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Does the artificial sweetener aspartame cause cancer?

According to WhileScienceSleeps:

The methanol contained in the diet soda produced in many countries of the world is dangerous. It comes from the artificial sweetener Aspartame. There is no safe level of consumption of methanol as there are with other less poisonous substances that can occasionally find their way into our foods.

Methanol is particularly dangerous to humans, more so than any other animal. When humans consume low doses of methanol it is metabolized directly into formaldehyde which is a cancer producing agent of the same level of danger as asbestos and plutonium. This conversion does not all happen in the Liver, a common misconception, but also in the brain and a woman’s breast. It is my belief that diet soda has contributed to the rise of breast cancer and multiple sclerosis that has been preceded by the use of Aspartame as a food ingredient in every country that has allowed its use.

I've heard this from other sources I cannot locate right now. What's the truth?

  • We've addressed this in the linked question (and more in general many times over).
    – Sklivvz
    Commented Oct 4, 2012 at 6:59
  • I apologize. I actually did a search before I submitted the question, but I just realized that I had misspelled aspartame as "aspartime" which found no answers. I corrected the spelling of my question at the last minute. However, I do appreciate the answer this question received - it added to my understanding beyond the other answers to the linked question. @tor-einor-jarnbjo, I suggest you move your answer to the linked question...
    – FrankH
    Commented Oct 4, 2012 at 12:32

1 Answer 1


First of all, it is true that aspartame decomposes to aspartic acid (~50%), phenylalanine (~40%) and methanol (~10%) when exposed to heat or in very acidic or alkaline environments and that methanol and formaldehyde are (can be) toxic. Comparing formaldehyde with asbestos and plutonium is very misleading. Smaller amounts of formaldehyde is both produced and required by the human body itself and ingested formaldehyde is rapidly metabolized. Asbestos and plutonium is accumulated in the body and can reach toxic levels after prolonged exposure.

A can of diet soda contains up to a few 100 mg of aspartame, e.g. a 355 ml can of Diet Coke contains 131 mg. If all the aspartame is decomposed, you will be exposed to about 13 mg (10%) of methanol by drinking such a can of Diet Coke. Most kinds of fruits and vegetables have a natural methanol content as well. Since pectin easily decomposes to methanol, eating fruit with high pectin levels exposes you to much higher amounts of methanol than drinking diet soda. Eating one kg of apples, will for example release up to 500mg of methanol in the digestive tract. I agree that one kg of apples is unusually much to eat at once, but comparing it with the 40 cans of Diet Coke required to ingest the same amount of methanol, there are obviously other things to worry more about than aspartame.

Is aspartame dangerous? I honestly can't answer that, but the amount of methanol you can be exposed to by eating or drinking "normal" amounts of food or beverages sweetened with aspartame is most likely not.

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