Can aspartame cause muscle pain?

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I’m no fan of the artificial sweetener aspartame. Not only is there no good evidence that artificial sweeteners aid weight control, there is also evidence linking aspartame to adverse effects on health. For example, aspartame liberates methanol into the body which can be converted to formaldehyde (used to preserve dead bodies), which has recently been added to the official ‘cancer-causing’ list of chemicals in the US. Animal work shows that aspartame at permitted levels increases the risk of several types of cancer.

I recently came across a piece in a rheumatology journal which describes what appears to be aspartame’s ability to induce fibromyalgia. This condition is characterised by pain and tenderness in the muscles. The paper describes two ‘case studies’ in whom fibromyalgia appears to be caused by ingestion of aspartame.

The first of these concerns a 50-year-old woman who symptoms of fibromyalgia (more than 10 years standing) evaporated on holiday when not consuming aspartame. The symptoms returned when she came home and resumed aspartame use, but resolved again once the aspartame was stopped once more.

I have twice been told by individuals with fibromyalgia that their symptoms have resolved when on holiday. The first thing I think about here is sunshine and vitamin D, because vitamin D deficiency can cause muscle pain, and boosting vitamin D does seem to have the capacity to resolve this symptom. See here and here for some relevant blog posts about this.

It is possible that in this woman’s case, sunlight and other factors had something to do with the resolution of her symptoms while abroad. However, the fact that her symptoms resolved on exclusion of aspartame strongly suggests this substance was the primary cause of her symptoms.

The second case described in the article was a 43-year-old man who had suffered with pain in his neck, forearms, wrists and hands for 3 years. Removing aspartame from his diet resolved his symptoms.

Case studies such as these don’t prove that these individuals’ symptoms were due to aspartame – it is possible that their improvement was due to the placebo response and the recurrence of symptoms due to what is called the ‘nocebo’ response (like the placebo response, but when the response is negative rather than positive). However, observations such as these can be the start of advancement in our understanding of the effect of treatments and, in my view, should not be dismissed.

Certainly, should I see an individual suffering from generalised pain and fibromyalgia in the future, I’ll be making doubly sure I ask about their consumption of aspartame, and will be advising them to stop it as a matter of course. Bearing in mind the fact that there is no good evidence that aspartame has benefits for health, such individuals will have nothing to lose by eliminating it, other than perhaps their ‘unexplained’ symptoms.


1. Ciappuccini R, et al. Aspartame-induced fibromyalgia, an unusual but curable cause of chronic pain. Clinical and Experimental Rheumatology 2010;28(63):S131-133

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