Artificial Sweeteners are Bad for You

“Artificial sweeteners are bad for you.” That’s about all the general population has to say about the topic, and by golly, they will say it whenever given the opportunity. I can’t tell you the number of times someone has tried to come at my neck for drinking a diet soda. It’s quite fascinating to me that people who have no formal education in nutrition (and know my background), feel the need to “educate” me on the supposed dangers of artificial sweeteners. Well, this one’s for you guys. 

There was also a time in a sports nutrition class where we were analyzing an athlete’s diet and had to make modifications in order to “optimize” the individual’s food choices. One of the recommendations the class decided on was to swap out a can of diet coke for water, you know, because artificial sweeteners are bad. That ticked me off. The overall diet was a mess and as nutrition professionals in training, we are supposed to understand that changes take time. As such, you should attack the biggest issues first, rather than overwhelming the individual with every little thing they need to change, and we’re going to focus on a can of diet coke in the athlete’s diet? Give me a break. 

Anyway, let’s get into the weeds, and find out if artificial sweeteners are in fact the spawn of the devil. 

In this article, I want to discuss the safety of artificial sweeteners in relation to three specific categories: carcinogenicity, body weight, and the gut microbiome. So, this one is going to be thicc, but I suppose if you actually read my articles, you’re into that sort of thing.


Artificial sweeteners go by a variety of names including nonnutritive sweeteners, low-calorie sweeteners, and intense sweeteners. Artificial sweeteners replicate the effect of sugar in taste, but are on average 200x sweeter and provide little to no calories. There are currently six artificial sweeteners that the Food and Drug Administration (FDA) have approved for consumption: acesulfame-K, aspartame, neotame, saccharin, sucralose, and advantame (1).

For the purpose of this article, I’m going to focus on aspartame, sucralose, and saccharin.

Aspartame is a low-calorie sweetener which provides 4 kcal per gram (2). It provides little to no calories because it is about 200x sweeter than sugar so very little has to be used in products (2). It is unstable if subjected to prolonged heating and therefore cannot be used in baking or cooking (2). The acceptable daily intake (ADI) for Aspartame is 50 mg/kg body weight/day (1).

Sucralose overtook aspartame in 2008 to become the most popular sweetener in the United States (3). It is made from sucrose. This occurs by a process that substitutes 3 chloride atoms for 3 hydroxyl groups on the sucrose molecule (2). Though it is made from sugar, our bodies cannot metabolize sucralose, so it does not provide any calories. Sucralose is about 450-650 times sweeter than sucrose and is stable over a wide range of pH and temperatures (2). The ADI for sucralose is 5 mg/kg body weight/day (1). 

Finally (I’ll spare you the chemistry details, here), saccharin, the first artificial sweetener, was discovered by Remson and Fahlberg in 1878 at the John Hopkins University, Baltimore (2). The typical qualms with artificial sweeteners, such as the infamous “don’t you know they cause cancer?” stem from saccharin (more on this later). It is about 300 times sweeter than sucrose (2), and the ADI is 15 mg/kg body weight/day (1)

More Background: ADI

For the purpose of verifying the safety of artificial sweeteners, it is very important to understand how the ADI is determined. The ADI for a sweetener is determined by establishing the No Observed Adverse Effects Level (NOAEL), usually from a chronic animal study within rodents and then applying a default safety factor of 100 (4). What this means is that they take the highest amount of the artificial sweetener consumed (expressed as mg/kg body weight/day) which did not cause adverse effects in rodents and then decrease it by using a 100-fold factor to ensure the recommendation is completely safe for humans. For example, if safety evaluation of a given substance demonstrates a NOAEL of 1,000 mg/kg body weight/day, the ADI would be 10 mg/kg body weight/day (5).

A diet soda typically contains 50-125 mg of aspartame. The ADI for aspartame is set at 50mg/kg body weight/day. If we take myself, a roughly 80 kg male, and an average can of diet soda which contains ~90 mg of aspartame, I could theoretically consume 44 cans of diet soda per day without any consequences.


The association between artificial sweeteners and cancer seems to stem from rodent studies conducted in the 1980s. An excess bladder cancer risk was found in more than one generation of rodents treated with extremely high doses of saccharin (6). It was then subsequently shown that metabolism of saccharin is species specific and that saccharin did not lead to the formation of either urinary tract stones or epithelial lesions in humans (7). In addition, larger epidemiological studies in humans failed to reproduce the original rodent findings (8).

This shouldn’t be too surprising considering the fact that we are not simply large rodents. Rodent research is a starting point to garner interest in a topic. It can act as a springboard for future human studies. Furthermore, these models are useful to pinpoint specific physiological mechanisms as rodents are easily controlled and experiments that would never be allowed in humans are fair game. However, it’s illogical to think the outcomes of these trials can be directly applied to humans.

It’s also important to note that the point of artificial sweetener studies in rodents is to elicit an effect. Since the goal is to determine a NOAEL, it’s common for rodents to be fed 3,000-5,000 mg/kg of body weight/day of an artificial sweetener. Do we need to run the math to figure out how many diet sodas that would mean for me in a day? I don’t think so. There would obviously be consequences for my health if I drank that much diet soda. 

Numerous reviews looking at the potential carcinogenic effects of particular artificial sweeteners are available. There does not appear to be a carcinogenic effect of sucralose (9), even when exposure levels are several orders of magnitude greater than the range of anticipated daily ingestion levels (10). The same goes for aspartame (11-13), though even heavy users of the product comes nowhere close to the ADI, consuming about 30% of it (14). Lastly, wait for it… There doesn’t appear to be any evidence that saccharin increases risk of cancer at several common sites in humans (15,16).

To conclude, artificial sweeteners are not carcinogenic, especially when consumed within the ADI, which as previously stated, is a very cautious figure. All of the artificial sweeteners currently on the market have undergone thorough safety evaluation, taking many years to complete (4). There is no reason to fear the consumption of artificial sweeteners due to an increased risk of cancer.

Weight Loss

The data on the use of artificial sweeteners for weight loss is actually pretty interesting, though as you’ll find out, the practical application is not. It’s pretty straight forward, to be honest.

In a very recent trial, 154 participants were randomly assigned to consume 1.25-1.75 L (depending on the subject’s body weight) of a beverage sweetened with either sucrose, aspartame, saccharin, sucralose, or rebaudioside A, every day for 12 weeks (17). Worth noting, this meant that the sucrose group consumed 400-560 calories per day strictly from their assigned beverage.

At the end of the trial, there was a statistically significant increase in body weight over the 12 weeks for participants in the sucrose (wow, what a surprise) and saccharin (okay, actually a surprise) groups.  There were no significant changes in body weight for aspartame, rebaudioside A, and sucralose of 0.73 +/- 0.35 kg, 0.60 +/- 0.36 kg, and -0.78 +/- 0.36 kg, respectively. 

What’s rather interesting is that hunger ratings in the saccharin group were significantly greater than for all other treatment groups. This would explain the increased weight in this group as the subjects must have acted on the physiological signal. What’s also fascinating is that the average weight trended downwards in the sucralose group, though there doesn’t appear to be a specific mechanism to explain this outcome.  

In another trial, 303 weight-stable people with overweight and obesity participated in a weight loss program (12 weeks of weight loss followed by 40 weeks of weight maintenance) featuring either 710 mL of water or artificially sweetened beverage (18). 

The results displayed that the artificially sweetened beverage group reached a higher maximum mean weight loss (8.6 kg by week 28) compared to the water group (5.5 kg by week 20). In addition, at year 1, the artificially sweetened beverage group maintained a mean weight loss of 6.21 +/- 7.65 kg, while the water group only maintained a mean weight loss of 2.45 +/- 5.59 kg.

These findings may be explained by the properties of diet beverages, mainly their sweet flavor, which could satisfy cravings for other sweet foods. Other research has noted a decrease in the consumption of desserts as a result of the addition of diet beverages (19).

In accordance with these results, reviews on the topic tend to conclude a modest reduction in body weight from the use of artificial sweeteners (20-23). Some epidemiological research associates the use of artificial sweeteners with overweight and obesity, but this is a product of reverse causality. It’s not that artificial sweeteners cause overweight or obesity, it’s more so that overweight or obese individuals are more likely to use artificial sweeteners as a result of an interest in weight loss. 

To end, artificial sweeteners can be a useful tool for weight loss if used appropriately. The sole inclusion of artificial sweeteners in the diet will not cause weight loss, but, if beverages which contain calories are swapped out for ones which are artificially sweetened (and nothing else in the diet changes), this will result in weight loss. It still all comes down to thermodynamics. You have to expend more energy than you consume to lose weight, and artificial sweeteners may facilitate this process by taking the place of a calorie-containing substance in the diet. 

Gut Microbiome

This a pretty trendy topic of discussion right now. The gut microbiome is a rapidly evolving field still in its infancy. There are very few things about the gut microbiome we can conclude with certainty, which is why I will keep this section brief, and also why if you come across a layperson ranting about how this and that random thing affects the gut microbiome, just run away… RUN… FASTER.

There are trillions of symbiotic microorganisms present in the human body, the majority of which are located within the gastrointestinal tract, and are collectively referred to as the microbiota or gut microbiome.

One study found that consuming the maximal daily ADI of saccharin (5 mg/kg body weight) for a week led to significantly poorer glycemic responses in 4/7 subjects, and this effect was associated with changes in the composition of the gut microbiome (24). In contrast, a more recent study reported that consuming the maximal ADI for two weeks did not alter microbial diversity or glucose tolerance (25)

Similarly, in a new randomized crossover trial, participants consumed either 10.5 packets of sucralose or 10 packets of aspartame daily for 14 days, followed by the other sweetener after a four-week washout period. In the end, it was found that neither sweetener had a measurable impact on the gut microbiome (26).

Overall, there is no clear and consistent evidence (at this point in time) that the consumption of artificial sweeteners has any adverse effects on the gut microbiome (27). With that being said, long-term trials in humans are needed to draw stronger conclusions.


Honestly, I didn’t think I would end up having to write this article, but I’ve heard one too many unsubstantiated remarks as of late. The data has been clear for decades that artificial sweeteners are completely safe. The government is not trying to poison you. Artificial sweeteners go through extensive testing before being placed on the market and an abundance of additional research has supported their safety. I’m sure there are other buzzword controversies surrounding artificial sweeteners that I have not addressed, but artificial sweeteners do not directly cause cancer, weight gain, or dysbiosis. 

Go have a diet soda. Enjoy.


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