Nighttime Pistachio Consumption Alters Stool Microbiota Diversity and Taxa Abundance Compared with Education to Consume 1–2 Carbohydrate Exchanges (15–30 grams) over 12 Weeks in Adults with Prediabetes: A Secondary Analysis from a Randomized Crossover Trial

In this randomized crossover trial of adults with prediabetes, nightly pistachio consumption caused small changes in the diversity and composition of gut bacteria compared to a higher-carbohydrate snack. However, the study did not control for other dietary factors, making it difficult to isolate the impact of pistachios alone. There were also no changes in blood sugar or other metabolic markers.

Two authors (JW and RL) are co-founders of Wright Labs LLC, where the 16S rRNA analyses were performed. KSP and PMK-E received a grant from the American Pistachio Growers to conduct the research.

This study utilizes a generally sound randomized crossover design, but lacks tight dietary control, limiting the ability to isolate the effects of pistachios. The analytical approach with 16s RNA sequencing is also a limiting factor, due to its inability to distinguish between closely related species and directly assess the functional potential of the gut microbiome. The presence of a carryover effect also raises concerns about lingering influence from the first intervention phase on the subsequent phase. These limitations lower the overall rating. However, the detailed methodology, large data set, and appropriate statistical analysis warrant a rating of 3.