In my practice as a gut health dietitian my patients sometimes ask me “is sugar bad for my gut microbiome?”⁠⁠. On Instagram @AndreaHardyRD, I talk all about sugar and the gut microbiome!

Is sugar bad for my gut microbiome? 🦠🍬

I’m seeing a LOT of ‘sugar is bad for your gut microbiome’ absolutism out there right now.

Slow your roll. Would you be surprised if I told you – it’s complicated?

There is a scarcity of literature looking at the impact of sugar on a human’s microbiome. However, we have data on dietary patterns, in particular a ‘Western diet’ (high sugar, high fat, low fibre) vs high fibre & low added sugar dietary patterns.

We see that poor diet quality is associated with negative impacts on microbial diversity, a reduction in ‘good’ bacteria, increased inflammation, intestinal permeability, and subsequent chronic disease. No surprises there.

We also have some incredible animal data, predominantly exploring high fructose diets. And we can see, excess sugar intake causes these very changes.


Dose matters! In animal research, we see huge amounts of calories replaced with fructose. When this happens, the animal cannot absorb it all – meaning it definitely fuels colonic bacteria. While interesting, 👏this👏is👏not👏directly👏applicable👏to👏humans.

We all malabsorb fructose if we eat enough of it. When this happens, yes it will feed your colonic bacteria. This is hypothesized to be a contributor towards chronic disease associated with excess fructose intake (ie. fatty liver disease).

However – it’s NOT all or nothing – most of the sugar you eat will be absorbed higher up in the gut. While we want to consider excess intake, we don’t need to be absolutist.

What are we displacing with excess sugar intake? Usually fibre and nutrient rich foods! Animal studies have shown the protective effects of exercise, prebiotics, and probiotics to ameliorate impact of sugar intake on the gut microbiome. So it’s important to note, this isn’t a simple ‘cause and effect’ thing – it’s your lifestyle as a whole that probably matters.

Bottom Line:
Sugar isn’t going to kill you or your microbes. Chances are it doesn’t even reach them most of the time.

Yes, we want to be mindful of excess sugar intake.

Yes, we want to be mindful to get in enough fibre rich foods.

But eat the damn sour patch kids – without the side of guilt.