As someone whose first choice in the beverages aisle of the supermarket is Diet Coke, I’ve heard a multitude of reasons offered to me as to why I should swear off my fizzy and extremely gratifyingly caffeinated, calorie-free aspartame-enriched drink: it’s giving me cancer. No, wait, it’s making me gain weight. On second thought: scratch that — it’s giving me Parkinson’s!
Being such a sweet little thing itself (come on, it’s practically sugar but contains zero calories — what more can you ask for?), how did aspartame attract its not-so-sweet reputation?
Aspartame is a non-nutritive sweetener (sold under brand names such as NutraSweet® and Equal®) which is nearly 200 times sweeter than sugar. This explains why so much less of it needs to used in order to achieve the same level of sweetness, rendering it virtually calories-free.
Chemists first synthesised aspartame in 1965 through joining phenylalanine and aspartic acid together. It was later approved by the FDA in 1974 in light of a large amount of evidence — from labs and clinics in the US, in addition to more than 90 other countries around the world — that demonstrated its safety for human consumption.
Aspartame causes cancer, right?
Ever since the FDA’s approval in 1974, aspartame’s history has been littered with scientific, political and even legal warfare: just Google the term “Donald Rumsfeld and aspartame” and you’ll be greeted with a bunch of conspiracy theories you can read up on in your free time.
Rumours and concerns about aspartame causing a number of health problems — with cancer being one of the top most cited issues — have been around for many years. Why? Well, quite possibly due to a few studies on rodents, which have found that exposure to aspartame is associated with various cancers in rats and mice.
Clear evidence of an association with cancer in humans have never been demonstrated in human carcinogenicity studies.
The last I checked, we are not rodents — while we do share some metabolic similarities with rats and mice, we have to take note that between us, we have countless differences too. Mechanisms that our bodies employ to process methanol — a byproduct of aspartame — are quite different from those in rodents. With this difference in mind, the applicability of aspartame testing results in rodent models to humans is honestly questionable.
Come on, isn’t aspartame toxic?
It’s a commonly held belief that toxicity is a black and white concept — that some substances are toxic, while others are not. Spoiler alert: not true! Every substance is toxic, even water! Yes, you can get poisoned by the glass of ordinary-looking water sitting on your desk right now.
Water intoxication, or water poisoning, is a potentially fatal disturbance in brain functions that results when the normal balance of electrolytes in the body is pushed outside safe limits by excessive water intake. It’s important to take note of the keyword here: excessive.
When we term a substance as harmful, or toxic, we’re simply talking about the fact that the dose of this substance, at which side-effects are experienced, isn’t much bigger than a normally-sized portion.
For example, a small amount of mercury can be very harmful, which is why it’s called toxic. However, you have to drink an absurd amount of water before you fall ill, which is why water is still classified to be safe.
The dose makes the poison.
So — how much aspartame can be consumed before it is potentially harmful? A can of diet soda typically contains 50–125 milligrams (mg) of aspartame. The Acceptable Daily Intake (ADI) of aspartame is 50 mg per kilogram of body weight per day.
If we take the highest aspartame content of 125 mg per can of Diet Coke, a 50 kg woman can consume 20 cans of Diet Coke without harmful effects!
Despite my ardent support for Diet Coke, there’s just absolutely no way I’m able to drink 20 cans of Diet Coke in one day.
Well, what about headaches?
One of the most common complaints about aspartame reported to the Center for Disease Control (CDC) are headaches. Specifically:
346 (67%) complainants reported neurological/behavioural symptoms, including headaches, dizziness, and mood alterations.
In an attempt to establish whether a difference exists between placebo and aspartame in regards to headaches, only one blinded study has been conducted in 1994. The researchers found that the self-proclaimed aspartame-sensitive subjects indeed reacted adversely to the aspartame. However, they also reacted just as adversely to the placebo.
The study was later critiqued as being riddled with errors due to its sampling and methodology. No further attempts to replicate the study’s results have been made thus far.
Due to the notoriety of aspartame, anxiety has also been theorised to be the cause of the “aspartame-induced headaches”. The CDC report notes that:
Overall, the 517 interviewed complainants were predominantly white (96%), female (76%), and between the ages of 21 and 60 years (79%). Complainants were approximately 1.5 times more likely to be female and 2.5 times more likely to be women between the ages of 20 and 59 than expected from 1980 census estimates. Reports came from all geographic regions of the country, with a heavy concentration of cases from Arizona, where the possibility of aspartame use leading to illness received particularly extensive press coverage.
The above excerpt highlighting the abnormal demographic dispersion suggests that unless there are genetic differences in Caucasian females from Arizona in comparison to the rest of the US, demographics and the media may play a part in explaining “aspartame-induced headaches”.
It turns out that there is not enough evidence to make a final conclusion either way — use your own judgement, as headaches are indeed something you are aware happens and can fortunately be easily avoided if caused by that can of Diet Coke.
So — Diet Coke, or no?
Look: nobody’s telling you to drink aspartame-enriched beverages all the time — it goes without saying (but I’m saying it anyway) that you should mainly be drinking water.
Just bear in mind that Diet Coke and other artificially sweetened beverages are not going to cause cancer, or poison you.
Like so many other things in life, moderation is key.
Ultimately, the current scientific literature available on aspartame points toward the fact that it’s safe for human consumption.
Will the FDA or other health organisations adjust their positions on the safe intake levels of aspartame in the future? It seems that only time and the march of research can determine that. For some people, peace of mind might be worth forgoing the pleasure of their favourite aspartame-sweetened diet drinks.
For those unwilling to do so, the weight of the human evidence and scientific literature is currently still in your favour. While caution and a healthy sense of skepticism are advised, it seems likely that we can have our (calories-free, sweetened) cake, and eat it too!
Thanks for reading! I have written plenty of articles on fitness and nutrition. If you’re interested, here’s one to get your started: weight loss tips that are actually backed by science.