Fact-checked & edited by Dr. Helen Okoye, MD, MBA, MS-Epi
Aspartame is one of the most controversial compounds in modern nutrition.
It is/was a common sweetener in many drinks, but has received massive backlash because many people believe that it causes cancer or a host of other chronic diseases. There’s a lot of discussion here, but all you need to know for now is that the discussion is a mess.
One side is shouting that aspartame causes cancer while others are shouting back that it doesn’t. For a relatively tame discussion of nutritional science, it’s picked up a lot of traction as many are linking it to corporate evils and the like.
We don’t care about that: today we’re going to discuss the science and practical facts about aspartame.
Aspartame is a very strong sweetener – often used in diet sodas to replace sugar. It doesn’t contain any calories and doesn’t provide the same insulin spike that you see with sugar. This means that it protects from a variety of the most common problems associated with sugar such as pronounced dental damage, higher calorie intakes and the possibility of insulin resistance.
It’s actually sweeter than sugars in many contexts and, for this reason, has been used to deal with the sweet cravings that many of us experience. It is also used as a common intervention for reducing liquid calories in many diets. This is an important piece of context that we’ll mention later.
All you need to know for now is that this compound is a non-nutritive sweetener. It has no sugar or other digestible, caloric ingredients. It simply doesn’t provide energy, so it can’t be converted into fat and, while it may provoke an insulin response, it’s not comparable to sugar.
The first argument against aspartame is rather extreme: it suggests that aspartame causes cancer.
Despite being part of a 21st-century obsession with cancer-risk scaremongering, we can’t dismiss this type of accusation. If there is a real link between aspartame and cancer risk then it makes total sense to cut it out of your diet entirely and focus on improving those health markers.
However, there’s yet to be any reliable, controlled studies discussing mechanical links between aspartame and cancer risk. There are some reasons to be concerned about the associations that NNS have, but cancer is hyperbolic: there’s no reliable evidence of any causal mechanism. This is the type of claim that has no ground and makes criticisms look like conspiracy theories.
Associative studies have suggested that there may be a link between aspartame intake and the incidence of metabolic syndromes like diabetes. This has been noted in meta-analyses that deal with the correlation between the two.
While this does provide some cause for concern, it deals with the association of groups who have one particular behavior with another group-outcome. In this case, it was the top quintile on diet sodas who experienced the highest quintile of cancer risk and outcomes.
Does this provide us with evidence that aspartame is going to cause diabetes and other such problems? No. Simply put, this misses out on things like dietary quality and habits that are a key player in both diet soda intake and metabolic syndromes.
These problems are caused by a uniting principle, rather than causing one another. For example, individuals who don’t consume diet sodas are more likely to consume water and have generally-healthier lifestyles, reducing cancer risk through independent mechanisms. This shows how the two behaviors can be associated without suggesting that aspartame is going to cause metabolic problems[1,2,3].
There is some suggestion in the research that sweetness needs to be associated with sugar or, counter-intuitively, there will be an increased intake of food.
The suggestion is that, when we decouple sweetness from caloric intake, the body stops providing satiety during these circumstances and the sweetness craving doesn’t go away. This leads to long-term calorie intake increases and, accordingly, obesity and diabetes risk factors[4,5].
This is combined with the fact that, despite containing no sugar, the body does have an insulin response to these drinks. It’s easy to see how these combine to cause problems: if you’re getting more hungry, you could be relying on more diet sodas, beginning an upward spiral of insulin response and dependency.
In this situation, it seems that we can look at three confounding factors that are more important than aspartame intake for the role it has in metabolic syndromes:
Does this mean that there are no problems with aspartame? No. It means that we can’t say for certain until we have better evidence between the two. We’re in a space where it’s clearly better to choose water over diet sodas, but diet sodas may have some benefits.
So, in light of what we’ve said, should you be concerned with aspartame? What benefits could it possibly cause?
To make sense of aspartame and how it should work in your life, it’s important to remember that it is used to reduce obesity and other serious concerns. Consider that obesity is associated with a variety of morbidities – including 9 of the top-10 natural causes of death.
In light of this, it’s a bit of a balancing act: is aspartame dangerous if it helps someone drop their body fat from 40% to 25%? The obvious answer is no – it’s a much better alternative to morbid obesity and the countless co-morbidities that are killing millions of people in the English-speaking world every year.
When we compare the two, it seems obvious why aspartame has been used. Even studies discussing its effect on satiety note that it seems to have positive effects in the obese and that its use should be reserved for cases where the risk of sugar is greater than the risk of aspartame-related metabolic effects.
After all, we know very well that the effects of uncontrolled sugar intake is a huge problem. We support well-moderated and well-timed sugar intake, but there’s no argument with the fact that too much sugar is a huge problem. Compare this to the possible negative effects of aspartame and it's clear which one is going to be a bigger gamble with your own health.
This only scales with intake. For example, the risks of consuming 3 full-sugar sodas a day (somewhere in the triple digits of sugar intake) is much more dangerous than 3 diet sodas. We see that the need for moderation in traditional sugary drinks is a matter of damage to the heart and metabolism in a way that diet drinks simply are not.
Overall, we’re not massive fans of aspartame in particular. It’s an out-dated sweetener and the skepticism surrounding it has been resolved by soda companies largely replacing it since 2002. Clearly, the whiff of a carcinogenic ingredient is a PR disaster, so that change was rapid.
With that being said, Aspartame is not per se dangerous. It can have problems when consumed in large amounts, but we tend to find that the association between NSS and health problems happens at the very end of the normal distribution: those who consume ridiculous amounts of diet soda during the day.
We’ve seen the same problem with Erythritol and similar sweeteners, that require 10+ drinks to cause significant problems. This is a totally different compound, but we’ve seen how these can skew associative studies by including anomalous results without controlling for astronomical intake. (as a brief aside, we also see this problem in discussions on gluten, which is also not a health concern in healthy people)
Obviously, we’re not pushing for you to consume more aspartame. The best alternative is to cut diet sodas all together and use a fruit-infused water, tea, or similar nutrient-dense calorie-free drink. However, it’s also important to cut through the hype and scaremongering around Aspartame.
Ironically, the same advice applies to diet sodas as their full-sugar counterpart: enjoy them in moderation and where they are better than the alternative. If you have to choose between a sugary soda with 50g of sugar or a diet soda with a small amount of artificial sweetener, the latter is probably the better choice. The same applies to morbid obesity (the clue’s in the name).
Just don’t drink 10 cans a day – that’s going to cause problems.
 Colagiuri, Stephen, John J. Miller, and Ronald A. Edwards. “Metabolic effects of adding sucrose and aspartame to the diet of subjects with noninsulin-dependent diabetes mellitus.” The American journal of clinical nutrition 50.3 (1989): 474-478.
 Okuno, Giichi, et al. “Glucose tolerance, blood lipid, insulin and glucagon concentration after single or continuous administration of aspartame in diabetics.” Diabetes research and clinical practice 2.1 (1986): 23-27.
 Stern, Sol B., et al. “Administration of aspartame in non‐insulin‐dependent diabetics.” Journal of Toxicology and Environmental Health, Part A Current Issues 2.2 (1976): 429-439.
 Blundell, J. E., and A. J. Hill. “Paradoxical effects of an intense sweetener (aspartame) on appetite.” The Lancet (USA)(1986).
Tordoff, Michael G., and Annette M. Alleva. “Effect of drinking soda sweetened with aspartame or high-fructose corn syrup on food intake and body weight.” The American journal of clinical nutrition 51.6 (1990): 963-969.
 Wurtman, Richard J. “Neurochemical changes following high-dose aspartame with dietary carbohydrates.” New England Journal of Medicine (USA) (1983).
 Gardner, Christopher. “Non-nutritive sweeteners: evidence for benefit vs. risk.” Current opinion in lipidology 25.1 (2014): 80-84.
Hu, Frank B. “Resolved: there is sufficient scientific evidence that decreasing sugar‐sweetened beverage consumption will reduce the prevalence of obesity and obesity‐related diseases.” Obesity reviews 14.8 (2013): 606-619.
Amanda is a gym instructor and a diet and nutrition fanatic that has reviewed 100s of supplements for the benefit of consumers. She struggled with obesity 7 years ago and after losing more than 30lbs, dedicates most of her time in helping others achieve similar results and transform their lives.