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It pains me to write this blog. I love Diet Coke. And it contains Aspartame. Aspartame, a food additive which makes things taste sweeter, is in everything from diet drinks to ice cream. Used in more than 6,000 products throughout the world, when consumed by humans, it breaks down chemically into aspartic acid, phenylalanine and methanol. The Coca-Cola Company and other food and beverage manufacturers and processors using Aspartame in their products would like consumers to believe that the methanol component in Aspartame is not a reason for concern – because methanol also “occurs naturally” in vegetables and fruit. And that methanol does not pose a problem because it is chemically attached (or bonded) to the pectin contained in the fruit or vegetable, and passes through the human digestive tract without doing harm. So, what's the big deal?

The big deal is that the methyl ester in Aspartame attaches itself to phenylalanine forming methanol which leaches into what Dr. Joseph Mercola calls “susceptible tissues” in the body, including the brain and bone marrow. (Huffington Post, 3/14/2013) Unfortunately, the problem is the human body converts this methanol (unlike that methanol found in fruit) into formaldehyde. Formaldehyde, for those who may require a refresher course in chemistry, is a preservative and the major component, along with methanol, in embalming fluid. Interestingly, in animals, this conversion to formaldehyde does not occur—making the habit of experimentation and testing of the effects of Aspartame in animals, a faulty model. (Huffington Post, 3/14/2013)

The effects of Aspartame have been the subject of review for years by the U.S. Food and Drug Administration (FDA), following the public outcry over the possible oncogenecity of other sweeteners, including Saccharin and Sodium Cyclamates. The FDA has received over 10,000 complaints about the 91 symptoms experienced due to Aspartame consumption. (Huffington Post, 3/14/2013) People who consume Aspartame should be aware of its side-effects and the symptoms of methanol poisoning. Side effects include headaches, ear buzzing, dizziness, nausea, gastrointestinal disturbances, weakness, vertigo, chills, memory lapses, numbness and shooting pains in the extremities, behavioral disturbances, and neuritis. (Huffington Post, 3/14/2013)

The journal, Lancet, has published the fact that multinational food companies frequently aggressively market health-harming foods, yet Aspartame is still used in many products that people consume at an exponential rate. The result? Aspartame toxicity is becoming an all-too common phenomenon, although most physicians are not aware of it. Dr Mercola suggests some tips if you think you may be having a reaction to artificial sweeteners:

  • Remove all artificial sweeteners from your diet for two weeks;
  • After the two weeks of no artificial sweeteners, reintroduce a single artificial sweetener (at about 3 servings/day) for about 3 days to see if you experience any reaction;
  • If there is no reaction, then you can probably tolerate the artificial sweetener; if there is a difference and you have a reaction, please report it to the FDA Consumer Complaint Coordinator (phone number listed on the following web page):

So now, it appears, I am faced with a decision about my love of Diet Coke.


  1. Gravatar for Sweetman

    The rather appalling history of aspartame can be found at SourceWatch

  2. Gravatar for John E. Garst

    Greg, these claims are completely fallacious. Over 90 regulatory authorities worldwide have examined aspartame and over twenty+ years found no safety problems when used as directed.

    Aspartame is degraded in the GI tract to its three constituents, phenylalanine, aspartate and methanol. Phenylalanine and aspartate are found in greater concentrations in normal foods, like milk and meat. Wurtman completely refuted his own earlier, but widely cited allegation, that phenylalanine or aspartame caused any problem with their conclusion: “Large daily doses of aspartame had no effect on neuropsychologic, neurophysiologic, or behavioral functioning in healthy young adults,” -

    Only methanol amongst aspartame degradation products presents any risk to normal people and, since all risk is dose-dependent, at the concentrations involved, methanol presents no risk. Methanol is oxidized to formaldehyde and formate--both are chemically directly converted by the (tetrahydro)folate vitamin system into very valuable methyl groups. These substances and the methyl groups produced detoxify really toxic homocysteine (see Wikipedia) and protect DNA (by converting uracil to thymine). For more on this cycle see the figure at the top of p 3000 here, -

    Any issue with aspartame is a purely PERSONAL issue. ALL these can be explained by PERSONAL matters like folate deficiency and corollary issues (both known and some likely yet unknown) like genetic folate enzyme issues (polymorphisms, Wikipedia: methylenetetrahydrofolate reductase), B12 deficiency (often vegetarian-related), (genetic) methionine synthase enzyme issues, and/or (genetic) homocysteine accrual. Folate, B12, and homocysteine are all functionally interrelated (see the metabolism of folic acid All involve not just the normal, natural recycling of otherwise essential formaldehyde and formate produced from methanol into methyl groups, but the availability of these methyl groups regulate vital-to-life (DNA) itself. Ethanol (primarily through its antagonist metabolite acetaldehyde) is also known inhibitor of these vital folate reactions. So in these borderline cases of aspartame sensitivity, alcohol consumption may be a prime factor explaining any increased sensitivity to aspartame as well. Realize ethanol, not methanol, is the cause of fetal alcohol syndrome, and ethanol is a documented factor in facilitating many cancer types, for example - and -

    Critics suggest aspartame causes about every ill effect known to man claiming some 92+ symptoms. Analysis of these, however, directly links all of these issues to the above described personal issues. In what I have written above I note that various folate, B12 and related issues better explain any problems with aspartame. This year’s Norwegian autism study, - - only confirms the current importance of the deficiency issue, but those results may also reflect the fact that most of Europe still has not mandated folate fortification. But this isn't particularly surprising both in view of methanol's requirement for folate for metabolism, but also because folate uptake into brain has been linked to childhood autism. -

    Consider aspartame’s most widely reported issue, migraine headaches. Migraines have been linked directly to the MTHFR C677T folate polymorphism - and - Both papers report complete resolution of these migraines with added folate alone. These investigations revealed that more than the normal daily recommended amounts are needed (2-5 mg), but in these papers increased folate doses ALONE solved the migraine problem [and aspartame was not even involved]. That alone suggests a human sub-population that is even more deficient in folate for which resolution of their symptoms requires even more folate. And that is confirmed by science; up to 40% of some populations have these genetic folate polymorphisms that require even more folate, but most don't even know it. For more -

    John E. Garst, Ph.D. (Medicinal Chemistry, Pharmacology, Toxicology, and Nutrition)

  3. Gravatar for Barbara .

    Aspartame is not safe! Anyone who says it is either needs to learn the truth or admit they are paid by someone. It gives me classic optic migraines. It gave my daughter seizures and she started going blind. She was admitted to a hospital in Boston for 3 days and carefully checked out. She was told to stop the aspartame and, of course, her problems vanished! I have studied it for 25 years and I know thousands of people made ill. Many brilliant, honest doctors also know and warn their patients never to use it.

  4. Gravatar for Greg Webb

    Dr. Garst,

    Thank you for that response, some of which was very technical. I would certainly hope that Aspartame is safe, at least at the levels that most folks would consume it. Almost anything can be harmful if consumed in large quantities - even water. I could not begin to tell you how much Aspartame I have consumed in diet sodas and "Equal" - those blue, artifical sweetener packets - that I put in unsweetened iced tea. My family also likes diet sodas. So far, we have no negative side-effects of which I am aware.

    Dr. Garst, in response to Barbara, the lady who has commented to this blog about Aspartame being unsafe, can you state what your background is? Are you employed or paid by any companies that have a financial interest in showing that Aspartame is safe?

    Greg Webb

  5. Gravatar for John E. Garst, Ph.D.
    John E. Garst, Ph.D.

    Regarding Sweetman's SourceWatch long outdated weblink arguments - - people really need to recognize the ridiculousness of these Rumsfeld-FDA approval arguments. Those arguments were made over 20 years ago. Folate deficiency was a widespread, yet little recognized issue at the time of aspartame approval. All of the early approval concerns raised were based on data from rats that are now understood to have been folate deficient--none could be repeated with more modern corn-based folate, adequate diets. FYI, the widespread folate deficiency problem also caused spina bifida and other birth defects in offspring of deficient mothers. That is what prompted the US, Chile, and Canada regulators to mandate the supplementation of grain products with folate. But that did not occur until 1998, more than a decade after aspartame approval. And this folate insufficiency issue is still inadequately recognized. Australia/New Zealand started fortification recently - But much of the world still hasn’t done this. It has been raised as an issue in the UK, -, but I don’t know that outcome. Still much of Europe still has not dealt with the issue. This year’s Norwegian autism study - - confirms the widespread deficiency in Norway. Check out these two free 2008 full text papers from the Canadian Family Physician about this matter - ( and ( Also please examine this US list of 909 citations - ( or this UK list of 221 citations - (

    To document the fallacy of Sweetman's weblink, I will choose just four ‘diseases’ as teaching examples (taken from Monte’s ridiculous Amazon book ‘While Science Sleeps’): heart disease, multiple sclerosis, autoimmune diseases, and autism. Go to the National Library of Medicine website - ( Then enter the searches below to find these results heart disease first (these numbers were gathered several months ago so current numbers might differ): heart disease, folate (1405 citations); heart disease, folate deficiency (252), heart disease, homocysteine (2364); heart disease, vitamin B12 (691); heart disease, folate polymorphisms (171) [this topic exists for each issue, but is typically smaller, so is not enumerated further]. Repeat this process for multiple sclerosis and find the following numbers, folate (48); folate deficiency (20); homocysteine (41); vitamin B12 (134). FYI, multiple sclerosis fits with B12 far better than anything else. B12 deficiency is most often linked to vegetarianism and that must make one wonder about that a vegetarianism connection to multiple sclerosis. Repeat this process again for autoimmune diseases like lupus, for example: folate (84); folate deficiency (21); homocysteine (157), and vitamin B12 (53). Lastly, let’s examine autism: folate (71), folate deficiency (10), homocysteine (22), and vitamin B12 (19). Note that these numbers were obtained before the recent JAMA Norwegian study that directly and solidly linked folate deficiency to autism - (

    This analysis can be successfully done for every issue raised in the Sweetman post - ( Hence all of this SourceWatch post is completely rejected by current science. No wonder 90+ regulatory agencies around the world agree that aspartame is perfectly safe used as directed in healthy people.

  6. Gravatar for Barbara .

    The only reason that aspartame is considered safe is that the modern Golden Rule is: He who hath the gold makes the rules!

    Drink all the diet soda you want, but when you are sick, you will know why. I can't waste my time with the truth.

  7. Gravatar for PCL

    I've never been bothered by the symptoms from the Aspartame contained in diet cola. But I tried it once or twice in coffee and found my body's reaction a little shocking; I couldn't concentrate on anything I was doing, and, for a short time, became totally unfit to drive. I know that by the time Aspartame-sweetened drinks have been hot for a while, the stuff has already begun to break down, eventually loosing all of its sweet taste. So, what you are drinking has a full dose of the decomposition products from Aspartame, rather than the gradual intake you would get when it decomposes slowly in your digestive tract ("the dose makes the poison"). For this reason, I'd strongly suggest avoiding Aspartame in anything hot, never using it for cooking and never leaving Aspartame-flavored diet drinks at room temperature for extended periods of time. These drinks go bad even in a sealed bottle, so watch the expiration dates when shopping for them, refrigerate them ASAP and don't hoard them. Observing these precautions, I've been able to consume diet drinks without any noticeable symptoms. I can't say the same for the Splenda/Ascuflame combination in some of the newer diet drink brands; something in those drinks gives me an achey, flue-like feeling for a few hours after consuming them. I wish someone would (re?)introduce diet drinks using calcium-saccarine; it seems like the safest artificial sweetener and doesn't have the strong aftertaste people remember from the old sodium-saccharine sweetened colas like 1970s-era Tab.

  8. Gravatar for Dqavid

    --This is the source you reference to back up your assertion that Aspartame is harmful?

    Dr. Mercola has been the subject of criticism from the business, medical and scientific communities. A 2006 BusinessWeek editorial criticized Mercola's marketing practices as "relying on slick promotion, clever use of information, and scare tactics.” In 2005, 2006, and 2011 the U.S. Food and Drug Administration warned Mercola and his company to stop making illegal claims regarding his products' ability to detect, prevent and treat disease. The medical watchdog site Quackwatch has criticized Mercola for making "unsubstantiated claims and clash with those of leading medical and public health organizations [and making] many unsubstantiated recommendations for dietary supplements."

    --How much research have you done on this subject?

    The data from the extensive investigations into the possibility of neurotoxic effects of aspartame, in general, do not support the hypothesis that aspartame in the human diet will affect nervous system function, learning or behavior. Epidemiological studies on aspartame include several case-control studies and one well-conducted prospective epidemiological study with a large cohort, in which the consumption of aspartame was measured. The studies provide no evidence to support an association between aspartame and cancer in any tissue. The weight of existing evidence is that aspartame is safe at current levels of consumption as a nonnutritive sweetener.

    However, there is no scientific evidence of any significant adverse affects from aspartame when it is consumed at sensible levels. Even with high doses, the metabolites of this sweetener do not accumulate in toxic amounts. If you need or wish to limit your intake of sugars, and/or reduce your energy intake, there are clear benefits in consuming foods sweetened with aspartame or other artificial sweeteners. Aspartame is well tolerated by healthy adults and children.

    There have been a number of misleading or unsubstantiated claims suggesting adverse human health effects from aspartame. These include possible toxicity from methanol; elevated blood levels of aspartic acid and phenylalanine; affects on nerves and the brain and a claimed link with epilepsy and brain tumours.

    Over 20 years have elapsed since aspartame was approved by regulatory agencies as a sweetener and flavor enhancer. The safety of aspartame and its metabolic constituents was established through extensive toxicology studies in laboratory animals, using much greater doses than people could possibly consume. Its safety was further confirmed through studies in several human subpopulations, including healthy infants, children, adolescents, and adults; obese individuals; diabetics; lactating women; and individuals heterozygous (PKUH) for the genetic disease phenylketonuria (PKU) who have a decreased ability to metabolize the essential amino acid, phenylalanine. Several scientific issues continued to be raised after approval, largely as a concern for theoretical toxicity from its metabolic components—the amino acids, aspartate and phenylalanine, and methanol—even though dietary exposure to these components is much greater than from aspartame. Nonetheless, additional research, including evaluations of possible associations between aspartame and headaches, seizures, behavior, cognition, and mood as well as allergic-type reactions and use by potentially sensitive subpopulations, has continued after approval. These findings are reviewed here. The safety testing of aspartame has gone well beyond that required to evaluate the safety of a food additive. When all the research on aspartame, including evaluations in both the premarketing and postmarketing periods, is examined as a whole, it is clear that aspartame is safe, and there are no unresolved questions regarding its safety under conditions of intended use.

    Each of the areas considered, including exposure data, brain function, satiation and appetite, allergenicity and immunotoxicity, metabolic aspects and diabetes, carcinogenicity (including cancer epidemiology) and genotoxicity were considered by the Organizing Team and reported on.

    Overall, the Organizing Team did not identify any major gaps in information on aspartame and the National Experts agreed with their view.

    In conclusion, the National Experts have not identified any new evidence that requires a recommendation to EFSA that the previous Opinions of EFSA and the SCF need to be reconsidered.

  9. Gravatar for Barbara

    I have spent more than 25 years leaning about the dangers of aspartame. I have spoken to brilliant doctors around the world.

    The day will come when people who drink it will realize how sick it makes them.

  10. Gravatar for Dqavid


    Would you care to share your sources of information with us?

    Does your research include the studies I have included?

    Do you believe that the majority of the world’s governmental regulatory agencies are in collusion with industry poison the public?

    Scientific advisory bodies such as the Scientific Committee for Food of the European Community, and the Joint Expert Committee on Food Additives (JECFA) of the United Nations Food and Agriculture Organization and World Health Organization have reviewed all the available safety studies and have found aspartame to be safe.

    More than ninety countries world-wide, including the United States, countries of the European Union, and Australia and New Zealand, have also reviewed aspartame and found it to be safe for human consumption and allow its use in various foods.

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