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Does aspartame cause cancer? Do you eat a pound of aspartame per day?

20 August 2011

Caitlin Bigelow of San Diego, CA writes:

My mom and I have had a few heated discussions on the health effects of diet soda. It came up yesterday when she purchased enough diet soda to drown a small child. I’m curious, do artificial sweeteners like sodium cyclamate and aspartame cause cancer? And if so in what quantities would you need to consume them for it to be a factor?

Cheers, Caitlin

Hi Caitlin,

Because sodium cyclamate is banned in the US (a controversial topic in itself) I will chose to discuss Aspartame for this article.

Aspartame is an artificial sweetener first synthesized in 1965 and approved by the FDA in 1974. It is ubiquitous in its use as a food sweetener in the US.

There are many reviews of scientific literature that suggest that aspartame probably does not cause cancer, and it is the current opinion of the FDA that it is safe (1).

Correlation and Causation:

A recurring theme in this blog is the distinction of correlation and causation. A correlation study would be one where the amount of aspartame consumed by individuals in a group was followed for some length of time, and their cancer rates recorded. Established statistical methods and universally accepted (yet arbitrary… but that is a topic for another time) thresholds are used to establish correlation. An example of this would be this one from 2007 in Italy of over 7,000 cancer patients and 7,000 matched controls (2). Although some ways of chopping up the data might indicate an association for a few types of cancer, the overall result appears to suggest no consistent association between aspartame consumption and cancer incidence.

An example of a causation study would be experimental in nature. Say, one was to feed mice aspartame (or not) for their lifetime and detect their cancer rates at a certain time point.

Actually, that is exactly what a group from Milan, Italy did in 2010 (3). The group found roughly a 20% increase in the rate of liver and lung cancers in mice fed the equivalent of 3900 mg/kg of body weight per day. Pound per pound, corrected for the faster metabolism of rodents, that amount is about the equivalent of 2/3 of a pound of aspartame for an 150lb human per day. A 12oz can of aspartame-sweetened soda often contains 0.0004 pounds of aspartame.

There are also numerous studies that report no such induction of tumors in a high aspartame diet (4).

Under extreme conditions aspartame might help promote cancer. Consumption in ranges that more accurately mirror dietary habits of humans do not see any measurable effect. Studies do not show any trends affecting the cancer rates in humans.

Ryon’s verdict: Based off of available epidemiological data and experimental models, aspartame appears to not cause cancer in humans.

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