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MIAMI – Cravings for a late-night snake could impact the gut microbiome in adults with prediabetes.

The gut microbiome is the complex, dynamic community of microorganisms including bacteria, viruses, fungi and archaea, that live in the gastrointestinal tract.

Often acting like an extra organ, it plays a vital role in digesting food, synthesizing vitamins, regulating the immune system and influencing brain health.

According to Mind Body and Green (MBG), a nutrition lifestyle website, researchers are exploring clinical trials on how specific nighttime snacks affect the gut microbiome.

Citing a study published in The American Journal of Clinical Nutrition, MBG said 50 adults with prediabetes, people whose blood sugar levels are elevated but not yet in the diabetes range.

For 12 weeks, participants ate about two ounces of pistachios as their bedtime snack, roughly two small handfuls. In another 12-week phase, the same participants swapped the pistachios for a typical carb-based snack, like crackers or toast (and yes, your beloved bedtime cookies fall into that category).

Researchers then analyzed stool samples taken before and after each phase to see how the two snack options influenced the gut microbiome.

Here’s what they found:

After 12 weeks of nightly pistachio snacking, participants’ gut microbiomes looked noticeably different from when they’d eaten carb-based snacks.
Specifically, the pistachio phase increased levels of beneficial bacteria like Roseburia and Lachnospiraceae, which are known for producing butyrate—a short-chain fatty acid that lowers inflammation, strengthens the gut lining, and supports metabolic balance.

At the same time, bacteria linked to poorer metabolic health, toxin buildup, and gut barrier dysfunction, such as Flavonifractor and Eubacterium, decreased.

These microbial shifts suggest that pistachios may help create a gut environment that’s more resilient and metabolically healthy, especially in people with blood sugar challenges.

While the researchers didn’t see major changes in fasting glucose or insulin resistance over 12 weeks, the microbiome changes hint that improvements could emerge with longer-term habits.

Swapping your usual late-night snack for pistachios is a simple, evidence-backed move that could help your gut bacteria thrive and your metabolism stay balanced, especially if you’re looking to support healthy blood sugar levels.