Aspartame Side Effects: Recent Research Confirms Reasons for Concern

Original and independent research from the last 3 years on this artificial sweetener demonstrates harmful aspartame side effects on the brain and on fibromyalgia and IBS symptoms; and it shows aspartame might increase the risk of lymphoma and leukemia. Since aspartame is used in over 6,000 foods and beverages and 500 pharmaceutical drugs, it is important to uncover the true unbiased facts about the safety of using this sweetener.

From Diet Coke to Crystal Light “Natural Lemonade,” aspartame is still the most commonly used artificial sweetener in diet beverages. Despite ongoing declarations of aspartame’s safety from the FDA and mainstream health organizations, researchers continue to explore and uncover evidence of aspartame side effects. Since 2011, original research has been published demonstrating aspartame’s negative effects on the brain and on symptoms of irritable bowel syndrome (IBS) and fibromyalgia, as well as its potential to increase the risk of cancer. 

What is aspartame and how common is it?

One of the most widely used artificial sweeteners in the world, aspartame was initially approved for limited use by the U.S. FDA in 1981 and for general use by the European Union in 1994. Today, aspartame is an ingredient in more than 6,000 foods and beverages and 500 pharmaceuticals. Once ingested, aspartame gets broken down into its three constituents: aspartic acid (an excitotoxin), phenylalanine, and methanol (which is then transformed into formaldehyde).[5]

Aspartame side effects on brain function

Our cells continuously generate reactive oxygen species during metabolism, including the metabolism of oxygen. Since brain cells consume a relatively large portion of the oxygen utilized by the body, they generate high levels of reactive oxygen species. This means that the detoxification of reactive oxygen species is an essential task within the brain. Glutathione is the main antioxidant the brain uses to protect brain cells against the ravages of reactive oxygen species.

Long-term aspartame consumption in rats decreases the antioxidant defense status of the brain and leads to oxidative stress by depleting brain levels of glutathione.[1] One research group reported in 2012 that rats who were repeatedly fed aspartame had 25-33% lower brain glutathione levels.[2] Not only that, they found that aspartame directly inhibited brain serotonin, noradrenaline and dopamine. All of these aspartame-induced brain changes impaired the rats’ memory performance; the rats given the most aspartame were significantly delayed in their ability to escape from a water maze.

Aspartame and cancer risk

The debate about whether aspartame increases the risk of certain types of cancer continues, and the latest study to be published on the issue suggests it does. In late 2012, a group of researchers from Brigham and Women’s Hospital and Harvard Medical School in Boston published a study in the American Journal of Clinical Nutrition showing that men and women who consume one or more daily servings of aspartame-sweetened diet soda had a 42% increased risk of leukemia.[3] Furthermore, they found that men, but not women, also had a 31% higher risk of non Hodgkin lymphomas and a 102% higher risk of multiple myeloma in comparison with men who did not consume diet soda. A set of previous studies in rats in 2006-2007 had also uncovered increased cancer risk, especially of leukemias and lymphomas, from long-term aspartame.[4] The rats in those studies were consuming aspartame in doses equivalent to those which humans can (and do) easily ingest.

Aspartame, fibromyalgia, and IBS

Aspartame side effects may also include exacerbation of fibromyalgia and/or IBS symptoms. As mentioned above, one of the compounds into which aspartame breaks down once in the body is aspartic acid. Aspartic acid is a toxin that causes hyperexcitability of neurons.[5] Aspartic acid also gets turned into other excitatory amino acids in the body called glutamates. These excitotoxins have been shown to cause the degeneration of neurons and other cells that make up the nervous system.[5] Both IBS and fibromyalgia are disorders that involve abnormal nervous system function.

Researchers from the Oregon Health & Science University in Portland reported improvements when they placed 57 fibromyalgia patients who also had IBS on a 4-week “excitotoxin elimination diet,” which included the elimination of aspartame as well as MSG.[6] Of the 37 people who completed the diet, 84% reported that more than 30% of their symptoms had resolved. Subjects who improved on the diet were then randomized to a 2-week double-blind placebo-controlled challenge with MSG or placebo. The MSG challenge, as compared to placebo, resulted in a significant return of symptoms; a worsening of fibromyalgia severity and a decreased quality of life in regards to IBS symptoms. According to the study authors, the findings suggest that dietary excitotoxins like aspartame or MSG may be contributing to fibromyalgia symptoms.

Summary of recent aspartame research

For most of us, the occasional diet soda isn’t going to harm us seriously. But for the millions of people who drink aspartame-sweetened beverages day in and day out, the risk for aspartame side effects and long-term harms are still unknown, despite the assurances of many in mainstream medicine. The latest research has uncovered some alarming findings about aspartame’s potential to increase cancer and its negative effects on the brain. It’s also shown how cutting aspartame out of the diet may improve symptoms of fibromyalgia and IBS.

For people who want to avoid aspartame, the easiest way to do this is to check the labels before buying or eating foods or drinks. If aspartame is in the product it will be listed in the ingredients. NutraSweet® and Equal® are brand names for aspartame, so these can be avoided as well. If you regularly consume aspartame, consider switching to more natural no-calorie sweeteners, such as those made with stevia or xylitol. Better yet, work on decreasing all added sweeteners, whether natural or artificial, from your diet.

We want to hear from you about your use of sweeteners. Have you experienced any aspartame side effects? Do you have any tips for other readers who are trying to reduce their use of sweeteners? Share your experience with other readers in the comments section below.

[1] Drug ChemToxicol. 2013 Apr;36(2):135-40.

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  • While the potential danger of artificial sweeteners deeply concerns me, I’m just as concerned about the conclusions drawn here. They’re not supported by the studies presented as evidentiary. In fact one involves MSG rather than aspartame in any sense! This kind of journalism is dangerous in its own right.

  • Indeed, all artificial sweeteners exacerbate my IBS symptoms a great deal. I get abnormal pain and diarrhoea. This happened the other day when I had some Actimel, believing it would be good for my tummy! The packages are insidious though normally I look out for lists about how the product is free from this and that… it usually covers up sweeteners. I have an underlying condition that relates to fibromyalgia.

  • I took Protos for osteoporosis for 7 years and it had aspartame in it. I had ibs for all that time. Then by chance i read about the bad effects and that some people would wash the aspartame off the medication so i did that too. Overnight the ibs got better.

  • For four years I have been suffering with pains in my hips, my hips would give way and muscle pain in the legs generally and on bad days struggled walking with every step being painful. Have had xrays and blood tests for fybromyalgia with no results. Recently I realised that symptoms were worse after an evening out. As I dont drink I carry my own little bottle of concentrated fruit juice to put into water. I drink this four or five times a day and then extra on an evening out. I stopped using this 4 weeks ago and all pains have gone, I can run up flights of stairs and have more energy. This is the only change I have made and cant believe something so simple could have such life changing consequences.

  • Even a cup of flavored water containing aspartame makes me feel motion sick-nauseous and a little dizzy unless I stay completely still.

  • After two bad episodes of bloating, stomach and abdominal pain, I eliminated diet tea and soft drinks all sweetened with aspartame. Overnight my symptoms disappeared. Water for me from now on.

  • Aspartame makes my son depressed and aggressive, completely overreacting to everything. For almost a year, we didn’t realise this was the reason but within 2 weeks of cutting it out of his diet completely, he had calmed down and became much better behaved at home and at school. I now avoid it for the whole family.

  • When this product came out, I thought I had the stomach flu! Most recently, I drank a half a glass (served by mistake), I have had three solid days of diarrhea, bloating, gas, headache, and a bitter taste in my mouth. I’m back to Sugar Forever!!

  • When the USDA uses language that indicate that a careful approach to Aspartam is near hysterical, when the evidence is only partly in, how can it, and other authorities in the USA declare it 100% safe? Check sources outside the economic interest zone. Such assertions about consumer implied radicalism and ignorance has no place in an official site. I expect apologies when the science replaces policy. Aspartam has a nasty after-taste. There are peer studies about the harm vs benefits of artificial vs normal. Aspartam vs “real, and of course “Sugar Blues”. White refined sugar is no sweetheart either.

  • I avoid aspartame in all products like the plague. Even tiny occasional amounts give me a massive migraine and put me out of commission for about a day. I know I’ve been “slipped” some aspartame in various foods whenever I get that sudden migraine for no apparent reason. Migraines like that teach me to read every single label to ensure I don’t consume any aspartame. Other no-calorie sweeteners don’t seem to bother me (a fraction of a serving of sacchrin is extremely sweet to me, but I don’t use it anymore); I don’t like the taste of stevia (it does not taste sweet to me); sucralose is okay, and aceulfame potassium doesn’t give me any negative side affects. I don’t get the opportunity to taste xylitol (small amounts are poisonous to pets) so can’t say; and I stopped taking propylene glycol because it just seems too much like I’m consuming antifreeze.

  • Months of feeling ill and many many tests later…I believe aspartame is the root cause. Since Monday I have cut this out of my diet as best possible, my symptoms are more or less gone.
    Symptoms before included nausea, bloating, headaches, horrendous diarrhoea that got steadily worse over time lasting up to over a month. Dizziness, fatigue, hair loss, infertility, tingling hands & feet, ringing ears, swollen lymph nodes on and off.
    Was feeling so sick that I had an MRI & CT as well as blood tests. Only things that showed up was inflammation markers in blood & swollen lymph nodes on scans.
    I started trying to eliminate possible causes such as anything medically wrong, stress and diet related. Long and short of it, after coming back to work following Christmas holidays, I put a single piece of chewing gum in my mouth & straight away I got nausea shortly followed by diarrhoea (which had ceased when I was off work and not consuming gum.) I tracked back to other times when nausea and diarrhoea had been particularly bad and low & behold I’d eaten gum. Gum has aspartame (phenylalanine). I urge you to stay away from theses synthetic products. Unfortunately it’s in lots of diet food stuffs like soda, gum, sweets etc.
    The symptoms I had are akin to those of many others with suspected aspartame ingestion.

  • I was diagnosed with high sugar so cut sugar out and got it down from 9 to avenge 4,5. But started drinking all the zero cool drinks . This has been over about 8 years . About 2 years ago I started feeling funny in my head . Pins a needles going over the left side and just feeling strange. So will cut qll the aspartame and associated stuff out as of from today and see if I feel better. Will keep you posted

  • I’ve been drinking about 3/4 gallon of diet koolaid for years. This might explain my ever increasing weight gain even tho I diet, Palo, keto. Stopped today. No more. Using steiva from now on. Pray this us why. Tired of paying drs and blood work, x-rays, etc

  • To get to the 1g/kg BW (1000mg/kg BW) drinking the highest soda aspartame content (125mg/oz) you’d have to drink 170L of soda each day (for those who weigh ~100 lbs) and 340L of soda each day (for those who weight ~200 lbs). So referencing the first study that has this insanely high dose is bad science. Nobody drinks that much soda.

    Reference 3 says it doesn’t have any evidence it hurts you. So “42% increased risk of leukemia” appears to have been made up.

    Later the article seems self aware of the non-validity of the previous studies 1&2 when it mentions that reference 4 finally uses real consumption quantities: “The rats in [study 4] were consuming aspartame in doses equivalent to those which humans can (and do) easily ingest.” So the article is further damning the first 2 references. Oddly enough reference 4 also has some internal contradictions first stating that the real consumption quantities are 2.5–5.0 mg/kg bw but then turns around and uses 20, & 100 mg/kg bw as the dose in the research. 4 & 20 times the high end of the realistic expected dose.

    This is a pathetic façade of science, it only applies in an extreme, chronic high dose, situation. These researchers need to step up and use real consumption doses and report the truth. They should have to pay back their research grants when they use plainly misleading methods.

  • Instant headache & nausea. I avoid it, but have been slipped it by someone who did dot believe me about my reactions. After, literally, two sips, my head felt like someone had shoved a spike into it & my stomach was roiling. We were camping, no aspirin or antacids. I drove out to the nearest store & got both, as well as soda crackers & mint tea bags. It took several hours before I felt better. So great that the government allows poison in foods.

  • I not only get the Nutrasweet Headache – headache that never goes away and is there day after day, but also a speech impediment which I believe is much more serious. It took a month for the headaches to stop and over 6 months for the speech problem to subside, although I still had it once in a while for probably a couple years. I called it a stutter, but it happens in the middle of speaking, it’s like I have to swallow before I can continue speakking.

    I had just stopped using Nutrasweet to see if that would help with the constant headaches and then a couple days later heard on the radio about it causing headaches.

    Now, if I’m accidentally given diet pop, the stutter comes back immediately and takes over 6 months to go away, even after one mishap.

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