Dietary sweeteners are extremely controversial. One can still hear at times that they “cause cancer”, are “much worse than sugar”, can raise blood glucose and that, although they contain no calories, they do not support weight loss at all. Some of these statements are myths, others are facts, and some of the questions we simply don’t know the answers to yet. However, sweeteners are undoubtedly a very controversial part of the menu.
Arguably nothing electrifies the scientific dietary discussion more than sweeteners. They are regarded by some as a saviour on a low-calorie, sugar-restricted diet, but others prefer to avoid them like the plague. Even experts don’t agree on their health effects, and practically every day new data emerges arguing “for” or “against” specific sweeteners. I attempt to delve into this sweet world without calories and debunk some of the most important myths about sweeteners in the form of a Q&A. Draw your own conclusions: do you prefer low-calorie sweeteners or definitely unhealthy, but at least familiar, sugar?
What are “sweeteners”, “artificial sweeteners” and “non-nutritive sweeteners”?
If someone tries to introduce you to the topic of sweeteners by lumping all of them together, take these speculations with a grain of salt. Sweeteners are a really broad group of ingredients that vary in their chemical composition, calorie content and taste. Sweeteners include: glycosides, peptides, alcohols, heterocyclines... Other than their sweet taste, they have few characteristics in common. Certainly, their safety and impact on the body cannot be evaluated jointly.
So called artificial sweeteners include, for example, aspartame, acesulfame K, saccharin, and sucralose. They are also often called “non-nutritive sweeteners” due to the fact that in the doses they are used, they provide close to 0 kcal. It is these substances that one most often has in mind when saying “sweeteners”. Another group of sweeteners – natural sweeteners – on the other hand, includes, for example, inulin, stevia, xylitol, but also coconut sugar, or honey.
In terms of harmfulness and health effects, the most controversy is around non-nutritive sweeteners, and it is these that will be the focus of most questions about the impact that sweeteners have on human health. They have no calories, but do they affect the body in any way?
How do sweeteners work and why are they sweet?
All sweeteners have one thing in common: they are sweet. Why is that? Because they connect to and stimulate the sweet taste receptors located in the taste buds. They achieve this effect with various chemical particles.
How were artificial sweeteners discovered?
Counterintuitively, sweeteners are not as modern an invention as is sometimes thought. The first artificial sweetener was saccharin, discovered around 1870. According to a popular anecdote, chemists Constantin Fahlberg and Ira Remsen made the discovery of saccharin by accident, when one of the scientists forgot to wash their hands during lunch break. It is said that the chemist licked their palm and felt the characteristic sweet taste, and registered the discovery under the name saccharin. The sweetener became very popular during World War I because, unlike sugar, it was not rationed.
Where are artificial sweeteners found in?
Artificial sweeteners are most strongly associated with zero-calorie drinks, and this is how they are consumed most often. However, sweeteners are found in many other food products. You can find them in:
- flavoured yoghurts,
- cereal cookies,
- “fit” food,
- chewing gums,
- desserts and puddings,
- flavoured mineral water,
- jams.
So you can eat sweeteners in ways other than adding a pure sweetener in coffee tablets, or drinking zero-calorie drinks. A very interesting study by Israeli scientists (which I will cite later on when discussing the effects of sweeteners on gut microbes) showed in black and white that people don’t realize they are eating a lot of sweeteners themselves. The study sought volunteers who avoided artificial sweeteners on a daily basis. Recruiters informed every participant about it and more than 1,000 people were found who declared that they avoided artificial sweeteners. After careful analysis of their dietary history, it was necessary to reject almost 90 percent of the volunteers as it turned out they had too many artificial sweeteners in their diets, which would have disturbed the results of the study. If you think the issue of sweeteners doesn’t concern you, think twice, because there’s a good chance you’re eating a lot of them anyway.
Does aspartame (or other artificial sweeteners) cause cancer?
Let’s begin our assessment of the health effects of artificial sweeteners with the most common argument against these substances. One of the more common reasons why people avoid consuming artificial sweeteners is the fear of cancerogenic effects of aspartame and saccharin. 1 in 4 people in the US believe artificial sweeteners cause cancer. This, however, is a long-debunked theory born out of a certain study on rats.
In fact, it was then recognized that rats watered with saccharin were more likely to develop certain types of cancer. This even led to a situation where for several years every product with saccharin had to have the words “may cause cancer in rats” on the packaging. However, the study turned out to be a one-off case, and the saccharin-induced tumours affected rats of only one particular breed and only the male sex. Saccharin has been pretty much cleared of the charges and is now considered 100 percent safe in terms of cancerogenic effects.
However, this is not the end of the controversy linking sweeteners to cancer. Aspartame, familiar to everyone from most zero-calorie drinks, was also at one point linked to tumorigenesis, more specifically brain tumours. All by observation: a significant increase in the incidence of brain tumours, coincided with the prevalence of aspartame in the US. However, any budding statistician knows that this is a correlation, not a causation, and is not proof of aspartame’s cancerogenic effects. Nevertheless, it is possible to present this relationship in a pictorial graph and induce panic: this is exactly what happened.
Over the years these allegations were very thoroughly and carefully refuted. A total of nearly 0.5 million people were surveyed over five years. It is currently believed that aspartame does not increase the risk of any type of cancer. It is one of the best tested and safest sweeteners, approved by EFSA and regularly tested.
Do scientists keep changing their minds about sweeteners?
You may think that scientists are constantly changing their minds, cannot be trusted, and their recommendations shouldn’t be taken seriously since studies often contradict each other. This is not true, however. Indeed, from the media you may get contradictory information about sweeteners, but it is the media frenzy that distorts and accentuates it. One small premise about the harmfulness of sweeteners tested on a small group of animals finds its way into the mass media and stirs up confusion. What does not change, though, are the recommendations, which are the best source of knowledge about the safety of sweeteners. You may think that things are continuously changing in this area, but contrary to appearances, EFSA’s recommendations remain constant, despite frequent evaluations and admission of the latest evidence. Instead of believing flashy headlines, trust reputable organizations, whose main goal is to ensure the safety of the food they bring to market.
Do sweeteners raise blood sugar or affect blood glucose level?
Non-nutritive sweeteners contain no calories, no glucose, or other sugars, so they have no direct effect on dietary glycemia. Natural sweeteners, such as honey, agave syrup, or date syrup, already contain glucose and will raise its level in the blood.
Non-nutritive sweeteners, however, have stirred up another controversy related to blood sugar level. There is some evidence that they may indirectly affect the body’s ability to metabolize glucose. This is especially true for saccharin and sucralose. This relationship may be explained by a very interesting, highly anticipated and fresh study by Israeli scientists on the effects of sweeteners on the gut microbiome. It turns out that the way sugar is metabolized after sweeteners may be influenced precisely by the bacteria inhabiting the gut.
How do sweeteners affect the gut microbiome?
Although artificial sweeteners are well studied and considered safe, there is one aspect that remains relatively unexplored: the effect of sweeteners on the bacteria that naturally populate the gut. This relationship may be the answer to the many conflicting studies and controversies about sweeteners. A 2014 study released by Israeli scientists stirred up the scientific world after discovering that the consumption of artificial sweeteners has a major impact on the microflora of rats that were given them. However, this is only an animal study, providing the rationale, but not scientific evidence. After 8 years, in August 2022, the same group of researchers provided new data from studies with humans that once again verify the view of sweeteners. This time the evidence is more solid.
A group of 130 volunteers, who were very wary of consuming sweeteners on a daily basis, were divided into 6 study subgroups, which were given a drink with a different sweetener:
- a group that consumed stevia,
- a group that consumed saccharin,
- a group that consumed sucralose,
- a group that consumed aspartame,
- a control group that consumed glucose,
- a control group that drank water.
All were carefully examined before the experiment began, especially in terms of how they metabolized glucose. For 2 weeks, they were given a sweetener-based drink to which they were assigned at doses below the ADI (acceptable daily intake). At the same time, faecal samples were collected from them to determine the content and composition of intestinal microbes.
It turned out that the composition of the intestinal microflora changed for all people in the sweetener-consuming group, while it remained unchanged for those in the control groups. What’s more, some people in the group that consumed saccharin and sucralose had markedly impaired glucose metabolism compared to how they responded to the same test before the two-week exposure to the sweeteners.
That’s not all: microflora taken from the people who reacted most strongly to the sweeteners by having their glucose metabolism worsened were implanted in mice with microbe-cleared intestines (germ-free mice). The result? Mice with microbes from human donors whose microflora changed after the sweeteners also had worse glucose metabolism. This is a big argument against sucralose and saccharin.
The potential negative impact on the gut microbiome is one mechanism that may be the strongest argument against the use of artificial sweeteners. Most likely, sweeteners affect and disrupt the intercommunication of gut microbes, but the exact mechanism remains unknown. It is also worth mentioning that the reaction to a given sweetener varied greatly among the different people tested and is extremely individual.
Do sweeteners help you lose weight?
Since zero-calorie drinks have no calories, they must perfectly support weight loss, right? This seems logical and obvious, but a review of the studies complicates the situation. Weight reduction in people swapping sugar-sweetened beverages for those with sweeteners is not a foregone conclusion: according to most studies, body weight remains unchanged or decreases slightly. This may be accounted for by the so called calorie offset, which is the fact that when you have a zero-calorie drink, the calories saved are simply eaten with another product. One thing is for sure: if you have sugary drinks on a daily basis, it’s worth switching to zero-sugar drinks because of the many other health benefits of limiting sugar. However, don’t expect this one change to slim you down.
Which is healthier: a drink with sugar, or a zero-sugar, sweetener-free drink?
Let’s summarize the knowledge about the effects of sweeteners on the human body with a simple table with advantages and disadvantages of each option.
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| Sugar-sweetened drink | |
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Summary: using low-calorie sweeteners is generally considered safe, and this is a much more recommended solution than using products with sugar. Sweeteners are well researched, but there are several areas where more research would be useful to realistically assess their health effects. The controversy is primarily over the effect of sweetener consumption on gut microflora, which is linked to glucose metabolism, but also affects many other systems in the body.