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Do Artificial Sweeteners Hurt the Human Microbiome?

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Artificial Sweeteners Microbiome

Artificial sweeteners are bad… right?

I want to start off with where I’m coming from on artificial sweeteners. Anytime I was asked about aspartame or Sucralose I always said.. they’re poison. Avoid them, always. I mean… this is a PALEO website at the core, of course I hated artificial sweeteners. They’ve got to be terrible, right? Well, after really questioning my beliefs and digging in to data and not emotion or bias I realized there was NO GOOD DATA showing any type of artificial or alternative sweeteners causing serious harm to either the gut OR blood sugar regulation and insulin production.

But there are some serious claims about artificial sweeteners, this post clears them up (with the data we have right now).

Why is it commonly believed artificial sweeteners negatively impact the gut’s microbiome?

It all started in 2018 when a study was published titled “Measuring Artificial Sweeteners Toxicity Using a Bioluminescent Bacterial Panel“. Let’s understand exactly what this study did and how it has very little to do with the ACTUAL human microbiome:

This particular study specifically looked at Sucralose (a common artificial sweetener in sugar free drinks) tested in isolated E. coli cells was found to be toxic (at high does) to isolated E. coli cells in a petri dish. Testing via direct cell in a petri dish is a great process to determine a mechanism to further explore how this impacts humans… However, this study in and of itself proves data related to high amounts of Sucralose to isolated E. coli cells in a petri dish. It has no clinical evidence or merit to determine the impact of Sucralose to the human microbiome. This data is a far cry from how artificial sweeteners impact the human microbiome. Read the details of this study here.

With this detailed as is, this mechanism proven via this study has no warrant or conclusion on artificial sweeteners and their impact on the human gut bacteria composition.

And recently, we’re getting news with headlines like this:

Gut Bacteria into Pathogens (& BLOOD POISONING)?

What exactly is this article warning of? Some serious stuff!

From the text of this fear-mongering article:

Artificial sweeteners can potentially turn healthy bacteria in the gut microbiome into harmful microbes and potentially cause serious health issues such as blood poisoning, scientists have said.

UK researchers have found that sugar substitutes such as saccharin, sucralose, and aspartame – found in soft drinks and processed foods – can cause beneficial bacteria in the intestines such as E. coli (Escherichia coli) and E. faecalis (Enterococcus faecalis) to become pathogenic, or disease causing.

Bacteria like E. faecalis are able to cross the gut wall and enter the blood stream, which can lead to a life-threatening condition caused by blood poisoning (septicaemia) known as sepsis. These disease-causing microbes can also accumulate in the liver, lymph nodes and spleen, and cause a number of other infections.

WHOA THAT SOUNDS REALLY DANGEROUS… Blood Poisoning?!?!?!

BUT – Where are the short and long term studies proving blood poisoning? Where are the accounts of blood poisoning in the general public showing relation directly tied to artificial sweeteners? There are none. NONE.

What about the study referenced above?

AGAIN – This was in vitro research (petri dish) AKA: not human (Taking a substance and directly applying it to a cell makes massive assumptions which may or may not convert to actual human interaction with the compound.) Like I wrote previously, this type of testing is wonderful as the start of research to better understand mechanism… but it concludes nothing about humans and our microbiome. NOTHING. Not until it’s tested further… IN HUMANS!

Artificial Sweeteners DO NOT Negatively Impact the Gut Microbiome in Humans

Currently, we have human trial data. Good data indicating and making definitive claims in relation to the our microbiome and artificial sweeteners. If at some point data refutes this current data, I will gladly recant everything. However, we have good data and it all points to a definitive answer: artificial sweeteners DO NOT seriously impact our microbiome.

Let’s look at the data:

  • Fecal samples collected before and after treatments were analyzed for microbiome and short-chain fatty acids (SCFAs).
  • There were no differences in the median relative proportions of the most abundant bacterial taxa (family and genus) before and after treatments with both NNSs.
  • The microbiota community structure also did not show any obvious differences.
  • There were no differences in fecal SCFAs following the consumption of the NNSs.
  • These findings suggest that daily repeated consumption of pure aspartame or Sucralose in doses reflective of typical high consumption have minimal effect on gut microbiota composition or SCFA production.

Was this tested in mice? Or maybe was it tested in a petri dish? No.

Seventeen healthy participants between the ages of 18 and 45 years who had a body mass index (BMI) of 20-25 were selected. They undertook two 14-day treatment periods separated by a four-week washout period.

Conclusion: There is no proof that aspartame or Sucralose (and I’ll stretch this out to other sweeteners that do not impact blood sugar or insulin response) have an effect on the gut microbiota.

What is Saccarin?

Saccharin is one of the oldest artificial sweeteners on the market (been in drinks for over 100 years). It’s made in a lab (by oxidizing the chemicals o-toluene sulfonamide or phthalic anhydride). Contains no calories or carbs.

I don’t typically consume it but it is an artificial sweetener and it’s what they used in this double-blind, placebo-controlled, parallel arm study.

Findings of the study:

  • Men and Women were randomized to placebo, saccharin, lactisole (STR inhibitor), or saccharin with lactisole administered in capsules twice daily to achieve the maximum acceptable daily intake for 2 weeks.
  • In parallel, a 10-week study administering pure saccharin at a high dose in the drinking water of chow-fed mice with genetic ablation of STRs (T1R2-KO) and wild-type (WT) littermate controls.
  • In humans and mice, none of the interventions affected glucose or hormonal responses to an oral glucose tolerance test (OGTT) or glucose absorption in mice.
  • Pure saccharin supplementation did not alter microbial diversity or composition at any taxonomic level in humans and mice alike.
  • No treatment effects were also noted in readouts of microbial activity such as fecal metabolites or short-chain fatty acids (SCFA).

Conclusion: Short-term saccharin consumption at maximum acceptable levels is not sufficient to alter gut microbiota or induce glucose intolerance in apparently healthy humans and mice.


It’s crazy how many people get this one wrong (including me prior to digging in a little deeper). If you’re out there and you’re trying to convince people that artificial sweeteners are impacting insulin, glucose, or your gut with a headline and news post, you’re wrong, you should probably stop.

Artificial Sweeteners are Safe

As of this writing, the data is very clear: artificial sweeteners like Aspartame and Sucralose will not spike your blood sugar, raise your insulin, induce blood poisoning, or negatively impact your gut microbiome. Human studies have determined accuracy while news outlets and zealots provide fear-mongering and misleading scare tactics. Further: alternative sweeteners derived from natural sources (Stevia, Erythritol, Allulose) are also safe for the human microbiota, and are phenomenal options for those trying to manage blood sugar and insulin response.

Disagree or have other data to show? Please let me know in the comments – the more data, the better.

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