The science of sweeteners

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By The Gut Health Doctor Team

Dr Megan Rossi in a lab looking through a microscope

As public health efforts with the war on sugar have ramped up, the use of no/ low calorie (nonnutritive) sweeteners has boomed and they’re popping up on more supermarket shelves than ever – so much so that the market was said to be worth a whopping $9.2 billion in 2019. When it comes to the science, there are some conflicting findings. Here’s the latest…


In a nutshell: Food safety tests for artificial sweeteners were mostly done before we knew much about our gut microbes, and early evidence looking at the impact on our GM is conflicting – ultimately, the jury is still out!


First, what actually are sweeteners?

When we talk about sweeteners, they’re usually artificial sweeteners made in a lab from various chemical substances, providing sweetness without the calories (or in some cases just reduced calories). They’re completely different to sugar (they have different chemical structures) and their sweetness is much more concentrated. Depending on the type of sweetener, their sweetness ‘power’ typically ranges between 300-13,000 times that of standard table sugar. For this reason, only tiny amounts are needed to add equivalent sweetness to food.


Common artificial sweeteners include aspartame, sucralose and saccharin.


What effect do sweeteners have on our gut health?

This is where things get really interesting. All additives (including sweeteners) must go through a rigorous safety assessment before they’re allowed to be used in our food.


However, historically, the safety assessments haven’t considered the impact of the various additives (over 400!) on our GM – because a lot of these assessments were carried out before we had a grasp on the importance of it.


Some early studies (keeping in mind most are in animals, not humans) show that certain types of artificial sweeteners (such as sucralose, saccharin and aspartame) negatively impact the GM, and can promote blood-sugar issues (despite not providing calories), liver inflammation and weight gain. Studies also show that these unwanted effects can be transferred between mice via a poop transplant – suggesting the gut microbes are directly involved in these negative side effects of sweeteners aka there is a causal relationship.


That said, only a subset of results from animal studies actually translate in humans – and that’s why we always need to be cautious when interpreting animal studies.


In terms of studies in humans for artificial sweeteners, the link isn’t straightforward (the joys of research!) with different studies finding different things. Some suggest they’re beneficial, as an alternative to added sugar, while others suggest they’re not so good.


The lack of consistent findings is likely explained by the fact that we all have different microbes, which can respond differently.


In fact, a very small but important study showed that daily intake of saccharin at a dose in line with the high end of the ‘safe’ amount (a level set by health authorities) for one week negatively impacted the blood sugars only in some people.  So, when it comes to artificial sweeteners and their impact on your gut microbes, the jury is still out.


Interestingly, another study has shown that sweeteners including saccharin and sucralose can be transferred to babies via breast milk. Although again the real meaning and consequences, if any, of this is still unknown, it is worth keeping in mind.


The bottom line

We need more long-term human studies before we have the full picture of the long-term effects (and there are lots of different sweeteners to study), but for now if you are fit and healthy, I’d generally recommend trying to stick mostly to the real deal – whole fruits, like bananas or Medjool dates in sweet desserts. That way, you not only get to treat your taste buds with the sweetness hit but your gut bacteria too – with all the other beneficial plant-chemicals (including prebiotics) found in these whole foods. Also try adding berries and lemon slices to sparkling water instead of soft drinks.


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