, I ordered a coke zero at lunch with a colleague. He asked me why the hell I was still drinking stuff with aspartame in it and warned me that it would soon be banned throughout the EU because it causes cancer! I panicked in silence, drinking nothing more of my coke zero as I watched mouthwatering beads of condensation form on the glass bottle.

    After searching the internet on the matter, I came across at the EFSA’s
    website. There is a good FAQ page on aspartame there if anyone is interested.

  • Andy Extance
    Posted April 29, 2015 at 12:31 pm 0Likes

    Two thoughts on this:

    First: Pepsi has only highlighted consumer preference for this move. While that could involve perceived health risks, as I understand it people tend to think aspartame has a weird taste, and prefer sucralose. Also, some patents on sucralose have expired, opening it up to production by anyone, which in turn is going to lower costs. So if sucralose tastes better and is becoming cost competitive with aspartame? Sweet move for Pepsi really, isn’t it.

    Second: When it comes to the evidence on the health effects on these sweeteners, it’s worth taking them all with a pinch of salt, be it positive or negative. There are huge business interests involved and that definitely has an influence. My favourite story (though it may be apocryphal) is how rival sweetener makers posed as the general public to bombard the FDA with complaints and concerns to slow the approval of sucralose. The prospects of making money definitely have a part to play.

    • Compound Interest
      Posted April 29, 2015 at 5:07 pm 0Likes

      Your first point is a good one – I hadn’t intended to imply that Pepsi were dropping aspartame for health reasons. I’ve amended the text of a small section near the top to clarify this.

      It’s also a very fair point that there are business interests. That said, call me naive, but I’d like to think that, from those 500+ studies, we’d have seen something approaching definitive with regards to serious health concerns (i.e. cancer and the like) if there were any substance to those claims. Milder side effects, such as headaches, still seem to be a bit more up in the air, or at least that’s certainly how the research I looked at for this post makes it appear.

      The story about rival manufacturers slowing the approval of sucralose is an interesting one, I’d love to find out if that’s one that’s actually got some substance to it.

      • Andy Extance
        Posted April 29, 2015 at 6:03 pm 0Likes

        True, there are a lot of studies. I’m with you on being optimistic that most of them are independent.

  • Dogan Doruk Demircioglu
    Posted April 29, 2015 at 12:35 pm 0Likes

    Nice summary on this highly debated topic. As a scientist, I always
    focus on realiable and reproducable data. Thus, I would be highly
    interested in the mentioned italian study. Unfortunately, there is no

    Thanks in advance.

    • Compound Interest
      Posted April 29, 2015 at 4:56 pm 0Likes

      Ah, apologies for that, I must have missed it off when I was collating the references. I’ve added the link in, but it’s here as well: The link to the FDA critique is provided in the references above.

      • Dogan Doruk Demircioglu
        Posted April 29, 2015 at 5:39 pm 0Likes

        No problem. Shit happens. 😉 Thank you very much for the missing link.

  • atonatiuhg
    Posted April 29, 2015 at 2:26 pm 0Likes

    Dear community,

    “Here we demonstrate that consumption of commonly used Non-caloric artificial sweeteners formulations drives the development of glucose intolerance through induction of compositional and functional alterations to the intestinal microbiota.”
    Nature (2014) 514, 181.

    “The findings could cause a headache for the food industry. According to BCC Research, a market-research company in Wellesley, Massachusetts, the market for artificial sweeteners is booming. And regulatory agencies, which track the safety of food additives, including artificial sweeteners, have not flagged such a link to metabolic disorders.”
    A. Abbot, Nature (2014) 513, 290.

    Please take a look at the following reference. I think this paper will provide you with a different perspective for discussion. Money drives decision making, let us always be cautious with governmental/regulatory agencies under the heavy influence of powerful stakeholders.

  • Nick G
    Posted April 30, 2015 at 3:19 am 0Likes

    Love this series you have going on undeserved reputations. I’d like to see one on BPA. I admit I have only done a handful of reading into its use, but in a similar fashion to aspartame, there’s an obvious BPA-free push my manufacturers based on consumer concern more than anything FDA cited health claims. I have also seen a few studies citing a greater environmental impact on it as well.

    Great stuff. Thank you Andy for sharing.

    • Compound Interest
      Posted May 2, 2015 at 6:15 pm 0Likes

      Thanks! I’m definitely planning on doing one looking at BPA in the future. A lot of research out there on it, so plenty of material to work with.

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  • Michelangelo Markus
    Posted June 18, 2015 at 3:19 pm 0Likes

    My problem with it is purely that it tastes disgusting. I’ve read a bunch of studies that also say its supposed to taste sweet because your taste buds should by and large be incapable of telling it apart from real sugar. Yet hand me a cup of cola at a party and I can tell the difference at the first sip. Tastes bitter and, for lack of a better word, chemical. I wonder if the bitter and chemical taste is what fuels the health concerns. I’ve read bitter is associated with poisonous plants, which is why we have an aversion to it, add that to the artificial, lab made taste and I can imagine that alone could convince many that it’s harmful.

    The other sweeteners, while still having a bit of that gross chemical taste, aren’t so bitter and do at least have some kind of sweetness to their flavour. Even though it still doesn’t actually taste good.

    To be fair, I can also taste quite clearly the difference between cane sugar and HFCS in sodas, but while I find cane sugar to be far more pleasant, at least I can still enjoy both.

    • Bubbawubba Gump
      Posted June 22, 2015 at 4:51 pm 0Likes

      I have the same reaction to regular soda. The diet tastes normal but the regular has a heavy sickly sweet taste with a pronounced caramel-like(bitter, burnt) aftertaste. In the HFCS it is more pronounced but it is there in real sugar too. Stivia has a wicked metallic aftertaste, especially in colas and coffee. I guess you like what you are used to, repetition makes it the norm. I am trying to cut out soda totally but sometimes it is just convenient.

  • rdbyrne
    Posted June 23, 2015 at 1:32 pm 0Likes

    Propaganda presented as news.

    • Compound Interest
      Posted June 23, 2015 at 8:54 pm 0Likes

      If you’ve scientific evidence which you think definitively shows aspartame to be a dangerous substance, I’ll gladly take a look at it. However, I read a lot into the literature surrounding aspartame to put this post together, and the overwhelming scientific consensus is that it is not harmful.

      There’s no propaganda here – I’m a chemistry teacher, so not sure exactly what I’d have to gain!

      • rdbyrne
        Posted June 24, 2015 at 2:46 am 0Likes

        The benefit might be to those who continue to use aspartame in their products. If you are not compensated yet the article is front page on Yahoo someone else was compensated.

  • triplehelix247
    Posted July 11, 2015 at 12:23 pm 0Likes

    Bull shit!
    Aspartame directly gives me migraines. A half of a diet coke will trigger it.
    Aspartame is cruel and unusual punishment.

    • Grumblin Grimace
      Posted July 16, 2015 at 9:00 pm 0Likes

      so don’t drink it!

  • Grumblin Grimace
    Posted July 16, 2015 at 9:05 pm 0Likes

    Here’s an idea: if you want to reduce caloric intake, drink water, not artificially sweetned beverages. I remember reading years ago about a man that developed severe headaches and tremors which he attributed to his aspartame consumption. Turned out he was drinking one GALLON of Crystal Light every day. Well, drink a gallon of coffee, beer or milk every day for a month and I bet most everyone would develop adverse effects. Remember the old toxicologists saying: The dose makes the poison! Too much of anything can be bad for you.

  • Tim
    Posted July 19, 2015 at 4:52 pm 0Likes

    Here’s a thought. How about we stop throwing artificial shit into our food and drinks. There is a good reason naturally produced compounds are better than artificially made ones. We only started doing this because people can not control their food and beverage consumption. There is a reason why Europe bans a lot of the stuff we put in our food. The author barely cited his sources, and the data he used is hardly discredits the preconceived notions surrounding the artificial sweetener. I know people out there that consume massive quantities of diet drinks a day (12-24 cans). At those levels mixed with the intake of other foods which might contain other artificial additives, there has to be some sort of effect on the body.

    • Compound Interest
      Posted July 19, 2015 at 5:17 pm 0Likes

      Hi Tim; firstly, the sources used are clearly stated at the foot of the article. I could add plenty more, but these are concise enough that readers can follow through and realistically look at all of them.

      I am based in Europe, for what it’s worth, and aspartame isn’t banned here either. We also really need to get away from the whole ‘natural compounds are always better’ fallacy. There are plenty of natural compounds that are just as dangerous, if not more so, than synthetic compounds. That’s not to say that we should be pumping our food and drink full of synthetic compounds for the sake of it, but in many cases, these compounds are required. The obvious example with artificial sweeteners is that, if those people you mention who drink 12-24 cans of diet drinks a day were to be drinking that volume of drinks sweetened with sugar, they’d very quickly have no teeth!

      12-24 cans per day is far too much, artificial sweeteners or no. Drinking or eating anything in excess can have ill effects – and not always as a result of synthetic compounds. Plenty of people exceed the recommended intake of salt, a ‘natural’ compound present in plenty of foodstuffs, and probably one to be more concerned about than aspartame!

      • Tim
        Posted July 19, 2015 at 6:42 pm 0Likes

        I understand that aspartame is not yet banned in Europe, but they do have bans on many artificial ingredients that we in the US use on a consistent basis. In addition, the fact that you can sit there, and tell me that it’s a fallacy that natural ingredients are not better then artificial is pure ignorance. What significant benefits does aspartame provide over natural sugar? Does it lower heart disease? Does it provide better digestion? The reason why sugar was replaced is because people can not control their consumption. Sugar is a natural fuel for the body.
        Your example of people “Losing their teeth” drinking the amount of soda that I stated is poorly related to sugar. First off the acids in the soda strip the enamel off your teeth, but if you have good hygiene and visit the dentist on the regular you wouldn’t lose your teeth that quickly(If at all). The fact of the matter is there are many people out there that drink soda in those quantities. It is the reality of the situation!
        You reference to people exceeding recommended intake on salt has no basis. I exceed that on a daily basis about half the time, but keep hydrated. Hell, I return to school at the age of 28 eat fast food more days than not, and still maintain more than healthy cholesterol levels. Why? It is because again I hydrate and workout on a daily basis. If you are conscious about your body and how you treat it you can easily off set many of the problems of natural ingredients. Our bodies evolved to be able to consume most of these ingredients over hundreds of years. Though when you start throwing in artificially created ingredients our bodies weren’t necessarily created to handle some of these substances. i feel like you are making this about chemistry when it is more about biology

        • Compound Interest
          Posted July 19, 2015 at 9:18 pm 0Likes

          Stating that natural ingredients are always better than synthetic ingredients is a gross simplification – it just isn’t that simple. There are chemicals that naturally occur in food that pose far more risk than those we add to it ourselves. Solanine is found naturally in green potatoes, but you certainly wouldn’t want to ingest it in large amounts, as it can have toxic effects. Similarly, we on occasion add synthetic versions of compounds to foods or supplements, but there’s absolutely nothing different about the chemistry of these synthetic versions compared to their natural counterparts.

          As you say, aspartame is not banned in the EU, and nor is it likely to be, with the scientific evidence from a large number of studies indicating that there are no harmful effects resulting from its ingestion. The only group of people to whom aspartame is a risk are phenylketonurics, and any drinks containing aspartame will display a warning label to this group. Some people think it has an odd taste, but that alone doesn’t make it harmful.

          In all honesty, I’d advocate that drinking large volumes of sweetened beverages, regardless of what they’re sweetened with, is probably not a great idea, and the advised daily intake is there for good reason. I’d suggest that if anyone’s drinking 32 cans of Diet Pepsi a day, that’s by no means going to be a good thing, but that has as much to do with the natural chemicals present as those that are added artificially!

          Sugar does have a link to dental caries, though I’ll concede it wasn’t the best example to provide. Exceeding recommended salt intakes has very definite health effects however; it increases blood pressure, and consequently risk factors for heart disease and stroke. Drinking water and working out won’t offset these effects.

          The one bit of common ground I think we can agree on is that the issue is, of course, a combination of chemistry and biology – in all honesty, our splitting of the sciences into these three branches is imperfect, as there’s plenty of crossover between the three. However, that’s beside the point – if extensive scientific research shows an ingredient to be safe, those tests will encompass both the chemical identity of the compound, and its effects in the body.

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