Artificial Sweeteners - Aspartame

A few weeks back I had the privilege to go on a road trip to Batemans Bay with some of my friends. It was a wonderful break from work, and allowed me to catch up with friends that, due to distance and/or conflicting schedules, I may only see a couple of times per year.

One morning, we were having breakfast, in preparation for a big day. Sitting at a big table, we were eating, drinking and generally being merry. During breakfast, one of my friends leant over towards me and gestured towards the diet soda that I was drinking, and began the following exchange:

Friend: "Hey, you shouldn't drink that!"
Me: "Yeah, it is a bit early in the day for soft drink, but I don't feel like coffee or juice this morning..."
Friend: "No, you shouldn't drink that. Didn't you know that the fake sugar in that was banned in the UK? It causes cancer!"
Me: "Really? I'd wager that a company can't distribute a product with a known carcinogen, and not be the subject of a law suit."
Friend: "No, it's true! I read it somewhere..."

"I read it somewhere"... A line that always makes me cringe inwardly. Perhaps it is the scientist in me, but I do prefer a good reference as opposed to an anonymous source.

At any rate, just what was my friend referring to? The nods of assent he received from my other friends from around the dining table made it seem that this substance was well known. Well, it would appear that based on my choice of beverage that fateful morning, it seems likely he was referring to aspartame, an artificial sweetener used as a sugar substitute.

Oh how sweet it is... Approximately 200 times sweeter than sucrose, in fact!

So, why does the above molecule have such a bad reputation? Well, aspartame was discovered way back in 1965 by a chemist working for G.D. Searle & Company. Originally synthesised in order to produce a potential antiulcer drug, the sweetness of aspartame was discovered when a chemist licked his finger in order to pick up a piece of paper. Evidently this chemist was not wearing gloves at the time, as during the aforementioned synthesis, his finger had been contaminated by aspartame.

Shortly after approval by the Food and Drug Administration, a chain letter posted under the pseudonym of Nancy Markle, warning of the inherent risks posed by aspartame. The alleged dangers of aspartame included an increased incidence of multiple sclerosis and brain tumors, and a dire warning that when exposed to heat, that aspartame decomposes to produce methanol, and hence consumption of products containing aspartame could lead to methanol poisoning.

Indeed, there have been numerous claims regarding aspartame and its relative safety for human consumption. The safety of aspartame has been studied extensively, and has repeatedly been deemed safe for human consumption. Regarding intake and consumption, the FDA has set the acceptable daily intake (ADI) of aspartame at 50 mg/kg of body weight. To put this into perspective, a 350-375 mL diet soft drink may contain around 180 milligrams of aspartame. For a 75 kg individual, it would therefore take approximately 20 cans of diet soft drink to exceed the ADI of aspartame.

One of the other claims made against consumption of aspartame is that it breaks down in the body to form highly toxic compounds, including aspartic acid, phenylalanine and methanol.

•  Aspartic acid: One of the most commonly encountered amino acid in a regular diet. A rather fascinating clinical study by Magnuson et. al. (2007), however, found no evidence of neurotoxic effects derived from consumption of aspartic acid. 
• Phenylalanine: One of the essential amino acids, one is likely to consume far more phenylalanine during their regular diet than from diet soft drink. That being said, those with phenylketonuria are advised to abstain from food products that contain significant amounts of phenylalanine or aspartame. 
• Methanol: The metabolism of methanol to formaldehyde, and then formaldehyde to formic acid, is implicated as one of the dangers of aspartame use. It should be noted, however, that the amount of methanol absorbed by the body as a result of consuming aspartame-containing products, is less than what would be absorbed if one consumed various fruit juices or fermented beverages. Indeed, in the article by Magnuson et. al. (above), it was found that consuming the maximum expected amount of aspartame did not result in elevated blood levels of methanol, formaldehyde or formic acid.

As for claims regarding aspartame's alleged ability to cause brain cancer, no significant links have been found to date. One study by European Ramazzini Foundation of Oncology and Environmental Sciences (ERF) alleged that aspartame is a carcinogen at normal dietary doses. However, this study has been discredited, and in fact, the European Food Safety Authority evaluated this study back in 2010. This evaluation found that there were multiple significant design flaws in the study by the ERF, and that as such, there was insufficient evidence to suggest that the safety of aspartame needed to be reconsidered.

Claims have also been made that have alleged that consumption of aspartame may result in negative neurological and psychiatric symptoms, including seizures, headaches and mood swings. Lajtha et. al. (1993) found that with regards to the biochemistry of aspartame, there is no evidence that aspartame could conceivably lead to neurotoxic effects.

So there you have it. One artificial sweetener and a number of concerns. Though it would not surprise me that in the future the safety of aspartame will be reviewed once again, for the moment it is crucial to note that there is no evidence to suggest that the use of aspartame represents any real cause for concern.

Now where did I put that can of soda...?