Aspartame linked with cancer in humans

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I, for a long time, have been suspicious of artificial sweeteners. At least some of my scepticism has been focused on the sweetening agent aspartame (Nutrasweet, Candarel, Equal). While studies with industry funding give aspartame a clean bill of health, independently-funded work generally does not. And we know that the constituents of aspartame (aspartic acid, phenylalanine and methanol) have the potential to affect the body and brain adversely. See this blog post on a review of the potential hazards of aspartame.

Recently, another concerning independently-funded piece of research concerning aspartame was published. It looked, amongst other things, at the association between diet-soda consumption and risk of cancer of the lymph system (non-Hodgkin lymphoma), leukaemia and another form of blood cancer known as multiple myeloma, in adults over a 22-year period [1]. Studies of this nature are referred to as ‘epidemiological’ studies and are prone to ‘confounding’. For example, individuals carrying excess weight may be at increased risk of blood cancers because of this, but might also be more likely to drink diet soda. In this case, an association between diet soda and blood cancer may not be due to the diet soda, but because diet soda drinkers tend to be heavier. In this study, though, confounding factors were taken into consideration and ‘controlled for’.

In short, the results of this study showed that:

  • In women, diet soda consumption was not associated with the risk of an increased risk of either non-Hodgkin lymphoma or multiple myeloma.
  • In men, drinking one or more serving of diet soda per day was associated with a 31 per cent increased risk of non-Hodgkin lymphoma (compared to lower intakes).
  • In men, drinking one or more serving of diet soda per day was associated with a more than doubling of risk of multiple myeloma (compared to lower intakes).
  • In men and women combined, drinking one or more serving of diet soda each day was associated with a 42 per cent increased risk of leukaemia (compared to lower intakes).
  • Positive associations also existed between intakes of aspartame specifically and non-Hodgkin lymphoma and multiple myeloma.

Now, epidemiological evidence of this nature cannot be used to suggest that aspartame causes these conditions. However, this evidence is suspicious when it is known that aspartame has been found to cause lymphoma and leukaemia when administered to rats in the long term in doses that equate to what would be regarded as acceptable in humans (doses as low as 20 mg per kg of body weight) [2].

If aspartame does cause cancer, how might it do it? Well, one constituent of aspartame is methanol (‘wood alcohol’ and the primary constituent in methylated spirits) which in the body can be converted into formaldehyde. Formaldehyde is what’s used to preserve dead bodies but it’s also a known cancer-causing agent.

This potential mechanism might also help explain why increased risk of cancer was seen in men and not women. There’s an enzyme known as ‘alcohol dehydrogenase type 1’ which speeds the conversion of methanol into carcinogenic formaldehyde. Alcohol dehydrogenase type 1 activity tends to be higher in men than in women. Alcohol consumption inhibits this enzyme, and it’s interesting to note that in the most recent study the men at most risk appeared to be those who drank the least alcohol.

This, for me, is not necessarily a good reason to throw a whiskey in one’s diet coke. This study is, I think, another piece of evidence that points to aspartame having toxic potential and something best avoided.


1. Schernhammer ES, et al. Consumption of artificial sweetener– and sugar-containing soda and risk of lymphoma and leukemia in men and women. Am J Clin Nutr 2012;96:1419–28.

2. Soffritti M, et al. First experimental demonstration of the multipotential carcinogenic effects of aspartame administered in the feed to Sprague-Dawley rats. Environ Health Perspect 2006;114:379–85

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