The Sweet Truth: Artificial Sweeteners and Gut Health

4th September, 2023
The sweet truth - Artificial sweeteners and gut health

Artificial sweeteners are synthetic substitutes for sugar. They provide all the sweetness but without the calories. That’s why you’ll usually find them in diet drinks, but they can also sneak into “health” foods like protein bars and yoghurts. Here, we’re breaking down the science on artificial sweeteners and gut health.

There’s been growing concern around whether artificial sweeteners are actually bad for our health. For example, the artificial sweetener aspartame, found in most diet sodas, was recently labelled by the World Health Organisation as a possible carcinogen.

There’s also a lot of research looking at the effects of artificial sweeteners on the gut health. Our gut cannot digest artificial sweeteners very well. Instead, they are broken down by our gut bacteria. Studies in animals suggest this can lead to negative changes in the balance of gut microbes, but what about humans?

We’ll look at that in a minute, but first, how to spot an artificial sweetener.

How to Spot an Artificial Sweetener

Artificial sweeteners are chemically synthesised, but they shouldn’t be confused with natural, low-calorie sweeteners. There are 8 sweeteners (4 artificial and 4 naturally occurring) approved in the UK and these are:

Artificial sweeteners Natural sweeteners
acesulfame K (E950) erythritol (E968)
aspartame (E951) sorbitol (E420)
sucralose (E955) stevia (E960)
saccharin (E954) xylitol (E967)

Artificial sweeteners can crop up in a whole range of foods. Here are some to look out for:

  • Chewing gum
  • Cordials and squash
  • Cough sweets and medicines
  • Diet drinks
  • Flavoured yoghurts
  • Jelly
  • Protein bars and powders
  • Toothpaste

Artificial sweeteners and cancer

The concerns about artificial sweeteners causing cancer go back to 1969 from a study done in rats. Since then, many more studies have found that artificial sweeteners, especially aspartame, appear to cause cancer in rodents.

However, these studies often examine large doses of aspartame, and the link has only been shown in rats and mice. Hence, the WHO have labelled aspartame as a possible carcinogen in group 2b rather than a probable (group 2a) or definite carcinogen (group 1). Also, in the same group as aspartame are electromagnetic frequencies from mobile phones and pickled vegetables like gherkins. There is some evidence to show that, compared to people who do not consume artificial sweeteners at all, people who do consume high amounts of artificial sweeteners are at increased risk of cancer.

However, correlation is not causation. It may be that people who consume more artificial sweeteners generally have poorer dietary and lifestyle choices compared to people who do not consume artificial sweeteners.

Artificial sweeteners and gut health

The human gut is home to trillions of microorganisms, known collectively as the gut microbiota. These microbes play a crucial role in your digestive health, but also your immune health and metabolic health.

There have been many studies in rodents showing that artificial sweeteners can alter the balance of gut microbes which negatively affects metabolism, even leading to increased weight gain. However, it’s important to note that most of the studies tend to use large doses of artificial sweeteners.

In humans, there has been far fewer studies to determine this. A couple of randomized, controlled trials showed conflicting results in that artificial sweeteners (within recommended daily amounts) may or may not change the balance of microbes in our guts. One of these studies did find that in some healthy people, the artificial sweetener sucralose, but not aspartame, negatively affected glucose metabolism.

Our Verdict

It’s unclear if artificial sweeteners have negative effects on gut and overall health at the recommended daily amounts. It is important to remember that animal research does not always translate to human research. The little data that we have in humans in conflicting, and the precise mechanisms even in animal studies is not fully understood.

As with many aspects of nutrition, moderation and individualised approaches are key. The occasional diet soda is almost certainly OK. However, if you consume artificial sweeteners every day, then you may want to consider alternatives, like naturally occurring, low-calorie sweeteners, such as erythritol or monk fruit extract

Swot up on the science

  • Ahmad SY, Friel J, Mackay D. The Effects of Non-Nutritive Artificial Sweeteners, Aspartame and Sucralose, on the Gut Microbiome in Healthy Adults: Secondary Outcomes of a Randomized Double-Blinded Crossover Clinical Trial. Nutrients. 2020 Nov 6;12(11):3408
  • Debras C, Chazelas E, Srour B, Druesne-Pecollo N, Esseddik Y, Szabo de Edelenyi F, Agaësse C, De Sa A, Lutchia R, Gigandet S, Huybrechts I, Julia C, Kesse-Guyot E, Allès B, Andreeva VA, Galan P, Hercberg S, Deschasaux-Tanguy M, Touvier M. Artificial sweeteners and cancer risk: Results from the NutriNet-Santé population-based cohort study. PLoS Med. 2022 Mar 24;19(3):e1003950
  • Suez J, Cohen Y, Valdés-Mas R, Mor U, Dori-Bachash M, Federici S, Zmora N, Leshem A, Heinemann M, Linevsky R, Zur M, Ben-Zeev Brik R, Bukimer A, Eliyahu-Miller S, Metz A, Fischbein R, Sharov O, Malitsky S, Itkin M, Stettner N, Harmelin A, Shapiro H, Stein-Thoeringer CK, Segal E, Elinav E. Personalized microbiome-driven effects of non-nutritive sweeteners on human glucose tolerance. Cell. 2022 Sep 1;185(18):3307-3328.e19

Share this page

This article was posted in News

Related articles

Want to be a part of the movement?

Join the Tummy MOT movement and grab yourself a free guide to 10 Tummy Truths.

Get the inside scoop to supercharge your gut health. Trusted tips, reliable recommendations and exclusive perks delivered to you every month.

Man and woman in multi coloured outfits arm in arm