A link came around tonight on my Facebook feed about aspartame: “Aspartame is linked to Leukemia and Lymphoma in new Landmark Study on Humans” (http://worldtruth.tv/aspartame-is-linked-to-leukemia-and-lymphoma-in-new-landmark-study-on-humans/)

I’ve seen these sorts of articles come around on social media before, usually in the form of an alternative health website hysterically exaggerating an irrelevant or pseudoscientific study, trying to prove some point about the evils of western medicine or society, or get more internet traffic through sensationalist click-bait.

And I’d heard the whole aspartame-causes-cancer thing before. I’d heard that there was maybe some evidence in animal studies, but that there was no definitive link in humans.

So just from the title, before I’d even read the article, my sceptical mind was primed to expect the opposite of the articles eye-catching headline.  I started searching the literature to see if there was any evidence to prove me right.

The first research article I came across that wasn’t on rats was from the American Journal of Clinical Nutrition in 2012, “Consumption of artificial sweetener – and sugar-containing soda and risk of lymphoma and leukemia in men and women” [1]. It was an impressive study in terms of its numbers and its quality. It was drawn from the data of the Nurses Health Study and the Health Professionals Follow-Up Study, which were both prospective studies (which follow a large number of subjects over a long time to see who gets the disease in question, rather than starting with who has the disease in question and trying to work backwards trying to ascertain causes, which is much less reliable). Both studies also had a large number of subjects which increased their statistical power, and made their findings more robust.

The results didn’t look very good for aspartame. There was a clear-cut increase in the risk of Non-Hodgkins Lymphoma for men who consumed two or more serves per day of diet drinks containing aspartame (Relative Risk: 1.69; 95% Confidence Interval: 1.17, 2.45; P-trend = 0.02) and Multiple Myeloma for men who consumed one or more serve per day of diet drinks containing aspartame (RR: 2.02; 95% CI: 1.20, 3.40). However, there was no change in the risks for women who consumed aspartame.

The results certainly caught me a little off guard. Perhaps there was some truth to the alternative website’s assertions after all. Interestingly enough, the study that the worldtruth.tv site reviewed was the same article I’d found. I was guilty of making a snap judgement, and I had to remind myself not to always jump to conclusions.

Still, even though the article wasn’t sensationalist click-bait, some unanswered questions remained. Why was the risk only found in men? Was there a real association, and if so, why the difference. Should we extrapolate this finding like worldtruth.tv did and justifiably ask “will future, high-quality studies uncover links to the other cancers in which aspartame has been implicated (brain, breast, prostate, etc.)?”

In terms of the gender difference, the authors of the original study did have a theory: “We hypothesized that the sex differences we observed may have been due to the recognized higher enzymatic activity of alcohol dehydrogenase type I (ADH) in men, which possibly induced higher conversion rates from methanol to the carcinogenic substrate formaldehyde.” In support of this theory, they looked at the risk of leukaemia and lymphoma in those aspartame users who were drinkers vs the aspartame users who weren’t. Ethanol stops the metabolic conversion of aspartame to formaldehyde, so if their theory was on the right track, those aspartame users who also drank alcohol would have a lower risk. As it turns out, their data was supportive, with aspartame non-drinkers having an increased risk for Non-Hodgkins Lymphoma (RR: 2.34; 95% CI: 1.46, 3.76; P-trend = 0.004) compared with aspartame users who also drank (RR: 0.96; 95% CI: 0.48, 1.90; P-trend = 0.99) [1].

However, despite the findings of Schernhammer et al, a more recent large prospective trial published in the Journal of Nutrition last year found there was no association between soft-drinks of any variety and blood cancers, including those containing aspartame [2].

So the jury is still out on aspartame. Based on what we currently know, if you’re a woman, then there’s no risk of developing leukaemia or lymphoma from drinking diet drinks. If you’re a man, there’s also probably no risk, but a glass or two of alcohol a day would probably make sure of that. Although the best advice is probably to not bother drinking diet drinks at all. The best diet drink is still plain old water, which has virtually no associated risks, is much cheaper, and probably tastes a whole lot better.

References

1. Schernhammer, E.S., 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(6): 1419-28 doi: 10.3945/ajcn.111.030833
2. McCullough, M.L., et al., Artificially and sugar-sweetened carbonated beverage consumption is not associated with risk of lymphoid neoplasms in older men and women. J Nutr, 2014. 144(12): 2041-9 doi: 10.3945/jn.114.197475