Researchers have found that eating pistachios as a bedtime snack may improve gut health in adults with prediabetes, according to a study published in The American Journal of Clinical Nutrition.
The study included about 50 adults with prediabetes, a condition where blood sugar levels are higher than normal but not yet in the diabetes range. For 12 weeks, participants ate roughly two ounces of pistachios, about two small handfuls, as their evening snack. In another 12-week phase, the same participants ate a typical carbohydrate-based snack such as crackers or toast instead.
Scientists analyzed stool samples taken before and after each phase to see how the snacks affected the gut microbiome. Results showed that after 12 weeks of eating pistachios at night, participants had higher levels of beneficial bacteria, including Roseburia and Lachnospiraceae. These bacteria produce butyrate, a short-chain fatty acid that helps lower inflammation, strengthen the gut lining, and support metabolic balance.
At the same time, bacteria linked to poor metabolic health and gut problems, such as Flavonifractor and Eubacterium, decreased. The researchers noted that while they did not see major changes in fasting glucose or insulin resistance over the 12-week period, the microbiome changes suggest that longer-term habits could lead to improvements.
Pistachios are high in fiber, plant-based protein, healthy fats, and antioxidants. Unlike many common nighttime snacks that can raise blood sugar, pistachios have a low glycemic impact. This means they may help keep energy levels steady and prevent overnight glucose dips that can disturb sleep.
The study suggests that swapping a typical carb-based snack for pistachios could help support gut bacteria and metabolic health, especially for people looking to manage blood sugar levels. Small changes to eating habits at the end of the day may have positive effects on long-term health.
