How do sweeteners and sugars affect your gut health?

New research shows that sweeteners have a negative impact on your microbiome. But is sugar worse for your gut?

Sweeteners, like those found in soft drinks, have a divisive reputation. Some see them as a better option than the sugary alternative, while on the other end of the spectrum there’s real concern about how they impact our health.

While the cancer fears are misguided (Cancer Research UK and the US National Cancer Institute have issued statements saying that artificial sweeteners do not increase your risk of developing the disease), new research has shone a light on some potential downsides of sweeteners – namely, how the affect our gut.

How do sweeteners impact the gut microbiome?

A recent published in the journal Cell tested the most common non-nutritive sweeteners (those that offer no nutrition), including artificial sucralose, saccharin and aspartame as well as stevia, a naturally occurring sweetener.

“They found that all of these sweeteners modified the microbiome composition, which means modifying the types of bacteria that live in the gut. But they also changed the functionality of the microbiome,” says Dr Berry. “That’s important because the very reason the microbiome is associated with improving our health is down to the different chemicals and signals produced. Those functions seem to be dampened by sweeteners.”

Do sweeteners impact your gut?

Without the gut functioning, many other bodily processes work less well. That includes control over our blood sugar.

“Researchers looked at how sweeteners affected our ability to process sugar and found that those who used sweeteners had worse blood sugar levels in the long term,” explains Dr Berry. “Big increases in blood sugar in your circulation impacts inflammation, oxidative stress and predisposes us to cardiovascular disease, type 2 diabetes and obesity.”

While other studies have previously shown that sweeteners may impact our glycemic control, this research seemed to link that a change in gut functionality was what was driving the change in blood sugar. For example, sucralose was shown to alter the microbiome the most, and it also had the largest impact on participants’ sugar levels. That’s not so great news if the reason you are opting for sweeteners is that you’re trying to avoid the spikes that come from sugar.

“It’s a little bit difficult to make sweeping statements about sweeteners because they are quite variable. And there are lots of different products that sweeteners are in, which makes ascertaining how much sweeteners people consume almost impossible.”

Are sweeteners worse than sugar?

In the same month as the study on sweeteners and gut health, a paper was released showing how sugar disrupts our microbiome. In a study on mice from Columbia University Irving Medical Center, it was found that dietary sugar alters the gut microbiome.

Is sugar worse for your gut health?

This isn’t necessarily news – sugary diets have long been associated with a disrupted gut microbiome. “We are still in the early stage of research on this, but early papers – usually in mice – claim that high-sugar diets can be detrimental for the microbiome,” says Dr Emily Leemer, senior nutrition scientist at Zoe.

“But, physiologically, sugar actually tends to be absorbed much higher in the gastrointestinal tract, in the small intestine – rather than in the colon, where we find most of our bacteria. So the jury’s still out on whether it’s having a direct impact.”

While there’s lots of information online that suggests that sugar ‘feeds’ the ‘bad’ bacteria, Dr Leemer says science isn’t that black and white. Instead, she says the negative impact may be because “high-sugar diets tend to be low in most things that are really important, like fibre, plants and polyphenols.”